CHAPTER 5. ENGINEERING ANALYSIS 

TABLE OF CONTENTS 

5.1 INTRODUCTION ........................................................................................................... 5-3

5.2 METHODOLOGY OVERVIEW .................................................................................... 5-3

5.3 COST MODEL ................................................................................................................ 5-4

5.3.1 Manufacturer Selling Price Estimates.................................................................. 5-4

5.3.2 Downstream Analyses .........................................................................................5-5

5.3.3 Structure of the Cost Model Spreadsheet.............................................................5-5

5.3.4 Material Prices .....................................................................................................5-6

5.3.5 Results..................................................................................................................5-7

5.4 ENERGY CONSUMPTION MODEL ............................................................................ 5-7

5.4.1 Screened-In Technologies.................................................................................... 5-7

5.4.2 Screened-In Technologies Not Considered in the Engineering Analysis............5-8

5.4.2.1 Higher Efficiency Evaporator and Condenser Fan Blades ......................5-8

5.4.2.2 Low-Pressure Differential Evaporators ................................................... 5-8

5.4.2.3 Defrost Mechanisms ................................................................................ 5-9

5.4.3 Design Options..................................................................................................... 5-9

5.4.3.1 Higher Efficiency Lighting and Ballasts..................................................5-9

5.4.3.2 Higher Efficiency Evaporator Fan Motors ............................................5-11

5.4.3.3 Evaporator Fan Controls........................................................................ 5-12

5.4.3.4 Improved Evaporator Design................................................................. 5-12

5.4.3.5 Insulation Increases or Improvements ................................................... 5-14

5.4.3.6 Improved Glass Pack ............................................................................. 5-14

5.4.3.7 Higher Efficiency Condenser Fan Motors .............................................5-15

5.4.3.8 Increased Condenser Surface Area ........................................................ 5-15

5.4.3.9 Higher Efficiency Compressors............................................................. 5-17

5.4.4 Baseline Specifications ......................................................................................5-17

5.4.5 Non-Numerical Assumptions............................................................................. 5-20

5.4.6 Numerical Constants and Assumptions ............................................................. 5-20

5.4.7 Model Components............................................................................................5-21

5.4.7.1 Component Energy Consumption.......................................................... 5-22

5.4.7.2 Compressor Energy Consumption ......................................................... 5-23

5.4.7.3 Component Load Model ........................................................................ 5-23

5.4.7.4 Radiation Load Model ........................................................................... 5-23

5.4.7.5 Conduction Load Model ........................................................................5-24

5.4.7.6 Infiltration Load Model..........................................................................5-24

5.5 COST-EFFICIENCY CURVES .................................................................................... 5-25

5.6 RESULTS ...................................................................................................................... 5-32

REFERENCES ..........................................................................................................................5-33

LIST OF TABLES 

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Table 5.3.1 Major Manufacturing Processes .............................................................................. 5-6

Table 5.3.2 Calculated Core Case MSP...................................................................................... 5-7

Table 5.4.1 Performance Details for “Class A Lighting” Design Option.................................5-10

Table 5.4.2 Performance Details for “Class B Lighting” Design Option.................................5-11

Table 5.4.3 Performance Details for “Evaporator Fan Motor” Design Option ........................5-12

Table 5.4.4 Performance Details for “Improved Class A Evaporator Coil” Design Option ....5-13

Table 5.4.5 Performance Details for “Improved Class B Evaporator Coil” Design Option ....5-13

Table 5.4.6 Properties of Standard and Enhanced Class B Evaporator Coil ............................5-13

Table 5.4.7 Properties of Standard and Enhanced Class A Evaporator Coil............................5-14

Table 5.4.8 Performance Details for “Improved Glass Pack” Design Option..........................5-15

Table 5.4.9 Performance Details for “Improved Glass Pack” Design Option..........................5-15

Table 5.4.10 Performance Details for “Improved Class A Condenser Coil” Design Option...5-16

Table 5.4.11 Performance Details for “Improved Class B Condenser Coil” Design Option ...5-16

Table 5.4.12 Properties of Standard and Enhanced Class A Condenser Coil............................5-16

Table 5.4.13 Properties of Standard and Enhanced Class B Condenser Coil............................5-17

Table 5.4.14 Baseline Specifications........................................................................................ 5-18

Table 5.4.15 Class A Equipment Class Baseline Specifications.............................................. 5-19

Table 5.4.16 Class B Equipment Class Baseline Specifications .............................................. 5-19

Table 5.4.17 Energy Consumption Model Numerical Constants and Assumptions.................5-21

Table 5.4.18 Engineering Constants......................................................................................... 5-21

Table 5.5.1 Cost-Efficiency Data for the Small-Size Class A Equipment Class......................5-27

Table 5.5.2 Cost-Efficiency Data for the Medium-Size Class A Equipment Class .................5-28

Table 5.5.3 Cost-Efficiency Data for the Large-Size Class A Equipment Class......................5-29

Table 5.5.4 Cost-Efficiency Data for the Small-Size Class B Equipment Class......................5-30

Table 5.5.5 Cost-Efficiency Data for the Medium-Size Class B Equipment Class..................5-31

Table 5.5.6 Cost-Efficiency Data for the Large-Size Class B Equipment Class......................5-32

LIST OF FIGURES 

Figure 5.3.1 Components of MSP............................................................................................... 5-5

Figure 5.3.2 Full Production Cost Assessment Stages ............................................................... 5-5

Figure 5.4.1 Components of the Energy Consumption Model................................................. 5-22

Figure 5.5.1 Cost-Efficiency Curves for the Small-Size Class A Equipment Class.................5-27

Figure 5.5.2 Cost-Efficiency Curve for the Medium-Size Class A Equipment Class..............5-28

Figure 5.5.3 Cost-Efficiency Curves for the Large-Size Class A Equipment Class.................5-29

Figure 5.5.4 Cost-Efficiency Curve for the Small-Size Class B Equipment Class..................5-30

Figure 5.5.5 Cost-Efficiency Curve for the Medium-Size Class B Equipment Class..............5-31

Figure 5.5.6 Cost-Efficiency Curve for the Large-Size Class B Equipment Class ..................5-32

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CHAPTER 5. ENGINEERING ANALYSIS 

5.1 INTRODUCTION 

The engineering analysis establishes the relationship between manufacturer selling price 

(MSP) and daily energy consumption (DEC), measured in kilowatt hours per day (kWh/day), for 

the refrigerated beverage vending machines covered in this rulemaking. This cost-efficiency 

relationship serves as the basis for cost/benefit calculations for individual customers, 

manufacturers, and the Nation. In determining this relationship, the U.S. Department of Energy 

(DOE) estimates the increase in the manufacturer selling price associated with technological 

changes that reduce the energy consumption of the baseline models. 

The primary inputs to the engineering analysis are baseline information, data for each 

equipment class addressed in the market and technology assessment (chapter 3 in the TSD) and 

technology options from the screening analysis (chapter 4 in the TSD). Additional inputs include 

cost and energy consumption data that DOE estimated using a cost model and an energyconsumption model, respectively. The primary output of the engineering analysis is a set of costefficiency curves that show the relationship between MSP and daily energy consumption. In the 

subsequent markups analysis (chapter 6 in the TSD), DOE determines customer prices by 

applying distribution markups, sales tax, and contractor markups to the MSPs developed in the 

engineering analysis. After applying these markups, the data serve as inputs to the energy use 

characterization (chapter 7 in the TSD) and the life-cycle cost and payback period analyses 

(chapter 8 in the TSD). 

In this chapter, DOE discusses representative baseline units for each class, the 

methodology used to develop MSPs, the methodology used to estimate energy consumption, and 

output cost-efficiency curves. 

5.2 METHODOLOGY OVERVIEW 

This section describes the analytical methodology used in the engineering analysis. In 

this rulemaking, DOE is adopting a design-option approach, which calculates the incremental 

costs of adding specific design options to a baseline model. For each equipment class, DOE 

analyzed three different machine sizes to assess how energy use varies with refrigerated volume. 

A small-, medium-, and large-sized machine were picked for Class A and Class B equipment 

based on machines currently on the market. See chapter 3 of the TSD for a detailed description 

of the Class A and Class B equipment classes and section 5.4.4 below for additional detail on the 

different size machines analyzed. 

For each equipment class and size, DOE developed a core case cost using a 

manufacturing cost model. The core case cost is the full production cost of the structure, walls, 

doors, shelving and fascia of the case, but does not include the cost of any energy-using 

components. DOE developed pricing for each design option and added the design option pricing 

to the core case costs to arrive at the fully absorbed production cost for each equipment class and 

size at various efficiency levels. To derive the MSP of a machine at each efficiency level, DOE 

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added a typical profit to the fully absorbed cost of production. DOE also calculated the impact of 

each design option on DEC using an energy consumption model. The results of the engineering 

analysis are a set of cost-efficiency curves, in the form of MSP versus DEC, for three sizes of 

each equipment class. 

5.3 COST MODEL 

The cost model is a key analytical model used in constructing cost-efficiency curves. For 

beverage vending machines, the cost model was used to estimate the core case cost of a machine. 

The beverage vending machine cost model was adapted from a cost model developed for DOE’s 

rulemaking on commercial refrigeration equipment (CRE).a

 DOE believes this approach is 

acceptable given the similarities in materials and manufacturing processes between the two types 

of equipment. Development of the CRE cost model involved the disassembly of a self-contained 

commercial refrigerator, an analysis of the materials and manufacturing processes, and the 

development of a parametric spreadsheet model. DOE modified the CRE model to apply to 

beverage vending machines using input from interested parties on price estimates and its 

assumptions. Use of interested party input also confirmed the accuracy of the model adaptation. 

5.3.1 Manufacturer Selling Price Estimates 

The MSP includes the full cost of production and profit. The full production cost includes all 

direct and indirect costs to produce a unit. The manufacturer production cost is the sum of all the 

direct manufacturing costs: direct labor, direct material, and overhead (including investment 

depreciation) costs. The indirect costs for each unit are non-production cost elements, which 

include sales, general and administrative, research and development, and interest. To convert the 

full cost of production to MSP, a profit is added. The MSP includes all the production and nonproduction costs that make up the full production cost, as well as a profit. The components of 

MSP are shown in 

Figure 5.3.1. 

The cost of specific modelsor cost to an individual manufacturer to produce a 

refrigerated beverage vending machinewill vary depending on the equipment’s precise design 

and features, actual manufacturing processes, the equipment mix in the factory, and other 

production factors. There are also considerable differences in the levels of vertical integration 

that affect cost structure and, thus, the cost of equipment. Companies with a large market share 

and/or revenue base tend to be more vertically integrated than their smaller competitors. Yet, all 

manufacturers potentially buy at least some of their parts and/or subsystems from outside 

vendors. 

 

a

 See http://www.eere.energy.gov/buildings/appliance_standards/commercial_products.html for further detail on and 

validation of the CRE cost model. 

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Figure 5.3.1 Components of MSP 

5.3.2 Downstream Analyses 

The MSPs derived in the engineering analysis are important inputs to the life-cycle cost 

analysis (LCC) and the manufacturer impact analysis (MIA). In the LCC, the MSPs are 

necessary to calculate the total installed cost of each unit. In the MIA, DOE constructs a number 

of scenarios that analyze how different pricing schemes impact manufacturers financially. In the 

MIA, both MSP and the direct production cost components of MSP are important drivers of 

results. DOE discusses how the engineering analysis is used in the other analyses in chapters 8 

(LCC) and 13 (MIA) of the TSD. 

5.3.3 Structure of the Cost Model Spreadsheet 

DOE used a detailed, component-focused manufacturing cost assessment methodology to 

estimate the full production cost of machines from each equipment class analyzed in the cost 

model. In doing so, DOE took into account many factors that affect cost, including, for example, 

direct materials, direct labor, and factory overhead costs. Figure 5.3.2 shows the three major 

steps in generating the full production cost. 

Raw 

Materials 

Fabrication 

Processes 

Purchased Parts

Finished 

Materials 

Assembly 

Processes 

Bill of 

Materials 

Figure 5.3.2 Full Production Cost Assessment Stages 

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The first step in the full production cost assessment was creating a complete and 

structured bill of materials (BOM) from the disassembly of a commercial refrigerator with 

transparent doors. The commercial refrigerator was dismantled, and each part was characterized 

according to weight, manufacturing processes, dimensions, material, and quantity. The BOM 

includes the costs of materials, components, and fasteners. It also estimates the cost of raw 

materials and purchased parts. DOE based assumptions about the sourcing of parts and in-house 

fabrication on industry experience, information in trade publications, and discussions with 

manufacturers. During the BVM rulemaking, DOE’s contractors conducted interviews and plant 

visits with manufacturers to guide the adaptation of the commercial refrigeration BOM. 

Information was gathered to account for equipment designs specific to BVMs and ensure that the 

model’s methodology and pricing were accurate. 

After developing a detailed BOM, DOE identified the major manufacturing processes, 

listed in Table 5.3.1, and developed a spreadsheet model. DOE estimated fabrication process 

cycle times and entered them into the BOM. For this analysis, $24.00 per hour was used as the 

average fully burdened labor rate based on typical annual wages and benefits of industry 

employees. In the final step of the cost assessment, DOE estimated assembly times and 

associated direct labor costs. Once the cost estimate for each unit was finalized, DOE prepared a 

detailed summary of relevant components, subassemblies, and processes. 

Table 5.3.1 Major Manufacturing Processes 

Fabrication Finishing Assembly/Joining 

Fixturing Washing Adhesive Bonding 

Stamping/Pressing Powder Coating Spot Welding 

Brake Forming De-burring Seam Welding 

Cut and Shearing Polishing Inspecting & Testing 

Insulating 

5.3.4 Material Prices 

DOE determined the cost of raw materials by using prices for copper, steel, and 

aluminum from the American Metals Market.1

 Prices for rifled and unrifled copper tubing were 

obtained directly from a tubing manufacturer. DOE noted that there have been drastic 

fluctuations in metal prices over the last few years. To account for these large fluctuations, DOE 

used prices of metals that reflect a 5-year average of the Bureau of Labor Statistics Producer 

Price Indices (PPIs) spanning 2002 to 2006 with an adjustment to 2008$.2

 DOE used the PPIs 

for steel mill products and copper rolling, drawing, and extruding, and adjusted to 2008$ using 

the gross domestic product implicit price deflator.3

Between 2003 and 2006, the price of steel rose over 60 percent and the price of copper 

rose over 140 percent. Because DOE used a 5-year average in material prices from 2002 to 2006, 

these drastic increases are normalized to better represent long-term material price averages. 

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5.3.5 Results 

In order to calculate how additional components increase MSP, DOE first calculated a 

core case MSP for each equipment class. The MSP of each core case lacks any of the design 

options studied by DOE in the engineering analysis. Calculating the MSP of a unit without any 

studied design options allows DOE to construct the cost-efficiency relationship in conjunction 

with the energy consumption model. Table 5.3.2 displays the core case MSP calculated for each 

equipment class. 

Table 5.3.2 Calculated Core Case MSP 

Equipment Class 12-Ounce Can 

Capacity Size Designation Calculated Core MSP $ 

A 300 Small 1,449 

A 400 Medium 1,758 

A 500 Large 1,906 

B 450 Small 1,159 

B 650 Medium 1,330 

B 800 Large 1,382 

5.4 ENERGY CONSUMPTION MODEL 

The energy consumption model is another key analytical model used in constructing costefficiency curves. This model estimates the DEC of beverage vending machines in kWh/day at 

various performance levels using a design-options approach. DOE developed the energy 

consumption model as a Microsoft Excel spreadsheet and is making the model available to the 

public on DOE’s website at 

http://www1.eere.energy.gov/buildings/appliance_standards/commercial/beverage_machines.ht

ml. Appendix A of the TSD provides instructions for using the spreadsheet. 

For a given equipment class, the model estimates a DEC value for the baseline and DEC 

values for each of several performance levels above the baseline. The model calculates energy 

consumption at each performance level separately. DOE selected ENERGY STAR Tier 1 as the 

baseline level for each equipment class and machine size.4

 For the baseline level, DOE 

calculated a corresponding full production cost using the cost model (described in section 5.3

above). For each level above the baseline, DOE used the cost increases of the various design 

options to recalculate the full production cost. 

5.4.1 Screened-In Technologies 

In the market and technology assessment (chapter 3 of the TSD), DOE defined an initial 

list of technologies that can be used to reduce the energy consumption of refrigerated beverage 

vending machines. DOE then analyzed the following technology options: 

 higher efficiency lighting 

 higher efficiency lighting ballasts 

 higher efficiency evaporator fan motors 

 evaporator fan motor controllers 

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 higher efficiency evaporator fan blades 

 improved evaporator design 

 low-pressure differential evaporators 

 insulation increases or improvements 

 defrost mechanism 

 improved glass pack (for Class A machines only) 

 higher efficiency condenser fan motors 

 higher efficiency condenser fan blades 

 improved condenser design 

 higher efficiency compressors 

5.4.2 Screened-In Technologies Not Considered in the Engineering Analysis 

In the screening analysis (chapter 4 of the TSD), DOE narrowed this list by eliminating 

those technologies that can reduce the annual energy consumption of beverage vending machines 

but do not reduce DEC. DOE then screened out those technologies that were not feasible, were 

not practical to manufacture, reduced equipment utility, or were considered unsafe. 

The remaining list of screened-in technologies became an input to the engineering 

analysis. However, for reasons noted below, DOE did not incorporate all of these technologies in 

the energy consumption model. These include higher efficiency evaporator and condenser fan 

blades, low-pressure differential evaporators, and defrost mechanisms. 

5.4.2.1 Higher Efficiency Evaporator and Condenser Fan Blades 

Higher efficiency evaporator and condenser fan blades reduce motor shaft power 

requirements by moving air more efficiently. Current BVM designs use stamped sheet metal or 

plastic axial fan blades. These fan blades are lightweight and inexpensive. DOE was not able to 

identify any axial fan blade technology that is significantly more efficient than what is currently 

being used but did identify one alternative fan blade technology that might improve efficiency: 

tangential fan blades. These blades can produce a wide, even airflow improving air distribution 

across the evaporator coil. Improved air distribution has the potential to increase the saturated 

evaporator temperature (SET) and reduce compressor power. However, tangential fan blades are 

small and less efficient at moving air, and thus require greater motor shaft power. Because of 

these competing effects, DOE did not consider tangential fan blades as a design option. 

5.4.2.2 Low-Pressure Differential Evaporators 

Low-pressure differential evaporators reduce energy consumption by reducing the power 

required by evaporator fan motors. However, in space-constrained equipment, such as beverage 

vending machines, this reduction usually comes from a decrease in evaporator coil surface area. 

This surface area reduction generally requires a lower SET to achieve the same discharge air 

temperature and cooling potential, which reduces compressor efficiency. Because of these 

competing effects, DOE did not consider low-pressure differential evaporators as a design 

option. 

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5.4.2.3 Defrost Mechanisms 

Beverage vending machine evaporator coil defrosting is typically accomplished with offcycle defrost. Because off-cycle defrost uses no energy (and decreases compressor on-time), 

there is no defrost mechanism to reduce defrost energy consumption. Therefore, DOE did not 

consider it as a design option. 

5.4.3 Design Options 

After conducting the screening analysis and removing from consideration those 

technologies described above, the following technologies were implemented as design options in 

the energy consumption model: 

 higher efficiency lighting and ballasts (a combination of the first two design options 

listed above) 

 higher efficiency evaporator fan motors 

 evaporator fan motor controllers 

 improved evaporator design 

 insulation increases or improvements 

 improved glass pack (for Class A machines) 

 higher efficiency condenser fan motors 

 improved condenser design 

 higher efficiency compressors 

Each design option has two to four technology levels, ranging from the worst performing 

to the best performing technology. The design options and the technology levels for each design 

option are described below. 

5.4.3.1 Higher Efficiency Lighting and Ballasts 

Lighting is an important characteristic of beverage vending machines: it makes the 

product visible to the consumer in Class A machines and provides backlighting for product 

advertising in Class B machines. Lighting systems typically operate continuously and provide an 

opportunity for significant energy savings. As lighting system efficiency increases, total energy 

consumption can be decreased in two ways: reducing the lighting system’s electricity 

consumption and reducing the heat generated inside the refrigerated volume, which reduces the 

compressor work. 

It is important to avoid a reduction in the illumination of the machine front (in the case of 

Class B machines) or of the vended product (in the case of Class A machines) with more 

efficient lighting design options, because it decreases equipment utility – specifically, advertising 

ability. Therefore, DOE made every effort to maintain constant system utility among the lighting 

design options. This approach meant that DOE had to consider lighting as a system, rather than 

distinguishing lamps and ballasts as separate design options. This approach became more 

important when considering light emitting diode (LED) lighting systems, which do not require 

ballasts like fluorescent lighting systems. 

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Although LED systems generally have a lower efficacy than the fluorescent systems they 

replace, the fixtures used with LEDs direct light more effectively. As a result, the total lumen 

output of LED systems is lower than that of comparable fluorescent systems, but the amount of 

light incident on a surface (illuminance) is roughly equivalent. BVM manufacturers, lighting 

manufacturers, and other technical experts indicated that current LED technology provides 

adequate product lighting for Class A machines and, in most cases, is comparable to fluorescent 

lighting. For Class B machines, DOE originally believed that LED technology would be 

adequate, but BVM manufacturers indicated that utility would be lost. 

To account for variations in design between equipment classes, DOE used two lighting 

design options in the energy-consumption model. The first was for Class A machines and the 

second was for Class B machines. 

Class A machines illuminate the beverage containers being vended. Lamps must be sized 

to fit within the refrigerated space. DOE used 4-foot fluorescent lamps, based on the size of the 

transparent display front in machines currently on the market. DOE started with a minimum 

technology of T12 fluorescent lamps and magnetic ballasts, but today is using a baseline of T8 

fluorescent lamps with electronic ballasts, based on market data and conversations with BVM 

manufacturers. Additionally, these lamps were required to have a color rendering index (CRI) of 

approximately 80, which is typical for this type of equipment. 

After the ANOPR, DOE re-evaluated its engineering analysis assumptions for Class A 

LED lighting system designs. The assumptions used in the ANOPR were adapted from those 

used in the CRE NOPR for Vertical Closed Transparent equipment. For the BVM NOPR 

engineering analysis, DOE modified its LED design assumptions by; (1) updating LED energy 

consumption data to be consistent with the changes made between the CRE NOPR and CRE 

final rule; and (2) updating the LED system pricing based on commercially available LED 

retrofit kits which are designed specifically for Class A beverage vending machines. The energy 

consumption (lamp rated power) for a 4-ft, 1 row LED fixture decreased from 27.2 W in the 

ANOPR to 11.6 W for the NOPR. In addition, the efficacy increased from 50 Lu/W to 53.9 

Lu/W. The cost of the same fixture increased from $50.81 in 2007$ to $60.00 in 2008$. The 

LED specification modifications are reflected in the data in Table 5.5.1 below. 

 

Table 5.4.1 Performance Details for “Class A Lighting” Design Option 

Level Description Lamp Type 

Lamp 

Rated 

Power 

[watts (W)] 

Lamp 

Rated Light 

Output 

[Lumens] 

System 

Efficacy 

[Lumens/

W] 

System 

Light 

Output 

[Lumens] 

T12 4-ft T12, Magnetic F34T12 34.0 2,650 68.6 2,332 

T8 4-ft T8, Electric F32T8 32.0 2,850 85.0 2,679 

T8S 4-ft “Super” T8, 

Electric F32T8/HL 32.0 3,100 91.4 2,697 

LED 4-ft LED 4-ft LED 11.6 625.6 53.9 625.6 

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Traditionally, Class B machines use 5- or 6-foot, high-output (HO) T12 fluorescent lamps 

and magnetic ballasts to draw consumers’ attention to product logos and signal that the machine 

is functioning. DOE used this configuration as the minimum technology option. However, with 

the increase in demand from customers for ENERGY STAR qualified machines, BVM 

manufacturers have started using T8 fluorescent lamps, so DOE used this as the baseline. Some 

beverage vending machine customers dictate certain size fluorescent lamps (to reduce the 

number of lamp types that lighting repair personnel carry on their trucks). As a result, DOE used 

a 4-foot and a 2-foot T8 lamp to replace a 6-foot T12 lamp. These lamps were also required to 

have a CRI of approximately 80, which is typical for this type of equipment. 

After the ANOPR, Class B LED lighting system assumptions were also modified. The 

assumptions used in the ANOPR were also adapted from those used in the CRE NOPR for 

Vertical Closed Transparent equipment. For the NOPR engineering analysis, Class B LED 

assumptions were modified by: (1) updating LED energy consumption and pricing data to be 

consistent with the changes made between the CRE NOPR and CRE final rule; and (2) updating 

the fixture replacement ratio when moving from a fluorescent to a LED lighting system. The 

energy consumption (lamp rated power) for a 6-ft, 1 row LED fixture decreased from 33.4 W in 

the ANOPR to 22.5 W for the NOPR. In addition, the efficacy increased from 50 Lu/W to 59.2 

Lu/W. The cost of the same fixture increased from $50.81 in 2007$ to $134.67 in 2008$. To 

model use of LED systems in Class B equipment for the ANOPR, DOE used a 1 to 1 fixture 

replacement ratio when substituting an LED lighting system for the fluorescent system. As 

mentioned previously, manufacturers commented that more LED fixtures than fluorescent 

fixtures are needed to sufficiently backlight a closed front machine. As a result, DOE increased 

the ratio to 1.5 to 1. For the NOPR, when the LED design option is implemented in the 

engineering analysis 1.5 LED fixtures are used to replace each fluorescent fixture. The Class B 

LED specification modifications are reflected in the data in Table 5.4.2 below. 

Table 5.4.2 Performance Details for “Class B Lighting” Design Option 

Level Description Lamp Type 

Lamp 

Rated 

Power 

[W] 

Lamp Rated 

Light 

Output 

[Lumens] 

System 

Efficacy 

[Lumens

/W] 

System 

Light 

Output 

[Lumens] 

T12HO 6-ft., T12 HO 

Magnetic 

F72T12/ 

HO/SP 85.0 6,550 64.9 5,960 

T8 2-ft. T8 & 4–ft. T8 

Electric 

F17T8 & 

F32T8 49.0 4,250 90.4 3,910 

LED 6-ft. LED - 22.5 2,001 59.2 2,001 

5.4.3.2 Higher Efficiency Evaporator Fan Motors 

In conjunction with fan blades, fan motors are necessary to transfer heat from the 

refrigerated space to the refrigerant. In most situations they operate nearly continuously and, 

therefore, use a significant amount of energy. As motor efficiency increases, energy consumption 

decreases due to a direct reduction in electricity consumption and waste heat inside the 

refrigerated space. 

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Table 5.4.3 shows details for the evaporator fan motor design option. Currently, DOE 

considers shaded-pole motors (SPM) as the minimum technology, permanent split capacitor 

(PSC) motors as the mid-level technology, and brushless direct current (DC) or electronically 

commutated motors (ECMs) as the maximum technology. The motor efficiencies listed in Table 

5.4.3 are from Energy Savings Potential for Commercial Refrigeration Equipment, prepared by 

Arthur D. Little in 1996.5 

Table 5.4.3 Performance Details for “Evaporator Fan Motor” Design Option 

Shaded-Pole Motor (SPM) Permanent Split Capacitor 

(PSC) Motor 

Brushless DC Motor 

(ECM) Rated Power 

[W] Actual 

Power 

[W] 

Efficiency 

Actual 

Power 

[W] 

Efficiency 

Actual 

Power 

[W] 

Efficiency 

15.0 75.0 20.0% 33 45.5% 20.5 73.2% 

9.0 53.0 17.0% 21 42.9% 12.5 72.0% 

6.0 40.0 15.0% 15 40.0% 8.5 70.6% 

5.4.3.3 Evaporator Fan Controls 

Beverage vending machine manufacturers typically design evaporator fans to operate 

continuously. Circulating warm air through the case during compressor off-times prevents the 

evaporator coil from icing over. However, manufacturers indicated during interviews that, under 

typical conditions, the evaporator fan is not required to run during all compressor off-times to 

keep the coils ice-free. Because of this, DOE developed a design option with controls to turn off 

the evaporator fan during compressor off-time and a period of fan operation to accomplish offcycle defrost. Based on discussions with outside experts and beverage vending machine 

manufacturers, DOE estimated that a total of 1.5 hours of off-cycle defrost operation would be 

required during a 24-hour period. To assess the total cost of this design option, DOE took into 

account the additional cost of parts, engineering, and increased labor for assembly. 

5.4.3.4 Improved Evaporator Design 

Evaporator coils are another component necessary to transfer heat from the refrigerated 

space to the refrigerant. Table 5.4.4 and 

Table 5.4.5 show details for the evaporator coil design option. Based on available 

information, DOE considered a minimum and a maximum technology level for this design 

option. DOE analyzed different evaporator coils given the differences in design load between 

Class A and Class B machines. For each level, DOE specified an overall UA-valueb

 and a coil 

cost. The UA-value is normalized to the standard coil, and the coil cost is normalized to the heat 

removal capacity of the coil. This allowed DOE to apply these details of coil design across all 

equipment sizes. In consultation with outside experts, DOE determined that the same coil 

improvements applied to different-sized coils would result in similar performance improvements. 

 

b

 The overall UA-value is the product of the overall heat transfer coefficient (British thermal units per hour (Btu/h)-

ft2

-°F) and the total surface area (ft2) of the coil. This value can be derived from the total heat transfer rate of the coil 

(Btu/h) divided by the log mean temperature difference of the air and refrigerant flows (ΔTLM). 

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EERE-2006-STD-0125 COMMENT 46
Table 5.4.4 Performance Details for “Improved Class A Evaporator Coil” Design Option 

Level Description Normalized UA [-] Normalized Coil Cost 

[$/Btu/h] 

FEV1 Standard Coil 1 $0.0058 

FEV2 High-Performance Coil 1.605 $0.0125 

Table 5.4.5 Performance Details for “Improved Class B Evaporator Coil” Design Option 

Level Description Normalized UA [-] Normalized Coil Cost 

[$/Btu/h] 

ZEV1 Standard Coil 1 $0.0066 

ZEV2 High-Performance Coil 1.646 $0.0143 

The details of coil construction (shown in Table 5.4.6 and Table 5.4.7) were based on a 

baseline and prototype high-performance coil evaluated in a study by the Refrigeration and 

Thermal Test Center (RTTC) at Southern California Edison.6

 The high-performance coil uses a 

combination of enhancements to the heat transfer surfaces that increased its overall UA-value. 

These enhancements include a slightly higher fin pitch and different fin material. In summary, 

these changes result in an increased UA-value and increased coil cost. The increase in UA-value 

leads to an increase in the coil SET. Because compressor performance is directly related to SET, 

reductions in total case energy consumption are realized through an improved energy efficiency 

ratio (EER) at the condensing unit. In consultation with outside experts, DOE determined that the 

same coil improvements applied to differently sized coils at different temperatures would result 

in similar UA-value improvements. 

Table 5.4.6 Properties of Standard and Enhanced Class B Evaporator Coil 

Property Standard Coil High-Performance Coil 

Overall Width (in) 24 24 

Overall Height (in) 6 6 

Overall Depth (in) 3 3 

Tube Rows per Circuit 15 15 

Number of Parallel Circuits 1 1 

Tubing Material Copper Copper 

Tubing Outer Diameter (in) 3/8 3/8 

Tubing Wall Thickness (in) 0.012 0.012 

Tubing Inner Surface Smooth Smooth 

Fin Material Aluminum Copper 

Fin Surface Flat Wavy 

Fin Dimensions (in) 3 x 6 3 x 6 

Fin Pitch (fins per inch) 6 7 

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EERE-2006-STD-0125 COMMENT 46
Table 5.4.7 Properties of Standard and Enhanced Class A Evaporator Coil 

Property Standard Coil High-Performance Coil 

Overall Width (in) 12 12 

Overall Height (in) 8 8 

Overall Depth (in) 3 3 

Tube Rows per Circuit 28 28 

Number of Parallel Circuits 1 1 

Tubing Material Copper Copper 

Tubing Outer Diameter (in) 3/8 3/8 

Tubing Wall Thickness (in) 0.012 0.012 

Tubing Inner Surface Smooth Smooth 

Fin Material Aluminum Copper 

Fin Surface Flat Wavy 

Fin Dimensions (in) 3 x 8 3 x 8 

Fin Pitch (fins per inch) 7 8 

5.4.3.5 Insulation Increases or Improvements 

Increasing or improving insulation decreases the conduction load, which reduces 

compressor energy consumption. DOE looked at two different methods of reducing the 

conduction load. The first method was a 1/8-inch increase in insulation thickness in all insulated 

panels. DOE assumed this addition required the machine to expand outward rather than inward, 

because an expansion inward would likely reduce the capacity to store canned or bottled 

beverages. DOE also accounted for the increased core case costs (due to the larger shell), design 

time, and fixture retooling. 

The second method DOE explored was changing the insulation material. Currently, 

beverage vending machines use foamed-in-place polyurethane as the primary insulation material. 

After discussions with insulation manufacturers, industry experts, and BVM manufacturers, 

DOE concluded that there are no significant variations among different polyurethane foams and 

blowing agents. Thus, DOE did not consider improvements in polyurethane foams or blowing 

agents. DOE also did not consider vacuum panels because they cannot provide the structural 

support of foamed-in-place designs, and cannot accept the bolts and fasteners typically used on 

the skins and frame that house the insulation. However, DOE did consider aerogels as a 

replacement for foamed-in-place polyurethane. DOE considered an open cell, silica-based 

aerogel that comes in an expansion pack and is expanded to fit the insulation cavity. 

5.4.3.6 Improved Glass Pack 

An improved glass pack design option only applies to Class A machines. Improvements 

to the glass pack (a prefabricated assembly of glass sheets, coatings, framing, and fill gas) result 

in less heat transfer to the refrigerated volume by radiation and conduction. This reduces the heat 

load on the refrigerant and hence the compressor load, thus reducing compressor energy 

consumption. The glass pack can be improved several ways, including adding panes of glass, 

adding low-emissivity (low-E) coating, changing from air fill to argon fill, and changing from an 

aluminum frame to a vinyl frame. Rather than examine each variation as an individual design 

option, DOE looked at three different option packages, shown in Table 5.4.8. 

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EERE-2006-STD-0125 COMMENT 46
The design options shown in Table 5.4.8 were then entered into WINDOW 5.27

 to yield 

U-valuesc

 that account for heat transfer due to radiation and conduction at each of the test 

conditions set forth in American National Standards Institute (ANSI)/American Society of 

Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) Standard 32.1–2004, 

Methods of Testing for Rating Vending Machines for Bottled, Canned, and Other Sealed 

Beverages.

8

 Table 5.4.9 catalogs the resulting U-values. 

Table 5.4.8 Performance Details for “Improved Glass Pack” Design Option 

Variable Baseline Enhanced Super Enhanced 

Frame Material Aluminum Aluminum Vinyl 

Number of Panes 2 2 3 

Glass Type: Panel 1 Clear Clear Clear 

Glass Type: Panel 2 Clear Low-E Low-E 

Glass Type: Panel 3 - - Clear 

Gas Fill Air Argon Argon 

Table 5.4.9 Performance Details for “Improved Glass Pack” Design Option 

Level Description 

Overall U-Factor at the 

ASHRAE 32.1 75F Test 

Condition [Btu/h-ft-°F] 

Overall U-Factor at 

the ASHRAE 32.1 

90F Test Condition 

[Btu/h-ft-°F] 

DOOR 1 Baseline 0.704 0.717 

DOOR 2 Enhanced 0.447 0.455 

DOOR 3 Super-Enhanced 0.292 0.298 

5.4.3.7 Higher Efficiency Condenser Fan Motors 

 Performance details for the condenser fan motor design option are identical to those 

shown in Table 5.4.3. As with evaporator fan motors, the SPM is the minimum technology level, 

the PSC motor is the mid-level technology, and the DC motor or ECM is the maximum 

technology level. Because condenser fan motors are outside the refrigerated space, efficiency 

improvements only impact the direct electrical consumption of the motors and not the total case 

heat load. 

5.4.3.8 Increased Condenser Surface Area 

Condenser coils reject heat from the refrigerant to the ambient air. Based on available 

information, DOE considered both minimum and maximum technology levels for this design 

option. For each level, DOE specified an overall UA-value and a coil cost, shown in Table 5.4.10

and Table 5.4.11. The UA-value is normalized to the standard coil, and the coil cost is 

normalized to the heat removal capacity of the coil. This allowed DOE to apply these details of 

coil design across all equipment sizes. In consultation with outside experts, DOE determined that 

the same coil improvements applied to different-sized coils would result in similar performance 

improvements. 

 

c

 U-value is a measure of air-to-air heat transmission (loss or gain) due to thermal conductance and the difference in 

indoor and outdoor temperatures. 

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EERE-2006-STD-0125 COMMENT 46
Table 5.4.10 Performance Details for “Improved Class A Condenser Coil” Design Option 

Level Description Normalized 

UA [-] 

Normalized Coil 

Cost [$/Btu/h] 

FCO1 Standard Coil 1 $0.006 

FCO2 High-Performance Coil 1.74 $0.015 

Table 5.4.11 Performance Details for “Improved Class B Condenser Coil” Design Option 

Level Description Normalized 

UA [-] 

Normalized Coil 

Cost [$/Btu/h] 

ZCO1 Standard Coil 1 $0.006 

ZCO2 High-Performance Coil 1.67 $0.019 

As previously mentioned, details of coil construction (shown in Table 5.4.12 and Table 

5.4.13) were based on a baseline and prototype high-performance coil evaluated in a study by 

RTTC. The high-performance coil uses a combination of enhancements to the heat transfer 

surfaces that increased its overall UA-value. These enhancements include higher fin pitch and 

different fin material. In sum, these improvements give the prototype coil a higher UA-value, 

allowing the coil to run at a saturated condenser temperature (SCT) cooler than the baseline coil 

while maintaining the same heat rejection rate. DOE did not consider rifled tubing because the 

refrigerant flow rates in beverage vending machines are typically not high enough to trigger 

turbulent flow. Because compressor performance is directly related to SCT, reductions in total 

case energy consumption are realized through an improved EER at the condensing unit. 

Table 5.4.12 Properties of Standard and Enhanced Class A Condenser Coil 

Property Standard Coil High-Performance Coil 

Overall Width (in) 21 21 

Overall Height (in) 10 10 

Overall Depth (in) 4 4 

Tube Rows per Circuit 36 36 

Number of Parallel Circuits 1 1 

Tubing Material Copper Copper 

Tubing Outer Diameter (in) 3/8 3/8 

Tubing Wall Thickness (in) 0.012 in 0.012 in 

Tubing Inner Surface Smooth Smooth 

Fin Material Aluminum Copper 

Fin Surface Flat Wavy 

Fin Pitch (fins per inch) 4 5 

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EERE-2006-STD-0125 COMMENT 46
Table 5.4.13 Properties of Standard and Enhanced Class B Condenser Coil 

Property Standard Coil High-Performance Coil 

Overall Width (in) 12.5 24 

Overall Height (in) 10 10 

Overall Depth (in) 2.25 3 

Tube Rows per Circuit 28 16 

Number of Parallel Circuits 3 2 

Tubing Material Copper Copper 

Tubing Outer Diameter (in) 3/8 3/8 

Tubing Wall Thickness (in) 0.012 in 0.012 in 

Tubing Inner Surface Smooth Rifled 

Fin Material Aluminum Aluminum 

Fin Surface Flat Flat 

Fin Pitch (fins per inch) 6 7 

5.4.3.9 Higher Efficiency Compressors 

In consultation with compressor manufacturers and external technical experts, DOE 

determined that two levels of technology were applicable for the compressor design option. The 

minimum technology level is a standard single-speed hermetic compressor, and the maximum 

technology level is a high-efficiency single-speed hermetic compressor (see chapter 4 of the TSD 

for a discussion of why variable-speed compressors were not considered). Reductions in total 

case energy consumption are realized through a reduction in compressor power consumption. 

DOE collected performance data for standard single-speed hermetic compressors from 

several manufacturers over a range of capacities applicable to the covered equipment (1,000 – 

4,000 Btu/h). This data set was used to look up appropriately sized compressors when 

developing each design-option curve (see section 5.4.7.2 below for information on the 

calculation of compressor energy consumption). Although several compressor manufacturers 

produce high-efficiency compressors, little data are currently available on their performance. 

Therefore, DOE approximated a set of high-efficiency compressors by adjusting the power 

consumption of the standard compressors using a constant multiplier. DOE developed this 

multiplier through research and consultation with experts. 

5.4.4 Baseline Specifications 

DOE defined baseline specifications for each equipment class. These specifications 

include dimensions, numbers of components, temperatures, nominal power ratings, and other 

case features that are necessary to calculate the energy consumption of each equipment class. In 

conjunction with the typical technological level of each design option (see section 5.4.3 above), 

the baseline specifications define the energy consumption and cost of the typical-efficiency 

equipment on the market. DOE also provided details on minimum technology options for design 

options that are typically below the efficiency of currently available equipment. DOE did this 

because a small portion of the market does not meet the voluntary ENERGY STAR Tier 1 level. 

Table 5.4.14 below shows the specifications and units that are defined for each equipment class. 

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EERE-2006-STD-0125 COMMENT 46
Table 5.4.14 Baseline Specifications 

Specification Units 

Refrigerated Volume ft3 

Number of Lamps in Refrigerated Volume - 

Number of Lamps not in Refrigerated Volume - 

Number of Ballasts in Refrigerated Volume - 

Number of Ballasts not in Refrigerated Volume - 

Evaporator Fan Nominal Rated Wattage W (Watts) 

Number of Evaporator Fans - 

Condenser Fan Nominal Rated Wattage W 

Number of Condenser Fans - 

Average Refrigerated Volume Temperature F (Fahrenheit) 

Nominal SET F 

Nominal SCT F 

Nominal Discharge Air Temperature (DAT) F 

Nominal Compressor Sizing Btu/h 

Solid Wall Area (including the door for Class B Machines) ft2

Glass Area ft2

Baseline Air Infiltration lb/hour 

Load from Electronic Components (bill changers, LED displays, etc.) kWh 

DOE established baseline specifications for each of the equipment classes modeled in the 

engineering analysis by reviewing available manufacturer data, selecting several representative 

units from available manufacturer data, and then aggregating the physical characteristics of the 

selected units. The baseline specifications were chosen so that the baseline machines met 

ENERGY STAR Tier 1 criteria (see chapter 3 of the TSD for further details on the criteria). This 

process created a representative unit for each equipment class with average characteristics for 

physical parameters (e.g., volume, wall area), and typical performance for energy-consuming 

components (e.g., fans, lighting). 

DOE modified some of the baseline specifications assumed in the ANOPR to represent 

equipment currently available on the market. For Class A, DOE modified the exterior case 

dimensions, can capacities, and other associated specifications. For Class B, DOE verified the 

assumed can capacities, but modified the exterior case dimensions and other associated 

specifications. For both classes, changes to case dimensions resulted in modifications to 

infiltration loads, refrigerated volumes and exterior wall areas. Table 5.4.15 and Table 5.4.16

show the results for each equipment class and size. Table 5.4.15 and Table 5.4.16 also include 

the 12-oz. can capacity of each size machine, for reference. 

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EERE-2006-STD-0125 COMMENT 46
Table 5.4.15 Class A Equipment Class Baseline Specifications 

Specification Small Medium Large 

Refrigerated Volume [ft3] 17 22 34 

12 oz. Can Capacity [#] 300 400 500 

Number of Lamps in Refrigerated Volume [#] 2 2 2 

Number of Lamps not in Refrigerated Volume [#] 0 0 0 

Number of Ballasts in Refrigerated Volume [#] 0 0 0 

Number of Ballasts not in Refrigerated Volume [#] 1 1 1 

Evaporator Fan Nominal Rated Wattage [W] 9 9 9 

Number of Evaporator Fans [#] 1 1 1 

Condenser Fan Nominal Rated Wattage [W] 9 9 9 

Number of Condenser Fans [#] 1 1 1 

Average Refrigerated Volume Temperature [F] 36 36 36 

Nominal SET [F] 8 8 8 

Nominal SCT [F] 95 95 95 

Nominal Discharge Air Temperature (DAT) [F] 19 19 19 

Nominal Compressor Sizing [Btu/h] 2,400 2,900 2,900 

Solid Wall Area (including the door for Class B Machines) [ft2] 34 46 51 

Glass Area [ft2] 8 9 11 

Baseline Air Infiltration [lb/hour] 7 8 11 

Load from Electronic components (bill changers, LED displays, 

etc.) [kWh] 0.45 0.45 0.45 

Table 5.4.16 Class B Equipment Class Baseline Specifications 

Specification Small Medium Large 

Refrigerated Volume [ft3] 17 22 26 

12 oz. Can Capacity [#] 450 650 800 

Number of Lamps in Refrigerated Volume [#] 0 0 0 

Number of Lamps not in Refrigerated Volume [#] 2 2 2 

Number of Ballasts in Refrigerated Volume [#] 0 0 0 

Number of Ballasts not in Refrigerated Volume [#] 1 1 1 

Evaporator Fan Nominal Rated Wattage [W] 9 9 9 

Number of Evaporator Fans [#] 2 2 2 

Condenser Fan Nominal Rated Wattage [W] 9 9 9 

Number of Condenser Fans [#] 1 1 1 

Average Refrigerated Volume Temperature [F] 39 39 39 

Nominal SET [F] 12 12 12 

Nominal SCT [F] 98 98 98 

Nominal Discharge Air Temperature (DAT) [F] 27 27 27 

Nominal Compressor Sizing [Btu/h] 2,300 2,400 2,400 

Solid Wall Area (including the door for Class B Machines) [ft2] 45 56 62 

Glass Area [ft2] 0 0 0 

Baseline Air Infiltration [lb/hour] 9 14 17 

Load from Electronic components (bill changers, LED displays, 

etc.) [kWh] 0.2 0.2 0.2 

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EERE-2006-STD-0125 COMMENT 46
5.4.5 Non-Numerical Assumptions 

In developing the energy consumption model, DOE made certain non-numerical 

assumptions concerning the analysis. These include general assumptions about the analysis as 

well as specific assumptions about load components and design options. 

DOE assumed that all conditions are based on new equipment tested in a controlledenvironment chamber and subjected to the methods of testing and rating in ANSI/ASHRAE 

Standard 32.1–2004. Manufacturers that certify their equipment to comply with Federal 

standards will be required to test new units using this method, which specifies ambient 

temperature, humidity, light level, and other requirements. 

DOE did not consider variable-speed compressors as a compressor design option. 

Variable-speed compressors reduce energy consumption under real-world conditions by 

matching their capacity to the refrigeration load, which can change due to variation in ambient 

conditions and product loading. This eliminates the inefficiencies that occur due to mismatched 

capacity and load in a single-speed compressor during part-load operation. The ANSI/ASHRAE 

Standard 32.1-2004 test procedure prescribes steady-state conditions. Thus, a variable-speed 

compressor would be limited to single-speed operation and the resulting EER would be no better 

than that of a properly sized single-speed compressor. Similarly, under ANSI/ASHRAE 32.1–

2004, the performance of a high-efficiency variable-speed compressor would be comparable to a 

high-efficiency single-speed compressor. 

Because baseline models must meet ENERGY STAR Tier 1 criteria, DOE assumed that 

Class B machines meet the Tier 1 criteria when tested at the ANSI/ASHRAE Standard 32.1-2004 

required 90°F test condition, and Class A machines meet the Tier 1 criteria when tested at the 

ASHRAE Standard 32.1-2004 required 75°F test condition. 

5.4.6 Numerical Constants and Assumptions 

In developing the energy consumption model, DOE identified constants and made 

assumptions concerning numerical values used in the analysis. These include ambient conditions, 

financial assumptions, and parameters necessary to calculate the component and non-electric 

loads. Details of these assumptions are shown in Table 5.4.17 and Table 5.4.18 below. 

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EERE-2006-STD-0125 COMMENT 46
Table 5.4.17 Energy Consumption Model Numerical Constants and Assumptions 

Numerical Constants and Assumptions Value Source 

Test Chamber Temperature [°F] 75 or 90 ASHRAE Standard 32.1-2004 

Test Chamber Relative Humidity [%] 45 or 65 ASHRAE Standard 32.1-2004 

Test Chamber Pressure [pounds per square 

in (psi), absolute] 14.7 Assumed 

List Price Markup [$/$] 2.00 Assumed 

Lighting Operating Time Per Day [hr] 24 Assumed based upon ASHRAE Standard 32.1-

2004 

Evaporator Fan(s) Run Time Per Day [hr] 24 or less, 

Less than 24 hours if the evaporator fan motor 

control option is selected, based on discussions 

with manufacturers 

Off-cycle defrost time per day if 

Evaporator Fan Control is Enabled [hr] 1.5 Assumed 

R Value of Foam Insulation [ft2F·h/Btu·in] 8 Discussions with foam manufacturers; 

manufacturer data sheets 

R Value of Aerogel Insulation 

[ft2·°F·h/Btu·in] 10 Discussions with aerogel manufacturers 

Convective Film Coefficient Inside Case 

Walls With Evap Fan On [Btu/h-ft2

-F] 4.00 Communication with RTTC 

Convective Film Coefficient Inside Case 

Walls With Evap Fan Off[Btu/h-ft2

-F] 1.00 ASHRAE Handbook–Fundamentals 2005 

Convective Film Coefficient Outside Case 

Walls [Btu/h-ft2

-F] 1.46 Communication with RTTC 

Evaporator Coil Overall Bypass Factor [%] 17 DOE estimate 

Density of Air @ Test Temperature [lb/ft3] 0.073 or 

0.071 ASHRAE Handbook–Fundamentals 2005 

High-Efficiency Compressor Cost 

Premium 6% Interviews with compressor manufacturers 

High-Efficiency Compressor Power 

Reduction 3% Interviews with compressor manufacturers 

Electricity Cost [$/kWh] 0.08 

Commercial Building Energy Consumption Survey 

(CBECS), Energy Information Administration 

(EIA), average commercial price in 2004 

Table 5.4.18 Engineering Constants 

Numerical Constants and Assumptions Number Source 

Specific Heat of Air @ Test Conditions 

[Btu/lb-R] 0.24 Thermodynamics by Cengel and Boles, 4th edition, 2002 

Latent Heat of Vaporization of Water/Water 

Vapor @ Test Temp [Btu/lb] 

1050 or 

1044 

Thermodynamics by Cengel and Boles, 4th edition, 

2002 

Latent Heat of Fusion of Water/Ice [Btu/lb] 143.5 ASHRAE Handbook–Fundamentals 2005 

Conversion from Watts to Btu/h [Btu/h-W] 3.415179 ASHRAE Handbook–Fundamentals 2005 

5.4.7 Model Components 

Figure 5.4.1 shows the components of the energy consumption model. The model 

calculates DEC in two major subsections: component energy consumption and compressor 

energy consumption. Component energy consumption is the sum of electrical energy directly 

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EERE-2006-STD-0125 COMMENT 46
consumed by each fan motor and lamp. Compressor energy consumption is calculated from the 

total heat load (expressed as Btu/h). 

The total heat load is the sum of the component load and the non-electric load. The 

component load is a sum of the heat emitted by evaporator fan motors and lighting inside the 

refrigerated space. (Condenser fan motors are outside the refrigerated space and do not 

contribute to the component heat load.) The non-electric load is the sum of the heat contributed 

by radiation through glass (for Class A machines), heat conducted through walls and doors, and 

warm air infiltration. 

Figure 5.4.1 Components of the Energy Consumption Model 

Total Heat 

Load 

[Btu/h]

Component 

Load

[Btu/h]

Non-Electric 

Load

[Btu/h]

Fan Motor 

Heat Load

[Btu/h]

Lighting Heat 

Load

[Btu/h]

Radiation 

Load

[Btu/h]

Conduction 

Load

[Btu/h]

Infiltration 

Load

[Btu/h]

Daily Energy 

Consumption [kWh/day]

Compressor 

Energy 

Consumption 

[kWh/day]

Compressor Model 

(ARI 540)

Electric Energy 

Consumption

[kWh/day]

Heat Load 

[Btu/h]

Legend:

Component 

Energy 

Consumption 

[kWh/day]

Fan Motor 

Energy

 Consumption 

[kWh/day]

Lighting 

Energy 

Consumption 

[kWh/day]

5.4.7.1 Component Energy Consumption 

Component energy consumption is the sum of electrical energy directly consumed by 

each fan motor and light fixture. 

Fan motor energy consumption is calculated by summing the power draw of each 

evaporator and condenser fan motor, and multiplying the total motor power by the total running 

time over 24 hours. This analysis assumed condenser fans only run when the compressor is on. 

The evaporator fan is assumed to run 24 hours a day, unless the evaporator fan motor control 

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EERE-2006-STD-0125 COMMENT 46
option is selected. In this case, the evaporator fan motor is off during compressor off-cycle times 

except for defrost periods. 

Lighting energy consumption is calculated by summing the power draw of each fixture 

and ballast, and multiplying the total by the total operating time of the lighting system over a 24-

hour period. 

5.4.7.2 Compressor Energy Consumption 

DOE calculated compressor energy consumption (CEC) using the compressor model 

described in section 6.4 of Air-Conditioning and Refrigeration Institute (ARI) Standard 540-

2004, Performance Rating of Positive Displacement Refrigerant Compressors and Compressor 

Units. This model is based on a 10-coefficient polynomial derived from empirical compressor 

performance data for power, mass flow, current, and efficiency. The coefficients are derived for 

each of these parameters as a function of SET and SCT. Compressor coefficients, or tabulated 

empirical data (from which coefficients can be derived), are available from compressor 

manufacturers. Similar to the method used for remote condensing equipment, the EER of any 

compressor can be determined given the SET and SCT. 

5.4.7.3 Component Load Model 

The component load is the sum of the heat emitted by each evaporator fan motor and 

lamps inside the refrigerated volume. This waste heat must be removed by the compressor. 

DOE assumed that all electrical energy consumed by the evaporator fan motors ends up 

as heat inside the refrigerated space. In any electric motor, irreversibilities in the motor windings, 

bearings, and other mechanical components convert much of the input electrical energy into heat. 

The rest of the energy is converted to moving air inside the case. This moving air is slowed by 

friction and eventually converted to heat as well. 

DOE assumed that all electrical energy consumed by lighting components inside the 

refrigerated space ends up as heat inside that space. In the ANOPR, DOE assumed that none of 

the electrical energy consumed by lighting components outside the refrigerated space ends up as 

heat inside that space. For the NOPR, DOE is modifying this assumption for Class B machines 

by attributing a fraction of the electrical energy consumed by lighting components outside the 

refrigerated space to added heat inside that space. DOE believes that, even though the lighting 

components are not inside the refrigerated volume, they are contained within the machine 

envelope and contribute some heat through conduction to the refrigerated space. (Note that 

having ballasts inside the refrigerated space is not typical of current beverage vending machine 

designs, but DOE wished to consider the possibility in the model.) 

5.4.7.4 Radiation Load Model 

The radiation heat load model accounts for the gray-body radiation between the warm 

surfaces of the surrounding environment (the test chamber) and the cold inner surfaces of the 

refrigerated space through the glass doors of Class A machines. The net radiation is incorporated 

into the overall U-value of the door calculated by WINDOW 5.2 (see Table 5.4.9 above for the 

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EERE-2006-STD-0125 COMMENT 46
U-values calculated). Within the WINDOW 5.2 program, the environmental conditions in the 

refrigerated volume and the test chamber were specified to match the two test conditions defined 

in ASHRAE Standard 32.1-2004. See section 5.4.7.5 below for a discussion of the calculation of 

the combined radiation and conduction loads for glass doors and other glass. 

5.4.7.5 Conduction Load Model 

The conduction load model accounts for the heat conducted through walls and doors. For 

solid walls and doors, the conduction load is given by: 

Q A

T T

h

d

k h

cond walls

room case

o

ins

ins i

 

 

1 1

 

 Eq. 5.1 

where 

Awalls is the area of the exterior of the refrigerated volume (ft2

), 

ho is the convective film coefficient on the outside of refrigerated volume walls (Btu/h-ft2-°F), 

hi is the convective film coefficient on the inside of refrigerated walls (Btu/h-ft2

-°F), 

dins is the insulation thickness (in), and 

kins is the insulation thermal conductivity (Btu-in/h-ft2

-°F). 

Because of its high thermal conductivity, the sheet metal that encloses the insulation does 

not have any significant effect on the conduction load, and therefore was not included in the 

calculation of conduction load. See Table 5.4.17 above for numerical constants pertaining to the 

conduction model. 

For glass doors, the conduction load is incorporated into the overall U-factor of the door 

assembly or glass calculated by WINDOW 5.2 (see Table 5.4.9 above for the U-values 

calculated). The combined radiation and conduction load for glass doors and other glass is 

calculated as: 

Q U AT T  Eq. 5.2 glass overall glass room case 

where 

Uoverall is the overall U-factor, including convection and radiation (Btu/h-ft2

-°F), and 

Aglass is the area of the glass (ft2). 

5.4.7.6 Infiltration Load Model 

The infiltration load model accounts for the heat that is added to a display case when 

warm, moist air enters the case (primarily through leaks and vend doors). The infiltration load is 

difficult to model because of the inherent complexity of the fluid phenomena of infiltration. 

Therefore, DOE used empirical data for defrost melt water to back-calculate the infiltration load. 

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EERE-2006-STD-0125 COMMENT 46
DOE calibrated this approach using input from manufacturers and empirical data for infiltration 

loads provided by Southern California Edison’s RTTC from beverage vending machine testing. 

Ambient room air infiltrated into the refrigerated space contributes to the load in two 

ways: a sensible load in the form of the heat contained in the dry air, and a latent load in the 

form of water vapor in the air that condenses on cold surfaces. Assuming the amount of 

condensation on the coil—and thus the amount of defrost melt water—is correlated to the 

amount of water that enters the case through infiltration, the defrost melt water mass flow can be 

used to estimate the mass flow of water that enters the case as water vapor in the air. Given the 

values both for the humidity level in the case and the ambient room air, the mass flow of air that 

enters the refrigerated case can be calculated as: 

   m

HR HR CBF air

defrostmelt

room case

   1

m

 

Eq. 5.3 

where 

mair is the mass flow of dry air into the case (lbs/hr),

mdefrostmelt is the mass flow of defrost melt water (lbs/hr), 

HRroom is the humidity ratio of the ambient air in the room (dimensionless), 

HRcase is the humidity ratio of the air inside the case (dimensionless), and 

CBF is the coil bypass factor (dimensionless). 

The coil bypass factor is a measure of the fraction of air in the case that is never 

influenced by the evaporator coil (or a measure of the fraction of air that does not deposit its 

moisture onto the evaporator coil). This factor allows the infiltration calculation to be correlated 

to empirical data. Communication with Southern California Edison’s RTTC was used to estimate 

the evaporator coil bypass factor. As shown in Table 5.4.17 above, the coil bypass factor was 

estimated to be 17 percent. 

Once the air flow rates were calculated, they were entered into DOE’s model. The mass 

flow of water vapor into the case is the mass flow of air multiplied by the difference of humidity 

ratios inside and outside the case. Using the mass flows of air and water vapor, the infiltration 

load can be approximated using: 

Q mC T T m H Eq. 5.4 inf air dryair room case vapor v H O ,    2

where 

Qinf is the infiltration load (Btu/h),

Cair is the specific heat of dry air (Btu/lb-°F), 

mvapor is the mass flow of water vapor into the case (lbs/hr), and 

Hv,H2O is the heat of vaporization of water. 

5.5 COST-EFFICIENCY CURVES 

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EERE-2006-STD-0125 COMMENT 46
The result of the engineering analysis is a set of cost-efficiency curves. DOE developed 

six curves representing the two equipment classes and three different size machines in each 

equipment class using the baseline specifications and design options described above. The 

method for developing curves started with determining the baseline energy consumption (chosen 

to be ENERGY STAR Tier 1) and manufacturer production cost. Above the baseline, design 

options were implemented in order of lowest to highest payback, and only one design option was 

implemented at each design option level. Design options were implemented until all technologies 

were at a maximum level. 

The six cost-efficiency curves are shown in Figure 5.5.1 through Figure 5.5.6 below and 

in tabular form in Table 5.5.1 through Table 5.5.6 below in the form of DEC versus MSP. More 

detailed results, including the design options used at each design option level, are provided in 

appendix B. The cost-efficiency curves were calculated at the 75°F test condition of ASHRAE 

Standard 32.1-2004. 

As stated above, DOE used the cost-efficiency curves from the engineering analysis as an 

input to the life-cycle cost (LCC) analysis to determine the price of beverage vending machines 

to the customer (see chapter 8 of the TSD). 

5-26

EERE-2006-STD-0125 COMMENT 46
$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

0.0 2.0 4.0 6.0 8.0 10.0

Daily Energy Consumption [kWh/day]

Manufacturer Selling Price [$]

Figure 5.5.1 Cost-Efficiency Curves for the Small-Size Class A Equipment Class 

Table 5.5.1 Cost-Efficiency Data for the Small-Size Class A Equipment Class 

Efficiency 

Level 

Daily Energy 

Consumption 

[kWh/day] 

Manufacturer 

Selling Price 

[$] 

1 6.10 $1,856.20

2 5.73 $1,868.92

3 5.57 $1,876.79

4 5.47 $1,881.93

5 5.27 $1,893.33

6 3.95 $2,003.03

7 3.73 $2,027.85

8 3.63 $2,043.67

9 3.58 $2,055.07

10 3.33 $2,204.35

11 3.25 $2,971.76

5-27

EERE-2006-STD-0125 COMMENT 46
$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

$4,000

0.0 2.0 4.0 6.0 8.0 10.0

Daily Energy Consumption [kWh/day]

Manufacturer Selling Price [$]

Figure 5.5.2 Cost-Efficiency Curve for the Medium-Size Class A Equipment Class 

Table 5.5.2 Cost-Efficiency Data for the Medium-Size Class A Equipment Class 

Efficiency 

Level 

Daily Energy 

Consumption 

[kWh/day] 

Manufacturer 

Selling Price 

[$] 

1 6.53 $2,222.07

2 5.97 $2,243.64

3 5.81 $2,251.52

4 5.70 $2,257.59

5 5.51 $2,268.99

6 4.19 $2,378.69

7 3.95 $2,408.68

8 3.83 $2,427.84

9 3.79 $2,439.23

10 3.52 $2,602.29

11 3.43 $3,456.21

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EERE-2006-STD-0125 COMMENT 46
$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

$4,000

0.0 2.0 4.0 6.0 8.0 10.0 12.0

Daily Energy Consumption [kWh/day]

Manufacturer Selling Price [$]

Figure 5.5.3 Cost-Efficiency Curves for the Large-Size Class A Equipment Class 

Table 5.5.3 Cost-Efficiency Data for the Large-Size Class A Equipment Class 

Efficiency 

Level 

Daily Energy 

Consumption 

[kWh/day] 

Manufacturer 

Selling Price 

[$] 

1 6.75 $2,426.95

2 6.62 $2,433.02

3 6.46 $2,440.90

4 6.21 $2,453.62

5 4.89 $2,563.32

6 4.60 $2,593.31

7 4.46 $2,613.58

8 4.41 $2,624.98

9 4.05 $2,840.85

10 3.94 $3,846.11

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EERE-2006-STD-0125 COMMENT 46
$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Daily Energy Consumption [kWh/day]

Manufacturer Selling Price [$]

Figure 5.5.4 Cost-Efficiency Curve for the Small-Size Class B Equipment Class 

Table 5.5.4 Cost-Efficiency Data for the Small-Size Class B Equipment Class 

Efficiency 

Level 

Daily Energy 

Consumption 

[kWh/day] 

Manufacturer 

Selling Price 

[$] 

1 4.96 $1,521.33

2 4.62 $1,544.13

3 4.51 $1,557.72

4 4.31 $1,591.67

5 4.28 $1,603.07

6 3.78 $2,023.72

7 3.69 $2,909.47

5-30

EERE-2006-STD-0125 COMMENT 46
$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Daily Energy Consumption [kWh/day]

Manufacturer Selling Price [$]

Figure 5.5.5 Cost-Efficiency Curve for the Medium-Size Class B Equipment Class 

Table 5.5.5 Cost-Efficiency Data for the Medium-Size Class B Equipment Class 

Efficiency 

Level 

Daily Energy 

Consumption 

[kWh/day] 

Manufacturer 

Selling Price 

[$] 

1 5.56 $1,716.84

2 5.20 $1,739.63

3 5.12 $1,744.77

4 4.99 $1,760.59

5 4.76 $1,796.01

6 4.72 $1,807.41

7 4.22 $2,228.06

8 4.12 $3,247.02

5-31

EERE-2006-STD-0125 COMMENT 46
5-32

$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

$4,000

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Daily Energy Consumption [kWh/day]

Manufacturer Selling Price [$]

Figure 5.5.6 Cost-Efficiency Curve for the Large-Size Class B Equipment Class 

Table 5.5.6 Cost-Efficiency Data for the Large-Size Class B Equipment Class 

Efficiency 

Level 

Daily Energy 

Consumption 

[kWh/day] 

Manufacturer 

Selling Price 

[$] 

1 5.85 $1,779.80

2 5.48 $1,802.60

3 5.33 $1,819.53

4 5.07 $1,854.95

5 5.03 $1,866.35

6 4.52 $2,287.00

7 4.41 $3,439.97

5.6 RESULTS 

DOE presents more detailed results and supporting data for the engineering analysis in 

appendix B of this TSD.

EERE-2006-STD-0125 COMMENT 46
 ** DRAFT ** 

REFERENCES 

1

 American Metals Market, http://www.amm.com/. 

2

 U.S. Department of Labor, Bureau of Labor Statistics, Producer Price Indices, 

http://www.bls.gov/ppi/. 

3

 U.S. Department of Commerce, Bureau Economic Analysis, Gross Domestic Product 

Implicit Price Deflator, https://bea.gov/bea/dn/nipaweb/TableView.asp#Mid. 

4

 Environmental Protection Agency and U.S. Department of Energy’s ENERGY STAR 

program, http://www.energystar.gov. 

5

 Arthur D. Little, Energy Savings Potential for Commercial Refrigeration Equipment, 

June 1996. 

6

 Southern California Edison, Next Generation Vending Machine, 2006 ACEEE Summer 

Study on Energy Efficiency in Buildings. 

7

 Lawrence Berkley National Laboratory, Window 5.0, available at 

http://windows.lbl.gov/software/window/window.html. 

8

 American National Standards Institute/American Society of Heating, Refrigeration and 

Air-conditioning Engineers, 2004. Standard 32.1-2004: Methods of Testing for Rating 

Vending Machine for Bottled, Canned, and Other Sealed Beverages. 

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