NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-8GO28308

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

303-275-3000 • www.nrel.gov

RM12-2703 Advanced Rooftop 

Unit Control Retrofit Kit Field 

Demonstration

Hawaii and Guam Energy 

Improvement Technology 

Demonstration Project

I. Doebber, J. Dean, J. Dominick, and 

G. Holland

Produced under direction of Naval Facilities Engineering 

Command (NAVFAC) by the National Renewable Energy 

Laboratory (NREL) under Interagency Agreement 11-01829

Technical Report

NREL/TP-5500-61072

March 2014
NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-8GO28308

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

303-275-3000 • www.nrel.gov

RM12-2703 Advanced Rooftop 

Unit Control Retrofit Kit Field 

Demonstration

Hawaii and Guam Energy 

Improvement Technology 

Demonstration Project

I. Doebber, J. Dean, J. Dominick, and 

G. Holland 

Produced under direction of Naval Facilities Engineering 

Command (NAVFAC) by the National Renewable Energy 

Laboratory (NREL) under Interagency Agreement 11-01829

Technical Report

NREL/TP-5500-61072

March 2014
NOTICE

This manuscript has been authored by employees of the Alliance for Sustainable Energy, LLC (“Alliance”) under 

Contract No. DE-AC36-08GO28308 with the U.S. Department of Energy (“DOE”).

This report was prepared as an account of work sponsored by an agency of the United States government. Neither 

the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or 

implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any 

information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned 

rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, 

manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring 

by the United States government or any agency thereof. The views and opinions of authors expressed herein do 

not necessarily state or reflect those of the United States government or any agency thereof.

Printed on paper containing at least 50% wastepaper, including 10% post consumer waste.
iii

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Acknowledgements

The authors wish to acknowledge Joint Base Pearl Harbor-Hickam personnel for hosting this 

demonstration and providing key support from initial design to project completion. We thank 

Peter Yuen and Chelsea Goto of the Naval Facilities Engineering Command (NAVFAC) Hawaii 

energy team, and CAPT Jeffrey W. James, joint base commander, and Col. David Kirkendall, 

deputy base commander. 

The project could not have met success without the coordination and oversight from NAVFAC 

Pacific and Hawaii, and we thank Florence Ching, Wah-Cheong Sze, James Low, David Stiner, 

April Teekell, and Susan Kim. 

We also thank Kevin Hurley of NAVFAC Headquarters for his guidance and administration of 

the demonstration program. 

There were numerous contributors at NREL and its subcontractor TWT that should be 

acknowledged. At NREL, contributors include Michael Deru, Dylan Cutler, Eric Kozubal, Gene 

Holland, Jeff Dominick, and Melissa Butheau. At Transformative Wave Technologies, we wish 

to thank Justin Sipe, Danny Miller, Jerry Scott, and Ken Hellewell. 
iv

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List of Abbreviations and Acronyms

AHJ authority having jurisdiction 

ARC advanced rooftop control 

ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers 

BLCC Building Life Cycle Cost program 

BMS building management system 

BPA Bonneville Power Administration

CAV constant air volume 

CNIC Commander Navy Installations Command 

CO2 carbon dioxide 

COLS Common Output Level Standards 

DCV demand controlled ventilation 

DOD U.S. Department of Defense 

DOE U.S. Department of Energy

DX direct expansion

ESM energy savings mode (ARC operation) 

FDD fault detection and diagnostic 

HECO Hawaiian Electric Companies

HNL Honolulu International Airport 

HR humidity ratio

HVAC heating, ventilation, and air conditioning 

IPT Integrated Product Team

JBPHH Joint Base Pearl Harbor-Hickam

MA mixed air

NAVFAC Naval Facilities Engineering Command
v 

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NEPA National Environmental Policy Act

NEBB National Environmental Balancing Bureau

NEMA National Electrical Manufacturers Association

NOAA National Oceanic and Atmospheric Administration

NREL National Renewable Energy Laboratory

non-ESM non energy savings mode (baseline RTU operation) 

PLC programmable logic controller

PPD people percentage dissatisfied

SEER seasonal energy efficiency ratio

SIR savings to investment ratio

SZVAV single-zone variable air volume 

OA outdoor air 

OAT outdoor air temperature 

O&M operation and maintenance

OM&R operation, maintenance, and repair

PNNL Pacific Northwest National Laboratory

RA return air

ROI return on investment 

RTD Resistance Temperature Detector

RTU packaged air conditioning rooftop unit 

SA supply air 

TAB HVAC testing, adjusting, and balancing 

TTF thermal test facility (NREL operated)

TRL technology readiness level

TMY3 Typical Meteorological Year 3
vi 

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TWT Transformative Wave Technologies; manufacturers of the CATALYST ARC 

technology and eIQ BMS 

UFC Unified Facilities Criteria

UFGS Unified Facilities Guide Specifications 

VFD variable-speed drive
vii 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Executive Summary

As part of its overall strategy to meet its energy goals, the Naval Facilities Engineering 

Command (NAVFAC) partnered with U.S. Department of Energy’s (DOE) National Renewable 

Energy Laboratory (NREL) to rapidly demonstrate and deploy cost-effective renewable energy 

and energy efficiency technologies. This was one of several demonstrations of new and 

underutilized commercial energy efficiency technologies. The common goals were to 

demonstrate and measure the performance and economic benefit of the system and to monitor 

any ancillary impacts related to standards of service and operation and maintenance (O&M) 

practices. In short, these demonstrations simultaneously evaluated the benefits and compatibility 

of the technologies with the U.S. Department of Defense (DOD) mission, and with NAVFAC’s

design, construction, and O&M practices.

A wide variety of DOD buildings such as offices, warehouses, gymnasiums, commissaries, 

exchange stores, and hangers are ventilated, cooled, and heated with packaged rooftop air 

conditioning units (RTUs). The term RTU refers to a pre-engineered unitary system that houses 

all the components of a heating, ventilation, and air conditioning (HVAC) system in a single 

package. Most RTUs are located on the roof but can also be located on concrete pads next to the 

buildings they serve. In Hawaii, RTUs provide only space cooling and outdoor air (OA) for 

ventilation, as no heating is needed. RTUs are popular for commercial buildings for three 

reasons: (1) minimal engineering design and specification; (2) low first costs compared to builtup systems (e.g., chillers with air handling units); and (3) quick installation. Unfortunately, 

RTUs have historically been one of the lowest efficiency HVAC systems on the market.

Consequently, the RTU retrofit market has significant opportunities for energy savings. Within 

the past 5 years, advanced rooftop control (ARC) retrofit kits have become commercially 

available to reduce RTU energy consumption and improve thermal comfort. ARC retrofit kits

boost the performance of RTU equipment by controlling its components with greater dexterity. 

Demonstration Description

This report summarizes the field demonstration of ARCs installed on nine RTUs serving a 

70,000-ft2 exchange store (large retail) and two RTUs, each serving small office buildings 

located on Joint Base Pearl Harbor-Hickam (JBPHH). Of the commercially available ARC 

systems, NREL chose the CATALYST, developed by Transformative Wave Technologies 

(TWT), because it: (1) has been successfully involved with other DOE- and utility-sponsored 

field demonstrations; (2) incorporates all the advanced control features NREL had specified to 

demonstrate for NAVFAC; and (3) can be packaged with TWT’s Web-based building 

management system (BMS) called the “eIQ” for remote monitoring. After overseeing their 

installation, NREL monitored the ARC systems’ performance to quantify their energy savings 

potential, return on investment (ROI), thermal comfort benefits, and other performance impacts 

for NAVFAC. 

Commercially available ARC technologies incorporate various advanced control features; 

however, all use a variable frequency drive (VFD) to convert the constant-speed fan to a 

variable-speed fan. Most ARC products supersede the RTU’s original controller with a new 

controller. Other advanced control features include demand controlled ventilation (DCV), 

enhanced economizing, and demand response. Some of the more sophisticated ARC retrofit 

systems can also be packaged with a Web-based BMS that provides remote control, monitoring, 
viii

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and automated fault detection and diagnostics (FDD). All these features were implemented with 

the CATALYST ARC system and eIQ BMS and closely monitored for this demonstration. The 

one feature that was available and not implemented was humidistat control. Although the Hawaii 

humidity is high, the RTUs were able to be controlled based on space temperature to maintain 

space RH < 65%.

NREL incorporated field-applied coil coatings into the demonstration to determine if this is 

another critical feature to include in ARC installations for maritime climates. The corrosive 

environment of Hawaii—and even more so that of Guam—reduces RTU life expectancy. The 

coil coating applied to new RTUs eventually wears down such that the condenser coil corrodes. 

This degrades performance and increases maintenance. During the ARC installation, NREL had 

the evaporator and condenser coils cleaned and then coated with HVACArmor DX on five of the 

11 RTUs. NREL chose the HVACArmor DX product because it can be field applied and it meets 

UFGS 23 82 02 00 10 requirement with a minimum of 1,000 hours exposure to the ASTM B117 

salt spray test.

For a baseline, each RTU’s operation was alternated weekly between non-energy savings mode 

(non-ESM) or baseline operation and energy savings mode (ESM). During ESM operational 

weeks, all the advanced control features of the ARC system were enabled. Instead of measuring 

the baseline operation before installing the ARC systems, alternating weekly exposed both 

operational modes to similar ambient conditions and building operations. The RTU baseline was 

a constant-speed supply fan, fixed OA damper (no economizing or DCV), and no demand 

response capability. 

Energy Savings and Return on Investment

NREL calculated the annual energy savings at the building level rather than evaluating each 

RTU individually for two reasons. First the nine RTUs on the exchange store influenced each 

other’s operation and worked as a “team” to condition the large space that they mutually served. 

Second, evaluation and deployment of this technology should be kept at the building level such 

that all RTUs serving a single space should be retrofitted together. Although the demonstration 

periods were short (3 to 6 months depending on the building), NREL used the monitored data to 

develop a linear regression model. Each building’s daily total RTU energy usage was correlated 

against ambient conditions (NOAA’s Honolulu International Airport weather station). NREL 

then applied the model to Honolulu International Airport Typical Meteorological Year 3 (TMY3)

normalized weather data to determine the annual energy savings. 

Table ES-1 shows the aggregated energy savings and ROI indices based on the Neptune eROI 

calculator and NIST Building Life-Cycle Cost (BLCC) program. The “Demo Actuals” ROI 

metrics are based on the actual demonstration ARC installation costs and calculated energy 

savings across the 11 RTUs. Still based on a set of 11 RTUs, the “Projected Follow-On

Deployment” analysis assumes that future ARC installations abide by the demonstration’s 

lessons learned as discussed in this report:

• Choosing facilities with multiple RTUs and significant building operating hours of at 

least 50 hours per week 
ix

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• Choosing ARC systems with variable-speed supply fan, DCV (authority having 

jurisdiction (AHJ) approved per UFC 3-410-01), and Web-based BMS capabilities

(permission confirmed through local NAVFAC CIO that meets IT security requirements)

• Choosing RTUs of at least 7 tons capacity and at most 10 years of age 

• Leveraging proper procurement methods with the testing, adjusting, and balancing 

(TAB) activity limited to balancing the SA and OA flow rates at each RTU (no air 

distribution balancing). 

Table ES-1. Economic Analysis Results

Demo Actuals Projected Follow-On

Deployment 

Annual Energy Savings 100 MWh 120 MWh

eROI Value 5.2 6.9 

Net Savings $170,000 $270,000 

Savings to Investment Ratio (SIR) 1.9 2.8 

Simple Payback in 5th year in 3rd year

Adjusted Internal Rate of Return 10% 14%

Table ES-2 shows the energy savings and the SIR for each building based on the actual 

demonstration costs. By choosing ARC systems with features that showed valuable energy 

savings in the Hawaii climate and limiting the TAB activity, the ROI can be improved; 2.8 SIR 

in Table ES-1 compared to a 0.3–2.3 SIR in Table ES-2. 

Table ES-2. Demonstration Results by Building

Building

Description

Annual Building 

HVAC

Energy Savingsa

Annual 

Energy 

Savings per 

RTU

Annual 

Cost 

Savings per 

RTUb

SIRc

1235H 

BXtra

• Big box retail

• 70,000 ft2

• 9 RTUs @ 175 

tons

• 5,840 h/yr

• 15% reduction

• 96,498 kWh

• normalized 94 

kWh/ton/1,000 h 

operation

10,722 kWh/yr $4,557 2.3

Building 

C27

• Small office 

• 2,706 ft2

• 1 RTU @ 12.5 

tons

• 2,210 h/yr

• 7% reduction

• 1,526 kWh

• normalized 55 

kWh/ton/1,000 h 

operation

1,526 kWh/yr $649 0.2

Building 

A13

• Small office 

• 7,834 ft2

• 1 RTU @ 20 tons

• 2,340 h/yr

• 5% reduction

• 1,803 kWh

• normalized 39 

kWh/ton/1,000 h 

operation

1,803 kWh/yr $766 0.3

a Normalized energy savings metric based on nominal cooling tons and annual building operating hours. b Electricity pricing reflect the average price of FY 2013 and FY 2014 rates at JBPHH. c SIR based on actual ARC installation costs. 
x 

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Additional Advanced Rooftop Control Performance Benefits

Beyond energy savings, the ARC technology provided the following performance benefits: 

• ARC operation achieved a lower relative humidity (RH) compared to the baseline 

operation for all three buildings because fan speeds were slower during cooling 

operation, the OA damper was shut during unoccupied times, and DCV reduced 

ventilation rates. The difference in the space temperature during occupied hours was 

negligible. The 1235H BXtra building showed the most dramatic improvement with a 5% 

reduction in average RH during occupied hours. 

• NAVFAC can realize additional energy savings by leveraging ARC systems with Webbased BMS capabilities. Local NAVFAC CIO needs to approve the web-based BMS to 

determine if it meet IT security requirements. If approved, the BMS can provide 

NAVFAC energy managers remote temperature set point and scheduling capability. 

NAVFAC can consistently implement and enforce the latest NAVFAC Hawaii and 

Common Output Level Standards (COLS) requirements. The lower space RH levels 

maintained by ARC systems provide improved thermal comfort under warmer 

temperature set points. The combination of ARC systems and COLS level 3 or 4 control 

will push the energy savings beyond that shown in this demonstration report. 

• The demand response sequence initiated on the 1235H BXtra showed a 12% (0.27 W/ft2) 

to 27% (0.60 W/ft2

) peak power reduction across the predefined demand response 

window (1:00 p.m. to 3:00 p.m.). The greatest demand response was realized during 

August (the hottest month). This demand response sequence would only be implemented 

if the local utility was providing additional rebates to NAVFAC for permanent load 

reduction or DR capabilities.

• The automated FDD built into the Web-based BMS worked as expected; however, the 

actions taken by the local HVAC service technicians and NAVFAC’s service technicians

based on the FDD alarms were mixed. The BXtra experienced two maintenance alarms 

during the demonstration. The first, a failing fan belt, was identified and replaced before 

it failed. The second lost communication to one of the nine RTUs. Whether the unit 

continued to run based on its own controller is unknown; neither TWT nor NREL were 

contacted about comfort issues. It took almost a full month until action was taken to 

reestablish communication. Similarly, the maintenance issues with C27 and A13 were 

properly identified by FDD alarms but the response by HVAC technicians did not 

improve compared to typical O&M activities. To leverage automated FDD in preventing 

future comfort calls and catastrophic failures, NAVFAC HVAC technicians and 

contracted HVAC service providers will need to adopt a more formalized procedure to 

respond to web-based alarming. 

Recommended Next Steps

The immediate next step will be for NREL to monitor ESM versus non-ESM performance 

through January 2014 and provide an addenda report to NAVFAC reflecting updated annual 

savings estimates. ARC retrofit technologies are TRL 9 and commercially available. Based on 

the results in this report, NAVFAC should adopt ARC retrofits on facilities in this climate zone

that meet the building and RTU attributes summarized in the bullets above. Although the large 

BXtra building for this demonstration was a big box retail facility, the energy savings 
xi

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implications would be applicable to medium and large buildings with extended operational hours 

(50 or more hours per week). These include recreation centers (bowling alleys, gymnasiums), 

conditioned hangers or warehouses, cafeterias, and commissaries. When evaluating potential 

ARC projects, NAVFAC should evaluate whether the variable ventilation rates will impact 

building or space pressurization requirements especially with independent exhaust systems such 

as kitchen hoods. 

For buildings smaller than 10,000 ft2 where one RTU serves a single space, NAVFAC should

conduct additional monitoring on ARC systems. Although NREL provides ARC energy savings 

information on A13 and C27 in this report, both buildings had issues during the demonstration 

period that mitigated ARC energy savings. The RTU serving building A13 experienced multiple 

maintenance issues unrelated to the ARC system, which minimized the valid dataset comparing 

ESM to non-ESM operation. The RTU serving building C27 experienced uncharacteristically 

long periods of second-stage cooling. After verifying that the first stage compressor was 

operating properly, NREL determined that the reason was because the temperature sensor was 

adjacent to an exit door and was significantly influenced by infiltration. Consequently, the ARC 

energy savings were lower than anticipated. Fortunately, the Integrated Product Team procured 

and had installed additional ARC systems at JBPHH. Similar to this demonstration, NAVFAC 

could monitor these installations to provide a larger sample size of ARC energy savings for small 

facilities across a broader range of building functions. With proper operation, ARC energy 

savings for NAVFAC’s prevalent small buildings like A13 and C27 may show greater energy 

savings than those presented here.

NREL could discern no consistent performance difference between the RTUs with and without 

the coil coating. As a recommended follow-on activity, NAVFAC should keep track of the five 

RTUs with the HVACArmor DX coil coating to determine if their lifetimes are extended. If the 

RTU lifetime is extended and, depending on how many additional years can be expected, 

NAVFAC should consider including coil coatings in the standard ARC installation.
xii

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Table of Contents

List of Abbreviations and Acronyms ....................................................................................................... iii

Executive Summary.................................................................................................................................. vii

Demonstration Description ................................................................................................................... vii

Energy Savings and Return on Investment ......................................................................................... viii

Additional Advanced Rooftop Control Performance Benefits ............................................................... x

Recommended Next Steps ...................................................................................................................... x

List of Figures .......................................................................................................................................... xiv

List of Tables ............................................................................................................................................ xvi

1 Introduction........................................................................................................................................... 1

2 Demonstration Objective ..................................................................................................................... 2

2.1 Technology Description ................................................................................................................ 2

2.1.1 Variable-Speed Supply Fan Operation ............................................................................. 4

2.1.2 Demand Controlled Ventilation ....................................................................................... 4

2.1.3 Enhanced Economizing .................................................................................................... 5

2.1.4 Peak Demand Reduction .................................................................................................. 5

2.1.5 Building Management System Functionality ................................................................... 5

2.2 Advanced Rooftop Control Retrofit Sequence of Operation ........................................................ 7

2.3 Coil Coating .................................................................................................................................. 8

3 Demonstration Design ......................................................................................................................... 9

3.1 Site Selection ................................................................................................................................. 9

3.1.1 BXtra 1235H .................................................................................................................... 9

3.1.2 Small Office Buildings A13 and C27............................................................................. 11

3.2 Sampling Protocol ....................................................................................................................... 14

3.3 Equipment Calibration and Data Quality Issues ......................................................................... 16

3.4 Baseline (non-Energy Savings Mode) Characterization ............................................................. 16

3.5 Performance Objectives .............................................................................................................. 16

3.5.1 Annual Energy Savings .................................................................................................. 18

3.5.2 Interior Thermal Comfort ............................................................................................... 18

3.5.3 Ventilation Quality ......................................................................................................... 18

3.5.4 Demand Response .......................................................................................................... 18

3.5.5 Economizer Hours .......................................................................................................... 18

3.5.6 Evaporator Coil and Condensing Coil Coatings ............................................................ 19

4 Technical Performance Analysis and Assessment ........................................................................ 21

4.1 Initial Adjustment Period ............................................................................................................ 23

4.2 Annual Energy Savings ............................................................................................................... 25

4.2.1 BXtra Energy Savings .................................................................................................... 25

4.2.2 C27 Energy Savings ....................................................................................................... 31

4.2.3 A13 Energy Savings ....................................................................................................... 37

4.3 Interior Thermal Comfort ............................................................................................................ 41

4.4 Ventilation Quality ...................................................................................................................... 44

4.4.1 1235H BXtra .................................................................................................................. 46

4.4.2 Building C27 .................................................................................................................. 46

4.4.3 Building A13 .................................................................................................................. 46

4.5 Demand Response ....................................................................................................................... 46

5 Economic Performance Analysis and Assessment........................................................................ 50

6 Project Management Considerations ............................................................................................... 54

6.1 Site Selection and Approval ........................................................................................................ 55

6.1.1 Site Selection .................................................................................................................. 55

6.1.2 Site Approval ................................................................................................................. 55

6.2 Contracts and Procurement ......................................................................................................... 56
xiii

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6.3 Design ......................................................................................................................................... 57

6.4 Installation and Construction (Include Permitting, Interconnect Agreements, Factory 

Acceptance Testing, Commissioning) ......................................................................................... 58

6.5 Operation and Maintenance......................................................................................................... 58

6.5.1 Automated Fault Detection and Diagnostic and Remote Monitoring Addressing 

Unforeseen Maintenance ................................................................................................ 59

6.5.2 Routine Maintenance...................................................................................................... 59

6.6 Training ....................................................................................................................................... 60

7 Commercial Readiness Qualitative Assessment ............................................................................ 61

7.1 Commercial Readiness ................................................................................................................ 61

7.2 Market Opportunities and Barriers .............................................................................................. 63

7.3 Usability and Functionality ......................................................................................................... 64

8 Recommended Next Steps ................................................................................................................ 66

References................................................................................................................................................. 69

Appendix A: NAVFAC-Defined Thermal Comfort .................................................................................. 70

Defining NAVFAC Thermal Comfort and Operational Requirements ................................................ 70

Applying ASHRAE Standard 55 to NAVFAC Operational Requirements ......................................... 75

Appendix B: Linear Regression Method and Results ........................................................................... 78

BXtra Linear Regression ...................................................................................................................... 79

C27 Linear Regression ......................................................................................................................... 80

A13 Linear Regression ......................................................................................................................... 82

Appendix C: CATALYST Advanced Rooftop Control Retrofit Field Demonstration List .................. 84

Appendix D: NAVFAC Routine Rooftop Unit Maintenance Procedures.............................................. 85

Appendix E: Testing, Adjusting, and Balancing Results...................................................................... 86

Appendix F: Buildings A13 and C27 Demand Response Results ....................................................... 92

Appendix G: Economizing Performance Objective............................................................................... 94

Appendix H: Coil Coating Performance Objective ................................................................................ 95

Appendix I: Summary of Advanced Rooftop Control Savings in Other U.S. Climates...................... 96

Appendix J: Practical Lessons Learned for Future NAVFAC Advanced Rooftop Control 

Installations......................................................................................................................................... 98

Benefits of Bundling Web-Based BMS with Advanced Rooftop Control Retrofit .............................. 98

Benefits of Testing, Adjusting, and Balancing Conducted by an Advanced Rooftop Control Retrofit 

Installer ........................................................................................................................................ 98

Space Temperature Sensor and Location ........................................................................................... 100

Space Relative Humidity Sensor (Recommended in Hawaii; Required in Guam) ............................ 101

CO2 Sensor Accuracy and Drift Concerns ......................................................................................... 102

Equalizing Duty Cycle across Multiple Rooftop Units Serving a Single Space ................................ 102

Post-Construction Meeting, Including NAVFAC HVAC Technician Training ................................ 102

Appendix K: Demonstration Economic Analysis and Cost Details................................................... 103

Cost Information ................................................................................................................................. 103

eROI Analysis Information ................................................................................................................ 103
xiv

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List of Figures Figure 1. Generic RTU schematic ................................................................................................................. 2

Figure 2. CATALYST retrofit kit ................................................................................................................. 3

Figure 3. eIQ RTU dashboard showing status and basic automated FDD .................................................... 6

Figure 4. eIQ BMS Web interface showing important RTU status and automated FDD, which are 

incorporated into the CATALYST-defined “health” of the RTU ............................................ 6

Figure 5. (a) One of the four 30-ton Carrier RTUs (left) and (b) one of the five Trane RTUs (right) ....... 11

Figure 6. Arial image of the BXtra building with designated RTU locations ............................................ 11

Figure 7. (a) 20-ton RTU serving Building A13 small office space; (b) 12.5-ton RTU serving Building 

C27 small office space ........................................................................................................... 12

Figure 8. Sample RTU graphic illustrating sensor location ........................................................................ 14

Figure 9. Corrosion and deterioration of the aluminum fins typical of all 11 RTUs* ................................ 20

Figure 10. BXtra 1235H time series of measured ESM and non-ESM energy usage (excluding known 

maintenance days) and average ambient dry bulb temperature. Note that no data are shown 

from August 9, 2013 to September 5, 2013 when Unit 01 lost wireless communication. ..... 27

Figure 11. BXtra 1235H non-ESM operation daily energy usage for each RTU versus daily average 

ambient dry bulb temperature ................................................................................................ 28

Figure 12. BXtra 1235H ESM operation daily energy usage for each RTU versus daily average ambient 

dry bulb temperature .............................................................................................................. 28

Figure 13. BXtra 1235H linear regression model applied to HNL TMY3 weather data ........................... 29

Figure 14. BXtra 1235H comparison of non-ESM daily energy usage between measured data and the 

regression model .................................................................................................................... 30

Figure 15. BXtra 1235H comparison of ESM daily energy usage between measured data and the 

regression model .................................................................................................................... 30

Figure 16. Building C27 time series plot of measured ESM and non-ESM energy usage (excluding 

weekends and known maintenance days) and average OAT and minimum OAT. Note that 

due to an error in the weekly alternating schedule, ESM operated an extra week in midOctober. .................................................................................................................................. 32

Figure 17. Building C27 linear regression model applied to HNL TMY3 weather data; zero energy values 

are for weekends when the RTUs are off per NAVFAC operational requirements ............... 33

Figure 18. Building C27 comparison of non-ESM daily energy usage between measured data and the 

regression model .................................................................................................................... 34

Figure 19. Building C27 comparison of ESM daily energy usage between measured data and the 

regression model .................................................................................................................... 34

Figure 20. C27 RTU operation (9/9/2013) .................................................................................................. 35

Figure 21. C27 space temperature versus space temperature set point (9/9/2013) ..................................... 36

Figure 22. Building C27 improperly located temperature sensor immediately next to the side exit door . 37

Figure 23. Building A13 time series plot of measured ESM and non-ESM energy usage (excluding

weekends and known maintenance days) and average OAT and minimum OAT. Note that 

due to an error in the weekly alternating schedule, ESM operated an extra week in midOctober. .................................................................................................................................. 39

Figure 24. Building A13 linear regression model daily total energy based on TMY3 weather data; note 

zero energy values are for weekends when the RTUs are off per NAVFAC operational 

requirements ........................................................................................................................... 40

Figure 25. Building A13 comparison of non-ESM daily energy usage between measured data and the 

regression model .................................................................................................................... 40

Figure 26. Building A13 comparison of ESM daily energy usage between measured data and the 

regression model .................................................................................................................... 41

Figure 27. BXtra dew point temperature histogram.................................................................................... 42

Figure 28. BXtra space temperature histogram .......................................................................................... 42
xv

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Figure 29. A13 dew point temperature histogram ...................................................................................... 43

Figure 30. A13 space temperature histogram ............................................................................................. 43

Figure 31. C27 dew point temperature histogram ....................................................................................... 43

Figure 32. C27 space temperature histogram .............................................................................................. 43

Figure 33. BXtra space hourly average RH including occupied and unoccupied hours versus hourly 

average ambient HR ............................................................................................................... 44

Figure 34. BXtra demand response for September ..................................................................................... 48

Figure 35. BXtra demand response for July and September ....................................................................... 49

Figure 36. Sensitivity analysis on electricity pricing .................................................................................. 52

Figure 37. Technology Readiness Level (TRL) .......................................................................................... 63

Figure A-1. ASHRAE Standard 55-2010 summer (0.5 clo) and winter (1.0 clo) thermal comfort zones 

compared with NAVFAC Hawaii and COLS requirements .................................................. 77

Figure B-1. BXtra 1235H predicted versus measured daily energy usage ................................................. 80

Figure B-2. Building C27 predicted versus measured daily energy usage ................................................. 82

Figure B-3. Building A13 predicted versus measured to evaluate goodness of fit of the regression model83

Figure D-1. NAVFAC quarterly RTU maintenance procedure .................................................................. 85

Figure F-1. C27 and A13 demand response for October ............................................................................ 93

Figure I-1. ARC energy savings based on detailed energy modeling study across 16 climates and four 

building types ......................................................................................................................... 97
xvi 

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List of Tables

Table ES-1. Economic Analysis Results ...................................................................................................... ix

Table ES-2. Demonstration Results by Building ......................................................................................... ix

Table 1. BXtra RTU Specifications ............................................................................................................ 10

Table 2. Buildings C27 and A13 RTU Specifications ................................................................................ 13

Table 3. Digital and Analog Monitoring Points on Each RTU ................................................................... 15

Table 4. Performance Objectives ................................................................................................................ 17

Table 5. Performance Objective Results ..................................................................................................... 22

Table 6. Building 1235H BXtra Thermostat and Operational Schedule during the Demonstration Period24

Table 7. Building A13 Thermostat and Operational Schedule during the Demonstration Period .............. 24

Table 8. Building C27 Thermostat and Operational Schedule during the Demonstration Period .............. 25

Table 9. BXtra 1235H Demonstration Period (8/3/13–11/9/13) Sample Set Summary ............................. 26

Table 10. Building BXtra 1235H Monitored Energy Usage Separated between Fan and Remaining EndUses (Compressors, Condenser Fans, Controller) Broken Down by ESM and Non-ESM 

Operation ................................................................................................................................ 26

Table 11. BXtra 1235H Linear Regression Energy Usage and Savings Applied to HNL TMY3 Weather 

Data ........................................................................................................................................ 29

Table 12. Building C27 Demonstration Period (July 1, 2013 to November 9, 2013) Measured Energy 

Usage between ESM and non–ESM Operation ..................................................................... 31

Table 13. Building C27 Monitored Energy Usage Separated between Fan and Remaining (Compressors, 

Condenser Fans, Controller) Broken Down by ESM and non-ESM Operation .................... 31

Table 14. Building C27 Linear Regression Energy Usage and Savings Applied to HNL TMY3 .............. 32

Table 15. Building A13 Demonstration Period (8/1/13–11/9/13) Measured Energy Usage between ESM 

and Non-ESM Operation ....................................................................................................... 38

Table 16. Building A13 Energy Usage Separated between Supply Fan and Remaining End Uses 

(Compressors, Condenser Fans, Controller) Broken Down by ESM and non-ESM Operation38

Table 17. Building A13 Linear Regression Energy Usage and Savings ..................................................... 39

Table 18. ASHRAE Standard 62.1-2010 Minimum Ventilation Rates for the 1235H BXtra, C27, and A13 

Buildings ................................................................................................................................ 45

Table 19. BXtra Monthly Demand Savings ................................................................................................ 47

Table 20. Economic Analysis Results ......................................................................................................... 51

Table 21. Normalized Savings Comparison Between Demonstration Facilities ........................................ 51

Table 22. Summary of Programmatic Elements of This Project ................................................................ 54

Table 23. UFGS—General Requirements .................................................................................................. 56

Table 24. UFGS—HVAC ........................................................................................................................... 57

Table 25. Commercially Available ARC Technologies ............................................................................. 62

Table 26. Follow-on ARC Retrofit Installation on 19 RTUs at JBPHH ..................................................... 67

Table 27. Follow-on ARC Retrofit Installation on 7 RTUs at AAFB ........................................................ 68

Table A-1. Navy Defined Utilities COLS ................................................................................................... 70

Table A-2. NAVFAC Hawaii “Region Energy Instruction” Issued September 2011 ................................ 72

Table A-3. Thermal Comfort PPD Based on Different NAVFAC Temperature Requirements and 

Maximum 65% RHa

 ............................................................................................................... 76

Table A-4. ASHRAE Standard 55-2010 0.5 clo Summer Conditions Applied to All Three Buildings ..... 76

Table B-1. BXtra 1235H Final Linear Regression Model Parameters ....................................................... 79

Table B-2. Building C27 Final Linear Regression Model Parameters ....................................................... 81

Table B-3. Building A13 Final Linear Regression Model Parameters ....................................................... 83

Table E-1. TAB Measured Ventilation Rates Measured Including Error Band Based on the Sensor and 

Environmental Uncertainties Measure Air Velocity at OA Inlet Hoods with Pitot Tubes .... 86

Table E-2. BXtra Supply Fan Flow Rates, Supply Fan Power, and OA Flow Rates at 100%, 90%, and 

40% VFD Speeds ................................................................................................................... 88
xvii 

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Table E-3. BXtra MA and Leaving Air Conditions with Both Compressor Stages Operational During 90% 

Capacity TAB ........................................................................................................................ 89

Table E-4. Buildings A13 and C27 Supply Fan Flow Rates, Supply Fan Power, and OA Flow Rates at 

100%, 90%, and 40% VFD Speeds ........................................................................................ 90

Table E-5. Buildings A13 and C27 MA and Leaving Air Conditions with Both Compressor Stages 

Operational During 90% Capacity TAB ................................................................................ 91

Table F-1. C27 and A13 Monthly Demand Savings ................................................................................... 92

Table G-1. Percent of Time in OA Economizer Mode ............................................................................... 94

Table I-1. Normalized RTU ARC Electrical Energy Savings from PNNL Report .................................... 97

Table K-1. Key Information Regarding eROI Analyses Performed for This Report ............................... 104

Table K-2. Key Information Regarding BLCC Analyses Performed for This Report ............................. 105
1 

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1 Introduction

As part of its overall strategy to meet its energy goals, the Naval Facilities Engineering 

Command (NAVFAC) partnered with U.S. Department of Energy’s (DOE) National Renewable 

Energy Laboratory (NREL) to rapidly demonstrate and deploy cost-effective renewable energy 

and energy efficiency technologies. This is one of several demonstrations of new or underutilized 

energy technologies. The common goals are to demonstrate and measure the energy savings and 

return on investment (ROI) of a system and to monitor any ancillary impacts related to standards 

of service and operations and maintenance (O&M) practices. The standards of service may 

include acceptable temperature and humidity ranges, power quality, allowable setbacks, noise 

criteria, air quality parameters, light levels, and other related factors. In short, demonstrations at 

DOD facilities simultaneously evaluate the benefits and compatibility of the technologies with 

the DOD mission, and with its design, construction, and O&M practices. 

The consistent year-round demand for air conditioning and dehumidification in Hawaii provides 

an advantageous demonstration location for advanced rooftop control (ARC) retrofit kits to 

packaged rooftop units (RTUs). The term packaged RTU refers to a pre-engineered unitary 

system that houses all the components of a heating, ventilation, and air conditioning (HVAC) 

system. Over the last few years, a number of innovative and cost-effective ARC retrofit kits have 

entered the marketplace. All convert a constant air volume (CAV) RTU into a single-zone 

variable air volume (SZVAV) RTU by controlling the supply fan with a variable frequency drive 

(VFD). The ARC retrofit supersedes the original controller, thereby improving energy usage 

compared with the simpler control logic typical of RTUs. Then depending on the ARC retrofit 

kit, other energy-saving features are included such as demand controlled ventilation (DCV) and 

enhanced economizing. Most commercially available ARC retrofit kits can be integrated into 

simple, Web-based building management systems (BMSs) to enable remote control and some 

automated fault detection and diagnostics (FDD). The ARC-BMS retrofit package provides a 

turnkey solution that can be purchased from a single manufacturer and then installed by a single 

contractor.

A wide variety of Navy buildings such as offices, warehouses, gymnasiums, commissaries, 

exchange stores, and hangers are air conditioned and dehumidified with RTUs. NAVFAC’s 

current method of saving HVAC energy has been to mandate allowable operational hours and 

warmer thermostat set points. Yet these mandates are not uniformly applied and maintained 

across NAVFAC’s large portfolio of buildings. NAVFAC can leverage the ARC-BMS retrofit 

package to realize energy savings through the ARC standalone features as well as the capability 

to strictly enforce operational hours and thermostat set points through a centralized BMS. The 

following demonstration quantifies the energy savings and ROI of the ARC-BMS package for 

hot-humid climates. 
2 

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2 Demonstration Objective

Innovative RTU retrofit kits can significantly reduce the energy usage of packaged RTUs, which 

are pervasive throughout the small- to medium-sized commercial buildings sector. Previous DOE 

studies have coined the term advanced rooftop control (ARC) retrofits for this product category.

This demonstration focused on ARC retrofit impacts on (1) annual energy savings and ROI; (2) 

thermal comfort; and (3) demand response. Independent modeling studies (Studer 2012; Wang 

2011) and other DOE and utility field demonstrations (Wang 2013; BPA 2013; Snohomish 2013; 

Appendix C) have shown significant energy savings potential and aggressive paybacks for ARC 

retrofits. Yet none of the demonstrations were in a hot-humid climate (ASHRAE climate zone 

1A), and to date no studies have analyzed the impacts on interior thermal comfort and demand 

response. Therefore, a field demonstration was the next logical next step in demonstrating 

performance benefits specific to the Navy’s Pacific Island facilities.

2.1 Technology Description

Typical RTUs in Hawaii and Guam use simple wall-mounted thermostat controls, constant-speed

supply fans, fixed position outdoor air (OA) dampers, and single speed compressors. Most RTUs 

are located on the roof but can also be located on concrete pads next to the building. 

Figure 1 shows the basic components of a standard RTU. An RTU uses a supply fan to draw in 

return air (RA) from the space along with a controlled amount of OA for ventilation. The mixed 

air (MA) is then cooled as it passes through an air conditioning evaporator coil filled with cold 

refrigerant. If the MA has a high enough humidity (all year for Hawaii and Guam), moisture 

condenses on the cold air conditioning evaporator coil surface and then drains from the unit. The 

cooled, dehumidified air is then supplied to the space. 

Figure 1. Generic RTU schematic
3 

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Through the use of a standard refrigeration air conditioning cycle, also called a direct expansion 

(DX) cycle, the heat absorbed by the refrigerant in the evaporator coil is pumped by the 

compressor to the condenser coil. The DX cycle rejects its heat outside the conditioned space by 

blowing OA across the condenser coil. Most RTUs with 10 tons of cooling capacity operate with 

two compressors, referred to as having two “stages.” Some RTUs are large enough to have four 

stages of cooling with four compressors. 

ARC retrofit technology is designed to integrate into existing RTUs (see Figure 2), regardless of 

make or model. Fortunately, there are only minor variations between manufacturers’ RTUs. The

ARC controller supersedes the RTU’s existing controller and controls the individual components 

(compressors, fans, OA damper) based on a signal from the BMS or thermostat/humidistat. 

While the retrofit is taking place, the RTU is retro-commissioned to ensure that all components 

are properly tuned. 

Figure 2. CATALYST retrofit kit

Of the commercially available ARC retrofit kits summarized in Section 7.1, NREL selected the 

CATALYST system for this demonstration. The CATALYST ARC retrofit consists of the 

following components: 

• Programmable logic controller (PLC) with multiple analog and digital input/outputs

• Supply fan variable frequency drive (VFD) (Yaskawa V1000) 

• Additional sensors providing input to the controller include: 

o Supply air (SA) temperature sensor

o RA temperature and relative humidity (RH) sensor 

o RA carbon dioxide (CO2) sensor,

o Outside air temperature (OAT) and RH sensor 

o Total RTU power meter 

o Fan power meter (embedded within the VFD) 

CATALYST 

Controller within 

NEMA 4 enclosure 
4 

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• Communication equipment via wireless modem or direct landline connection. 

Typical of ARC retrofit systems, the CATALYST is installed inside the RTU cabinet if 

sufficient room is available; otherwise, it can be installed in a National Electrical Manufacturers 

Association (NEMA) 4 rated enclosure outside the RTU cabinet (Figure 2). 

The CATALYST ARC uses five primary features to reduce energy use, improve thermal 

comfort, and shift peak demand. 

2.1.1 Variable-Speed Supply Fan Operation 

An RTU’s airflow rate is sized to meet the most demanding heating or cooling day of the year. 

RTUs are typically configured with a constant-speed supply fan that moves more air than is 

necessary during part load operation (which constitutes most of the year). The ARC retrofit VFD 

modulates the supply fan speed based on the mode of operation, moving only the amount of air 

necessary to meet the space demands.

2.1.2 Demand Controlled Ventilation

Based on Unified Facilities Guide Specifications (UFGS) 23 81 00 00 20, NAVFAC facilities 

are to be ventilated according to the ASHRAE 62.1-2010 standard. The 62.1 standard’s 

“ventilation rate procedure” stipulates that the OA flow rate must meet a summation of two 

minimum requirements: (1) ventilation to offset material off-gassing (OA flow rate per 

conditioned square footage); and (2) ventilation to offset human odors and meet breathing needs 

(OA flow rate per occupant). These requirements depend on building type (e.g., office, retail). 

The OA damper must provide sufficient ventilation that equals or exceeds the sum of both 

ventilation requirements. 

By enabling DCV, ARC retrofits can control the OA damper to maintain a lower ventilation rate 

to offset the material off-gassing minimum requirements. Most commercially available ARC 

technologies, including the CATALYST, implement DCV by actuating the OA damper based on 

a CO2 sensor in the RA duct. When the CO2 concentration exceeds a defined threshold, typically 

1,000 ppm, the OA damper opens. The ventilation rate is increased until the CO2 concentration 

drops below the threshold minus a defined deadband, typically 250 ppm. 

DCV saves energy throughout the year regardless of climate because it reduces the heating or 

cooling needed to condition the ventilation air. Other ARC studies, particularly Wang et al. 2011, 

showed that the most significant DCV savings were in heating-dominated climates. Heating of 

ventilation air requires significantly more energy than does cooling or dehumidification. Yet the 

energy savings can be appreciable in humid climates such as Hawaii and especially Guam.

The CATALYST ARC retrofit uses electronically actuated OA. Depending on the condition of 

the OA damper and actuator, they may need to be replaced to ensure proper operation. 

UFC 3-410-01 section 401.1 states that “Use of CO2 sensors for ventilation control is prohibited 

unless approved by AHJ”. AHJ stands for authority having jurisdiction. Based on 

correspondence with NAVFAC, the reason for this stipulation is regarding the concern that CO2
5 

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sensors are inaccurate and will drift overtime. There are a wide range in CO2 sensor quality and 

different methods by which these sensors auto-calibrate overtime.

1

 If the AHJ decides that CO2

sensors will not provide sufficient accuracy over time then the DCV feature of the ARC 

technology will need to be eliminated. Although another method of measuring real-time 

occupancy may be acceptable. According to ASHRAE Standard 62.1, other methods include: 

population counters, timers, occupancy schedules, or occupancy sensors. Yet NREL has not 

found ARC technologies that use these other methods of measuring occupancy. 

2.1.3 Enhanced Economizing

During the swing season (spring and summer in most U.S. climates), OA flow rates beyond the 

minimum ventilation rates can be used to provide cooling. This “free cooling” leverages OA to

reduce compressor runtime and save energy. Building engineers and HVAC technicians 

primarily apply a dry-bulb temperature based control sequence in dry climates because it is 

simple and does not require a humidity sensor. The CATALYST applies a differential dry bulb 

with dew point lockout sequence. The CATALYST disables economizer operation when the OA

dew point exceeds 60°F. Unfortunately, Hawaii’s and Guam’s climate is so humid that the OA

dew point exceeds the 60°F lockout during most of the year. For this demonstration, NREL 

enabled the OA economizer control sequence to evaluate its effectiveness in this climate zone to 

determine if this feature should be included in future Hawaii ARC retrofit installations.

2.1.4 Peak Demand Reduction

Because utilities reach their peak generation capacity on extremely hot days, peak demand 

charges for commercial buildings have been increasing much faster than energy rates in densely 

populated parts of the country. ARC retrofit systems have sufficient intelligence to be set up to 

cycle compressors and increase space temperature set points as needed during a demand event.

The demand event can be triggered based on a signal from a BMS, a building operator, or a 

“load-shed” signal from the utility company. This is not a standard feature of the CATALYST

system; however, NREL had this feature added to evaluate the peak demand reduction 

capabilities of ARC technologies. The peak demand capability demonstrated was a proof of 

concept. It would only be implemented if the local utility agreed to provide specific rebates for 

the ARC system based on its permanent load reduction and DR capabilities. Currently the only 

applicable rebate for the CATALYST system on JBPHH was approximately $15 per motor hp 

for adding a VFD. The capability for end-uses like RTUs to shed load when the utility needs too 

will be valued and incentivized in the near future. 

2.1.5 Building Management System Functionality

RTUs are typically controlled through standalone, wall-mounted thermostats. These simplified 

controls are not typically tied into a centralized BMS and are primarily used to set an operational 

schedule and space set point temperature. Typically the OA damper operation is tied to the 

thermostat set point. Some ARC manufacturers integrate Web-based BMSs that were developed 

 

1 The Iowa Energy Center conducted a study evaluating the accuracy of 15 wall mounted CO2 sensors from 13 

manufacturers. All of the sensors were found to have an accuracy range of +/-100 to 200 ppm over a CO2

concentration range of 400 to 1,800 ppm. These accuracies were for new sensors and do not include the error 

induced by drift over time. For more information, see www.iowaenergycenter.org/wpcontent/uploads/2012/05/PTR_CO2.pdf. 
6 

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for their own retrofit kits. Specifically for this demonstration, the CATALYST was packaged 

with the “eIQ Energy Intelligence Platform” that serves as a standalone Web-based BMS or can 

tie into an existing BMS. A screenshot of the eIQ user interface for a single RTU is provided in 

Figure 3. NAVFAC can access the eIQ website at www.eiqonline.com. 

Figure 3. eIQ RTU dashboard showing status and basic automated FDD

Beyond remote control of thermostat set points and occupancy schedules, these ARC-BMS 

packages can provide energy management and various levels of automated FDD. 

The CATALYST ARC retrofit has a number of proprietary automated FDD control sequences 

such as detecting fan belt slippage and breaks, determining filter replacements, ensuring 

adequate airflow, and ensuring appropriate discharge air temperatures. To understand the O&M 

impact of automated FDD, NREL monitored the notifications throughout the demonstration and 

documented whether these improved or hindered typical NAVFAC O&M procedures. Figure 4

provides another snapshot of the eIQ Web interface providing high-level RTU status 

information. If a maintenance issue with the RTU were alerted by an automated FDD algorithm, 

the “health” icon would indicate a problem and have an associated notification to provide some 

insight into the cause.

Figure 4. eIQ BMS Web interface showing important RTU status and automated FDD, which are 

incorporated into the CATALYST-defined “health” of the RTU
7 

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ARC systems use wireless communication from RTU to RTU and then cellular communication 

from the building to a central database located on a cloud server. The CATALYST used Wi-Fi 

standard 802.11a and broadcast at 5 GHz on its own network at each building. Each building 

then communicated back to an Amazon server through a Verizon Private Network. Prior to 

installing, the local NAVFAC CIO will need to approve the RTU-to-RTU communication at the 

building and then the cellular communication from the building. Additionally, the local CIO will 

need to approve NAVFAC HVAC technician and building energy manager access to the ARC’s 

Web-based BMS to ensure it meets NAVFAC IT requirements. 

2.2 Advanced Rooftop Control Retrofit Sequence of Operation

An RTU has several modes of operation to maintain comfortable temperature and humidity 

ranges and sufficient ventilation. Each is explained below, using an example of a 10-ton RTU 

with maximum SA flow of 4,000 cfm and a two-stage DX system operating at a cooling set point 

of 76°F, and a heating set point of 70°F. The operation of a “baseline RTU” with a constantspeed fan is compared to an RTU enhanced with the ARC retrofit system. The following 

sequence is based on the CATALYST system. Other ARC retrofit systems may have slightly 

different sequences.

• Ventilation operation. When the space temperature (75°F for example) is lower than the 

thermostat cooling set point plus a 1°F deadband (76°F) but higher than the thermostat 

heating set points minus 1°F deadband (69°F), no heating or cooling stages will be on. A 

baseline RTU supplies 4,000 cfm and maintains the OA damper at a fixed position. The 

ARC RTU dials down the supply fan speed to 40% (supplies 1,600 cfm) when its RA

CO2 sensor confirms adequate occupancy-based ventilation is being provided. Under this 

mode, the baseline and ARC RTU simply provide ventilation air and mix the space air. If 

properly balanced, the ARC RTU provides half the ventilation air as the baseline RTU.

• First-stage cooling operation. If the thermostat registers that the space temperature 

(77.3°F for example) is more than a 1°F deadband above set point (77°F) but less than a 

1.5°F deadband above set point (77.5°F), a signal is sent to the RTU that a small amount 

of cooling is needed. The baseline and ARC initiate the first stage of cooling by turning 

on the lead compressor. While the baseline unit supplies 4,000 cfm, the ARC RTU 

supplies only 3,000 cfm by maintaining the VFD at 75% of the maximum fan speed. The 

ARC RTU modulates the OA damper based on the monitored CO2 concentrations to 

ensure sufficient ventilation but not wasting energy by over ventilating. Typically the 

CO2 concentration is below the 1,000 ppm threshold such that the ARC provides 75% of 

the ventilation of the baseline. 

• Second-stage cooling operation. When the space temperature (78.4°F) is more than a 

1.5°F deadband above set point (77.5°F), the thermostat signals the RTU that a large 

amount of cooling is needed. Both RTUs activate both stages of cooling such that all 

compressors operate. The baseline RTU supplies 4,000 cfm and the SZVAV RTU 

supplies 3,600 cfm to maintain the VFD at 90% of maximum fan speed. The baseline 

RTU maintains the same damper position as in first-stage cooling operation. The ARC 

RTU slightly closes the OA damper from its first-stage position because the supply fan 

has increased speed but no additional ventilation is needed. The ARC RTU continues to 
8 

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monitor the CO2 concentration and modulate the OA damper accordingly. If the system 

is properly balanced, the ARC will provide 50% of the ventilation of the baseline. 

• Economizer operation. During a cooling call (either first stage or second stage), the 

ARC checks whether the OAT is colder than the RA temperature (differential 

economizing sequence) and whether the OA dew point is below the 60°F lockout. If the 

OA meets both conditions, the ARC will open the OA damper to leverage the OA for 

space cooling. Under first-stage cooling commands, only the economizer is allowed to 

operate. Under second-stage cooling commands, only the first-stage DX is allowed to 

operate along with the economizer (this is called integrated economizer operation).

NREL initiated the CATALYST economizer sequence for the demonstration to 

determine if Hawaii has enough economizing hours to justify this ARC feature.

2.3 Coil Coating

The marine environment of Hawaii and Guam is corrosive. NREL evaluated NAVFAC’s current 

requirements for coil coatings on new HVAC equipment. UFGS 23 82 02 00 10 Section 2.10.1.1 

“Coil Corrosion Protection” covers the factory coating requirements for new unitary heating and 

cooling equipment. The main requirement is that the coating “shall be capable of withstanding a 

minimum 1,000 hours exposure to the salt spray test specified in ASTM B117 using a 5 percent 

sodium chloride solution.” During the site surveys, NREL noted the aluminum fins to be 

corroded and brittle. Stickers on the RTUs indicated that the condenser coils had received a 

Blygold coating which NAVFAC Hawaii has applied to new RTUs by a local Oahu company. It 

would appear that the Blygold coating in Hawaii does not properly protect the RTU, namely 

condenser coils, for its entire life. 

ARC retrofits improve the performance of existing RTUs that still have at least several years of 

life until they are replaced. Therefore, NREL included a field-installed coil coating as a part of 

the ARC retrofit’s retro-commissioning process to evaluate the potential to extend the life of the 

RTU. Corrosion of the condenser coil is one of the main drivers behind performance degradation 

and factors into decisions to replace old equipment. NREL wanted to investigate whether (1) coil 

coatings boost or decrease RTU performance immediately; and (2) coil coating would extend the 

RTU’s lifetime and therefore decrease the ARC retrofit life cycle cost. 

NREL specified the HVACArmor DX coating product since it can be field applied. 

HVACArmor DX is composed of Hempel Hempathane DX 55610 polyurethane impregnated 

with 65% by weight of aluminum. Applied after the coil is power washed with a solvent, the 

HVACarmor DX forms a 1-mil coating over the fins and coils. The aluminum doping is meant to 

prevent the coating from inhibiting heat transfer. Section 3.5.6 provides a summary of how many 

RTUs received the coating and the differences between Blygold and HVACArmor DX.
9 

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3 Demonstration Design

This section provides a detailed description of the site selection process, field data acquisition, 

equipment calibration and testing procedures, and baseline characterization. 

3.1 Site Selection

JBPHH and NAVFAC PAC were selected as the demonstration sites because the hot-humid 

climate poses unique challenges for ARC retrofit technologies. Other utility- and DOEsponsored ARC field demonstrations have not included this climate. The following criteria were 

used to select the RTUs:

1. The supply fan motor electrical service must be three phase.

2. The RTU must be controlled to have the fan constantly on during occupied hours to meet 

ventilation requirements (not “auto” fan control). 

3. The RTU had to be less than 15 years old for Hawaii. Any RTU that is more than 15 

years old should be considered for replacement because it is nearing the end of its 

operational life, particularly in a marine climate. Guam typical RTU life expectancy is 7 

years.

4. The larger the RTU capacity, particularly the supply fan motor size, the greater the 

savings and the quicker the payback. RTUs larger than 7 tons were targeted for this

demonstration. 

A site visit was conducted in May 2012 and 11 RTUs across three buildings were selected for 

demonstration. These are described in the following sections. 

3.1.1 BXtra 1235H

ARC retrofit kits were installed on all nine RTUs serving the BXtra 1235H, an exchange store 

located on Hickam Air Force Base. The entire building has a total floor area of 118,338 ft2 based 

on the Navy’s iNFADS report, and is operated 7 days per week. The RTUs have a combined 

capacity of 175 cooling tons and serve the 69,576-ft2 sales floor and one small back of house 

storage room. The space type was chosen because it has a significant number of annual operating 

hours, a large cooling load, and experiences large occupancy fluctuations. 

Table 1 provides detailed information about the RTUs. The fixed OA dampers on the four 30-ton 

Carrier units originally provided all the ventilation. A third-party vendor could not be found to 

provide a means to motorize these OA dampers, so they were forced closed. Instead, four of the 

other RTUs were fitted with OA dampers and connected to the ARC retrofit controllers. 

Appendix E provides in-depth information based on the TAB report conducted as a part of the 

ARC retrofit installation.

Figure 5 shows a picture of the two main RTU types serving the BXtra. Table 1 provides 

additional BXtra RTU characteristics. Figure 6 shows an aerial view of the BXtra with the RTU 

locations.
10 

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Table 1. BXtra RTU Specifications

Eq_Id

RTU Supply Fan Motor Compressor OA Damper HVACArmor

Evap. and 

Cond. Coil 

Coating

Tons Brand

Model 

HP

Motor Motor Motor Number 

and 

Stages

RLA per 

Compressor

Non-ESM ESM

NO. FLA Nominal 

Efficiency

Power 

Factor Operation Operation

Unit 

01 30 Carrier

50AJ- 10 13.4 89.50% 78% 4 comp 10.2 Forced Shut Yes

030CC 2 stages

Unit 

02 30 Carrier

50AJ- 10 13.4 89.50% 78% 4 comp 10.2 Forced Shut Yes

030CC 2 stages

Unit 

03 30 Carrier

50AJ- 10 13.4 89.50% 78% 4 comp 10.2 Forced Shut No

030CC 2 stages

Unit 

04 30 Carrier

50AJ- 10 13.4 89.50% 78% 4 comp 10.2 Forced Shut No

030CC 2 stages

Unit 

05 10 Trane TCD120 3 4.3 ?? 75%

2 comp

2 stages 

10

All Day

20% Fixed 

Open 

6% @ 90% capacity

Yes 12.5% @ 40% capacity

Open 5:00 am – 9:00 pm

/ 7 days a week

Unit 

06 10 Trane TCD120 3 4.6 ?? 75%

2 comp

2 stages

10

All Day

20% Fixed 

Open 

6% @ 90% capacity

No 12.5% @ 40% capacity

Open 5:00 am – 9:00 

pm / 7 days a week

Unit 

07 12.5 Trane TCD150 3 4.6 ?? 75%

2 comp

2 stages 

10.8

All Day

20% Fixed 

Open 

6% @ 90% capacity

Yes 12.5% @ 40% capacity

Open 5:00 am – 9:00 

pm / 7 days a week

Unit 

08 10 Trane TCD120 3 4.6 ?? 75%

2 comp

2 stages 

10

All Day

20% Fixed 

Open 

6% @ 90% capacity

No 12.5% @ 40% capacity

Open 5:00 am – 9:00 

pm / 7 days a week

Unit 

09 12.5 Trane TCD150 3 4.6 ?? 75% 2 comp 10.8 No OA damper Yes

2 stages

Total 175 – – 55 – – – – – – – – 
11 

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Figure 5. (a) One of the four 30-ton Carrier RTUs (left) and (b) one of the five Trane RTUs (right)

Figure 6. Arial image of the BXtra building with designated RTU locations 

3.1.2 Small Office Buildings A13 and C27

An ARC retrofit was installed on the 20-ton RTU serving the west side of building A13, a singlestory 7,889-ft2 office building. The RTU was ducted throughout the entire office space; three 

other mini-split DX systems served the conference room, north offices, and several cubicles.

Each DX system was controlled by its own thermostat. 

An ARC retrofit was installed on one of the three RTUs serving building C27, which is also a 

small office building. The CATALYST was installed only on the 12.5-ton RTU serving 2,706 ft2

of the total building’s 17,285 ft2

. The remaining space is a separate server room that is 
12 

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conditioned by two other RTUs that are not part of this demonstration. Building C27 also has a 

few mini-split DX systems serving each conference room.

Table 2 summarizes the RTU characteristics serving A13 and C27. Figure 7 shows pictures of 

the A13 and C27 RTUs. 

(a) (b)

Figure 7. (a) 20-ton RTU serving Building A13 small office space; (b) 12.5-ton RTU serving 

Building C27 small office space
13 

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Table 2. Buildings C27 and A13 RTU Specifications

EQ_ID 1

RTU Supply Fan Motor Compressor OA Damper

HVACARMor DX

Evaporator and 

Condenser Coil 

Coating

Tons Brand Model No. HP

Motor Motor

Number and 

Stages 

non-ESM ESM 

FLA Power Factor Operation Operation

A13 Unit 02 20 Trane TCH240 5 6.3 75% 2 comp 

2 stages

All Day 

20% Fixed 

Open

6% @ 90% Capacity

Yes

12.5% @ 40% 

Capacity

Open 8:00 a.m.–3:30 

p.m. (May–October) 

weekdays only

Open 9:00 a.m.–3:30 

p.m. (November–

April) 

weekdays only

C27 Unit 01 12.5 Carrier 50HJ-014 3 7.5 75% 2 comp 

2 stages

All Day 

20% Fixed 

Open

6% @ 90% Capacity

No

12.5% @ 40% 

Capacity

Open 8:00 a.m.–3:30 

p.m. (May–October) 

weekdays only

Open 10:00 a.m.–

3:30 p.m. 

(November–April)

weekdays only
14 

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3.2 Sampling Protocol

The ARC retrofit controller’s built-in data acquisition with standard sensors was used for this 

demonstration. Additional temperature and RH sensors were installed inside each building to 

monitor their impact on thermal comfort. Throughout the demonstration, the monitored data 

were collected on a 1-minute time scale. Figure 8 shows a schematic of a typical RTU 

illustrating the location of each sensor. 

Table 3 provides a list of sensors, including manufacturer, model number, and sensor accuracy. 

Once each day, the monitored data were transferred through a cellular modem connection to 

TWT’s data server on the Amazon cloud. The raw data was then sent to NREL and postprocessed via a SQL database. This database was used to clean and roll up data into hourly and 

daily averages. The cleaning algorithms also corrected the non-ESM energy usage by eliminating 

the VFD drive loss impacts on fan power. The VFD manufacturer provided drive watt loss data 

at normal duty (swing PWM equal 3 kHz) for each VFD model. NREL calculated a VFD 

efficiency that was assumed to be constant at the different fan speeds. The VFD parasitic energy 

usage was subtracted from the energy use of the non-ESM RTU operation to more accurately 

represent a baseline RTU with the standard factory drive package. 

Figure 8. Sample RTU graphic illustrating sensor location
15 

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Table 3. Digital and Analog Monitoring Points on Each RTU

Digital or 

Analog 

Signal

Monitoring Point

CATALYST

Standard Sensor 

or Demonstration 

Add

Sensor 

Manufacturer/ 

Model

Sensor Accuracy Sensor Notes

Digital-1 Occupied status Standard N/A N/A Controller calculated based on programmed schedule

Digital-2 First-stage cooling Standard N/A N/A Signal from controller

Digital-3 Second-stage

cooling Standard N/A N/A Signal from controller

Digital-4 Supply fan power Standard Yaskawa VFD 

Output

Could not be 

obtained from 

Yaskawa

Value is monitor via a communication output on the 

drive; power is measured internally on the drive.

Digital-5 Total RTU power Add 

Continental WattNode WNC-3D

with ACT current 

transducers

± 3%

at leading power 

factor of 0.866

100 Hz resolution Watt-Node; accuracy combines 

Watt-Node and current transducers 

(www.ccontrolsys.com/w/Metering_System_Accuracy) 

Analog-1 OA temp sensor Standard Senva HD-3B

± 2 ̊C (3.6 ̊F) Full 

Range; 0.5 ̊C 

(0.9 ̊F) typ @ 25 ̊C 

(77.0 ̊F)

Resistance Temperature Detector (RTD); positioned 

inside the OA hood always in the shade

Analog-2 RA temp sensor Standard Senva HD-3B

± 2 ̊C (3.6 ̊F) Full 

Range; 0.5 ̊C 

(0.9 ̊F) typ @ 25 ̊C 

(77.0 ̊F)

RTD; Positioned at the RA inlet into the RTU

Analog-3 SA temp sensor Standard ACI-AN Series ± .36 F RTD in SA ductwork

Analog-4 MA temp sensor Add ACI-AN Series ± .36 F Single RTD measurement located at the filter inlet

Analog-5 OA RH sensor Standard Senva HD-3B ± 3%, 20-80% 

Range

Capacitance sensor; Positioned inside the OA hood 

always in the shade

Analog-6 RA RH sensor Standard Senva HD-3B ± 3%, 20-80% 

Range

Capacitance sensor; positioned at the RA inlet into the 

RTU

Analog-7 RA CO2 sensor Standard AirTest TR-9291 ± 30 PPM; ±3% 

reading CO2 sensor positioned in RA ductwork

Analog-8 Space 

temperature Add ACI A/1K-2W ± 1.1 ̊C (1.9 ̊F) Wall mounted temperature sensor at the existing thermostat location

Analog-9 OA damper 

controller Standard CAT-371 0-10 VDC signal at 8 Bit resolution Control signal generated by controller CAT-371

Analog-10 Fan speed Standard Communicating

Modbus signal N/A Control signal generated by controller CAT-371
16 

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3.3 Equipment Calibration and Data Quality Issues

Prior to the ARC installation at JBPHH, a CATALYST was installed on a 5-ton, 15-seasonal 

energy efficiency ratio (SEER) Trane RTU at NREL’s Thermal Test Facility (TTF). The RTU 

was outfitted with all the same data monitoring equipment and sensors shown in Figure 8. The 

Trane RTU was connected to the TTF’s HVAC laboratory, which can create MA conditions for 

the evaporator coil and OA conditions for the condenser to capture any climatic condition in the 

United States. The TTF’s high accuracy temperature, RH, and power sensing equipment were

used to verify the accuracy of the CATALYST sensors. The CATALYST manufacturer, 

Transformative Wave Technologies (TWT), does not calibrate its sensors in the field or purchase 

single- to multipoint factory calibrations because of the extra cost. The laboratory testing 

revealed that many of the sensors (except for the ± 3% RH sensors) were within the 

manufacturer’s stated accuracy range. Consequently, NREL had TWT replace three temperature 

and RH sensors in the field with temperature and RH sensors NREL had verified to meet the 

manufacturer’s specification. Two of the replacement sensors had a ± 3% RH accuracy; one had

a ± 2% RH accuracy. 

3.4 Baseline (non-Energy Savings Mode) Characterization

Before the ARC was installed, a retro-commissioning process was conducted that included 

tightening fan belts, ensuring proper refrigerant charge, calibrating temperature sensors, and 

cleaning condenser coils. This ensured that the baseline and ARC retrofit performance was 

measured on properly commissioned equipment. 

The baseline performance and ARC performance were measured in tandem by alternately 

operation between two modes: ESM which enabled all the ARC retrofit features and non-ESM. 

The non-ESM mimicked the original RTU control sequences on a code-compliant RTU. Every 

other week, the eIQ BMS was remotely controlled to switch between ESM and non-ESM. For 

the rest of the report, baseline operation is referred to as non-ESM and ARC retrofit operation is 

referred to as ESM.

3.5 Performance Objectives

Six quantitative and two qualitative performance objectives were created (see Table 4). All the 

performance objective results are presented in Section 4 except for “Economizing Hours” and 

“Evaporator Coil and Condenser Coil Coatings,” which are discussed in Appendix G and 

Appendix H, respectively.
17 

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Table 4. Performance Objectives

Performance 

Objective Metric Data Requirements Success Criteria

1 Annual energy 

savings

kWh/ton per 1,000 h of NAVFACpermitted RTU operation

Annualized ESM versus

non-ESM RTU energy 

usage

Minimum energy savings of 80 kWh/ton/1,000 

h of NAVFAC permitted RTU operation

2 

Interior 

thermal 

comfort

ESM versus non-ESM difference 

between occupied dry bulb and 

dew point temperatures; RH <

65% for occupied and unoccupied 

hours

Space dry bulb

temperature, RH, and 

dew point temperature

ESM maintains a lower space dew point

temperature profile; ESM and non-ESM

maintain similar occupied dry bulb temperature 

profiles; ESM and non-ESM maintain RH < 

65% for occupied and unoccupied hours

3 Ventilation 

quality

OA flow rate (cfm); RA CO2

concentration (ppm)

TAB report;

RA CO2 concentration 

(ppm)

Maintaining sufficient ventilation per ASHRAE 

62.1-2010; OA damper opened if DCV enabled

4 Demand 

response

Total building power draw (kW) RTU power Minimum peak demand savings of 15% during 

scheduled demand events

5 Economizing 

hours

Time in economizing and 

integrated economizing (h)

Supply fan speed;

OA damper position; 

compressor on/off 

status

Minimum of 1,300 h/yr in economizer mode

6 

Evaporator 

coil and

condenser coil 

coatings

Visual comparison of the 

evaporator and condenser coils 

with and without the coating

Site visit pictures preand post-coil coatings

Measurable energy savings of RTUs that 

received coil coating compared to RTUs that 

did not receive coil coatings
18 

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3.5.1 Annual Energy Savings

The annual energy savings performance objective was established based on NREL’s evaluation 

of PNNL modeling results that looked at the ARC retrofit technology in Miami (Wang et al. 

2011). Because this is the climate closest to Hawaii from that modeling study, NREL used the 

modeling results to calculate the fan only energy savings for a small office building. The 

modeling results predicted that the ARC retrofit would provide a fan savings of approximately 

80 kWh/ton per 1,000 h of building operation. To be conservative, NREL did not incorporate the 

DX cooling energy savings. A combination of the DCV and potential economizing hours should 

provide some DX cooling energy savings. The energy savings for the retail building (BXtra 

1235H) should be greater than for the small office buildings (C27 and A13) because it has longer 

operating hours, is larger and has more varied occupancy. 

3.5.2 Interior Thermal Comfort

The interior space temperature and RH were monitored for the duration of the demonstration 

under ESM and non-ESM operation. ARC retrofit technologies might be able to improve 

moisture control by further dehumidifying the space, but this had not been evaluated in other 

field demonstrations. ESM slows the airflow across the evaporative coil and provides a colder 

and lower dew-point air than non-ESM. ARC operation should maintain a lower space RH with 

the same temperature profiles (see Appendix A for defining NAVFAC’s thermal comfort 

requirements about space temperature and RH). 

3.5.3 Ventilation Quality

By enabling DCV, the ARC retrofit needs to maintain only the OA/ft2

 requirement. It then meets 

the OA/occupant requirement using a CO2 sensor in the RA. The ARC retrofit opens the OA 

damper from its minimum position if the CO2 concentration exceeds 1,000 ppm. The OA flow 

rates measured during the TAB must show that the baseline and ARC operations meet the 

minimum ASHRAE 62.1-2010 OA/ft2 requirement. To meet the OA/occupant requirement, the 

ARC operation must show that the OA damper is properly operated to maintain the CO2

concentration under 1,000 ppm. Finally, the NAVFAC AHJ will need to authorize the ARC 

retrofit to enable CO2 based DCV according to UFC 3-410-01. 

3.5.4 Demand Response

Some utilities employ a peak demand charge in addition to charging for energy consumption. 

The target was set to measure the ARC retrofit’s ability to reduce peak demand during a 2 hour 

window. Two demand response sequences were implemented, one for the BXtra and one for 

buildings C27 and A13. For the BXtra building, the peak demand for all nine RTUs was limited 

to 160 kW between 3:00 p.m. and 5:00 p.m. on Tuesdays, Thursdays, and Saturdays. The BXtra

demand response sequence is outlined in detail in Section 0. Buildings C27 and A13 were 

controlled to prevent both RTUs from operating in second stage cooling simultaneously from 

1:30 pm to 3:30 pm. Appendix F reviews the C27-A13 demand response results. For both 

sequences, the demand response goal was to reduce peak demand by 15% compared to a 

standard day’s operation during the designated 2-hour window. 

3.5.5 Economizer Hours

Currently, NAVFAC facilities in Hawaii incorporate no economizing. Based on several site 

surveys, NREL found the OA dampers operated in a fixed position. Hawaii’s humid climate
19 

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minimizes the number of hours per year that a differential dry bulb temperature with dew point 

lockout economizing could operate. Yet the enhanced sensing and control provided by an ARC 

retrofit may be adept enough to enable economizing for sufficient hours across the year. The OA

economizer performance objective was set to meet at least 1,300 h/year of operation. 

3.5.6 Evaporator Coil and Condensing Coil Coatings

During the spring 2012 site visit to select the demonstration RTUs, many of the aluminum fins 

on the condenser coils were showing significant corrosion. The marine climate was making the 

condenser coil aluminum fins brittle. Air conditioning performance was degrading (see Figure 

9). Based on discussions with NAVFAC HVAC technicians, new RTUs installed in Hawaii are 

not ordered with copper fins or with a factory coil/cabinet coating. Instead a local Oahu firm 

applies a Blygold PoluAl XT coating to the condenser coils when the RTUs arrive on the island 

before they are shipped to the job site. 

Based on its website,

2

 Blygold is an aluminum pigmented polyurethane for aluminum and 

copper substrates. The polyurethane provides protection from UV, salt, and acidic conditions. 

The aluminum pigment is to mitigate the coating’s impact on the coil’s heat transfer. Blygold 

sent NREL third party lab results of an ASTM B117 neutral salt spray test with 4,000 hour 

exposure and an ASTM G85 acidic salt-spray test with 4,000 hour exposure. The Blygold PoluAl 

specimens from both tests showed slight discoloration but no corrosion was present. Based on 

these tests, the Blygold manufacturer states 3,000 hours + protection according to ASTM B117 

and ASTM G85. Blygold also provides a limited 5-year manufacturer warranty. 

Despite the Blygold coating that was applied when the RTUs were first installed, the condenser 

coils needed refurbishment. The 1235H BXtra RTUs, installed in 2006, were 7 years old. The 

A13 RTU, installed in 1998, was 15 years old. The C27 RTU age is unknown as no nameplate 

data was shown. Based on the age of these RTUs and the condition of the condenser coils, NREL 

surmised that the Blygold coating will not last the typical 15 year lifetime of an RTU in Hawaii. 

The typical lifetime of an RTU in Guam is approximately 7 years due to the more extreme 

marine climate. If NAVFAC was going to invest in ARC retrofit technologies to realize energy 

savings to existing RTUs, NREL wanted to investigate a field applied coil coating that may 

extend RTU life expectancy. 

 

2 For more information, see www.blygold.com/ba/coilcoating.html. 
20 

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Figure 9. Corrosion and deterioration of the aluminum fins typical of all 11 RTUs*

*Note: Picture of one of the Carrier 50AJ-030CC 30-ton RTUs serving the BXtra 1235H building was installed in 

2006 and was labeled to have received a Blygold coil coating before installation. 

NREL specified the HVACArmor DX coil coating product since it can be field applied. The

evaporator and condenser coils on four of the 1235H BXtra RTUs and the A13 RTU were first 

cleaned with a solvent and then coated. The remaining six RTUs did not receive the coil coating 

to provide a control with which to compare the immediate performance impacts. The 

HVACArmor DX product (also identified as Hempel 55610) is a polyurethane coating marketed 

to “rejuvenate and restore” marginally deteriorated aluminum coils and copper tubes. It is 

marketed to provide corrosion and ultraviolet protection with a single coat at a 1 mil thickness to 

minimize airside pressure drop increases. Similar to the Blygold PolyAl coating, HVACArmor 

DX is impregnated with aluminum paste to mitigate negatively impacting coil heat transfer. 

Based on independent lab test results, the HVACArmor DX showed no blistering or red rust and 

less than 0.1 mm rust creep from a scribe after 1628 hours exposure to ASTM B117 neutral saltspray test. 

Based on the independent lab test results provided to NREL from the respective manufacturers, 

NREL cannot state that HVACArmor DX will or will not outperform Blygold. Adding a coil 

coating to the demonstration was to investigate whether a field applied coating can extend the 

life of an RTU. NREL evaluated the monitored data to determine if statistically significant 

results indicated that the coil coating improved performance immediately (see Appendix H). In 

Section 8, NREL recommends comparing the maintenance and lifespan of the RTUs receiving 

the HVACArmor DX coating with typical expectations for a NAVFAC follow on activity to this 

demonstration. 
21 

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4 Technical Performance Analysis and Assessment 

The ARC technology reduced RTU energy consumption and improved interior comfort through 

lower RH. The results for each demonstration objective are summarized in Table 5. Section 4.1

summarizes the initial months of monitoring and configuring the ARC system before the official 

demonstration periods began. The following subsections go into more detail about each 

demonstration objective. The economizing and coil coating demonstration objectives are 

summarized in Appendix G and Appendix H, respectively.
22 

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Table 5. Performance Objective Results

Performance 

Objective Success Criteria Results

1 Annual energy 

savings

Minimum energy savings of 80 kWh/ton 

per 1,000 h of NAVFAC-permitted RTU 

operation

• BXtra 1235H (9 ARCs) met the objective by saving 94 kWh/ton 

per 1,000 h operation (15% HVAC reduction—Table 11) 

• Building C27 (1 ARC) did not meet the objective by saving 55 kWh 

per ton per 1,000 h operation (7% HVAC reduction—Table 14) 

• Building A13 (1 ARC) did not meet the objective by saving 39 

kWh/ton per 1,000 h operation (5% HVAC reduction—Table 17)

2 

Interior 

thermal 

comfort

• ESM maintains a lower space RH and 

dew point temperature profile

• ESM and non-ESM maintain similar 

occupied dry bulb temperature profiles

• ESM and non-ESM maintain < 65% 

RH for occupied and unoccupied 

hours

• All three buildings showed that ESM operation maintained a lower 

space RH and dew point compared to non-ESM operation; 

• All three buildings showed negligible difference in the dry bulb

temperature profiles

• Except for a few hours, all three buildings showed that the 

occupied and unoccupied space RH never exceeded 65%

3 Ventilation 

quality

• Maintaining sufficient ventilation per 

ASHRAE 62.1-2010

• OA damper opened if DCV call

• TAB measurement uncertainty too significant to conclude whether 

ventilation rates met ASHRAE 62.1 requirements

• No RTU CO2 concentration exceeded 1,000 ppm to initiate the 

DCV sequence

4 Demand 

response

Minimum peak demand savings of 15% 

during scheduled demand events 

compared to previous day’s peak 

demand

• BXtra demand response sequence achieved the objective by 

reducing the peak demand 12% to 27% depending on the month

• C27 and A13 demand response sequence did not work properly

and no conclusive demand reduction could be calculated

5 Economizing 

hours

Minimum of 1,300 h/yr in economizer 

mode

Economizer sequence operated properly but infrequently due to 

Hawaii climate—unlikely 1,300 hours are possible due to climate

6 

Evaporator 

condenser 

coil coatings

Measurable energy savings of RTUs that 

received coil coating compared to RTUs 

that did not receive coil coatings

There was no conclusive difference in performance between the 

RTUs with and without the HVACArmor DX coating.
23 

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4.1 Initial Adjustment Period

Performance monitoring began on January 1, 2013. NREL configured the CATALYST system 

during the first 4 months of operation to ensure that: 

• NAVFAC’s standards of service (operational schedules, space temperature, and space 

RH) were being met.

• Non-ESM versus ESM performance could be clearly distinguished. 

Regarding differentiating performance, NREL originally configured the controls to alternate 

daily between non-ESM and ESM operation. During the initial monitoring, NREL discovered 

that non-ESM operation was “piggy-backing” on ESM’s improved dehumidification for all three 

buildings. NREL defined the phenomena as latent cross-talk. Non-ESM operation was using less 

energy because it was handed a drier space from the previous day’s ESM operation. NREL found 

that alternating weekly provided a clearer performance distinction between non-ESM and ESM 

operation. All the demonstration objectives summarized in the following subsections are based 

on monitored data from alternating weekly between non-ESM and ESM operation. 

For the 1235H BXtra (nine of 11 RTUs demonstrated), the official demonstration period was 

May 3, 2013 through November 9, 2013 (thermostat and operational schedules are summarized 

in Table 6). The demonstration period had two different daily operational hours because of an 

error occurred in the ARC optimum start sequence. Before August 22, 2013, the RTUs were 

incorrectly turning on at 1:00 a.m. for ESM and non-ESM operation and operating for 20 h/day.

Once identified, adjustments were made so the RTUs came on correctly at 5:00 a.m. for 16 h/day 

for the remainder of the demonstration. 

The demonstration start dates for the two units on C27 and A13 were later because standards of 

service issues needed to be addressed. NREL worked with NAVFAC to determine the proper 

thermostat set points and schedules for buildings A13 and C27. Section 0 outlines how 

NAVFAC’s thermostat set points and operational schedules were defined and applied. During 

the initial months of monitoring, NREL discerned that high infiltration rates in buildings A13 

and C27 caused excessive moisture buildup between 4:00 a.m. and 6:00 a.m. The space RH was 

exceeding 65%. These hours are before the NAVFAC-approved RTU operational hours, which 

start at 8:00 a.m. in the summer and 10:00 a.m. in the winter. 

Over the course of several weeks, NREL applied various control strategies with the aim of 

mitigating energy usage and maintaining NAVFAC’s approved comfort standards for non-ESM

and ESM operation. The selected control strategy was to turn the RTUs on at 6:00 a.m., before 

NAVFAC-approved summer operating hours. During this “morning dehumidification period,” 

the OA dampers remained fixed at 20% open under non-ESM operation but remained closed 

under ESM operation. NREL found that early RTU operation from 6:00 a.m. to 8:00 a.m. 

sufficiently drove the space RH below 65% before occupancy for both operational modes. The 

RTUs were then able to maintain proper moisture control throughout the occupied period of 8:00 

a.m. to 3:30 p.m. 

Building C27 started the demonstration period on July 1, 2013 (thermostat and operational 

schedules are summarized in Table 8). Maintenance issues unrelated to the CATALYST system
24 

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delayed building A13’s official start date to August 1, 2013 (thermostat and operational 

schedules are summarized in Table 7). Buildings A13 and C27 had the optimum start sequence 

replaced with the “morning dehumidification period” discussed above. 

A demand response sequence was applied to ESM and non-ESM operation for all three buildings 

on Tuesdays, Thursdays, and Saturdays (if there was weekend operation) and is summarized in 

Section 0. 

Table 6. Building 1235H BXtra Thermostat and Operational Schedule 

during the Demonstration Period

Space Type Large Retail

Area served by 9 RTUs* 69,576 ft2

May 1 to August 8, 2013

Set point = 74°F

Setback = N/A (RTU off per NAVFAC 

Hawaii Region Energy Instruction)

1:00 a.m. to 9:00 p.m. every day

20 h × 365 days 

= 7,300 h/yr

August 9 to November 9, 2013

Set point = 74°F

Setback = N/A (RTU off per NAVFAC 

Hawaii Region Energy Instruction)

5:00 a.m. to 9:00 p.m. every day

16 h × 365 days

= 5,840 h/yr

RH Constraints Maximum of 65% RH

including occupied and unoccupied hours

Scheduled Demand Report Event 3:00 p.m. to 5:00 p.m. every Tuesday, Thursday, Saturday 

both ESM and non-ESM operation

Total Tonnage/Conditioned Area 398 ft2/ton

Table 7. Building A13 Thermostat and Operational Schedule during the Demonstration Period

Space Type Small Office

Area served by RTU 7,834 ft2

August 1 to November 9, 2013

Set point = 76°F

Setback = N/A (RTU off per NAVFAC Hawaii 

Region Energy Instruction)

Summer (May–October): Monday–Friday

6:00 a.m. to 8:00 a.m. “Morning Dehumidification Period” 

(2 h/day)

8:00 a.m. to 3:30 p.m. NAVFAC Approved Operation (7.5 

h/day)

Winter (November–April): Monday–Friday

7:00 a.m. to 9:00 a.m. “Morning Dehumidification Period” 

(2 h/day)

9:00 a.m. to 3:30 p.m. NAVFAC-approved Operationa

(6.5 h/day)

RH Constraints Maximum of 65% RH

including occupied and unoccupied hours

Annual Operational Hours 2,340 h

Scheduled Demand Report Event 1:30 p.m. to 3:30 p.m. every Tuesday and Thursday

ESM and non-ESM operation

Total Tonnage/Conditioned Area 392 ft2/ton

a Based on Bonnie White, building energy manager for A13, occupants were permitted to have the RTU turn on 1 hour before 

NAVFAC-approved operation at 10:00 am for winter months. 
25 

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Table 8. Building C27 Thermostat and Operational Schedule during the Demonstration Period

Space Type Small Office

Area served by RTU 2,706 ft2

Set pointa = 75°F

Setback = N/A (RTU off per NAVFAC 

Hawaii “Region Energy Instruction”) 

Summer (May–October): Monday–Friday

6:00 a.m. to 8:00 a.m. “Morning Dehumidification 

Period” (2 h/day) 

8:00 a.m. to 3:30 p.m. NAVFAC-approved operation 

(7.5 h/day) 

Winter (November–April): Monday–Friday

8:00 a.m. to 10:00 a.m. “Morning Dehumidification 

Period” (2 h/day) 

10:00 a.m. to 3:30 p.m. NAVFAC-approved operation 

(5.5 h/day)

RH Constraints Maximum of 65% RH

Including occupied and unoccupied hours

Annual Operational Hours 2,210 h

Scheduled Demand Report Event

1:30 p.m. to 3:30 p.m. every Tuesday and Thursday

ESM and non-ESM operation

ESM and non-ESM operation

Conditioned Area/Total Tonnage 216 ft2

/ton

a Based on Bonnie White, building energy manager for C27, occupants were permitted to drop the thermostat temperature to 75°F 

from accepted interpretation of NAVFAC approved set point 76°F.

4.2 Annual Energy Savings

The principal goal of this demonstration was to quantify the ARC retrofit technologies’ energy 

savings in hot-humid climates. Measurements of daily non-ESM and ESM energy usage at 

buildings 1235H, A13, and C27 were rolled up from 1-minute monitored data. The results are

presented in two ways: 

• Measured energy usage in each operational mode for each building’s demonstration 

period. Processing consisted of grouping the data into ESM and non-ESM sets and

totalizing the energy use, and calculating daily average energy consumption for ESM and 

non-ESM operation; the difference equals the energy savings of the ARC retrofit 

technology. 

• Calculated annual average energy savings using a linear regression model with Honolulu 

International Airport (HNL) Typical Meteorological Year (TMY3) weather data to 

calculate annual ESM and non-ESM energy usage; the difference equals the energy 

savings. For details on the regression method and models see Appendix B. 

The results from both methods are presented below for each of the three buildings. 

4.2.1 BXtra Energy Savings

The measured data from the official demonstration period from August 3, 2013 through 

November 9, 2013 were cleaned by eliminating 32 days when known maintenance issues 

impacted daily energy usage. The main maintenance issue was that Unit 01 lost wireless 

communication for 28 days (August 9, 2013 to September 5, 2013). Table 9 shows that across 
26 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

the clean 159-day sample, ESM operation saved a daily average of 335 kWh; a 17% reduction in 

total HVAC energy usage. Yet this is a not a true apples-to-apples comparison, because the ESM 

sample experienced a 0.5°F lower average daily temperature, a known predictor of daily energy 

usage. Table 10 shows that most ESM savings consisted of a 55% reduction in supply fan energy 

compared to a 5% reduction in the compressor and condenser fan energy. The supply fan energy 

savings met NREL’s expectations. Yet NREL anticipated larger compressor and condenser fan 

energy savings from the DCV feature. 

Table 9. BXtra 1235H Demonstration Period (8/3/13–11/9/13) Sample Set Summary

Total Raw 

Sample

(Days)

Maintenance

Issues 

(Days)

Cleaneda

Sample

(Days)

Average

OA

Tempa

Total 

Energy 

Usagea

Average 

Daily 

Usagea

Non-ESM

Operation 86 17 69 78.5°F 138,049 

kWh 2,001 kWh

ESM

Operation 105 15 90 78.0°F 149,891 kWh 1,665 kWh

191

total

32

total

159

total

0.5°F

delta

287,940 

kWh total

335 kWh

(17%) 

savings

a From the raw sample, NREL eliminated days when known maintenance issues impacted daily energy usage.

The BXtra 1235H operated on weekends, which were included in the sample set.

Table 10. Building BXtra 1235H Monitored Energy Usage Separated between

Fan and Remaining End-Uses (Compressors, Condenser Fans, Controller) Broken Down by ESM 

and Non-ESM Operation

Fan Energya

Comp/Cond 

Fan/Controller 

Energya

Fan Average 

Daily Usagea

Comp/Cond 

Fan/Controller 

Average Daily 

Usagea

Non-ESM

Operation

31,824 kWh

(23% of total) 

106,225 kWh

(77% of total) 461 kWh 1,539 kWh

ESM

Operation

18,489 kWh

(12% of total) 

131,402 kWh

(88% of total) 205 kWh 1,460 kWh

256 kWh (55%) 

ESM Savings

79 kWh (5%) 

ESM Savings

a From the raw sample, NREL eliminated days when known maintenance issues impacted daily energy usage.

The BXtra 1235H operated on weekends, which were included in the sample set.

Figure 10 provides a time series visual of the total daily energy usage in each operational mode 

across the entire demonstration period. The figure also includes the daily average dry bulb 

temperature, which was the second most statistically significant predictor in the regression 

model. The most significant predictor was the daily hours of operation, 20 h/day before August 

22, 2013 compared to 16 h/day for the remainder of the demonstration. Figure 10 shows a 
27 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

noticeable reduction in daily energy usage for ESM and non-ESM operation after August 22, 

2013, when the RTUs were operating 4 fewer h/day.

Figure 10. BXtra 1235H time series of measured ESM and non-ESM energy usage (excluding 

known maintenance days) and average ambient dry bulb temperature. Note that no data are

shown from August 9, 2013 to September 5, 2013 when Unit 01 lost wireless communication.

Figure 11 and Figure 12 provide more details about the daily energy usage for each of the nine 

RTUs for non-ESM and ESM operation, respectively. In both operational modes, the BXtra 01 

(Unit 01) consumes the most daily energy. During the demonstration NREL surmises that the 

temperature sensor for BXtra 01 was impacted by the infiltration load because of its proximity to 

the main entrance (Figure 6). 

During the writing of this report, it turned out that the temperature sensors was reading 2-3°F 

higher than a calibrated handheld temperature sensor. Each temperature sensors was supposed to 

be calibrated during the commissioning process before the construction was closed out. Either 

the sensor went out of calibration during the demonstration period or the temperature sensors 

were never calibrated. NREL is uncertain that the energy savings would be larger or smaller if 

Unit 01 had a calibrated temperature sensor. If Unit 01 behaved like Unit 04, the savings would 

have been larger. This is a significant finding and shows the importance of ensuring calibrated 

sensors. In Appendix J, NREL includes this finding as a practical lesson learned for future ARC 

installations. 

Another observation is the unequal RTU loading that could create maintenance issues. Unit 04 

and probably Unit 01 with a calibrated sensor would provide more conditioning compared to the 

other identical 30 ton Carrier RTUs, Units 02 and 03. In Appendix J, NREL recommends that for 

60.0

70.0

80.0

90.0

100.0

110.0

120.0

130.0

140.0

800

1,000

1,200

1,400

1,600

1,800

2,000

2,200

2,400

4/285/12

5/26

6/9

6/23

7/7

7/21

8/4

8/18

9/1

9/159/29

10/1310/27

Daily Average Dry-Bulb Temperature

Daily Energy Usage [kWh/day]

nonESM

Measured

ESM

Measured

NonESM

Avg OA

Temp

ESM Avg

OA Temp
28 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

follow-on ARC installations, the duty cycle of the RTUs be monitored after the installation and 

that the sequence be adjusted to equalize the loading across the RTUs. 

Figure 11. BXtra 1235H non-ESM operation daily energy usage for each RTU 

versus daily average ambient dry bulb temperature

Figure 12. BXtra 1235H ESM operation daily energy usage for each RTU 

versus daily average ambient dry bulb temperature

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

70.0 71.0 72.0 73.0 74.0 75.0 76.0 77.0 78.0 79.0 80.0 81.0 82.0 83.0

Daily Energy Usage [kWh]

Daily Average Dry-Bulb Temperature [°F]

Bxtra 01 Bxtra 02

Bxtra 03 Bxtra 04

Bxtra 05 Bxtra 06

Bxtra 07 Bxtra 08

Bxtra 09
29 

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Table 11 shows the annual energy usage and savings of the regression model applied to HNL

TMY3 weather (for details on the regression method and models see Appendix B). ESM 

operation saved 15% of the total HVAC energy, which normalized to 94 kWh/ton per 1,000 h of 

operation at 16 h/day and 7 days/week. The hour of operation used to normalize the energy 

savings is based on the total annual hours the RTU is operating. For the BXtra, the annual 

operating hours is 5,840 h/yr for 365 days and 16 h per day (see Table 6). 

Table 11. BXtra 1235H Linear Regression Energy Usage and Savings Applied to 

HNL TMY3 Weather Data

 Energy Normalized Energy

Non-ESM Annual Energy Usage 627,061 kWh 614 kWh/ton per 1,000 h 

operation

ESM Annual Energy Usage 530,564 kWh 519 kWh/ton per 1,000 h 

operation

Annual Energy Savings 96,498 kWh

(15%) 94 kWh/ton per 1,000 h operation

Figure 13 plots the daily energy usage between ESM and non-ESM operation based on TMY3 

weather data. For a visual comparison of the regression model versus the actual measured data, 

Figure 14 and Figure 15 show non-ESM and non-ESM operation, respectively. The ARC retrofit 

technology applied to the BXtra exceeded the energy savings performance objective of 80 

kWh/ton/1,000 h of operation.

Figure 13. BXtra 1235H linear regression model applied to 

HNL TMY3 weather data

0

500

1,000

1,500

2,000

2,500

65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85

Daily Total Energy Usage (kWh)

TMY3 Daily Avg Dry-Bulb Temperature [°F]

nonESM TYM3 Regression

ESM TMY3 Regression
30 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 14. BXtra 1235H comparison of non-ESM daily energy usage 

between measured data and the regression model

Figure 15. BXtra 1235H comparison of ESM daily energy usage 

between measured data and the regression model

800

1,000

1,200

1,400

1,600

1,800

2,000

2,200

2,400

70

7172

7374757677787980818283

Daily Energy Usage [kWh/day]

Daily Average Dry-Bulb Temperature [F]

nonESM Measured

nonESM Regression Model

800

1,000

1,200

1,400

1,600

1,800

2,000

2,200

2,400

707172

73

7475

76

77787980818283

Daily Energy Usage [kWh/day]

Daily Average Dry-Bulb Temperature [F]

ESM Measured

ESM Regression Model
31 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

4.2.2 C27 Energy Savings

From the raw sample of days, NREL eliminated weekend days (not occupied on weekends) and 

days with known maintenance issues (see Table 12). Based on the 87 cleaned sample days, ESM 

operation saved on average 13 kWh/day (11%) compared to non-ESM operation. Yet this is a not 

a true apples-to-apples comparison, because the ESM sample experienced a 0.9°F lower average 

daily temperature, a known predictor of daily energy usage. Table 13 provides a breakdown of 

the energy usage between the fan and remaining components (compressors, condenser fans and 

controller). Similar to the BXtra results, the supply fan constituted most of the savings, although 

the BXtra fan percentage savings were considerably greater at 55%. Also similar to the BXtra 

results, building C27 ESM operation saved 5% for the non-fan energy usage. 

Table 12. Building C27 Demonstration Period (July 1, 2013 to November 9, 2013) Measured Energy 

Usage between ESM and non–ESM Operation

Total Raw 

Sample

(Days)

Maintenance

Issues

(Days)

Weekends

Cleaneda

Sample

Days

Avg 

OA

Tempa 

Total 

Energy 

Usagea 

Avg 

Daily 

Usagea 

Non-ESM

Operation 57 6 16 35 79.9°F 4,016 

kWh

115 

kWh

ESM

Operation 77 3 22 52 79.0°F 5,290 kWh

102 

kWh

134

total

9 

total

38

total

87

total

0.9°F

delta

9,307

kWh

total

13 kWh

(11%) 

savings

a Based on cleaned data eliminating weekend days and days when known operational issues impacted daily energy 

usage. 

Table 13. Building C27 Monitored Energy Usage Separated between Fan and Remaining 

(Compressors, Condenser Fans, Controller) Broken Down by ESM and non-ESM Operation

Fan Energya 

Comp/Cond 

Fan/Controller 

Energya 

Fan Avg Daily 

Usagea 

Comp/Cond 

Fan/Controller Avg 

Daily Usagea 

Non-ESM

Operation

755 kWh

(19% of total) 

3,261 kWh

(81% of total) 22 kWh 93 kWh

ESM

Operation

704 kWh

(13% of total) 

4,586 kWh

(87% of total) 14 kWh 88 kWh

8 kWh (37%) 

ESM savings

5 kWh (5%) 

ESM savings

a Based on cleaned data eliminating weekend days and days when known operational issues impacted daily 

energy usage. 

For a visual of the cleaned sample days, NREL plotted the time series of the measured daily 

energy as well as average and minimum ambient dry bulb temperatures shown in Figure 16. At 

the beginning of the demonstration, the hotter summer months masked the energy usage 

difference between ESM and non-ESM operation. Yet, toward the end of the demonstration 
32 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

period (after mid-October), the ESM operation clearly shows a lower daily energy usage at 

cooler ambient conditions. 

Figure 16. Building C27 time series plot of measured ESM and non-ESM energy usage (excluding 

weekends and known maintenance days) and average OAT and minimum OAT. Note that due to 

an error in the weekly alternating schedule, ESM operated an extra week in mid-October.

The building C27 linear regression was applied to HNL TMY3 weather data to calculate the 

annualized energy usage for ESM and non-ESM operation. Across the year, operating Monday–

Friday, the regression model calculates that ESM operation saves 1,526 kWh at a 7% total RTU 

energy reduction (Table 14). 

Building C27 energy savings did not meet the performance objective of 80 kWh/ton/1,000 h 

operation. NREL expected building C27 (and similarly building A13) to experience less savings 

compared to the BXtra, but the savings of 55 kWh/ton per 1,000 h operation shown in Table 14

were even lower than expectations. For C27, the annual operating hours is 2,210 h/yr based on 

weekday only operation (see Table 8). NREL looked deeper into the monitored data to determine 

whether an operational issue impacted RTU operation and hence ESM energy savings. 

Table 14. Building C27 Linear Regression Energy Usage and Savings Applied to HNL TMY3

 Energy Normalized Energy

Non-ESM Annual Energy Usage 23,185 kWh 839 kWh/ton per 1,000 h operation

ESM Annual Energy Usage 21,658 kWh 784 kWh/ton per 1,000 h operation

Annual Energy Savings 1,526 kWh (7%) 55 kWh/ton per 1,000 h operation

60

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90

100

110

120

130

140

6/30

7/5

7/107/157/207/257/30

8/48/9

8/148/198/248/29

9/39/8

9/139/189/239/2810/310/8

10/1310/1810/2310/28

11/211/7

11/12

Daily Avg OA Temp / Daily Energy Usage [kWh/day]

nonESM Measured

ESM Measured

NonESM Avg OA Temp

ESM Avg OA Temp

NonESM Min OA Temp

ESM Min OA Temp
33 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 17 shows the resultant ESM and non-ESM daily energy usage versus TMY3 daily 

average ambient dry bulb temperature. Figure 18 provides confidence that the regression model 

accurately reflects most of the variance of measured non-ESM daily energy usage versus average 

ambient dry bulb temperature. Figure 19 provides similar confidence in the regression model to 

capture ESM operation. See Appendix B for more details about the building C27 regression 

model. 

Figure 17. Building C27 linear regression model applied to HNL TMY3 weather data; zero energy 

values are for weekends when the RTUs are off per NAVFAC operational requirements

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85

Daily Total Energy Usage (kWh)

TMY3 Daily Avg Dry-Bulb Temperature [°F]

nonESM TYM3 Regression

ESM TMY3 Regression
34 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 18. Building C27 comparison of non-ESM daily energy usage 

between measured data and the regression model

Figure 19. Building C27 comparison of ESM daily energy usage 

between measured data and the regression model

60

70

80

90

100

110

120

130

140

74 75 76 77 78 79 80 81 82 83

Daily Total Energy Usage (kWh)

Daily Avg Dry-Bulb Temperature [°F]

nonESM Measured

nonESM Regression Model

60

70

80

90

100

110

120

130

140

74 75 76 77 78 79 80 81 82 83

Daily Total Energy Usage (kWh)

Daily Avg Dry-Bulb Temperature [°F]

ESM Measured

ESM Regression Model
35 

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Compared to BXtra and building A13, the C27 RTU operated in second-stage cooling for almost 

the entire operational period of 6:00 a.m. to 3:30 p.m. Figure 20 provides an example on 

September 9, 2013 (Monday); except for 0700-0800, the second-stage cooling was always 

operational indicated by the purple squares. At first NREL thought that the RTU was undersized 

relative to the load. The infiltration load in these small offices must be significant, because as 

soon as the RTU shuts off at 3:30 p.m., the space temperature increases beyond the OAT in 

about 4 hours (see Figure 21). The confusing part was that the 216 ft2/ton RTU size to 

conditioned floor area parameter shown in Table 8 indicated that the RTU was oversized. A 

typical size of 300–400 ft2/ton would be expected. 

Figure 20. C27 RTU operation (9/9/2013)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

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9/8 22:00

9/9 0:009/9 2:009/9 4:009/9 6:009/9 8:00

9/9 10:009/9 12:009/9 14:009/9 16:009/9 18:009/9 20:009/9 22:009/10 0:009/10 2:00

Fan Speed [%] / Compressors [on/off]

Temperature [F]

 

Space Setpoint Space Temp CoolCmd_1 CoolCmd_2 Fan Speed [%]
36 

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Figure 21. C27 space temperature versus space temperature set point (9/9/2013)

NREL is confident that the location of the temperature sensor immediately next to an exit door 

(see Figure 22) was reason the RTU operated improperly. The temperature sensor is influenced 

by the infiltration at the door and is not representative of the average air temperature across the 

space. During a site visit to building C27, NREL used a calibrated field temperature sensor to 

measure a 6°F temperature difference from the temperature sensor location to the furthest cubicle 

still inside the RTU’s conditioned area. As a lesson learned for follow-on ARC retrofit 

installations in Appendix J, NREL recommends that temperature sensors be located near the 

center of the conditioned space and at least 4 feet from any doors if along the same wall or 20 

feet if along a wall perpendicular to the door. For an ARC retrofit with a properly located 

temperature sensor, the energy savings will have a higher probability of exceeding the 55 

kWh/ton per 1,000 h operation measured in this field test. 

71

73

75

77

79

81

83

85

87

89

91

9/8 22:00

9/9 0:009/9 2:009/9 4:009/9 6:009/9 8:00

9/9 10:00

9/9 12:00

9/9 14:009/9 16:009/9 18:009/9 20:009/9 22:009/10 0:009/10 2:00

Temperature (F)

 

Space

Set

Point

Space

Temp

OA

Temp
37 

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Figure 22. Building C27 improperly located temperature sensor 

immediately next to the side exit door

4.2.3 A13 Energy Savings

Because of maintenance issues unrelated to the CATALYST system, building A13 experienced 

the shortest demonstration period (August 1, 2013 to November 9, 2013). ESM operation saved 

22 kWh/day at a 12% reduction in HVAC usage for the cleaned sample set shown in Table 15. 

Like building C27, this energy savings does not provide a true apples-to-apples comparison 

because ESM sample experienced a 1.0°F lower average daily temperature.

Table 16 shows that the supply fan provides the most energy savings. Figure 23 provides a time 

series of the measured daily energy use across the demonstration period. Unfortunately, the 

sample days do not extend past October 22, 2013 through the end of the demonstration on 

November 19, 2013. An error in the demand response sequence caused the first-stage 

compressor to come on and never shut off from October 22, 2013 through November 15, 2013. 

Consequently, during the days when the first-stage compressor was operating 24 h/day, the daily 

energy usage was inflated such that those days needed to be eliminated from the sample set. The 

error occurred because building A13’s demand response sequence was modified and caused

operational errors during demand response and non-demand response days. In Appendix J, for 

follow-on ARC retrofits, NREL recommends conducting a post-construction meeting to review 

ARC system operation and using the monitored data to identify similar operational issues. 

CATALYST 

Thermostat
38 

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Table 15. Building A13 Demonstration Period (8/1/13–11/9/13) Measured 

Energy Usage between ESM and Non-ESM Operation

Total 

Raw 

Sample

(Days)

Maintenance 

Issues 

(Days)

Weekends

(Days)

Cleaneda 

Sample

(Days)

Avg 

OA 

Temp*

Total 

Energy 

Usagea

Avg Daily 

Usagea

Non-ESM

Operation 41 13 11 17 80.0°F 3,268 kWh 192 kWh

ESM

Operation 60 15 15 30 79.0°F 5,103 kWh 170 kWh

101

total

28

total

26

total

47

total

1.0°F

delta

8,371 

kWh

total

22 kWh

(12%) 

savings

a Based on cleaned data eliminating weekend days and days when known operational issues impacted daily energy 

usage. 

Table 16. Building A13 Energy Usage Separated between Supply Fan and Remaining End Uses 

(Compressors, Condenser Fans, Controller) Broken Down by ESM and non-ESM Operation

Fan Energya 

Comp/Cond 

Fan/Controller 

Energya 

Fan Avg Daily 

Usagea 

Comp/Cond 

Fan/Controller Avg 

Daily Usagea 

Non-ESM 

Operation

465 kWh

(14% of total) 

2,803 kWh

(86% of total) 27 kWh 165 kWh

ESM Operation 462 kWh

(9% of total) 

4,641 kWh

(91% of total) 15 kWh 155 kWh

 12 kWh (44%) 

ESM savings

10 kWh (6%) 

ESM savings

a Based on cleaned data eliminating weekend days and days when known operational issues impacted daily 

energy usage.
39 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 23. Building A13 time series plot of measured ESM and non-ESM energy usage (excluding 

weekends and known maintenance days) and average OAT and minimum OAT. Note that due to 

an error in the weekly alternating schedule, ESM operated an extra week in mid-October.

Table 17 shows the building A13 regression model applied to HNL TMY3 weather data. ESM 

operation saved 1,803 kWh annually, resulting in a 5% HVAC energy reduction. Building A13 

(with a 20-ton RTU) experienced smaller absolute and percentage energy savings compared to 

the 12.5-ton RTU serving building C27. The normalized energy savings was 39 kWh/ton per 

1,000 h of operation. For A13, the annual operating hours is 2,340 h/yr for weekday only 

operation (see Table 7). 

Table 17. Building A13 Linear Regression Energy Usage and Savings

 Energy Normalized Energy

Non-ESM Annual Energy Usage 38,612 kWh 825 kWh/ton per 1,000 h 

operation

ESM Annual Energy Usage 36,809 kWh 787 kWh/ton per 1,000 h 

operation

Annual Energy Savings 1,803 kWh

(5%) 

39 kWh/ton per 1,000 h 

operation

NREL believes that had building A13’s demonstration period been longer, the energy savings 

would be been greater than building C27’s. A longer demonstration would also have 

incorporated the impacts of larger humidity ratio (HR) ranges and diluted human behavior-based 

impacts. Figure 24 shows the non-ESM and ESM daily energy usage versus TMY3 weather data. 

Figure 25 and Figure 26 compare the regression model versus the measured data. Again, had the 

demonstration period been longer, the regression model would have most likely incorporated HR

and possibly Friday as statistically significant predictors, which would have explained some of 

the scatter in Figure 25 and Figure 26.

50

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170

190

210

230

250

7/257/30

8/48/9

8/148/198/248/29

9/39/8

9/139/189/239/28

10/310/8

10/1310/1810/2310/28

Daily Avg OA Temp / Daily Energy Usage 

[kWh/day]

nonESM Measured

ESM Measured

NonESM Avg OA Temp

ESM Avg OA Temp

NonESM Min OA Temp

ESM Min OA Temp
40 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 24. Building A13 linear regression model daily total energy based on TMY3 weather data; 

note zero energy values are for weekends when the RTUs are off per NAVFAC operational 

requirements

Figure 25. Building A13 comparison of non-ESM daily energy usage 

between measured data and the regression model

0

20

40

60

80

100

120

140

160

180

200

220

240

260

65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85

Daily Total Energy Usage (kWh)

TMY3 Daily Avg Dry-Bulb Temperature [°F]

nonESM TYM3 Regression

ESM TMY3 Regression

90

110

130

150

170

190

210

230

250

74 75 76 77 78 79 80 81 82 83

Daily Total Energy Usage (kWh)

Daily Avg Dry-Bulb Temperature [°F]

nonESM Measured

nonESM Regression Model
41 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 26. Building A13 comparison of ESM daily energy usage 

between measured data and the regression model

NREL will continue to monitor building A13’s performance through January 2014 and will 

provide an addenda report with updated energy usage and savings. NREL chose the A13 RTU 

because it has larger capacity (20 tons) than other RTUs on the potential demonstration list. 

NAVFAC technicians stated that it was not experiencing uncharacteristic levels of maintenance. 

In hindsight, building A13’s RTU should not have received the ARC retrofit but should have 

been replaced. The RTU was 15 years old and at the end of its life based on the reoccurring 

maintenance issues during the demonstration period. At the end of the demonstration period, 

NAVFAC told NREL that it was going to replace the A13 RTU with a new high efficiency unit 

in early 2014. 

4.3 Interior Thermal Comfort

The interior space temperature and RH were monitored in all three buildings for the duration of 

the demonstration to characterize the impact of ARC system operation on interior thermal 

comfort. At the onset of the demonstration, NREL determined that the NAVFAC-approved 

thermostat set points and allowable RTU on/off times caused the RH to exceed 65% for 

buildings A13 and C27. In addition to thermal discomfort, NREL was concerned about mold. 

The moisture problem was exacerbated when NREL was directed in April 2013 to increase the 

space temperature set point to 80°F based on Commander Navy Installations Command (CNIC) 

direction to operate at Common Output Level Standards (COLS) level 4 until further notice. 

NREL brought the moisture issue and imminent COLS level 4 directive to NAVFAC Hawaii’s 

and NAVFAC Headquarters’ attention. From April through June 2013, NREL held weekly 

conference calls to identify concerns and establish NAVFAC’s standards of service regarding 

thermal comfort and allowable RTU on/off times. Appendix A reviews how NAVFAC and 

90

110

130

150

170

190

210

230

250

74 75 76 77 78 79 80 81 82 83

Daily Total Energy Usage (kWh)

Daily Avg Dry-Bulb Temperature [°F]

ESM Measured

ESM Regression Model
42 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

NREL established the final demonstration thermostat set points, RH constraints, and required 

RTU on/off times. Table 6, Table 7, and Table 8 summarizes these operational parameters for 

buildings 1235H, A13, and C27, respectively. 

RTUs provide thermal comfort through sensible cooling (maintaining space temperature near set 

point) and latent cooling (maintaining space RH lower than a predefined threshold). ASHRAE 

standard 55 recommends the space RH be maintained at < 65% for thermal comfort and mold 

concerns. ARC retrofits will improve the latent cooling capability of an RTU. Space RH will 

reduce and comfort will improve especially for the humid Hawaii climate. ARC retrofits improve 

latent cooling two ways: (1) the slower fan speeds under first- or second-stage cooling supplies 

colder air at a lower dew point temperature, which will drive the space dew point lower; and (2) 

ARC retrofits can close the OA damper during unoccupied operation and leverage DCV to 

reduce the ventilation flow rate during occupied operation. 

For the latent cooling analysis, NREL included both space dew point and RH. RH was evaluated 

to determine whether both ESM and non-ESM operation maintained the space at < 65% RH for 

occupied and unoccupied hours. Yet RH is not solely a measure of moisture content but is also a 

function of dry bulb temperature, which was impacted by the operational mode. Therefore, dew 

point temperature was used to compare the latent cooling capability of ESM versus non-ESM

operation. 

Histograms of hourly average space temperature and dew point are shown in Figure 27 through 

Figure 32. All three facilities demonstrated a reduction in space dew point under ESM operation; 

the BXtra shows the greatest reduction. The relatively larger infiltration loads on buildings C27 

and A13 reduced the dew point difference between ESM and non-ESM operation. The 

differences in space temperature were less defined and varied by building. The BXtra ESM 

operation showed a slightly warmer temperature. Building C27 showed ESM operation 

maintaining a slightly cooler temperature. Building A13 showed a negligible difference in space 

temperature. 

Figure 27. BXtra dew point temperature 

histogram

Figure 28. BXtra space temperature histogram

0

100

200

300

400

500

600

52 54 56 58 60 62 64

Frequency

Dewpoint Temperature (F)

ESM

Non ESM

0

100

200

300

400

500

600

700

73 73.5 74 74.5 75 75.5 76 76.5 77 77.5 78

Frequency

Space Temperature (F)

ESM

Non ESM
43 

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Figure 29. A13 dew point temperature histogram Figure 30. A13 space temperature histogram

Figure 31. C27 dew point temperature histogram Figure 32. C27 space temperature histogram

NREL found that both ESM and non-ESM maintained the space RH at < 65% except for a few 

hours for all three buildings. Figure 33 shows the hourly average space RH for the BXtra as a 

function of OA HR in ESM and non-ESM during occupied hours. Reinforcing the dew point 

histogram in Figure 27, ESM clearly maintains a drier space. Over the course of the 

demonstration, the average RH for the BXtra in non-ESM was 58% compared to 53% in ESM. 

0

20

40

60

80

100

120

140

160

54 56 58 60 62 64 66 68 70

Frequency

Dewpoint Temperature (F)

ESM

Non

ESM

0

20

40

60

80

100

120

140

160

180

75 75.5 76 76.5 77 77.5 78 78.5 79 79.5 80

Frequency

Space Temperature (F)

ESM

Non ESM

0

20

40

60

80

100

120

140

160

50 52 54 56 58 60 62 64 66

Frequency

Dewpoint Temperature (F)

ESM

Non ESM

0

20

40

60

80

100

120

72

72.5

73

73.5

74

74.5

75

75.5

76

76.5

77

77.5

78

Frequency

Space Temperature (F)

ESM

Non ESM
44 

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Figure 33. BXtra space hourly average RH including occupied and 

unoccupied hours versus hourly average ambient HR

4.4 Ventilation Quality

None of the CO2 sensors in the three buildings measured a concentration > 1,000 ppm such that 

the CATALYST needed to initiate its DCV sequence and open the OA dampers. In fact, the CO2

concentrations never exceeded 700 ppm. There were no reports of occupant complaints about air 

quality. Based on work with other retail type buildings, NREL found that CO2 rarely achieves 

the DCV limit except under extreme conditions such as Black Fridays in retail buildings. Office 

spaces rarely if ever achieve the DCV limit because their occupancy density never reaches their 

design occupancy level throughout the year. 

NREL was not concerned about over-ventilation since the CO2 ppm levels were within expected 

ranges; 400-450 ppm during unoccupied times (close to ambient CO2 concentration at 400 ppm) 

and 450-700 during occupied times for all 3 buildings. NREL did not want to close the dampers 

further until the CO2 concentration reached 1,000 ppm since the ventilation flow rate still needed 

to meet the minimum ASHRAE 62.1 cfm/ft2 requirement for material off-gassing. NREL 

determined that the OA damper configurations during the demonstration period maintained

acceptable CO2 concentrations and therefore met the ASHRAE 62.1 cfm/occ requirement. 

Table 18 shows the ASHRAE Standard 62.1 minimum ventilation requirements for all three 

buildings. By enabling DCV, the ARC system can reduce the minimum ventilation rate by 48% 

for retail buildings and 29% for office buildings. Yet to practically apply these ASHRAE 62.1 

minimum requirements, NREL found the TAB results had too significant an uncertainty. NREL 

decided to maintain the CATALYST default OA damper sequence at 6% open at 90% fan speed 

and 12% open at 40% fan speed. The following paragraphs summarize the uncertainty in the 

TAB measurements and why this decision was made. 
45 

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Table 18. ASHRAE Standard 62.1-2010 Minimum Ventilation Rates 

for the 1235H BXtra, C27, and A13 Buildings

Building Area

Served 

Space

Type

Occ

Vent

Rate

Default

Occ

Density

Area

Vent

Rate

Min Req’d

Vent Rate

(No DCV 

Operation)

Min Req’d

Vent Rate

(DCV

Operation

Only)

1235H

BXtra 69,576 ft2 Retail

Sales

7.5

cfm/occ

15 occ/

1,000 ft2

0.12

cfm/ft2 16,176 cfm 8,349 cfm

(48% reduction)

C27 2,706 ft2 Office 5.0

cfm/occ

5 occ/

1,000 ft2

0.06

cfm/ft2 230 cfm 162 cfm(29% reduction) 

A13 7,834 ft2 Office 5.0

cfm/occ

5 occ/

1,000 ft2

0.06

cfm/ft2 666 cfm 470 cfm

(29% reduction) 

NREL had a TAB conducted per UFGS 23 05 93 to verify that actual ventilation rates were 

meeting the minimum requirements shown in Table 18. The TAB measured the total supply and 

OA flow rates at 90% fan speed (CATALYST second-stage cooling mode) and 40% fan speed 

(CATALYST fan only mode). The uncertainty for the total supply flow rate NREL determined 

to be +/-15 to 20% based on the +/-3% sensor accuracy at each air velocity measurement of the 

duct traverse. Yet the uncertainty of the ventilation flow rates NREL determined to be 

significantly more.

The TAB procedure implemented a pitot tube traverse of the OA intake velocities at the damper. 

Directly measuring OA with a pitot tube is actually recommended by NEBB TAB procedure 

standards as referenced by UFGS 23 05 93. Compared to built-up air handling units, RTUs 

provide so little ventilation that the air velocities at the damper are well below the 50 fpm 

threshold at which pitot tube accuracy significantly diminishes. The Short Ridge AirData 

Multimeter ADM-860 used for the TAB has a stated air velocity accuracy of +/-3% from 50 to 

8,000 fpm. The TAB report showed the OA damper traverse velocity readings ranging from 0 to 

225 fpm. 

The resultant OA flow rates based on these velocity readings did not make intuitive sense. 

Identical RTUs with the same OA damper configuration were reported as having drastically 

different ventilation. For example, at a 90% fan speed and 6% OA damper, BXtra Unit 05 and 

Unit06 ventilation flow rates were reported at 2,406 cfm and 168 cfm, respectively. In some 

cases, the same RTU was reported as providing significantly more ventilation at 40% fan speed 

with a 12% OA damper than 90% fan speed with a 6% OA damper. BXtra Unit01 reported a 

1,316 cfm at the 40% fan speed configuration and 613 cfm at the 90% fan speed configuration. 

Most of the other RTUs showed the opposite trend. 

NREL determined that a combination of sensor error (air velocities below 50 fpm) and 

environmental air (impacts of wind) were the causes. While not the recommended method, 

NEBB TAB procedure accepts a pitot tube traverse of the total supply minus the total return to 

calculate OA flow rate. The TAB should have implemented this procedure considering that 

measuring the return air would have been at velocities over 50 fpm and minimally influenced by 

the wind. While there is additional uncertainty of subtracting two calculated air flows, the 

uncertainty would have been significantly reduced.
46 

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This demonstration showed that despite extensive evaluation of the TAB results, no definitive 

conclusions could be drawn about whether the ARC systems were maintaining sufficient DCV 

minimum ventilation per ASHRAE 62.1-2010. NREL still recommends that the TAB activity 

includes balancing the ventilation rates at different fan speeds. Yet to maintain confidence in the 

TAB measurements, the ventilation flow rates should be calculated based on the measured SA 

flow minus the measured RA flow. The OA damper should be configured accordingly at each 

fan speed. The CO2 sensor will then enable the ARC system to respond appropriately if 

occupancy (cfm/occ) based ventilation is needed. 

The following subsections summarized how NREL interpreted the TAB results acknowledging 

the significant uncertainty of the measurements. For buildings A13 and C27, the ventilation 

measurements were not valid for the demonstration period. Based on scheduling complications, 

the TAB took place before the electronic actuators were installed in these RTUs. The TAB report 

indicated that the measurements were taken with the OA damper manually adjusted to 50% 

open. To simplify the installation process and ensure the TAB is conducted at the correct time, 

NREL recommends that the ARC installs, not a third party TAB certified contractor, balance the 

supply and ventilation flow rates. This recommendation along with NREL’s recommendation for 

how to conduct the TAB is summarized further in Appendix J. Appendix E summarizes the 

sensor and environmental uncertainty as well as the detailed TAB results. 

4.4.1 1235H BXtra

The aggregated ventilation rate measured for all nine RTUs at 90% fan speed was 7,346 cfm, 

which is slightly less than the DCV minimum required at 8,349 cfm but well within the 

uncertainty of the TAB measurement. At 40% fan speed, the aggregated ventilation rate was 

3,871 cfm, much less than the minimum required but again within the uncertainty of the TAB 

measurement. 

4.4.2 Building C27 

The 176 cfm ventilation rate at the 90% fan speed indicated that the minimum ventilation rate 

was meeting the DCV minimum required at 162 cfm. Yet at 40% fan speed, the RTU was under 

ventilating at 53 cfm yet within the uncertainty of the TAB measurement. These measurements 

were made before the electronic actuator was installed. The TAB report stated that the OA 

damper was manually adjusted to 50% open. 

4.4.3 Building A13 

Compared to the DCV minimum requirement of 470 cfm, the 851 cfm ventilation rate at the 90% 

fan speed indicates overventilation. The 335 cfm at 40% fan speed indicates slight 

underventilation but within the uncertainty of the TAB measurement. These measurements were 

made before the electronic actuator was installed. The TAB report stated that the OA damper 

was manually adjusted to 50% open. 

4.5 Demand Response

Demand response events can be triggered by a schedule or a communication signal. The 

CATALYST ARC can respond to any method of communication. The Navy demonstration 

demand event was scheduled through the ARC’s BMS function. Scheduled demand events are 

set up to occur between 3:00 p.m. and 5:00 p.m. every Tuesday, Thursday, and Saturday for the 
47 

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BXtra in ESM and non-EM and between 1:30 p.m. and 3:30 p.m. for A13 and C27 in ESM. The 

BXtra demand response results are summarized below. Buildings C27 and A13 demand response 

results are summarized in Appendix F. 

The BXtra sequence of operation is set up to limit the maximum demand across all nine RTUs to 

160 kW during a demand event. The peak power draw of all nine RTUs is approximately 194 

kW. To maintain the demand level, the sequence targets equipment with the lowest cooling load 

based on space temperature versus set point. As the cooling load changes, the available electric 

capacity is passed to units with highest demand based on the following rules: 

• If the cooling load is greater than 60% (based on the difference between the temperature 

set point and current space temperature) a minimum of one compressor will run. 

• The unit will be locked into an operating mode for 15 minutes following a demand call. 

A temperature set point shift is used before the demand event. The cooling set point temperature 

is lowered by 2°F before the demand period. During the demand event, the space temperature is 

allowed to float up 2°F above set point. At the end of the demand event, the space temperature is 

reset to its normal set point temperature. The monthly peak demand savings over a 4-month 

period are provided in Table 19 for the BXtra building. 

Table 19. BXtra Monthly Demand Savings

Month

Maximum Demand 

3:00 p.m. to 5:00 p.m. 

Non Demand 

Response Day (kW)

Maximum Demand 

3:00 p.m. to 5:00 p.m. 

Demand Response 

Day (kW)

Demand Savings 

During Demand 

Response Event (kW)

Maximum Daily 

Demand on Demand 

Response Day (W)

Maximum Daily 

Demand Non Demand 

Response Day (kW)

Demand Reduction 

(kW/Ton)

Demand Reduction 

(Watt/ft2) 

July 117.7 96.5 21.2 (18%) 127.9 119.9 0.12 0.30

August 153.8 112.1 41.7 (27%) 186.8 154.3 0.24 0.60

September 152.0 125.8 26.2 (17%) 199.6 170.0 0.15 0.38

October 151.2 132.4 18.8 (12%) 196.2 160.0 0.11 0.27

The peak demand savings during the demand response period ranged from 41.7 kW in August to 

18.8 kW in October. Although the demand was reduced during the demand response period, the 

precool sequence increased overall demand for the demand response days (Figure 34).
48 

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Figure 34. BXtra demand response for September

During September, when the units were operating 16 h/day, the increased peak demand 

associated with precooling the space before the demand event increased overall demand by an 

amount that is roughly equivalent to the reduction in demand during the demand event. Yet, 

based on NREL’s work with utilities, the main focus is on the peak power during the demand 

event. Utilities are less concerned with the peak demand that occurs before the demand event. 

The demand response analysis also indicated that the overall demand for the BXtra is sensitive to 

the operational schedule. When the units operate 16 h/day, the baseline peak increases by about 

30 kW over the baseline peak when the units are operating 20 h/day. When the schedule was 

changed to 16 h/day, the baseline peak occurred first thing in the morning rather than around 

1:00 p.m. (Figure 35). 

0

50

100

150

200

250

12:00 AM12:30 AM

1:00 AM1:30 AM2:00 AM2:30 AM3:00 AM3:30 AM4:00 AM4:30 AM5:00 AM5:30 AM6:00 AM6:30 AM7:00 AM7:30 AM8:00 AM8:30 AM9:00 AM9:30 AM

10:00 AM10:30 AM11:00 AM11:30 AM

12:00 PM12:30 PM

1:00 PM1:30 PM2:00 PM2:30 PM3:00 PM3:30 PM4:00 PM4:30 PM5:00 PM5:30 PM6:00 PM6:30 PM7:00 PM7:30 PM8:00 PM8:30 PM9:00 PM9:30 PM

10:00 PM10:30 PM11:00 PM11:30 PM

Peak Demand (kW)

 

6th

8th

9th

11th

13th

15th

16th

18th

20th

22nd

23rd

27th

29th

30th

DR - 5th

DR - 7th

DR - 10th

DR - 12th

DR - 14th

DR - 17th

DR - 19th

DR - 21st

DR - 24th

DR - 26th

DR - 28th
49 

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Figure 35. BXtra demand response for July and September

In addition to the baseline peak shifting to the beginning of the day, the reduced operation of the 

unit also caused a larger spike in energy use to precool the space. The peak demand analysis for 

the BXtra provided valuable insights into the complexities of trying to maintain space comfort 

and simultaneously shift peak demand without increasing overall demand. The sequence 

successfully shifted peak demand, but the analysis revealed that the peak demand profile is 

sensitive to the operational schedule of the RTUs and the space load before the demand event. 

The expectation that an RTU can maintain a comfortable space while shifting demand is a 

challenging goal. More work is needed to determine general procedures that can effectively meet 

this goal. A simpler sequence that simply shifts demand or turns off a series of compressors 

based on a control signal from a utility is easy to implement, but commercial building owners are 

not universally open to sacrificing thermal comfort during these demand events. Further peak 

demand analysis should be conducted to determine a truly optimal strategy for this location that 

can maintain acceptable space temperatures and shift the peak demand. 

The demand response feature of ARC technologies is not recommended for NAVFAC currently. 

This demonstration of demand response was to show the magnitude of the peak reduction. Since 

it will typically increase building energy consumption, utilities will need to provide building 

owners like NAVFAC rebate incentives to enable a demand response feature for ARC systems. 

NREL is currently working with utilities to evaluate these demand response capabilities further 

and determine if additional utility rebates can incentive the ARC technology as a combined 

demand response and energy efficiency asset. With prescriptive based rebates, ARC systems 

would realize an improved ROI. 
50 

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5 Economic Performance Analysis and Assessment

Economic results of the demonstration indicate application of the ARC technology in Hawaii can 

yield appreciable energy and cost savings. Demonstration actual net savings are projected at 

$170,000 over a 10-year operational life, with a savings to investment ratio (SIR) of 1.9. Results 

are promising and indicate the U.S. Navy, on an economic basis, should consider further 

investment and deployment of ARC retrofit technologies in the Pacific region. 

Further, there may be additional, improved savings for follow-on deployments. Comparing perunit results between facilities, BXtra building performance was appreciably better than small 

office buildings A13 and C27. These results indicate selecting facilities with multiple RTUs and 

longer building operating hours will improve energy efficiency and economic return. Assuming 

follow-on deployments apply the demonstration’s lessons learned for improved facility and RTU 

selection, energy savings for 11 RTUs could increase to 120 MWh/yr (16% increase) resulting in 

$270,000 savings over the same 10-year economic life. Assuming pricing efficiencies will also 

be realized in transitioning from a demonstration to deployment scale activity, economic return is 

expected to increase more significantly.

3

 

Table 20 provides a full summary of the economic results, in addition to key analysis inputs. Key 

economic results were calculated using the latest version of the National Institute of Standards 

and Technology (NIST) developed Building Life-Cycle Cost (BLCC) Program. eROI values 

were provided using the latest available version of the Neptune eROI calculator, as provided by 

NAVFAC.4 Appendix K includes a detailed accounting of the economic analysis performed.

Economic results were reviewed to evaluate performance sensitivities and potential sources of 

error in the estimates provided. Four key factors were identified: 

1. Performance dependency on facility selection. Proper selection of facilities presents a 

key factor in energy and cost savings performance. As presented in Table 21, per-unit 

energy and economic yields were significantly greater for the BXtra building than for 

buildings C27 and A13. Of specific note, the SIR for BXtra is significantly greater than 

unity, whereas C27 and A13 are significantly lower. For future deployments, careful 

consideration should be given to facility and RTU types, with best performance yields 

coming from large facilities with multiple RTUs and operating hours exceeding 50 

h/week. 

 

3 See Appendix K for facility price savings assumptions.

4 eROI is a Navy-specific metric for evaluating benefits of investment in energy technologies. The benefit figure 

reflects the present value of the project’s anticipated contribution to energy as well as it contribution, in dollarequivalent terms, to other Navy objectives such as improving energy reliability for critical infrastructure, reducing 

greenhouse gas emissions, meeting regulatory mandates, and so on. An eROI greater than 1.0 indicates the project’s 

benefits are anticipated to exceed its costs. The higher the eROI value, the more attractive the project.
51 

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Table 20. Economic Analysis Results

DD1391 Estimatea Demo Actualsa Projected Follow-On

Deploymenta

Economic Analysis Results

eROI Value 3.6 5.2 6.9 

Net Savings $75,000 $170,000 $270,000 

SIR 1.3 1.9 2.8 

Simple Payback in 7th year in 5th year in 3rd year

Adjusted Internal Rate of Return 6% 10% 14%

Key Analysis Inputs

Annual Energy Savings 168 MWh 100 MWh 120 MWhc

Electricity Priceb $0.24/kWh $0.425/kWh $0.425/kWh 

Initial Investment Cost $221,130 $166,624 $136,000c

Economic Life 10 years 10 years 10 years 

Units Installed 11 11 11 a DD1391 estimate column reflects analysis as performed as part of site approval/DD1391 process in 

September of 2012. Demonstration Actuals column reflects economic results based on actual, realized costs 

of procurement and installation and measured energy savings results. Project follow-on column reflect 

estimated results for future installations of this technology using a more efficient acquisition strategy and 

refined RTU selection. b Electricity pricing for demo actuals and projected follow-on reflect the average price of FY13 and FY14 

rates at JBPHH. c For follow-on activity, per RTU energy savings are assumed consistent with BXtra building, i.e. selection 

is optimized for best energy savings results. Detail of cost reductions presented in Appendix K.

Table 21. Normalized Savings Comparison Between Demonstration Facilities

BXtra C27 A13

Annual Energy Savings per RTU 10,722 kWh/yr 1,526 kWh/yr 1,803 kWh/yr

Normalized Annual Energy 

Savingsa 94 kWh/ton per 1,000 h operation

55 kWh/ton per 

1,000 h operation

39 kWh/ton per 

1,000 h operation

Annual Cost Savings per RTU $4,557/yr $649/yr $766/yr

SIR per RTU 2.3 0.2 0.3 a Total annual energy savings normalized based on nominal tonnage and annual hours of operation; BXtra has 

5,840 annualized hours; C27 has 2,210 annualized hours; A13 has 2,340 annualized hours.

2. Utility electricity rate volatility. Significant volatility in JBPHH utility rates from FY

2013 to FY 2014 indicate analysis results as presented may be susceptible to uncertainty 

in projecting future year utility rate pricing. More specifically, utility rates have jumped 

from $0.24/kWh in FY 2013 to $0.58/kWh in FY 2014. The expectation, based on 

discussions with NAVFAC Hawaii personnel, is for utility rates to decline in FY 2015, 

but an exact value remains uncertain. This volatility in pricing must be considered in 

evaluating economic results of the CATALYST technology, as applied to JBPHH. 

A preliminary sensitivity analysis was performed to evaluate the effect of electricity 

pricing uncertainty on economic yield. Figure 36 shows net savings estimates for a 15-

year economic yield across an electricity price range of $0.325–$0.525/kWh. This range 

encompasses a ± $0.10/kWh sensitivity band around the nominal rate applied to our 
52 

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economic analysis.5 As indicated by the figure, electricity pricing has a significant impact 

on savings. CATALYST technology savings, however, remain appreciable, even at a 

conservative price of $0.325/kWh. 

Figure 36. Sensitivity analysis on electricity pricing

3. Economic life of the ARC technology. Estimation of the economic life of the ARC

technology depends on several factors such as the operational life of the ARC device, the 

operational life and maintenance of the RTU on which it is installed, and the age of the 

RTU when the retrofit is performed. 

For this report, the CATALYST system’s average economic life was estimated at 10 

years. This estimate was based on simple assumptions of an average RTU operational life 

of 15 years in Hawaii. The CATALYST unit is then utilized, on average, for 10 years of 

the RTU’s lifetime. Reinstallation of half of the CATALYST units was assumed at 7.5 

years (half of RTU average operational life), to account for retrofitted RTUs being 

decommissioned and CATALYST units being reused. 

The actual, realized economic life of the deployed ARC technology will have a 

significant impact on aggregate energy savings and realized economic yield. Depending

on the age criteria used in selecting RTUs, the ARC’s economic life may easily vary by 

several years. In selecting RTUs for ARC retrofits, careful consideration should be given 

to estimated ARC economic life in this climate zone because RTU lifetimes are much 

shorter in marine environments, and related factors such as RTU operational life and the 

technical/price viability of reusing ARCs on progressively decommissioned RTUs. 

4. Results are region specific. Electricity pricing, weather patterns and climate, and 

regional pricing for construction costs are key input parameters in estimating energy and 

 

5 The nominal rate of $0.425/kWh is the average rate between FY 2013 and FY 2014 known rates.

$0

$50,000

$100,000

$150,000

$200,000

$250,000

$300,000

$350,000

$400,000

$0.305 $0.405 $0.505

Net Savings, 10 yr Economic Life

Electricity Price ($/kWh)

Actual

Follow-On

Deploy.
53 

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cost savings. Hawaiian values for these parameters, although reasonably attributable to 

other areas of the Pacific, deviate considerably relative to other applicable regions such as 

the continental United States. Therefore, energy and cost saving estimates as presented, 

although promising, are not directly translatable to other geographic regions. 
54 

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6 Project Management Considerations

Execution of this technology demonstration was programmatically straightforward. Most 

commercially available ARC technologies are packaged based on a “kit” concept for ease in 

specification, procurement, and installation. Consequently, acquiring and deploying ARC

technologies require minimal time and resources. Table 22 provides a summary of programmatic 

elements of this project and a high-level timeline of events. 

Table 22. Summary of Programmatic Elements of This Project

The project life cycle consisted of four sequential tasks: 

1. Identify the site. To initiate the project, NREL provided NAVFAC the criteria, 

summarized in Section 3.1, to identify candidate RTU equipment to receive the ARC

technology. Based on an established list, the Integrated Product Team (IPT) visited each 

site and narrowed the list to 11 RTUs. 

2. Approve the site. Once the site was selected, the IPT approved the site (DD1391), and 

performed National Environmental Policy Act (NEPA) determination activities. 

3. Procure and install the equipment. The design-build contractor, TWT, procured and 

installed the equipment. Design activities were negligible, and overall acquisition was 

straightforward with few challenges.

4. Demonstrate the equipment. As discussed in Section 4, after the ARC was installed and 

commissioned, the demonstration period began with troubleshooting and evaluation of 

Navy standards of service. Once operational schedules were finalized, the demonstration 

monitoring period started. 

Programmatic challenges experienced on this project were minimal from an 

acquisition/technology implementation perspective. Challenges were, however, evident in 

operation of the ARCs during the demonstration period because of unexpected adjustments to 

Navy COLS in tandem with ensuring that space comfort and humidity requirements were 

properly defined and implemented. A key takeaway was that additional, formalized guidance on 

operational space condition requirements is needed. Valuable lessons learned about moisture 

control (e.g., morning charge to mitigate interior space moisture) and operational schedules used 

in this demonstration may also apply to future ARC deployments. 

Programmatic Summary

Implementation Method Design-build contractor, minor construction

Key Contractor TWT

Period of Performance 1 year, 8 months

Project Timeline

Site identification: March 2012–May 2012

Site approval: June 2012–September 2012

Procurement/installation: September 2012–January 2013

Demonstration: February 2013–November 2013
55 

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In summary, this technology was acquired in a straightforward manner, executed quickly, and 

presented minimal challenges. Proper operation did cause appreciable delays. These challenges, 

however, were not attributable to the ARC technology. Rather, they related to time delays 

associated with developing a full interpretation of facility space comfort requirements and 

subsequent translation to ARC operational requirements. 

6.1 Site Selection and Approval

6.1.1 Site Selection

Careful selection of facilities and RTUs is a key factor in ensuring optimal ROI for ARC

technologies. For the demonstration, selection of facilities and RTUs was initiated by screening 

RTUs against a short list of technical criteria and identifying candidate options. RTU options 

were prioritized, accounting for the technical screening criteria, estimated energy savings, and 

pragmatic factors such as accessibility and client-facility interest. The IPT then performed a site 

survey of best candidate options, which led to final selection of RTUs. Overall, the site selection 

activity encompassed a 3-month period, with coordination between NREL, NAVFAC, and site 

personnel. 

Lessons learned from the demonstration, recommended for consideration in site selection for 

future deployments, follow: 

• The RTU supply fan must use a three-phase motor because the VFD that comes with the 

TWT ARC package works on three-phase motors only. 

• Facility use is an important factor in RTU screening. More specifically, screening RTUs 

by energy savings potential depends on occupancy schedules, temperature and RH set 

points, and maximum allowable humidity levels. 

• RTUs that are undersized for the intended facility are not recommended for ARC

applications because the system will almost always operate in second-stage cooling. This 

significantly reduces fan savings. The RTU must be controlled to have the fan constantly 

on during occupied hours to meet ASHRAE 62.1-2010 ventilation requirements per 

UFGS 23 81 00.0020 paragraph 1.6. RTUs that provide ventilation and that operate in 

auto mode will cycle the supply fan based on a heating or cooling call which is not code 

compliant. These RTUs will also have a reduced energy savings from an ARC

technology, because the ARC operates the fan at a partial speed during ventilation mode, 

rather than completely turning the unit off. 

• The estimated remaining operational lifetime of the RTU should be longer than the 

estimated payback period of the ARC retrofit. Newer RTUs are therefore more attractive 

for ARC applications. NREL recommends RTUs under 10 years old for the ARC 

technology. 

• The larger the RTU capacity (particularly the supply fan motor size), the greater the 

savings and the quicker the payback. 

6.1.2 Site Approval

Site approval, NEPA, and DD1391 activities were required for this demonstration. All these 

activities presented minimal administrative burden and were performed over a few months. For 
56 

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the NEPA evaluation, the NAVFAC Hawaii Environmental Program determined a categorical 

exclusion (CATEX) in accordance with OPNAVINST 5090.1C CH-1. 

For future deployments of the ARC technology, it should be noted that physical and aesthetic 

impacts to the site are negligible. Most ARC technology elements are housed in the RTU 

cabinet. In the specific instance of the ARC technology offering demonstrated in this project, a 

small NEMA 4 electrical box was also installed on the exterior of the RTU housing containing 

the controller and wireless modem (see Figure 2).

Site communication and ARC monitoring and control options should also be considered during 

site approval activities in deploying this technology. For this demonstration, a remote monitoring 

package using a Web-based interface and cellular modem was used for offsite monitoring and 

control of the ARC units. Before deploying these packages, the IPT worked with JPBHH 

communications personnel to develop an appropriate communications plan for remote access. 

Several other ARC technology offerings provide remote BMS solutions (see Table 25), making 

military communications requirements relevant for future deployments. Before implementing a 

remote BMS solution, the DOD communications requirements for the specific installation need 

to be understood and the impacts of applicable approval processes and security issues evaluated. 

The local NAVFAC CIO should be consulted regarding these communication requirements. 

6.2 Contracts and Procurement 

The implementation strategy for this project used a design-build contract, awarded to the 

provider of the ARC technology. Although structured as design-build, this contract had minimal 

design requirements and focused largely on procurement, installation, and commissioning. As 

executed, direct acquisition of this technology via the provider presented minimal challenges, 

largely because it was easy to install and had few site requirements and impacts. 

This project used applicable Division 01, General Requirements. These requirements and related 

follow-on activities are presented in Table 23. 

Table 23. UFGS—General Requirements

UFGS

Division 01—General Requirements

01 14 00 Work Restrictions

01 30 00 Administrative Requirements

01 33 00 Submittal Procedures

01 35 26 Governmental Safety Requirements

01 42 00 Sources for Reference Publications

01 45 00.10 20 Quality Control for Minor Construction

01 78 00 Closeout Submittals

A summary of lessons learned from the demonstration, which should be considered when

acquiring equipment for future ARC deployments, follows: 

• Facility set points and schedules. Facility thermal comfort, ventilation needs, and 

operational schedules should be well articulated and included in the acquisition. For each 

RTU, temperature set point schedule, maximum allowable RH (or dew point), OA 
57 

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damper open schedule (when ventilation should be provided), and required RTU on/off 

times should be clearly defined. 

• Pre-proposal/solicitation site visit. Solicitations should benefit from a pre-proposal site 

walkthrough by potential offerors. Accurate pricing will likely depend on the offerors’ 

ability to evaluate supply fan motor size and other RTU design features that are relevant 

to their specific ARC offerings. Eagerness to bid will likely also depend on an evaluation 

of the general condition of the RTUs and determination of necessary maintenance work.

6.3 Design 

Packaged ARC technologies have been developed as turnkey product solutions. Integration of 

ARC technologies with standard RTUs requires a negligible level of site design. For this project, 

significant design activities comprised a detailed field investigation to evaluate the RTUs for any 

maintenance issues before the ARC units were installed. 

UFGS facility construction/technical design specifications were developed as presented in Table 

24. 

Table 24. UFGS—HVAC

UFGS

Division 23—Heating, Ventilating, and Air Conditioning

23 05 93 Testing, Adjusting, and Balancing for HVAC

Division 26—Electrical

26 00 00.00 20 Basic Electrical Materials and Methods

26 20 00 Interior Distribution System

For future deployments, site design requirements should be minimal. Technical specifications 

will need to be developed; however, the list of UFGS specifications should not be extensive. 

Some care and client attention should be given to tailoring UFGS 23 05 93 “Testing, Adjusting, 

and Balancing for HVAC” to ARC installation activities. TAB testing, if not specified carefully, 

may be overprescribed and present unnecessary escalations in cost and schedule. Specific 

considerations for TAB specifications follow: 

• The ARC technology is applicable to a single-zone control. Balancing should be limited 

to the SA and OA flow rates only. Balancing the air distribution system (diffusers) has

minimal value.

• OA flow rates should be verified to meet ASHRAE 62.1-2010 ventilation requirements at 

various ARC fan speed sequences. OA flow rate should be calculated by subtracting the 

RA from the SA as acceptable by NEBB procedures.

• Maximum SA flow rates should be verified to meet the operating window of the RTU, 

which is typically 350–450 cfm/ton. Based on the ARC sequence of operation, the TAB 

should validate that under any DX operation (first stage, second stage, etc.) the supply 

fan is providing at least 300 cfm/ton. Slower flow rates will only decline over time as 

filters clog, and may cause icing of the DX coil. 
58 

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6.4 Installation and Construction (Include Permitting, Interconnect 

Agreements, Factory Acceptance Testing, Commissioning) 

ARC installation was straightforward and easily executed through a series of sequential work 

activities. Outstanding RTU maintenance issues were addressed first. The CATALYST systems

were installed. Remote communication was established. System commissioning and TAB were 

performed. Maintenance and ARC installs were completed within a 3-week period.

Commissioning/TAB required an additional month of work because the independent TAB 

contractor had a schedule conflict. Total construction time took approximately 2 months. 

After the construction was finished, several months of evaluation were needed to accommodate 

thermal comfort requirements. The driver behind this prolonged evaluation was an unexpected 

adjustment to the Navy’s COLS. The COLS directly regulate thermostat set-points. CNIC 

changed from COLS 3 to COLS 4 shortly after the installation. Determining the proper ARC

operation to meet these standards required significant time and resources. For effective ARC 

implementation, NAVFAC should clearly articulate the facility comfort requirements to the ARC 

provider and ensure that these requirements are met.

Other considerations for future ARC installs are as follows:

1. HVAC unit downtime. RTUs will need to be shut down during installation. Acceptable 

downtime relative to facility thermal comfort and temporary cooling requirements will 

need to be considered. 

2. Crane requirements. At least one ARC product presented in Table 25 will require a 

crane for access. 

3. Commissioning. The commissioning process should, at a minimum, include:

a. A functionality test to ensure that all the modes of operation (first-stage cooling, 

fan-only, etc.), are operating according to the sequence of operation. 

b. Validation of system performance relative to facility thermal comfort and 

ventilation requirements (temperature set points, RH maximum, OA damper 

schedule, and RTU hours of operation).

c. Temperature, RH and CO2 sensors should be calibrated.

6.5 Operation and Maintenance 

TWT oversaw O&M of the installed ARC units and retrofitted RTUs for almost 1 year. 

NAVFAC routine maintenance procedures are shown in Appendix D. Routine maintenance 

requirements of the ARC technology are generally minimal and should be fulfilled by standard 

inspections. 

ARC technologies should improve O&M when packaged with a BMS solution. Like some of the 

other ARC-BMS packages listed in Table 25, TWT developed the eIQ BMS to integrate with its 

CATALYST ARC system. NREL found mixed results for the ARC-BMS package improving 

O&M. 

The following subsections divide the ARC-BMS package impacts on O&M into two categories: 

unforeseen maintenance and routine maintenance. The impact on routine maintenance is neutral 
59 

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in the worst-case scenario. The impact on unforeseen maintenance depends on the maintenance 

staff’s acceptance of the Web-based monitoring and alarming through automated FDD. Although 

the online dashboards can always become more intuitive and automated FDD algorithms more 

sophisticated, the adoption of ARC-BMS as a maintenance avoidance and troubleshooting tool 

depends on the training. 

6.5.1 Automated Fault Detection and Diagnostic and Remote Monitoring 

Addressing Unforeseen Maintenance

Unforeseen maintenance refers to the inevitable issues related to failures of RTU components 

such as fan belts and compressors. The automated FDD capabilities built into most ARC-BMS 

packages should alert HVAC service technicians of potential maintenance issues that should be 

inspected and possibly addressed before components fail. During the demonstration, NREL saw 

distinct examples where the ARC-BMS package improved RTU O&M and where it did not. 

• Positive impact on O&M. The BXtra 1235H RTUs had only one known maintenance 

issue. The automated FDD worked as expected by identifying a fan belt that showed

signs of potential failure. TWT sent a service technician to fix the belt before it failed. 

• Neutral impact on O&M. The RTU serving A13 had multiple maintenance issues, one 

of which was related to the CATALYST system. The first issue was that the supply fan 

was left in a manual override mode during the TAB. It did not run when the compressors 

were turning on. Both DX stages iced up the coils and building A13 was not conditioned 

for 11⁄2 days. An automated FDD should have alerted personnel when the compressors 

were coming on but the supply fan was not. Unfortunately, this automated FDD did not 

occur. 

• The subsequent six maintenance failures were not due to the CATALYST but to typical 

field issues and the fact that the A13 RTU is 15 years old and at the end of its life. For 

four of the issues, TWT was alerted based on automated FDD, yet too late; the office 

space in A13 had become uncomfortable such that the NAVFAC HVAC technicians 

were already on site before TWT responded. In two cases NAVFAC HVAC technicians 

had already addressed the issues before TWT learned about them. 

One solution is to improve the automated FDD algorithms to acknowledge a broader array of 

failure mechanisms. Yet the more important obstacle to ARC-BMS packages improving O&M is 

having buy-in by the NAVFAC HVAC technicians. These technicians will bring another tool 

into their arsenal only if it is intuitive to use and enables them to work more nimbly. Although 

the eIQ dashboard can always be made more user friendly, the obstacle to adoption is with the 

training of NAFAC HVAC technicians. (See Section 6.6 for a summary of the training 

conducted during the demonstration and how that should be improved.) For future ARC

installations, NAVFAC should emphasize the training and buy-in by the HVAC technicians.

6.5.2 Routine Maintenance

Some of the automated FDD algorithms may improve routine maintenance procedures, such as 

when filters need to be changed. For future ARC installations, NAVFAC should not consider 

ARC-BMS packages as having any impact on routine maintenance. NAVFAC HVAC service 

technicians should continue their routine maintenance schedules. 
60 

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6.6 Training 

After the installation was complete, TWT held a training session for HVAC technicians with the 

Hickam, Pearl Harbor, and NAVFAC Hawaii ACEM shops. The training started with 1 hour in 

the classroom, including a presentation of the CATALYST and eIQ systems followed by 

questions and answers. TWT also provided reference materials organized in binders for each 

HVAC technician present. The training concluded with an in-field overview of the CATALYST 

hardware on the C27 RTU. 

After the training, TWT visited the NAVFAC Hawaii ACEM shop to ensure that its computers 

were capable of logging into the eIQ webpage. TWT put together a comprehensive service guide 

covering how to access and use the Web-based BMS system and diagrams of the entire hardware 

configuration. Unfortunately, TWT was unable to provide website access because of what is 

most likely a NAVFAC firewall. At the writing of this report, TWT was still trying to obtain 

access for the NAVFAC Hawaii ACEM shops to the Web-based BMS. 

For on-site access to the CATALYST system, TWT provided each ACEM shop a handheld 

computer tablet that can plug directly into the controller and enable read-write capability. This 

way NAVFAC HVAC technicians can communicate with the CATALYST to troubleshoot and 

override operation. Also through technical support over the phone, TWT can remotely connect to 

the RTUs and provide troubleshooting advice as well as override operation. 
61 

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7 Commercial Readiness Qualitative Assessment 

The commercially available ARC systems should be evaluated from three perspectives: (1) 

straightforward design and specification; (2) ease and speed of installation; and (3) seamless 

integration into NAVFAC’s O&M procedures. 

7.1 Commercial Readiness

The ARC retrofit technology is commercially available from multiple vendors and 

manufacturers. Although it is a relatively new product type (less than 10 years old), ARC 

systems are composed of very mature components. NREL assessed the ARC technology at 

technology readiness level (TRL) 9 (Figure 37).

NREL performed a cursory product survey and identified several commercially available ARC 

solutions that are summarized in Table 25. Each ARC technology includes slightly different 

energy-saving features. The table is not a comprehensive list. Some big box retailers with large 

RTU portfolios have engaged energy service companies and HVAC original equipment 

manufacturers to provide custom-built ARC solutions. These solutions do not have significant 

standalone intelligence since they are integrated into the retailer’s BMS. 

These ARC products require services to install the unit, perform O&M, and deliver BMS 

functionality (if applicable). There is no single business model for accomplishing this, and some 

ARC manufacturers work through local HVAC providers for installation and O&M services. As 

discussed in Section 6, the demonstration showed the importance of procuring the monitoring 

services to ensure long-term savings and potentially improved O&M via automated FDD and 

enhanced troubleshooting. 
62 

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Table 25. Commercially Available ARC Technologies

Primary Manufacturer

VariableSpeed Supply 

Fan Control

Web-Based

BMS or EMS 

Control

DCV Demand 

Response

Advanced 

Economizing

Automate

d FDD

Feature Priority for Realizing Energy Savings

in Hawaii/Guam 1 2 3 NA N/Ab 5 

TWT CATALYST

http://transformativewave.com Yes Yes TWT's eIQ BMSa Yes Yes Yes Yes

NexRev DrivePak www.nexrev.com Yes

Yes NexRev’s 

FREEDOM EM

Sa Noe Yes Noe Yes

Enerfitc www.enerfit.com Yes No Yes No Yes Yes

Bes-Tech Digi-RTUd www.bes-tech.net Yes Yes BesTech’s EMCS Yes No Yes No

Trane SZVAV Retrofit Yes Yesf Yes Yes Yes No

a The BMS solution provided by TWT and the EMS solution provided by NexRev are compatible through open protocols: BACnet, LonWorks, and ModBus.

b The field demonstration results, summarized in Section 4.8, showed minimal energy savings potential with economizer operation in Hawaii because of its high humidity

levels. Similarly, Guam will realize no benefit from installing economizers. Yet many Navy locations, particularly on the West Coast, may save significant energy with

advanced economizer operation integrated into ARC technologies.

c The Enerfit ARC solution also includes another actuated damper that is added to control the OA and RA before they enter the evaporator coil. This unique damper 

configuration is used to enhance the RTU’s dehumidification capability. NREL has not tested—or seen test results of—this feature and therefore cannot state whether it 

would improve dehumidification or save energy.

d The Digi-RTU technology also retrofits the lead compressor from constant to variable-speed. NREL has not tested or seen third-party testing of the energy savings 

associated with incorporating variable-speed compressor control.

e NexRev DrivePak does not control the OA damper and therefore does not provide DCV capability or advanced economizing. Based on correspondence, NexRev stated 

that most of its clients have already used a BMS to enable DCV and advanced economizer control. Consequently NexRev has not integrated these features into DrivePak.

f

Trane offers this retrofit only on Trane RTUs that already have a Trane BMS.
63 

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Figure 37. Technology Readiness Level (TRL)

Source: DOD Defense Acquisition Guidebook (DAG) and NASA TRL Thermometer 

7.2 Market Opportunities and Barriers

The ARC market addresses retrofitting code-compliant RTUs 5 tons and larger. It is a costeffective alternative to replacing the RTU with a more efficient unit when the RTU has at least 5 

years of remaining life. ARCs deliver the best returns where electricity prices are high, in 

climates with significant swing seasons (spring and fall), in building types that experience highly 

variable occupancies, and in buildings that require 50 or more hours of operation each week. 

Larger RTUs also save more energy relative to the installed cost, which improves the ROI. 

To expedite the market adoption of ARC technologies and high efficiency RTUs, the DOE 

Federal Energy Management Program, ASHRAE, and the Retail Industry Leaders Association 

have formed the “Advanced RTU Campaign” (www.advancedrtu.org). The campaign is “a 

recognition and guidance program designed to encourage building owners and operators to take 

advantage of savings opportunities from high efficiency RTUs.” 

Utility, state, and local incentive programs help to drive retrofits and high efficiency 

replacements. In the continental United States, particularly the in Pacific Northwest and along 

the West Coast, companies that provide ARC technologies work extensively with utilities to 

conduct field demonstrations to develop prescriptive rebate programs. (For example, see 

Appendix C for a list of utilities and energy efficiency organizations TWT has worked with to 

develop CATALYST-specific rebates.) For certain utilities such as Snohomish Public Utilities 

District, the rebate program covers up to 60% of the installed cost. 

Hawaiian Energy Company’s (HECO) current incentive program administrator is Hawaii 

Energy. Based on its website, www.hawaiienergy.com/hvac, the current prescriptive rebate for 

adding VFDs to HVAC fan motors is $50/hp. At the request of NAVFAC, NREL will provide 
64 

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the field demonstration results to HECO and Hawaii Energy to see if they would be interested in

developing a prescriptive ARC rebate program beyond the current VFD program. HECO will 

likely be interested in ARC technologies because they couple energy savings and demand 

response capabilities into a single packaged solution. 

As described above, the technology presents many near-term opportunities. Longer term, the 

need for the technology may change as codes and standards “raise the bar” on energy 

consumption. ASHRAE Standard 90.1-2013 requires new RTUs in certain applications to have 

SZVAV control (variable-speed supply fans), DCV, and economizing. Consequently, the 

ASHRAE 90.1 standard is now driving beyond energy efficiency ratio and integrated energy 

efficiency ratio requirements and essentially mandating that most ARC features be fully 

integrated into new RTU equipment. ARC retrofits enable building owners to realize RTU 

energy savings now rather than having to wait until their equipment ages to the point where it 

needs replacing.

7.3 Usability and Functionality

The usability and functionality of ARC systems should be evaluated from three perspectives: (1) 

straightforward design and specification; (2) ease and speed of installation; and (3) seamless 

integration into NAVFAC’s O&M procedures. 

• Straightforward specification. ARC systems are simple to specify, regardless of size. 

The VFD size and electrical service would be based on the evaporator fan motor size. In 

the case of the Bes-Tech Digit-RTU technology (see Table 25), the compressor size and 

electrical service would need to be known as well. The remaining components such as the 

controllers and sensors would be the same regardless of the RTU size or manufacturer. 

Consequently, ARC systems can be configured quickly based on a 1- to 2-hour site 

inspection per RTU to determine component health and the RTU’s nameplate, supply fan 

motor nameplate, and OA damper configuration. The main part of this site inspection is 

determining the maintenance costs to retro-commission the RTU before the ARC is 

installed. 

• Ease and speed of installation. ARC technologies can be considered “kits” that a 

certified HVAC technician can install quickly and easily. For example, two HVAC 

technicians trained to install the CATALYST ARC system can complete an installation, 

including the eIQ BMS, in less than 8 hours depending upon the RTU size. Then the 

TAB and commissioning process would take one HVAC technician another 4 hours to 

complete. Based on the “kit” concept, local HVAC contractors or NAVFAC’s HVAC 

technicians can install ARC technologies. Compared to a bulk purchasing concept on 

which an energy service company or HVAC original equipment manufacturer-based 

custom-built ARC product focuses, packaged ARC “kits” can be purchased individually 

or in bulk. 

• Seamless integration into NAVFAC’s O&M procedures. The ACEM shops in Hawaii 

and Guam are severely overloaded and struggle to maintain the HVAC equipment in their 

jurisdictions. Beyond correcting equipment malfunctions, each ACEM has its own 

routine O&M schedule (see Appendix D). Unfortunately, at the onset, NAVFAC’s 

HVAC technicians viewed the energy-saving features of an ARC technology as another 
65 

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system to troubleshoot and that could malfunction. Instead, an ARC system paired with 

an integrated BMS with Web-based monitoring can provide automated alarming (FDD) 

of potential malfunctions, remote troubleshooting leveraging a Web-based dashboard, 

and improved on-site troubleshooting by enabling technicians to remotely communicate 

with the controller. In fact, the Enerfit ARC technology (see Table 25) provides a 

handheld device for HVAC technicians that will talk via Bluetooth with their controller. 

The CATALYST ARC technology can use a handheld tablet to communicate with the 

controller via an Ethernet cable. Figure 4 provides an example screenshot of TWT’s eIQ 

BMS solution that can be accessed over the Web and shows the user real-time operation. 

Of course, a new system always presents a learning curve, but the Web-based dashboards 

are user friendly enough to allow HVAC technicians to leverage these features to reduce 

the site visits and troubleshooting time for RTU O&M.
66 

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8 Recommended Next Steps

The most immediate next step will be for NREL to monitor ESM versus non-ESM performance 

through January 2014 and provide an addenda report to the Navy that reflects updated, more 

accurate annual savings estimates. The regression model for all three buildings will be updated to 

include monitored data during Hawaii’s cooler winter months. The final normalized energy 

savings metric, kWh/ton/1,000 h of operation, will be recalculated for all three buildings. 

Based on the results to date, other near-term actions are recommended, both for tropical climates 

and for almost any other climate type. ARC retrofit technologies are TRL 9 and commercially 

available. For tropical climates, NAVFAC should adopt ARC retrofits on large buildings where 

multiple standard efficiency RTUs less than 10 years old serve a single space to realize 

significant energy savings. The ARC retrofit on the BXtra exchange building showed a 15% 

HVAC annual energy reduction savings of 96,498 kWh (94 kWh/ton/1,000 h of operation). 

Although this is a big box retail facility, the energy savings implications would be applicable to 

other large buildings, including exchange stores, recreation centers (bowling alleys, 

gymnasiums), conditioned hangers or warehouses, cafeterias, and commissaries. 

For buildings smaller than 20,000 ft2 where one RTU serves a single space, the tropical 

application recommendations are less clear. NREL’s addenda report should offer better nearterm guidance, and NAVFAC could conduct additional performance monitoring of additional 

units being installed in early 2014. NREL procured and will install additional CATALYST ARC 

systems for 19 RTUs at JBPHH (Table 26). At the time of writing this report, 7 CATALYST 

were pending approval for installation in Guam (Table 27). 

These RTUs provide a comprehensive cross-section of the NAVFAC building types in Guam 

and Hawaii. For all 26 RTUs, NREL included the Web-based BMS eIQ system that will provide 

remote monitoring to NAVFAC. The statement of work states that “The Subcontractor shall 

ensure all remote monitoring capabilities are furnished for a period of three years (3) post 

completion of all installation activities, including eIQ online and wireless network access.”

NAVFAC could use this monitoring capability to assess the energy savings on a broader base of 

building types if interest and resources allow. 

Based on successful field test results in nontropical climate zones, NAVFAC should consider 

transitioning the ARC technology to its facilities in other climate zones to realize even greater 

savings. Unlike tropical climates, most continental U.S. climates enable the ARC system to save 

more energy from enhanced economizing, greater DCV savings, and more operational hours in 

ventilation mode. Appendix I includes a summary of other ARC retrofit demonstrations in U.S. 

climates and how those results can be applied for NAVFAC facilities. For future ARC 

installations, NREL developed practical lessons (see Appendix J). 
67 

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Table 26. Follow-on ARC Retrofit Installation on 19 RTUs at JBPHH

Count Building 

Type

Bldg #, Name, and

Location Size Model Condition

1 

Medium 

Office

284 Federal Fire Station,

JBPHH

20 tons Carrier 50TM-025 Very Good

2 18 tons Carrier 50TM-020 Very Good

3 25 tons Carrier 50TM-028 Very Good

4 

Medium 

Mixed Use 1750H Chapel, JBPHH

10 tons Carrier 50HJ-012 Good

5 12.5 tons Carrier 50HJ-014 Good

6 12.5 tons Carrier 50HJ-015 Good

7 20 tons Carrier 50AY-020 Good

8 7.5 tons Carrier 50HJ-008 Very Good

9

Large Retail 1232H Exchange, JBPHH

6 Carrier 50TC Very Good

10 NA–chilled water coil Reliance Frame 256T, Type P, Design B Very Good

11 NA–chilled water coil Carrier 39MW03C011K7Z11XPS Very Good

12 NA–chilled water coil Carrier 39MW03C011K7Z11XPS Very Good

13 NA–chilled water coil Carrier 39MW03C011K7Z11XPS Very Good

14 NA–chilled water coil Carrier 39MW03C011K7Z11XPS Very Good

15 NA–chilled water coil Carrier 39MW03C011K7Z11XPS Very Good

16 NA–chilled water coil Carrier 39MW03C011K7Z11XPS Very Good

17 Recreation 

Center

1859H Makai Recreation 

Center, JBPHH 40 York Y14FC02A Fair/Good

18 Medium 

Office

1200H Base Engineer 

Administration, JBPHH 30 Carrier 50EW-034 Good

19 Cafeteria 1860H Hale Aina Dining 

Facility, JBPHH 18 Carrier 50HJ-020 Very Good
68 

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Table 27. Follow-on ARC Retrofit Installation on 7 RTUs at AAFB

Count Building 

Type Bldg #, Name, and Location Size Model Condition

1 Recreation 

Center 1605 Teen Center, AAFB 20 tons Carrier 50TC-D24 Good

2 Small 

Office 23010 Mobility Response Sq., AAFB

10 tons Carrier RAS121H Good

3 10 tons Carrier 50TFF Fair

4 Small 

Office 20011 Communications Sq., AAFB 18 tons Trane TCH180 Good

5 Terminal 17002 Passenger Terminal, AAFB 10 tons Carrier 50TC-A12 Good

6 Small 

Office 18001 36 CEs Motor Pool Building, AAFB 10 tons Carrier 50TC-A12 Good

7 Recreation 

Center 1622 Youth Center Gym, AAFB 20 tons Carrier 50TC-D2 Very good
69 

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References

ASHRAE. (2012). ASHRAE Handbook: HVAC Systems and Equipment. Atlanta, GA: American 

Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 

BPA. Advanced Rooftop Unit Control (ARC) Retrofit. Retrieved October 1, 2013 

from www.bpa.gov/energy/n/emerging_technology/ARC.cfm. 

Snohomish County PUD. (March 1, 2013). “New Technology Savings Energy, Sparking 

Excitement.” Highlights Newsletter, pp. 1–2. Accessed April 10, 2013 from 

http://transformativewave.com/Media/Default/docs/SnoPUD_highlights_CATALYST.pdf. 

Studer, D.; Romero, R.; Herrmann, L.; Benne, K. (2012). Energy Implications of Retrofitting 

Retail Sector Rooftop Units with Stepped-Speed and Variable-Speed Functionality. NREL/TP5500-51102. Accessed from www.nrel.gov/docs/fy12osti/51102.pdf. 

Wang, W.; Huang, Y.; Katipamula, S.; Brambley, M. (2011). Energy Savings and Economics of 

Advanced Control Strategies for Packaged Air-Conditioning Units with Gas Heat. PNNL-20955. 

Accessed from www.pnnl.gov/main/publications/external/technical_reports/PNNL-20955.pdf. 

Wang, W.; Katipamula, S.; Ngo, H.; Underhill; R., Taasevigen, D.; Lutes, R. (2013). Advanced 

Rooftop Control (ARC) Retrofit: Field-Test Results. PNNL-22656. Accessed from 

www.pnl.gov/main/publications/external/technical_reports/PNNL-22656.pdf. 
70 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix A: NAVFAC-Defined Thermal Comfort

During the initial monitoring months, NREL determined that the RH in buildings A13 and C27 

exceeded 65% and caused thermal comfort issues and mold concerns. NREL brought this to the 

attention of NAVFAC Hawaii and NAVFAC Headquarters. This appendix summarizes the 

outcome of the weekly conference calls from April through June 2013, which identified 

NAVFAC standards of service for temperature set points, RH thresholds, and allowable RTU 

on/off times. The appendix also includes recommendations for incorporating ASHRAE Standard 

55-2010 thermal comfort criteria into UFC and UFGS for HVAC sizing and operational 

requirements. The last subsection summarizes how ARC retrofit systems provide lower space 

RH so proper thermal comfort can be maintained even with warmer COLS temperature set 

points.

Defining NAVFAC Thermal Comfort and Operational Requirements

NAVFAC establishes thermal comfort and HVAC operational requirements through a 

combination of criteria and mandates. For NAVFAC’s energy teams, building energy managers, 

and HVAC technicians, reconciling these requirements to determine the proper temperature set 

points and schedules can be cumbersome and confusing. Thus, the actual temperature set points 

and schedules applied are not consistent across buildings and do not always adhere to the latest 

NAVFAC requirements. 

These criteria and mandates are summarized below. In addition to the conflicting temperature 

requirements, none of these requirements properly define what the operational (not design) RH

thresholds should be. 

COLS. To control energy usage in real time, Commander Navy Installations Command (CNIC) 

established four COLS levels. Summarized in Table A-1, the underlined and bolded text 

highlights the verbiage that applies to HVAC and thermal comfort. (The text shown in Table A-1

was not edited from the version sent to NREL.) In addition to each COLS level, CNIC provided 

an appendix on the specific actions needed to meet these requirements.

Table A-1. Navy Defined Utilities COLS

COLS 1. Utility is available to meet all mission requirements. Commodity availability has no risk to 

mission, quality of life, or routine station operations. Energy and water efficiency and awareness are 

utilized and no forced reduction measures are required. Other services are available to meet all mission 

requirements.

COLS 2. Utility is available to substantially meet mission requirements with minor difficulty. Utilities 

funding status and/or weather conditions present LOW risk to customer operational 

requirements. Building occupants and supported tenants forced to make minor operational adjustments 

to meet mission requirements in accordance with health/safety regulations. Minimal forced reduction 

measures include (but are not limited to): (1) Reduction measures resulting in LOW risk to warfighter 

support and operational requirements of host activity and tenant commands. Suggested measures are 

listed in Appendix. (2) Heating and Air Conditioning delayed/interrupted no more than two weeks 

(3) Operation of climate control systems is reduced to lower energy consumption. Goal is to reach 

average temperatures that have minimum impact on warfighter support: 68 or 69 degrees in heating 

season (68<avg temp<70) and 77 or 78 degrees in the cooling season (78>avg temp>76) (4) 5% or less 

reduction required for electrical service delivery facilities without direct support function to the 
71 

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warfighter (e.g., ball field lighting, decorative lighting) (5) 5% or less reduction required for steam service 

delivery facilities without direct support function to the warfighter (e.g., warehouses, gymnasiums) (6) 

5% or less reduction required in water use for facilities without direct support function to the warfighter 

(e.g., irrigation, car washes) (7) Water rationing for no more than seven days

COLS 3. Utility is available to marginally meet mission requirements with major difficulty. Utilities 

funding status and/or weather conditions present MODERATE risk to customer operational 

requirements. Building occupants and supported tenants forced to make minor operational adjustments 

to meet mission requirements in accordance with health/safety regulations. Forced reduction measures 

include (but are not limited to): (1) Reduction measures resulting in MODERATE risk to warfighter 

support and operational requirements of host activity and tenant commands. Suggested measures are 

listed in Appendix. (2) Heating and Air Conditioning availability delayed/interrupted no more than four 

weeks (3) Operation of climate control systems is reduced to lower energy consumption. Goal is to 

reach average temperatures that have moderate impact warfighter support: 66 or 67 degrees in heating 

season (66<avg temp<68) and 79 or 80 degrees in the cooling season (80>avg temp>78) (4) 6% to 10% 

reduction required for electrical service delivery facilities without direct support function to the 

warfighter (e.g., ball field lighting, decorative lighting) (5) 6% to 10% reduction required for steam 

service delivery facilities without direct support function to the warfighter (e.g., warehouses, 

gymnasiums) (6) 6% to 10% reduction required in water use for facilities without direct support function 

to the warfighter (e.g., irrigation, car washes). 

COLS 4. Utility is not available to marginally meet mission requirements due to funding shortfalls and/or 

weather/climate conditions even after making significant mission adjustments. Program requires 

additional resources to meet basic customer requirements. While meeting bare minimum health/safety 

regulations, building occupants and supported tenants will experience significant hardships that 

include: (1) Reduction measures resulting in HIGH risk to warfighter support and operational 

requirements of host activity and tenant commands. Suggested measures are listed in Appendix. (2) 

Heating and AC availability delayed/interrupted more than four weeks (3) Operation of climate control 

systems reduced to prevent equipment failure/breakdown, regardless of impact on warfighter support. 

May achieve average temperatures less than 66 degrees in heating season, and greater than 80 degrees 

in cooling season (4) Greater than 10% reduction in all utilities service to all facilities without direct 

warfighter support function (5) Imposed 2 or more brief rolling blackout of utilities services in order to 

reduce consumption.

APPENDIX: SHORE ENERGY REDUCTION ACTIONS

This is a list of specific actions that can be implemented to reduce an installation's consumption of utilities. Taking 

actions like these will generally require building occupants to make adjustments to their 

standard daily operations. As a result, if an installation/region takes enough of these actions, there will be 

some risk to building occupants' ability to accomplish their mission. Additionally, Installation Managers 

should be careful instituting these types of actions measures to ensure they do not create costs 

in other areas (ie. undue excessive equipment wear and tear, requirements to pay labor 

overtime, etc.)

· Reduce delivery of Installation Services that are not direct warfighter support functions including (but not limited 

to): MWR, Chaplain/ministry services, Fleet and Family Support, etc.

· Adopt, where practical, Alternative Work Schedules (AWS)/Compressed Work Schedule (CWS) to reduce 

commuting costs and installation energy usage.

· Institute large scale AWS/CWS across entire commands, entire sites or entire installations.
72 

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· Mandate night-time operations as a peak-shaving effort and as an energy consumption 

reduction measure.

· Prohibit all use of energy intensive personal appliances such as space heaters and electric 

fans.

· Implement drastic evening and weekend setbacks for HVAC systems.

· Limit travel to mission essential requirements. Substitute use of video and telephone conferencing.

· Provide command attention to energy management training and awareness 

· Encourage turning off computers after hours or when not in use

· Ensure that lights are turned off in buildings at night

· Contract for Resource Efficiency Managers dedicated to lowering energy consumption

· Maximize use of training simulators

· Identify load-shedding techniques to cut electricity consumption in buildings and facilities.

Examples of these techniques include: 

· Adjust equipment controls to reduce hours of operation, e.g. air compressors, water heaters, 

air handling equipment 

· Restrict use of window air-conditioning 

· Turn off unneeded lights with motion sensors and separate lighting circuits

· Disconnect vending machine lights 

· Remove portable electric heaters and fans

· Reduce street and parking lot lighting where safety considerations permit

· Tune up boilers and HVAC. 

· Make sure steam traps functioning properly.

· Replace incandescent light bulbs with compact fluorescent in buildings and housing.

· Advise family housing residents to run clothes and dish washers only when full. 

NAVFAC Hawaii “Region Energy Instruction.” In addition to the Navy-wide COLS 

requirements, NAVFAC Hawaii issued its own energy reduction instruction. Shown in Table A2, the highlighted text shows the mandate of not lower than 78°F thermostat temperatures from 

10:00 a.m. to 3:00 p.m. winter hours (November 01 to April 30) and 8:00 a.m. to 4:00 p.m. 

summer hours (May 1 to October 31). 

Table A-2. NAVFAC Hawaii “Region Energy Instruction” Issued September 2011

UNCLASSIFIED////

REROUTE DETECTED ADMINISTRATIVE MESSAGE

ROUTINE

R 122119Z SEP 11 ZYB PSN 317101H13

FM COMNAVREG PEARL HARBOR HI

TO ALL NAVACTS HAWAII

INFO ZEN/COMNAVREG PEARL HARBOR HI

ZEN/HQ PACAF HICKAM AFB HI

ZEN/15AW HICKAM AFB HIBT

UNCLAS

ALL NAVACTS HAWAII 114/11MSGID/GENADMIN/MIL-STD-6040(SERIES)/B.0.01.00

/COMNAVREG PEARL HARBOR HI/-/-/-/-/-/-//

SUBJ/ENERGY CONSERVATION//

REF/A/DESC:DOC/COMNAVREGHIINST/4101.1D/21JUL2010//

REF/B/DESC:DOC/SECNAVINST/4100.9A/01OCT2001//

NARR/REF A IS THE NAVY REGION HAWAII ENERGY MANAGEMENT PROGRAM INSTRUCTION. REF B IS THE DEPARTMENT OF THE 

NAVY (DON) SHORE ENERGY MANAGEMENT INSTRUCTION.//POC/STEHN, KRISTA/CIV/UNIT:NAVFAC/NAME:PEARL HARBOR 

HI/TEL:808-471-0440/EMAIL:KRISTA.STEHN(AT)NAVY.MIL//

GENTEXT/REMARKS/

1. YOUR CONSERVATION EFFORTS THIS FISCAL YEAR WITHIN NAVY REGION HAWAII HAVE SAVED THE NAVY 7.61 MILLION 
73 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

DOLLARS AND IS VERY MUCH APPRECIATED, HOWEVER WE MUST DO MORE. GIVEN CURRENT TRENDS OF UTILITY 

CONSUMPTION, WE WILL NOT MEET MANDATED FEDERAL REDUCTION GOALS FOR FISCAL YEAR 2011. THE ENERGY 

INDEPENDENCE AND SECURITY ACT OF 2007 REQUIRES REGION HAWAII TO ACHIEVE AN 18 PERCENT ENERGY REDUCTION IN 

FISCAL YEAR 2011; WE HAVE ONLY ACHIEVED A 12 PERCENT REDUCTION, A DIFFERENCE OF APPROXIMATELY 20,000 

MEGAWATT HOURS.

2. LEADERSHIP FROM ALL COMMANDS, LARGE AND SMALL, ARE STRONGLY URGED TO REVIEW AND RE-ENERGIZE THE 

FOLLOWING CONSERVATION POLICIES PROMULGATED REF (A):

A. AIR CONDITIONING (AC) OPERATING HOURS FOR ALL FACILITIES WITHIN REGION HAWAII ARE 

LIMITED TO BETWEEN 1000 TO 1500 HOURS FROM 01 NOVEMBER TO 30 APRIL AND 0800 TO 1600 

FROM 01 MAY TO 31 OCTOBER.

B. PER REF (B), THERMOSTATS FOR CENTRAL AC AND WINDOW AC UNITS MUST BE SET NO LOWER 

THAN 78 DEGREES FAHRENHEIT. FOR AC UNITS WITHOUT THERMOSTATS, CONTACT YOUR BUILDING ENERGY MANAGER 

FOR A WALL MOUNTED THERMOMETER AND ADJUST THE AC UNIT TO ACHIEVE 78 DEGREES FAHRENHEIT SPACE COOLING.

C. AC SHALL BE SET NO LOWER THAN 76 DEGREES FAHRENHEIT IN SERVER ROOMS AND NAVY/MARINE CORPS INTRANET 

(NMCI) POINTS OF PRESENCES (POP), OR INTERMEDIATE DISTRIBUTION FRAME (IDF) ROOMS.

D. PERIMETER WINDOWS AND DOORS SHALL BE KEPT CLOSED WHEN AC IS OPERATING.

E. SECURE OUTDOOR LIGHTING DURING DAYLIGHT HOURS AND ENCOURAGE OTHERS TO TURN OFF LIGHTS AS NEEDED.

F. DURING UNOCCUPIED HOURS, TURN OFF LIGHTING SYSTEMS, OFFICE EQUIPMENT, AIR 

CONDITIONERS, AND COMPUTERS.

G. REPORT MALFUNCTIONING PLUMBING FIXTURES, SUCH AS LEAKING FAUCETS, DEFECTIVE TOILET FLUSH VALVES, AND 

LEAKING SHOWER HEADS TO YOUR BUILDING FACILITY MANAGER.

H. KITCHEN APPLIANCES; INCLUDING BUT NOT LIMITED TO REFRIGERATORS, COFFEE MAKERS, MICROWAVES, AND 

TOASTERS; SHALL NOT BE PERMITTED IN PERSONAL WORK SPACES. REFRIGERATORS SHALL BE LIMITED TO ONE FOR EVERY 

20 FULL TIME EMPLOYEES.

I. ONLY ENERGY-STAR RATED OR ENERGY EFFICIENT EQUIPMENT AND APPLIANCES SHALL BE 

USED.

J. WHERE IDENTIFIED, COMMANDS ARE REQUESTED TO AGGRESSIVELY MAKE RECOMMENDATIONS TO IMPROVE BUILDING 

ENERGY AND WATER EFFICIENCY TO THE REGION ENERGY TEAM AT 471-0440.

3. IT IS OUR OBLIGATION, ESPECIALLY IN THIS FISCAL ENVIRONMENT, FOR EACH OF US TO BE RESPONSIBLE STEWARDS 

OF TAXPAYER DOLLARS AND OUR ENVIRONMENT. WE MUST BE SENSITIVE TO THE LIMITED ENERGY RESOURCES AVAILABLE 

AND THE ENVIRONMENTAL AND FISCAL IMPACTS OF OVERUSE. BY FOLLOWING PRESCRIBED POLICIES, WE WILL 

SIGNIFICANTLY IMPACT AND REDUCE NAVY REGION HAWAII ENERGY AND WATER USAGE. MAHALO FOR YOUR CONTINUED 

EFFORTS TO ENSURE THAT WE BUILD A STRONG ENERGY CONSERVATION CULTURE THROUGHOUT NAVY REGION HAWAII.

4. RDML SMITH SENDS.

5. THIS ALL NAVACTS HAWAII IS IN EFFECT UNTIL FURTHER NOTICE.//

UFC 3-410-01. UFC 3-410-01 is the only specification throughout UFCs and UFGSs that 

acknowledges both space temperature and RH. Section 3-4.3.1 stipulates that cooling HVAC 

equipment should be sized to meet 78°F (26°C) dry bulb and a maximum of 55°F (12.8°C) dew 

point (equates to 45% RH) and account for the moisture gain in the space. These requirements 

apply only for sizing HVAC system purposes. Even the old UFC 3-400-10N “Mechanical 

Engineering” criterion, which was replaced by UFC 3-410-01, provided operational and sizing 

thermal comfort guidance, stating: “Space Design conditions shall be 76 Fdb & 50% RH, during 

the Design Cooling Day outside air conditions. At all other than design day, occupied times, 

maintain the space within the ‘Summer’ conditions shown in the latest edition of ASHRAE 

Handbook of Fundamentals, but not less than 76 Fdb.” Again, this guidance was for sizing 

purposes only. 

During the April through June 2013 conference calls, NAVFAC established that buildings A13 

and C27 temperature set points and schedules would adhere to NAVFAC Hawaii “Region 
74 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Energy Instruction,” and NAVFAC obtained a temporary waiver to the current COLS level 4 

mandate that CNIC issued in April 2013. Two additional items were clarified. 

1. Shown in Table A-2, the “Region Energy Instruction” mandates “THERMOSTATS FOR 

CENTRAL AC AND WINDOW AC UNITS MUST BE SET NO LOWER THAN 78 

DEGREES FAHRENHEIT.” Yet NREL was directed to use 76°F as the set point and told 

that the “Region Energy Instruction” was interpreted to allow the temperature set point to 

be below 78°F to maintain the warmest area of the conditioned space at approximately 

78°F. 

2. NAVFAC Hawaii procedure allows each building to have its energy managers apply to 

REGCOM for exceptions to the “Region Energy Instruction.” Because building C27 was 

allowed to reduce its set point, NREL was directed to use a 75°F set point. Similarly, 

building A13 was allowed to have the RTU operate starting at 9:00 a.m. instead of 10:00 

a.m. during the winter months. 

Once the temperature set points and operational schedules were established, NREL and 

NAVFAC focused on the RH issue. Because none of the criteria or mandates addressed RH, 

NREL proposed—and NAVFAC agreed—to use 65% RH as the threshold for the space, 

including occupied and unoccupied times. A maximum RH of 65% is based on ASHRAE 

Standard 55-2010 (discussed further in the following subsection), meets thermal comfort 

requirements, and mitigates mold issues. NAVFAC agreed to let NREL evaluate different 

control strategies over several weeks to determine an RTU on/off schedule that would maintain 

buildings C27 and A13 at < 65% RH and not significantly impact daily energy usage. NREL 

found that a “morning charge” with the RTUs starting operation at 6:00 a.m. (2 hours before 

approved operation) sustained the RH to < 65%. NREL then received approval from REGCOM 

to turn the RTUs on at 6:00 a.m. for buildings C27 and A13. 

Section 0 summarizes a recommendation to NAVFAC to streamline its temperature set point and 

schedule requirements, include RH requirements, and establish how NAVFAC defines thermal 

comfort according to ASHRAE Standard 55-2010. Beyond improving HVAC efficiency with 

new or retrofit technologies, NAVFAC can realize significant energy savings by enforcing these 

strict operational mandates. Most of the infrastructure is there and the building energy manager’s 

role is clearly defined. Yet NAVFAC currently does not realize those savings because the 

direction for the building energy managers is not clear. The questions, “How can these mandates 

be interpreted?” and “Which mandates take precedence?” need to be answered.

The wrap-up of this demonstration provides a great example of the confusion that has arisen 

about the interpretation and application of these mandates. While writing this document, NREL 

realized that the 3:30 p.m. RTU off times for A13 and C27 during the demonstration period did 

not follow NAVFAC’s “Region Energy Instruction,” which stipulates 4:00 p.m. in the summer 

months and 3:00 p.m. in the winter months. NREL asked the NAVFAC Hawaii energy office 

and the building energy manager why 3:30 p.m. was the directed off time for summer and winter 

operation. Both parties replied that there was no official reason for that direction. This example 

shows the importance of streamlining these HVAC energy mandates and providing clear 

direction to appropriate NAVFAC personal for enforcement. 
75 

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The following subsection summarizes how ASHRAE Standard 55-2010 defines thermal comfort 

and how NAVFAC should implement this methodology when establishing HVAC operational 

requirements. The final subsection in this appendix summarizes how ARC systems can help 

NAVFAC achieve warmer temperature set points while balancing thermal comfort and 

mitigating mold issues.

Applying ASHRAE Standard 55 to NAVFAC Operational Requirements

ASHRAE Standard 55-2010 uses the Fanger Comfort Method to define thermal comfort as a 

function of dry bulb temperature, RH, mean radiant temperature, clothing (defined by the metric 

“clo”), metabolic rate (defined by the metric “met”), and air velocity. The Fanger Comfort 

Method is used to calculate the People Percentage Dissatisfied (PPD). PPD establishes the 

percentage of building occupants who would be uncomfortable based on a given set of the 

aforementioned parameters. In mechanical design, it is considered almost impossible to make all 

occupants comfortable given the variations in clothing and metabolic rates, especially between 

women and men. As defined in ASHRAE standard 55, the space conditions were considered 

comfortable when the PPD was < 10%. 

Neither the UFCs nor the UFGSs establish how NAVFAC defines thermal comfort in terms of 

space temperature and RH. During the weekly conference calls, NAVFAC headquarters relayed 

some guidance from a Mechanical Engineering Criteria Manager who in an email stated: 

We do say to stay within the ‘summer’ (clo=0.5) or ‘winter’ (clo=1.0) conditions 

of the ‘ASHRAE Summer and Winter Comfort Zones’ chart in the ASHRAE 

Fundamentals Handbook chapter on ‘THERMAL COMFORT’. The chart is 

better shown in ASHRAE Standard 55. Using the summer “clo” factor of 0.5 

would require a humidity below 65%. The ASHRAE Comfort zones have no 

minimum humidity requirement but we call for no lower than 30% in the winter. 

Low humidity is not a problem in the summer season. 

NREL recommends that similar verbiage be added to the appropriate UFC and UFGS regarding 

applying ASHRAE Standard 55-2010 summer (0.5 clo) and winter (1.0 clo) comfort criteria 

when sizing HVAC equipment and establishing operational temperature set points and RH

thresholds. 

Table A-3 calculates the PPD for each NAVFAC temperature requirement using the Fanger 

Comfort Method and ASHRAE Standard 55-2010 summer thermal comfort metrics of 0.5 clo, 

1.2 metabolic rate (office work), and 50 fpm air velocity. NREL used the 65% RH as the peak 

acceptable moisture condition except for the UFC 3-410-01 requirement, which identifies the 

acceptable moisture condition as 55°F dew point. As shown, the maximum 65% RH along with 

even the COLS level 4 space temperature mandates of 80°F still maintain the PPD at < 10%. 

Table A-4 shows the calculated PPD for all three buildings in the demonstration applying the 

ASHRAE Standard 55-2010 0.5 clo summer conditions. 
76 

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Table A-3. Thermal Comfort PPD Based on Different NAVFAC Temperature Requirements and 

Maximum 65% RHa 

Dry Bulb

Temperature RH Dew PointTemperature PPD

UFC 3-410-01

Section 3-4.3.1 

Design to 78°F db and 55°F dp

78°F 45% 55°F 6%

NAVFAC Hawaii 

“Region Energy Instructions” 78°F 65% 65°F 5%

CNIC COLS Level 1 Not 

Specified 65% – – 

CNIC COLS Level 2

78>avg temp>76 77°F 65% 64°F 6%

CNIC COLS Level 3

80>avg temp>78 79°F 65% 66°F 6%

CNIC COLS Level 4

> 80 80°F 65% 67°F 8%

a Thermal comfort parameters based on ASHRAE Standard 55-2010 summer conditions with 0.5 Clo, 1.2 metabolic 

rate (office work), and 50 fpm air velocity. 

Table A-4. ASHRAE Standard 55-2010 0.5 clo Summer Conditions Applied to All Three Buildings

 BXtra A13 C27

Calculated PPD 6 8 12

Thermostat Set Point 74°F 76°F 75°F

RH Limit < 65% RH < 65% RH < 65% RH

Clothing (clo) 0.5 0.5 0.5

Metabolic Rate (met) 1.7 (walking about) 1.2 (seated, filing) 1.2 (seated, filing)

Air Velocity 130 fpm (1.5 mph) 50 fpm (0.6 mph) 50 fpm (0.6 mph)

Figure A-1 plots the ASHRAE Standard 55 summer and winter comfort zones on a 

psychrometric chart compared to NAVFAC Hawaii and COLS requirements. The checkered 

pattern represents NREL’s recommended thermal comfort zone for NAVFAC based on a 

minimum 30% and maximum 60% RH. 
77 

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Figure A-1. ASHRAE Standard 55-2010 summer (0.5 clo) and winter (1.0 clo) thermal comfort 

zones compared with NAVFAC Hawaii and COLS requirements
78 

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Appendix B: Linear Regression Method and Results

Previous ARC retrofit technology demonstrations in drier climates (most notably Wang et al. 

2013) showed a strong correlation between daily energy usage and daily average ambient dry 

bulb temperature. Consequently, these demonstrations created linear regression models using 

daily average ambient dry bulb temperatures as the sole predictor of energy consumption and 

energy savings. For this demonstration, NREL found significant scatter in the daily energy usage 

versus the average ambient dry bulb temperature. Therefore, NREL included additional 

predictors in the regression analysis to account for this scatter. 

• Daily average HR. Because buildings C27 and A13 had a combination of high ambient 

humidity and high infiltration rates, NREL included daily average ambient HR as a 

predictor. 

• Demand response days. Because the demand response sequence may have impacted 

daily energy usage, NREL included a separate predictor of “–1” for days when the 

demand response sequence was on and “+1” when it was not. 

• Friday operation. For buildings A13 and C27, the predictor for demarking Friday or not 

was introduced because the data indicated that Fridays have a lower daily energy usage, 

most likely from reduced occupancy. 

• Daily minimum ambient dry bulb temperature. NREL found that despite different 

days experiencing the same average dry bulb temperature and similar HR, the daily 

minimum dry bulb temperature impacted energy usage throughout the day. 

• Daily maximum ambient dry bulb temperature. Because the daily minimum was 

included, NREL also included the daily maximum ambient dry bulb temperature.

For each building, NREL started with the linear model shown in Equation 1. The initial model 

included first-order predictors, second-order predictors (squared terms), and interaction 

predictors with mode (“mode · avgOAT”, “mode· avgHR”). NREL first evaluated whether the 

ESM or non-ESM predictor was statistically significant; in other words, whether ESM operation 

changed the energy usage signature. For all the initial regressions for all three buildings, NREL 

found that ARC retrofit’s impact on daily energy usage was statistically significant. 

(1) Daily Energy Use = c0 + (c1 ∙ mode) + (c2 ∙ Friday) + (c3 ∙ DR) + (c4 ∙ avgOAT) +

(c5 ∙ avgOAT2) + (c6 ∙ avgOAT ∙ mode) + (c7 ∙ avgHR) + (c8 ∙ avgHR2) + (c9 ∙ avgHR ∙

mode) + (c10 ∙ avgOAT ∙ avgHR) + (c11 ∙ minOAT) + (c12 ∙ minOAT2) + (c13 ∙ minOAT ∙

mode) + (c14 ∙ maxOAT) + (c15 ∙ maxOAT2) + (c13 ∙ maxOAT ∙ mode)

where: mode = mode of operation that day [–1 = non-ESM or +1 = ESM] 

 Friday = whether day is Friday [–1 = Friday or +1 = not Friday] 

 DR = demand response sequence initiated that day [–1 = DR initiated or +1 = no DR] 

avgOAT = coded daily average ambient dry bulb temperature [–1 = min to +1 = max] 

 avgHR = coded daily average ambient humidity ratio [–1 = min to +1 = max]
79 

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minOAT = coded daily minimum ambient dry bulb temperature [–1 = min to +1 = max]

maxOAT = coded daily maximum ambient dry bulb temperature [–1 = min to +1 = max] 

NREL then reduced the model by eliminating predictors that would definitely not be significant 

in the final regression model where all the predictors have p-values < 0.05. As a rule, NREL 

eliminated predictors when their p-values were > 0.25. NREL chose the final regression model 

when all the predictors were statistically significant. For all three buildings, NREL applied the 

final regression model to Hawaii International Airport TMY3 weather data to calculate the 

annual energy usage for ESM and non-ESM operation and thereby energy savings. The energy 

savings were normalized based on cooling-ton/1,000 h of RTU operation (kWh/ton/1,000 h). 

As shown in the following subsections, the final regression model for each of the three buildings 

is different. At initial observation, the statistically significant predictors should be the same so

the final regression model equation should be the same for at least buildings A13 and C27. 

Further investigation showed that each building had different energy use behavior, which 

consequently identified different predictors for explaining these variances. The following 

subsections also explain why the final regression model was different for each building. 

BXtra Linear Regression

Table B-1 and Equation 2 show the BXtra final regression model. The demand response 

predictor was found to be statistically significant. As expected, average ambient dry bulb 

temperature and HR predictors were found to be statistically significant, as was the day-hours 

predictor. Figure B-1 plots the measured versus predicted energy usage. Although the regression 

model does not account for the entire scatter, an adjusted R-squared of 0.899 provides sufficient 

confidence that the model explains the monitored data. 

Table B-1. BXtra 1235H Final Linear Regression Model Parameters

R-Squared 0.899

Intercept 1,752 coefficient 0.0000 p-value

mode –132 coefficient 0.0000 p-value

Day_Hours 97 coefficient 0.0000 p-value

DR –17 coefficient 0.0064 p-value

avgOAT 356 coefficient 0.0000 p-value

avgHR 89 coefficient 0.0000 p-value

(2) Building 1235H Daily Energy Use = 1,752 + (−132 ∙ mode) + (97 ∙ Day_Hours) +

(−17 ∙ DR) + (356 ∗ avgOAT) + (89 ∗ avgHR)

where: mode = mode of operation that day [–1 = non-ESM or +1 = ESM] 

 DR = demand response sequence initiated that day [–1 = DR initiated or +1 = no DR] 
80 

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 Day_Hours = hours of operation per day [–1 = 16 hours or +1 = 20 hours] 

avgOAT = coded daily average ambient dry bulb temperature [–1 = min to +1 = max] 

 avgHR = coded daily average ambient humidity ratio [–1 = min to +1 = max]

Figure B-1. BXtra 1235H predicted versus measured daily energy usage

C27 Linear Regression

Table B-2 and Equation 3 summarize the final linear regression model for building C27. Figure 

B-2 shows the measured versus predicted daily energy usage. Like the 1235H BXtra regression 

model, building C27 found the avgOAT and avgHR predictors to be statistically significant. Yet 

building C27 did not include the DR predictor because the DR sequence implemented on 

building C27 worked for only a few days of the demonstration period. The remaining days, the 

sequence was overridden because the space temperature sensor indicated that the space had 

become too warm during the demand event, causing the RTU to go into standard cooling 

operation. A major influence of RTU operation was the improper location of the space 

temperature sensor (immediately next to an exit door). Consequently, the influence of infiltration 

on the temperature sensor was exaggerated. The minOAT predictor was significant for this 

reason. NREL found that on warmer mornings, the space sensor initiated cooling much earlier 

compared to a cooler morning. 

1200

1400

1600

1800

2000

2200

2400

1200 1400 1600 1800 2000 2200 2400

Predicted Daily Energy Usage (kWh/day)

Measured Daily Energy Usage (kWh/day)
81 

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Table B-2. Building C27 Final Linear Regression Model Parameters

Adjusted R-Squared 0.730 

Intercept 105.8 coefficient 0.0000 p-value

mode –2.9 coefficient 0.0009 p-value

Friday 2.5 coefficient 0.0130 p-value

avgOAT 8.6 coefficient 0.0015 p-value

avgHR 9.3 coefficient 0.0001 p-value

minOAT 14.7 coefficient 0.0000 p-value

(3) Building C27 Daily Energy Use = 105.8 + (−2.9 ∙ mode) + (2.5 ∙ Friday) +

(8.6 ∙ avgOAT) + (9.3 ∙ avgHR) + (14.7 ∙ minOAT)

where: mode = mode of operation that day [–1 = non-ESM or +1 = ESM] 

 Friday = whether day is Friday [–1 = Friday or +1 = not Friday] 

avgOAT = coded daily average ambient dry bulb temperature [–1 = min to +1 = max] 

 avgHR = coded daily average ambient humidity ratio [–1 = min to +1 = max]

minOAT = coded daily minimum ambient dry bulb temperature [–1 = min to +1 = max] 
82 

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Figure B-2. Building C27 predicted versus measured daily energy usage

The 0.730 adjusted R-squared indicates that the final predictors explain most of the variance in 

the sample dataset. By including the “Friday” predictor, the model does account for some 

occupant behavior. Most of the remaining unexplained variance is due to occupant behavior 

impacting the other HVAC systems that serve the building. Two mini-splits serve two 

conference rooms adjacent to the space being served by the RTU apart from this demonstration. 

The mini-splits are controlled by separate thermostats and are turned on during conference room 

usage. Two other RTUs serve a separate wing of building C27 and may slightly influence the 

daily energy usage. 

A13 Linear Regression

Table B-3 and Equation 4 provide building A13’s final linear regression model. Compared to the 

BXtra and building C27, the only two predictors are mode of operation and daily average 

ambient dry bulb temperature. NREL was surprised that the HR predictor was not significant 

when reducing the regression models. When comparing against building C27 demonstration 

period, building A13 has a significantly smaller sample set and misses several extremely humid

days in late July when the daily average HR reached 121 gr/lb. Consequently, the building A13 

demonstration period was not long and consistent enough to flesh out other predictors such as 

HR and Friday operation. Yet an adjusted R-squared of 0.707 provides a reasonable explanation 

of the variance in the sample data. Figure B-1 plots the predicted versus measured energy usage. 

60

70

80

90

100

110

120

130

140

60 70 80 90 100 110 120 130 140

Predicted Daily Energy Usage (kWh/day)

Measured Daily Energy Usage (kWh/day)
83 

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Table B-3. Building A13 Final Linear Regression Model Parameters

Adjusted R-Squared 0.707

Intercept 163.1 coefficient 0.0000 p-value

mode –3.5 coefficient 0.0382 p-value

avgOAT 42.6 coefficient 0.0000 p-value

(4) Building A13 Daily Energy Use = 163. 1 + (−3. 5 ∙ mode) + (42. 6 ∙

avgOAT)

where: mode = mode of operation that day [–1 = non-ESM or +1 = ESM] 

avgOAT = coded daily average ambient dry bulb temperature [–1 = min to +1 = max] 

Figure B-3. Building A13 predicted versus measured to evaluate goodness of fit 

of the regression model

90

110

130

150

170

190

210

230

250

90 110 130 150 170 190 210 230 250

Predicted Daily Energy Usage (kWh/day)

Measured Daily Energy Usage (kWh/day)
84 

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Appendix C: CATALYST Advanced Rooftop Control 

Retrofit Field Demonstration List
85 

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Appendix D: NAVFAC Routine Rooftop Unit 

Maintenance Procedures

NAVFAC provided its quarterly “Job Plan and Task Report,” which is shown in Figure D-1. 

Figure D-1. NAVFAC quarterly RTU maintenance procedure
86 

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Appendix E: Testing, Adjusting, and Balancing 

Results

The TAB was completed on February 16, 2013 for all 11 RTUs on all three buildings. Other than 

the tables showing the TAB results, this appendix focuses on TAB measurement error. Table E-1

shows the measured ventilation rates at two fan speeds: 40% and 90%. Unfortunately, measuring 

OA flow rates directly at the RTU OA intake has significant sensor and environmental 

uncertainties. 

• Sensor uncertainty. The TAB balancer used a pitot tube array that has a manufacturerspecified measurement range of 50–2,500 fpm; uncertainty is the larger of 7 fpm or 3% 

of reading. Based on the final TAB report, the OA inlet velocities were 0–600 fpm at the 

90% fan speed and 0–220 fpm at the 40% fan speed. Consequently, some of the velocity 

measurements for the 90% fan speed and most of the velocity measurements for the 40% 

fan speed were slower than the 50 fpm threshold measurement of the pitot tube array. 

• Environmental uncertainty. The TAB measured the OA intake velocity measurements 

outside the RTU cabinet and consequently was extremely susceptible to the wind. Even a 

1 mph wind equates to 88 fpm, which exceeded most of the air velocity measures at the 

40% fan speed. Typical TAB balancers will try to shield from the wind but will never 

block all impacts. 

Table E-1. TAB Measured Ventilation Rates Measured Including Error Band Based on the Sensor 

and Environmental Uncertainties Measure Air Velocity at OA Inlet Hoods with Pitot Tubes 

Building

Area 

Served 

by the 

RTUs

90% Fan Speeds

(Stage 1+2 DX @ 6% Damper 

Position)

40% Fan Speeds

(Fan Only @ 12% Damper Position)

+50% 

Error 

Banda

Actual 

TAB 

Readinga

–50% 

Error 

Banda

+150% 

Error 

Banda

Actual 

TAB 

Readinga

–150% 

Error 

Banda

1235H 

BXtra 69,576 ft2 11,019 cfm 7,346 cfm 3,673 cfm 9,678 cfm 3,871 cfm 0 cfm

C27 2,706 ft2 264 cfm 176 cfm 88 cfm 133 cfm 53 cfm 0 cfm

A13 7,834 ft2 1,277 cfm 851 cfm 426 cfm 838 cfm 335 cfm 0 cfm

a As shown in Unit 01, OA flow rate was 1,316 cfm at 40% capacity, which reduced to 613 cfm at 90% capacity. Realistically the 

slower fan speed at 40% capacity should have reduced the OA flow rate significantly. Furthermore, for Units 01–04, the OA 

damper blades were fixed shut, which should have reduced the OA flow rate to a reasonable leakage rate of ~200–300 cfm. 

Consequently, OA flow rates documented in the TAB procedure have a significant error. 

Based on the significant uncertainty with measuring ventilation flow rates, NREL assigned an 

error band around the actual TAB measurement shown in Table E-2 E-1. The 40% fan speed 

received three times the error caused by sensor and environmental uncertainties at its much small 

air velocities. NREL created the ± 50% uncertainty at the 90% fan speed and ± 150% uncertainty 

at the 40% fan speed (see Table E-1). NREL did not conduct a rigorous uncertainty analysis to 

develop these error bands and could find no documentation by the National Environmental 

Balancing Bureau, the Air Movement and Control Association International, Inc., or the 
87 

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Associated Air Balance Council to help quantify typical error bands. Each building was 

evaluated separately in Section 0. Tables E-2 thru E-4 provide the results of the TAB report. 
88 

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Table E-2. BXtra Supply Fan Flow Rates, Supply Fan Power, and OA Flow Rates at 100%, 90%, and 40% VFD Speeds

Eq_IDa

Calculated Performance 

at 100% Fan Speed

Based on TABb

TAB Report

CATALYST Ventilation Mode

(90% Capacity; Both Compressor Stages On) 

TAB Report

CATALYST Ventilation Mode

(40% Capacity; Fan Only) 

SA Total 

Static Powerc ɳtot SA Total Static Powerc OAFlowd

OA 

Damper

OA

Frac SA Total Static Powerc OA 

Flowd

OA 

Damper 

Position

OA

Frac

Unit 01 9,672 

cfm

1.95 

in. w.c. 8.2 kW 27% 8,705 cfm

1.58 

in. w.c. 6.0 kW 613 cfm

Fixed 

Closed 7% 3,513 cfm

0.28 

in. w.c. 1.0 kW 1,316 cfm – 37%

Unit 02 10,834 

cfm

1.96 

in. w.c. 7.0 kW 36% 9,751 cfm

1.59 

in. w.c. 5.1 kW 1,477 cfm

Fixed 

Closed 15% 3,630 cfm

0.29 

in. w.c. 0.7 kW 508 cfm – 14%

Unit 03 9,259 

cfm

2.07 

in. w.c. 7.0 kW 32% 8,333 cfm

1.68 

in. w.c. 5.1 kW 868 cfm

Fixed 

Closed 10% 3,637 cfm

0.28 

in. w.c. 0.8 kW 504 cfm – 14%

Unit 04 9,443 

cfm

2.00 

in. w.c. 6.0 kW 37% 8,499 cfm

1.62 

in. w.c. 4.4 kW 562 cfm

Fixed 

Closed 7% 3,818 cfm

0.29 

in. w.c. 0.7 kW 562 cfm – 15%

Unit 05 5,626 

cfm

1.60 

in. w.c. 1.9 kW 55% 5,063 cfm

1.30 

in. w.c. 1.4 kW 2,406 cfm 6% 48% 1,646 cfm

0.21 

in. w.c. 0.1 kW 790 cfm 12% 48%

Unit 06 4,124 

cfm

1.93 

in. w.c. 1.9 kW 49% 3,712 cfm

1.56 

in. w.c. 1.4 kW 168 cfm 6% 5% 1,251 cfm

0.24 

in. w.c. 0.1 kW 60 cfm 12% 5%

Unit 07 3,518 

cfm

0.81 

in. w.c. 1.2 kW 28% 3,166 cfm

0.66 

in. w.c. 0.9 kW 1,132 cfm

No 

Response 36% 810 cfm 0.11 in. w.c. 0.1 kW ?? No Response ??

Unit 08 3,310 

cfm

1.81 

in. w.c. 2.6 kW 27% 2,979 cfm

1.47 

in. w.c. 1.9 kW 120 cfm 6% 4% 1,182 cfm

0.22 

in. w.c. 0.3 kW 131 cfm 12% 11%

Unit 09 5,187 

cfm

0.59 

in. w.c. 1.6 kW 23% 4,668 cfm

0.48 

in. w.c. 1.2 kW NA – – 1,766 cfm

0.10 

in. w.c. 0.1 kW NA – – 

Total 60,973 

cfm

1.82 

in. w.c.

37.5 

kW 35% 54,876 cfm – 27.3 kW 7,346 cfm – 13% 21,253 cfm – 3.9 kW 3,871 

cfm – 18%

a RTU IDs based on numbering system previously established at the BXtra. All RTUs were numbered with spray paint on the roof, most likely during their installation.

b SA flow at 100% fan speed calculated based on the 90% speed SA flow rate assuming the maximum flow is 10% faster. Resultant fan power and total static based on fan laws using

90% fan speed TAB data.

c Power calculated as a function of average volts-amps across all three phases multiplied by the motor rated power factor. Note: actual power factor not measured by TAB balancer, 

which increases the uncertainty of the power calculation.

d OA flow rate measured by the TAB balancer at the damper entrance instead of being calculated based on the difference between the SA and RA duct traverses. Consequently, OA 

flow rates have a significant sensor error at low air velocities and environmental error caused by wind during the TAB measurements. For example, as shown in Unit 01, OA flow rate 

was 1,316 cfm at 40% capacity, which decreased to 613 cfm at 90% capacity. Realistically, the slower fan speed at 40% capacity should have reduced the OA flow rate significantly. 

Furthermore, for Units 01–04, the OA damper blades were fixed shut which should have reduced the OA flow rate to a reasonable leakage rate of ~200–300 cfm. Consequently, OA 

flow rates documented in the TAB procedure have a significant error.
89 

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Table E-3. BXtra MA and Leaving Air Conditions with Both Compressor Stages Operational During 90% Capacity TAB 

Eq_IDa

TAB Reporte

CATALYST Ventilation Mode

(90% Capacity; Both Compressor Stages) 

SA Total

Static Powerb OAFlowc

OA 

Damper 

Position

OA

Frac

MA Dry 

bulb

MA

WetBulb

MA

Dew 

Point

SA Dry 

bulb

SA

WetBulb

SA

Dew 

Point

Delta T

Dry 

bulb

Delta 

T 

Dew 

Point

SA RH

Unit 01 8,705 

cfm

1.58 

in. w.c. 6.0 kW 613 cfm Fixed Closed 7% 76.0°F 65.6°F 59.9°F 58.0°F 54.3°F 51.5°F 18.0°F 8.4°F 79%

Unit 02 9,751 

cfm

1.59 

in. w.c. 5.1 kW 1,477 cfm

Fixed 

Closed 15% 69.0°F–note d 61.8°F 57.5°F 49.0°F 46.5°F 44.1°F 20.0°F 13.4°F 83%

Unit 03 8,333 

cfm

1.68 

in. w.c. 5.1 kW 868 cfm Fixed Closed 10% 68.0°F–note d 63.6°F 61.2°F 50.0°F 47.1°F 44.4°F 18.0°F 16.8°F 81%

Unit 04 8,499 

cfm

1.62 

in. w.c. 4.4 kW 562 cfm Fixed Closed 7% 69.0°F–note d 61.8°F 57.5°F 54.0°F 51.5°F 49.5°F 15.0°F 8.0°F 85%

Unit 05 5,063 

cfm

1.30 

in. w.c. 1.4 kW 2,406 cfm 6% 48% 75.0°F 68.5°F 65.4°F 55.0°F 52.8°F 51.1°F 20.0°F 14.3°F 87%

Unit 06 3,712 

cfm

1.56 

in. w.c. 1.4 kW 168 cfm 6% 5% 77.0°F 68.5°F 64.4°F 54.0°F 50.7°F 47.9°F 23.0°F 16.4°F 80%

Unit 07 3,166 

cfm

0.66 

in. w.c. 0.9 kW 1,132 cfm

No 

Response 36% 72.0°F 65.8°F 62.6°F 53.0°F 49.6°F 46.6°F 19.0°F 15.9°F 79%

Unit 08 2,979 

cfm

1.47 

in. w.c. 1.9 kW 120 cfm 6% 4% 74.0°F 63.5°F 57.3°F 55.0°F 52.3°F 50.2°F 19.0°F 7.2°F 84%

Unit 09 4,668 

cfm

0.48 

in. w.c. 1.2 kW No OA Damper – – 72.0°F 62.4°F 56.6°F 58.0°F 53.7°F 50.4°F 14.0°F 6.2°F 76%

Total 54,876 

cfm – 27.3 kW 7,346 cfm – 13% – – – – – – – – – 

a RTU IDs based on numbering system previously established at the BXtra. All RTUs were numbered with spray paint on the roof, most likely during their installation. b Power calculated as a function of average volts-amps across all three phases multiplied by the motor rated power factor. Note power factor not measured by TAB balancer, which 

increases the uncertainty of the power calculation. c OA flow rate measured by the TAB balancer at the damper entrance instead of being calculated based on the difference between the SA and RA duct traverses. Consequently, OA 

flow rates have a significant error because of wind during the TAB measurements. For example, as shown in Unit 01, OA flow rate was 1,316 cfm at 40% capacity, which 

decreased to 613 cfm at 90% capacity. Realistically, the slower fan speed at 40% capacity should have reduced the OA flow rate significantly. Furthermore, for Units 01–04, the 

OA damper blades were fixed shut, which should have reduced the OA flow rate to a reasonable leakage rate of ~200–300 cfm. Consequently, OA flow rates documented in the 

TAB procedure have a significant error.

d MA temperatures were lower than expected because significant SA was entrained into the RA for Units 02–04. This entrainment also resulted in the inability to infer the space 

RH based on the RA RH. Entrainment also reduces the efficiency of the DX circuits by driving down the suction pressure and reducing the sensible cooling capacity. Note that 

Unit 01 has reasonable mix air temperature because it has sufficient ductwork that prevents SA entrainment into the RA.

e Dry bulb temperature drop across the evaporator coil ranging from 15°F to 23°F indicates that both DX stages are working adequately for all 9 RTUs.
90 

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Table E-4. Buildings A13 and C27 Supply Fan Flow Rates, Supply Fan Power, and 

OA Flow Rates at 100%, 90%, and 40% VFD Speeds

Eq_IDa

Calculated Performance 

at 100% Fan Speed

Based on TABb

TAB Report

CATALYST Ventilation Mode

(90% Capacity; Both Compressor Stages) 

TAB Report

CATALYST Ventilation Mode

(40% Capacity; Fan Only) 

SA Total 

Static Powerc ɳtot SA Total Static Powerc OA Flowd

OA 

Damper

OA

Frac SA Total Static Powerc OA 

Flowd

OA 

damper

OA

Frac

A13

Unit 02

6,726 

cfm

1.31 

in. w.c. 2.2 kW 47% 6,053 cfm

1.06 

in. w.c. 1.6 kW 851 cfm

Hand set to 

~50%-

motorized 

damper not 

installed yet

14% 2,633 

cfm

0.21 

in. w.c. 0.2 kW 335 cfm

Hand set to 

~50%-

motorized 

damper not 

installed yet

13%

C27

Unit 01

4,257 

cfm

1.60 

in. w.c. ? ? 3,831 cfm

1.30 

in. w.c. ? 176 cfm

Hand set to 

~0%-

motorized 

damper not 

installed yet

5% 1,571 

cfm

0.27 

in. w.c. 0.2 kW 53 cfm

Hand set to 

~0%-

motorized 

damper not 

installed yet

3%

a RTU IDs based on the numbering system previously established at the BXtra. All RTUs were numbered with spray paint on the roof, most likely during their installation.

b SA flow at 100% fan speed calculated based on the 90% speed SA flow rate assuming the maximum flow is 10% faster. Resultant fan power and total static based on fan laws using

90% fan speed TAB data.

c Power calculated as a function of average volts-amps across all three phases multiplied by the motor rated power factor. Note power factor not measured by TAB balancer, which 

increases the uncertainty of the power calculation. d OA flow rate measured by the TAB balancer at the damper entrance instead of being calculated based on the difference between the SA and RA duct traverses. Consequently, OA flow 

rates have a significant sensor error at low air velocities and environmental error caused by wind during the TAB measurements. For example, as shown in Unit 01, OA flow rate was 

1,316 cfm at 40% capacity, which decreased to 613 cfm at 90% capacity. Realistically, the slower fan speed at 40% capacity should have reduced the OA flow rate significantly. 

Furthermore, for Units 01–04, the OA damper blades were fixed shut which should have reduced the OA flow rate to a reasonable leakage rate of ~200–300 cfm. Consequently, OA 

flow rates documented in the TAB procedure have a significant error.
91 

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Table E-5. Buildings A13 and C27 MA and Leaving Air Conditions with Both Compressor Stages Operational During 90% Capacity TAB 

Eq_IDa

TAB Reportd

CATALYST Ventilation Mode

(90% Capacity; Both Compressor Stages) 

SA Total 

Static Powerb OA Flowc

OA 

Damper

OA

Frac

MA

Dry 

bulb

MA

WetBulb

MA

Dew 

Point

SA Dry 

bulb

SA

WetBulb

SA

Dew 

Point

Delta 

T 

Dry 

bulb

Delta 

T 

Dew 

Point

SA RH

A13

Unit 02

6,053 

cfm

1.06 

in. w.c. 1.6 kW 851 cfm

Hand set to 

~50%-

motorized 

damper not 

installed yet

14% Stage 2 Compressors not running at time of the TAB

C27

Unit 01

3,831 

cfm

1.30 

in. w.c. ? 176 cfm

Hand set to 

~0%-

motorized 

damper not 

installed yet

5% 70.0°F 64.7°F 61.9°F 53.0°F 51.9°F 51.0°F 17.0°F 10.8°F 93%

a RTU IDs based on a numbering system previously established at the BXtra. All RTUs were numbered with spray paint on the roof, most likely during their installation.

b Power calculated as a function of average volts-amps across all three phases multiplied by the motor rated power factor. Note power factor not measured by TAB balancer,

which increases the error band of the power calculation. c OA flow rate measured by the TAB balancer at the damper entrance instead of being calculated based on the difference between the SA and RA duct traverses. Consequently, 

OA flow rates have a significant error because of wind during the TAB measurements. For example, as shown in Unit 01, OA flow rate was 1,316 cfm at 40% capacity, which 

decreased to 613 cfm at 90% capacity. Realistically, the slower fan speed at 40% capacity should have reduced the OA flow rate significantly. Furthermore, for Units 01–04, the 

OA damper blades were fixed shut, which should have reduced the OA flow rate to a reasonable leakage rate of ~200–300 cfm. Consequently, OA flow rates documented in the 

TAB procedure have a significant error. d Dry bulb temperature drop across C27’s evaporator at 17°F indicates that both its DX circuits are operating properly. Unfortunately, stage 2 on building A13 needed 

maintenance and its operation was not documented during the TAB.
92 

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Appendix F: Buildings A13 and C27 Demand 

Response Results

The demand response sequence for A13 and C27 was slightly different compare to the BXtra. 

Both RTUs were included into the same sequence despite serving distinct buildings. The 

methodology is for applying one sequence to RTUs serving multiple buildings. 

The demand response sequence defines one RTU as lead and the other as lag. For buildings C27 

and A13, the units that were lead and lag alternated depending on the day. During a demand 

event, the second compressor is turned off in the lead unit for 15 minutes. If only one compressor 

is running, that compressor will be turned off. If no compressors are running, the system will 

take no action. At the end of each 15-minute period, one compressor in the lag unit will be turned 

off for 15 minutes while the lead RTU can turn back on one compressor. This process will 

continue for the entire demand period. The lead/lag sequence is alternated each day the demand 

response sequence is required.

The cooling set point temperature is lowered by 2°F before the demand period begins. During 

the demand event, the space temperature is allowed to float up 2°F above set point. At the end of 

the demand event, the space temperature is reset to its normal set point temperature. The monthly 

peak demand savings comparing the standard day, October 25, versus the demand response day, 

October 24, is provided in Table F-1. 

Table F-1. C27 and A13 Monthly Demand Savings

Maximum Peak 

on Standard 

Day

1:30pm-3:30pm

October 25, 

2013

 (kW) 

Maximum Peak 

on Demand 

Response Day

1:30pm-3:30pm

October 24, 

2013

 (kW) 

Maximum 

Peak 

Reduction

(kW) 

Maximum 

Peak 

Reduction

 (Watt/ft2) 

36.5 15.4 21.1 2.0

TWT had problems implementing the demand response sequence at C27 and A13. The sequence 

did not activate for the first few months of operation. A control technician reinitiated the control 

sequence and it operated successfully for 2 days. On the second day, A13 stopped responding to 

control signals from the ARC controller due to a maintenance issue unrelated to the 

CATALYST. When the A13 RTU was repaired, NREL decided to eliminate the C27-A13 DR 

sequence to focus on the energy savings. 

For the 2 days the sequence worked, the maximum peak demand from 1:30 pm to 3:30 pm was 

reduced by 21.1 kW. The power profiles for October 24 and 25 are provided in Figure F-1. 

Compared to the demand response sequence implemented on the BXtra, this sequence did not 

perform well. Small office buildings such as A13 and C27 have minimal thermal inertia and do 

not have the HVAC operational diversity to accommodate this sequence. Consequently, these 

types of buildings cannot be “charged” like a thermal battery such that the space can ride through 

a demand response event while maintaining thermal comfort. While there is some W/ft2

 demand 

response capability; however, the demand response sequence needs to be reworked. 
93 

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Figure F-1. C27 and A13 demand response for October

0

5

10

15

20

25

30

35

40

45

12:00 AM12:45 AM

1:30 AM2:15 AM3:00 AM

3:45 AM4:30 AM5:15 AM6:00 AM6:45 AM7:30 AM8:15 AM9:00 AM9:45 AM

10:30 AM11:15 AM

12:00 PM12:45 PM

1:30 PM2:15 PM3:00 PM3:45 PM4:30 PM5:15 PM6:00 PM

6:45 PM7:30 PM8:15 PM9:00 PM9:45 PM

10:30 PM11:15 PM

Peak Demand (kW)

C27 and A13 Demand Response for October 24th - 25th 

25th

DR -

24th
94 

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Appendix G: Economizing Performance Objective

OA economizers are not typically applied to HVAC systems in this climate zone. Yet these are a 

standard feature of ARC retrofit systems. Five units on the BXtra, C27, and A13 were retrofitted 

with electronic damper actuators and a differential dry bulb with dew point lockout economizer 

sequence. The percent of time that each unit operated in OA economizer mode from February 1 

through October 31 was calculated. Although there was slight variation from one unit to the next, 

the overall time in economizer mode was minimal (Table G-1). 

Table G-1. Percent of Time in OA Economizer Mode

Month

BXtra 05 BXtra 06 BXtra 07 BXtra 08 BXtra 09 C27 A13

Percent of 

Time in 

Economizer 

Mode

Percent of 

Time in 

Economizer 

Mode

Percent of 

Time in 

Economizer 

Mode

Percent of 

Time in 

Economizer 

Mode

Percent of 

Time in 

Economizer 

Mode

Percent of 

Time in 

Economizer 

Mode

Percent of 

Time in 

Economizer 

Mode

February 0.00% 0.00% 0.03% 0.00% 0.00% 0.51% 3.28%

March 0.02% 0.05% 0.02% 0.00% 0.00% 0.21% 1.53%

April 0.01% 19.57% 0.04% 0.11% 0.00% 0.28% 0.18%

May 0.00% 25.11% 0.00% 0.00% 0.00% 0.31% 0.25%

June 0.00% 40.32% 0.00% 0.02% 0.00% 0.06% 0.06%

July 0.00% 25.56% 0.00% 0.00% 0.00% 0.00% 0.01%

August 2.99% 30.09% 0.00% 0.00% 0.00% 0.00% 0.00%

September 0.0% 24.8% 0.0% 0.0% 0.0% 0.0% 0.0%

The average time in OA economizer mode across all units over the monitored period was 0.2%. 

In summary, the analysis shows that an OA economizer sequence is not recommended for this 

climate zone; the performance objective of operating in OA economizer mode for 1,300 hours 

annually could not be met. 
95 

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Appendix H: Coil Coating Performance Objective

The HVACArmor DX coating was applied to five of the 11 RTU evaporator and condenser coils 

shown in Table 1 and Table 2. All units of identical size were the same model and vintage. The 

units that did not receive the coating were intended to serve as the baseline to which the newly 

coated units could be compared. To provide a consistent basis of comparison, only data from 

March 7, 2013 to May 29, 2013 that met the following criteria were included in the analysis: 

• OA dry bulb temperature: 70°–80°F 

• RA dew point: 60°–65°F 

• Minimum 4-minute runtime for steady state condition

• Fan speed @ 100% (non-ESM operation only) 

• OA damper @ minimum position. 

A methodology was developed to compare the real-time coefficient of performance of RTUs 

with and without HVACArmor DX. Although the overall uncertainty of the calculated 

coefficient of performance is significant by compounding multiple measurement uncertainties, 

NREL considered the exercise likely to at least identify a performance trend. The results were 

inconsistent such that no trend could be established. In addition to the significant uncertainty, the 

other variables that impact RTU coefficient of performance such as refrigerant charge, poor oil 

distribution, condenser fan motor health, and thermostatic expansion valve operational impacts 

had too large an impact on coefficient of performance. Most of these variables cannot be 

measured with any level of confidence. 

To properly evaluate whether coil coatings impact RTU performance, a more detailed evaluation 

of the refrigeration cycle would need to be used to evaluate a sample of more than 30 similarly

sized RTUs. NREL recommends using a field monitoring product such as the ClimaCheck 

(www.climacheck.com) that can measure both the real-time cooling and compressor only power 

draw to a much greater accuracy than the methodology NREL used for this demonstration. The 

ClimaCheck could monitor the sample set pre- and post-coil coating such that each RTU’s

performance would be compared to itself. The combination of the larger sample set, improved 

measurement accuracy, and pre/post measurement should provide the level of detail needed to 

determine whether coil coatings impact RTU performance. 
96 

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Appendix I: Summary of Advanced Rooftop Control 

Savings in Other U.S. Climates

A multiyear research study was conducted by Pacific Northwest National Laboratory (PNNL), 

with funding from DOE’s Building Technologies Office and Bonneville Power Administration 

(BPA) to monitor the performance of 66 RTUs across eight locations (Wang et al. 2013). The 

objective was to determine the magnitude of energy savings achievable by retrofitting packaged 

RTUs with ARC systems. The evaluated RTUs were located in Cleveland, Ohio, (ASHRAE 

climate zone 5A); Oaks, Pennsylvania, (ASHRAE climate zone 4A), Valencia, California, 

(ASHRAE climate zone 3B), and Seattle, Washington, (under which all Washington sites fall)

(ASHRAE climate zone 4C). The building types included retail, office, food sales, and 

healthcare. Seventeen of the RTUs tested were heat pumps and the rest were traditional packaged 

units with gas heat.

The CATALYST ARC system evaluated in this Navy demonstration was the same used in the 

PNNL study. All the energy efficiency features evaluated were the same except for the specific 

type of economizer control. The PNNL demonstration evaluated differential dry-bulb control 

with a dry-bulb lock out. This demonstration evaluated differential dry-bulb control with a dewpoint lock out. 

The PNNL study focused solely on energy savings and did not measure the impacts on thermal 

comfort or demand response. PNNL did apply some FDD software tools to the various 

sequences of operation to ensure the OA economizer, DCV, and variable-speed fan settings were 

operating correctly.

Major findings from the PNNL report are highlighted below: 

• The ARC reduced the normalized annual RTU energy consumption by 22%– 90%, with 

an average of 57% reduction for all the RTUs. 

• Fan energy savings made a dominant contribution to the total RTU electricity savings; 

the heating and cooling energy savings varied by unit and were relatively smaller. The 

fan energy savings were 26%–94%, with an average of 74%.

• Normalized annual electricity savings per hour of fan/unit operation ranged from 0.47 

kWh/h (kWh per hour of fan/unit operation) to 7.21 –kWh/h, with an average of 2.39 

kWh/h. 

• Three utility rates were used to calculate a simple payback period: $0.05/kWh, 

$0.10/kWh and $0.15/kWh, resulting in average payback of 6, 3, and 2 years, 

respectively. This payback included the ARC system and labor for installation. 

Compared to the Navy demonstration in Hawaii, the PNNL demonstration showed a much 

higher average energy savings across the 66 RTUs, because the OA economizer and DCV 

features saved significantly more energy in the demonstration climate zones. Also compared to 

typical Hawaii operation, the RTUs in these other climate zones all spent less time in first- and 

second-stage cooling or heating modes and more time in ventilation mode, which increased the 

fan savings in the PNNL study. 
97 

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In summary, ASHRAE climate zone 1A will always have the lowest energy savings of all U.S. 

climate zones. The normalized energy savings from the PNNL report are provided in Table I-1. 

NREL modified the PNNL energy savings to match the metric used in this demonstration. These 

energy savings are averaged across the four climate zones in the PNNL report. As shown, the 

normalized energy savings changed dramatically based on the RTU system size. 

Table I-1. Normalized RTU ARC Electrical Energy Savings from PNNL Report

RTU Size Range Energy Savings

< 10 tons 103 kWh/ton per 1,000 h

10–15 tons 150 kWh/ton per 1,000 h

> 15 tons 282 kWh/ton per 1,000 h

Before the field demonstration began, PNNL conducted a thorough simulation study of ARC 

system energy savings across 16 climate zones in the continental United States (Wang 2011). 

Four building types were modeled: small office, standalone retail, strip mall, and supermarket. 

The annual energy savings from the PNNL energy simulation results are provided in Figure I-1. 

Figure I-1. ARC energy savings based on detailed energy modeling study across 16 climates and 

four building types 

Source: Wang et al. 2011
98 

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Appendix J: Practical Lessons Learned for Future 

NAVFAC Advanced Rooftop Control Installations

The following practical lessons learned are offered for follow-on ARC retrofit installations on all 

building types. Most were the result of insight gleaned during the demonstration. Some are 

specific to NAVFAC, predominantly based on COLS and NAFVAC Hawaii strict temperature 

set point and HVAC operating time requirements. 

Benefits of Bundling Web-Based BMS with Advanced Rooftop Control 

Retrofit

Sophisticated controls should be coupled with sufficient monitoring to extract their full value. 

The ARC retrofit can act as a standalone controller and can provide the annualized energy 

savings summarized in this report in the first 2 or 3 years after installation. However, HVAC 

energy-saving measures, especially those that focus on improved control, can lose their initial 

energy savings over the years. Oversight is necessary to ensure sustained energy savings. 

Bundling the Web-based BMS service with the ARC retrofit technology provides the necessary 

feedback so that: 

• Building energy managers can quickly ensure that temperature set points and schedules 

meet the latest NAVFAC requirements. 

• HVAC service technicians can quickly and easily verify proper system operation and 

leverage automated FDD alarming to be made aware of an issue before the system fails. 

The ARC energy savings shown in this report can be boosted through the BMS functionality, 

which enables NAVFAC to strictly enforce HVAC operational and temperature set point 

requirements. During the initial site surveys, NREL found nine of the 11 RTUs operating outside 

the correct temperature and operational schedules. The non-ESM baseline used in the 

demonstration used the proper set points and schedules. These energy savings are commonly 

called soft energy savings. They are very real but hard to quantify because they are due to 

improper operation based on human-machine interaction. Finally, the Web-based BMS provides 

monitored data of past performance that will be crucial for adjusting space temperature set points 

to meet RH requirements and other crucial adjustments. 

Benefits of Testing, Adjusting, and Balancing Conducted by an 

Advanced Rooftop Control Retrofit Installer

For this demonstration, NREL enforced a parsed down version of UFGS 23 05 93 “Testing, 

Adjusting, and Balancing for HVAC.” This modified specification still required a third-party 

TAB-certified contractor to balance the supply and OA flows. Although TWT’s standard 

CATALYST installation includes no TAB activity, TWT complied. 

Taking a step back, a comprehensive TAB for RTU ventilation rates is typically conducted on 

new construction projects when design drawings are available. RTU replacements or retrofits on 

existing buildings typically do not have engineered drawings and therefore no TAB is conducted. 
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When asked about standard procedure regarding balancing RTU OA dampers, a NAVFAC 

HVAC technician responded: 

I assume if an installation is being performed via a contract with a TAB 

requirement, then the damper would be adjusted to design specs. If we do an 

installation, we just use our judgment and leave the damper about 20% to 50% 

open depending on the actual damper size and tonnage of the unit. If the unit is 

undersized we tend to keep the OA at a very minimum position. If the occupants 

are complaining we would open the damper further. 

This comment matches NREL’s observations of OA damper positions during site visits. Before 

the CATALYST was installed, the six RTUs that had OA dampers seemed to be arbitrarily set to 

a 5%–20% open fixed position. 

Examining the benefits of the TAB activity and deliverables, NREL recommends an even further 

streamlined TAB procedure for future ARC retrofit installations: 

1. SA TAB. The SA shall be balanced according to NEBB TAB Procedural Standards 2005. 

The fan sheave, VFD, and ARC sequence shall be adjusted to ensure SA flow equals or 

exceeds (1) 300 cfm per nominal ton under first-stage cooling; (2) 350 cfm per nominal 

ton under second-stage cooling; and (3) 150 cfm per nominal ton during “fan only” 

operation. For cooling stages and fan only operation, the final TAB report will show the 

measured airflow, each phase amp draw and voltage upstream of the VFD, and makemodel of the TAB instruments used, including last calibration dates. 

2. OA TAB. NREL does not recommend balancing the ventilation flow rate at the OA 

damper because of the significant uncertainty caused by measurement inaccuracy at air 

speeds lower than 50 fpm and impacts of wind. The uncertainties will realistically exceed 

100% of the measured ventilation flow rate (see Appendix E). Instead, the OA flow rates 

should be calculated based on the measured SA flow rate minus the measured RA flow 

rate. The overall uncertainty of the SA and RA flow rates are significantly reduced 

because these air speeds exceed 50 fpm. 

3. Third-party, TAB-certified contractor. NREL recommends not using a third-party, 

TAB certified contractor to conduct the TAB activity. Instead, NREL recommends that 

the ARC contractor, whether TAB certified or not, conduct the TAB activity during the 

installation. One of the main reasons the ARC retrofit is cost effective is its fast and lowcost installation, typically taking 1 day per RTU. By using a third-party TAB contractor, 

the entire ARC installation activity becomes more complicated and expensive with 

minimal additional energy cost savings to offset the cost. Although a third-party TAB 

contractor enforces some level of independent oversight, balancing the SA properly is in 

the best interest of the ARC installer. An improperly balanced airflow rate will cause the 

coils to ice and require a call to the installer. It is in the installer’s best interest to conduct 

the SA TAB properly. Yet NAVFAC will need to use the TAB measured ventilation 

airflow rates to ensure that the OA damper configuration at different fan speeds meets 

ASHRAE 62.1 ventilation rates. 

4. DX Coil Performance Documentation. The TAB should include documenting the 

temperature deltas across the DX coils under first and second stage operation. To be 
100 

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assured of proper DX performance, the temperature delta should be 5-10°F under first 

stage cooling and 15-20°F under second stage cooling. Temperature deltas outside these 

ranges would indicate potential DX maintenance issues. The temperature reading 

measured downstream of the DX coil should be made after the supply fan to ensure that 

the air is properly mixed. Measuring the air immediately after the DX coil and before the 

supply fan may provide inaccurate readings since the air can be stratified for split-face 

coil arrangements.

5. Sight Inspection of Existing Ductwork and Gravity Dampers. Rather than conducting 

a detailed TAB to evaluate duct leakage, there is a greater cost benefit of conducting a 

visual inspection. Any unsealed seams or holes should be properly sealed. Also any 

gravity dampers that are provided on the RTU for return air relief should be sealed if the 

building is determined to not have sufficient positive pressure. Return air relief dampers 

are notoriously leakage and being located near the suction of the supply fan can cause 

unintentional OA intake. 

6. Building pressurization. The ventilation flow rates at the different fan speeds should be 

compared against any exhaust streams from the single zone. Most buildings have 

bathroom exhaust and some buildings will have additional exhausts such as commissaries 

with kitchen hoods. NAVFAC should ensure that the RTUs are properly balanced against 

any exhaust fans and ensure proper building pressurization. 

Space Temperature Sensor and Location

With aggressively warm temperature set point and HVAC operational requirements through 

NAVFAC Hawaii energy instructions and NAVFAC COLS requirements (see Appendix A), the 

ARC retrofit should include replacing the old thermostat with an accurate temperature sensor 

located near the center of the conditioned zone. Compared to a typical thermostat, the 

temperature sensor will transmit the actual space temperature to the ARC rather than simply 

cooling commands. Knowing the space temperature allows the ARC to make more detailed 

decisions about RTU operation. 

For future control flexibility, NREL recommends that the space sensor includes tenant set point 

adjustment and tenant override. To ensure that NAVFAC Hawaii and NAVFAC COLS 

operational and set point requirements are met, NREL recommends that the ARC sequence 

ignore the tenant set point adjustment and tenant override. This way, only NAVFAC-designated 

personnel, such as the building energy managers, have BMS Web access to adjust those 

schedules and set points. Yet, depending on the application, NAVFAC may decide to allow the 

tenants some override privileges. For example, during the demonstration, NREL enabled late day 

and weekend RTU operation for NAVFAC’s contracts department in building A13 at the end of 

the fiscal year. Rather than having the building energy manager make all these specialty changes, 

allowing the tenants some level of control for non-typical building operation may be easier. In 

short, including the space sensor tenant adjustment and override provides enough flexibility to 

find the correct control balance, including future flexibility if the building function changes. The 

NAVFAC AHJ should stipulate whether the tenant override control is included. 

The model series of temperature sensor, including transmitter, must have NIST-traceable 

accuracy to ± 2.0°F within the range of 60°–100°F. Although this is not required, NREL 

recommends that the space temperature sensor is ordered with a three-point factory calibration at 
101 

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60°F, 75°F, and 90°F reference temperatures. Sensor manufacturers typically charge only $25 to 

$50 for a three-point factory calibration, which ensures that the sensor meets or exceeds the 

manufacturer’s stated accuracy. If a factory calibration is not ordered, the temperature sensor 

once installed should be compared to a calibrated hand-held temperature sensor during the 

commissioning process. If the temperature sensor is not accurate, then it should be replaced. 

Space temperature sensor location is important. Building C27’s space temperature sensor was 

improperly located next to an exit door and was causing the RTU to provide too much cooling 

(see Section 4.2.2). The space temperature sensor should be located on an interior wall or column 

near the center of the conditioned space. The sensor should be 4–5 feet off the finished floor for 

a standard 8-foot ceiling. In the case of high ceilings, such as a retail space or warehouse, the 

space temperature sensor can be located above 5 feet but not more than 10 feet off the finished 

floor surface. The sensor should be at least 4 feet from any doors if along the same wall or 20 

feet if along a wall perpendicular to the door. If the thermostat does not meet these requirements, 

the space temperature sensor will need to change locations and new control wire will need to be 

pulled from the RTU. 

Space Relative Humidity Sensor (Recommended in Hawaii; Required 

in Guam)

This demonstration showed that RTU humidity control was not necessary for non-refrigerated 

spaces in Hawaii; however, NREL recommends that the space temperature sensor include a 

humidity sensor. NAVFAC Hawaii and NAVFAC COLS requirements are extremely aggressive 

about allowable RTU operation and warm temperature set points. NREL found that these 

aggressive requirements result in space RH > 65% during occupied and unoccupied times, which

causes occupant discomfort and potential mold growth (see Appendix A). 

For non-refrigerated Hawaii buildings, the space humidity sensor can be monitored through the 

Web-based BMS and provide feedback to NAVFAC about whether the temperature set points 

and schedules need to be adjusted to ensure the space RH does not exceed 65% during occupied 

and unoccupied hours. For example, in the case of buildings C27 and A13, a “morning 

dehumidification” sequence was added to enable the RTUs to operate 2 hours earlier than

NAVFAC Hawaii allowed for HVAC hours. The space RH was still maintained at < 65%, which 

provided acceptable thermal comfort despite warm occupied temperature set points. The RH also 

stayed below 65% during unoccupied times, which mitigates mold issues.

For all Guam buildings and refrigerated Hawaii buildings such as commissaries, the space RH

sensor should be installed to enable a separate dehumidification control sequence when the RH 

exceeds 65% during either occupied or unoccupied hours. The ARC system should then respond 

to a dehumidification call enabling both cooling stages plus reheat (hot gas or electric) if 

available. The humidity sensor series should have a NIST-traceable accuracy of ± 3% RH of 

40%–80%. 

The RH should never be inferred from an RA humidity sensor, as NREL found these to be 

influenced by ambient conditions if the ductwork was leaky or entrainment from the SA due to 

poorly designed air distribution systems. 
102 

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CO2 Sensor Accuracy and Drift Concerns

If the AHJ will accept the use of CO2 sensors for determining occupancy-based ventilation rates, 

there are certain installation and control provisions that can help ensure that the DCV operation 

maintains proper ventilation. The CO2 sensor can be factory calibrated and come with a 

certificate of calibration that is NIST traceable. This will cost an extra $50-100 per sensor but 

worth ensuring that the sensor being sent from the factory meets their specifications. Then during 

the commissioning process, the CO2 sensor in the space or RA duct should be spot checked 

against a calibrated hand-held CO2 sensor measuring the space CO2 concentration. NAVFAC 

can then be assured that the CO2 sensor whether in the space or RA duct is within a certain 

accuracy of the actual space CO2 concentration. Finally, the AHJ can stipulate a more 

conservative CO2 ppm concentration to initiate a call for additional ventilation. Typically, 1,000 

ppm is used as the concentration limit. The AHJ may want to specify 700 ppm as the 

concentration limit. Over the lifetime of the ARC system, the CO2 sensor should be spot checked 

by a calibrated hand-held CO2 sensor to maintain accuracy. The frequency should be based on 

the CO2 sensor manufacturer’s recommendations, which ranges from 5 to 15 years. Sometimes 

the expected life of the RTU will be shorter than the next time the CO2 sensor will need to be 

checked. In this case, the CO2 sensor can be expected to maintain sufficient ventilation over the 

life of the ARC technology. 

Equalizing Duty Cycle across Multiple Rooftop Units Serving a Single 

Space

The monitored data for the BXtra showed that Unit 01 under ESM and non-ESM operation 

provided most of the cooling. NAVFAC or the ARC retrofit installer (or both) should evaluate 

the monitored data and determine if the operational sequence and/or temperature sensor locations 

need to change to balance the duty cycle across the RTUs serving the same space. Having one 

RTU operate significantly longer than the other RTUs will cause O&M issues for that unit.

Post-Construction Meeting, Including NAVFAC HVAC Technician

Training

As a part of NAVFAC construction procedures, the ARC retrofit contractor must have a 

preconstruction meeting with the appropriate NAVFAC construction manager and engineering 

technician. NREL recommends that a post-construction meeting occur at some specified time, at 

least 1 month after the ARC installation and TAB are completed. NAVFAC and the ARC 

installer can review the performance data and ensure that expectations for RTU operational hours 

and space conditions are being met. This meeting can close the loop on several items, including 

whether proper space RH is being achieved, RTU duty cycles are balanced (if multiple RTUs 

serve the same space), ventilation rates are sufficient (satisfy occupant and CO2 concentrations), 

and the space temperature sensor is in the correct location. During this meeting, the ARC 

installer should provide training about Web-based BMS access and on-site troubleshooting to the 

applicable NAVFAC HVAC service technicians.
103 

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Appendix K: Demonstration Economic Analysis and 

Cost Details

Cost Information

As referenced in Section 5, cost reductions were assumed for the economic analysis of follow-on 

deployments of the CATALYST technology relative to demonstration actuals. Specific 

reductions and rationale follow: 

• Local distributor versus technology provider installation. For the demonstration, the 

ARC systems were installed by the technology provider. For non-demonstration 

acquisition, ARC systems would likely be provided and installed through a local 

distributor, significantly reducing travel and installation costs. 

• Overprescribed commissioning. Post-demonstration review of the TAB specifications 

used for the demonstration indicate they were likely overprescribed and presented a set of 

requirements and procedures that are not necessary in general acquisition and deployment 

of this technology. Estimated costs for commissioning follow-on installations were 

reduced based on engineering judgment. See Appendix J for recommendations regarding 

the follow-on TAB scope. 

eROI Analysis Information

Table K-1 provides a summary of key information regarding the eROI analyses developed for 

this project.
104 

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Table K-1. Key Information Regarding eROI Analyses Performed for This Report

eROI Analyses: Key Information

Input Type DD1391 Estimate Demo Actuals Follow-On Estimate

Date of Analysis August 21, 2012 Dec. 14, 2013 Dec. 14, 2013

eROI Version v.2.914 v2.9.16B v2.9.16B

Project Overview Tab 

Project Category Facility En. Impr. Facility En. Impr. Facility En. Impr.

Regional Priority Project No No No

Max. Financial Benefits Tab 

Salvage Value $4,000 $0 $0 

Provide Reliable Energy Tab 

MDI Critical Facilities 0 0 0 

Regulatory & SH Expect. Tab 

Regulatory Compliance 3 2 2 

Public Perception 0 0 0 

Quality of Service, Goals 1 1 1 

Quality of Service, # People 3 3 4 

Develop. Enabling Infrast. Tab 

Question 1, Data 

Improvement 2 2 2 

Question 2, Flex. Energy Inf. 2 1 1 

Question 3a, Energy Indep. 2 2 2 

Question 3b, % of 

Installations 25% 25% 25%

Project Risk Tab 

1. Timeline and Cost ± 10% ± 10% ± 25%

2. Energy Reduction ± 25% ± 10% ± 10%

3. a Facility Energy Reliance ± 10% ± 10% ± 10%

3.b Facility Outages ± 10% ± 10% ± 10%

3.c Backup Power ± 10% ± 10% ± 10%

4. Regulatory & Stakeholders ± 10% ± 10% ± 10%

5. Enabling Infrastructure ± 10% ± 10% ± 10%

6. Aggregate Benefits ± 25% ± 10% ± 10%

Impact of Deferring Tab 

Impact of Deferring 1 Year 100% Loss 0% Loss 0% Loss
105 

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Building Life Cycle Cost Analysis Information

Table K-2 provides a summary of key information regarding the BLCC analyses developed for 

this project.

Table K-2. Key Information Regarding BLCC Analyses Performed for This Report

BLCC Analyses: Key Information

Input Type Value

Report Type: MilCon

BLCC Version: 5.3

Location: Hawaii

Discounting Convention: Mid-Year

Analysis Type: Constant dollars

Base Date: October 1, 2013

Beneficial Occupancy: October 1, 2013

Length of Study: 10 years

Energy Usage Index: 100% throughout economic life

Investment Cost, Cost-Phasing: 0%

Major Repair and Replacement Costs: 

At 7.5 years $14,000 

Energy Escalation Factor:

a

 0%

Real Discount Rate: 3.0%

a DOE and state-specific escalation rates were not used because of recent pricing variability.