CHAPTER 5. ENGINEERING ANALYSIS

TABLE OF CONTENTS

5.1 INTRODUCTION

........................................................................................................... 5­1

5.2 EQUIPMENT CLASSES ANALYZED.......................................................................... 5­1

5.3 METHODOLOGY OVERVIEW

.................................................................................... 5­4

5.4 COST MODEL

................................................................................................................ 5­6

5.4.1 Manufacturer Production Cost Estimates and Assumptions................................ 5­6

5.4.2 Structure of the Cost Model Spreadsheet............................................................. 5­8

5.4.3 Material Prices

..................................................................................................... 5­9

5.4.4 Results.................................................................................................................. 5­9

5.5 MANUFACTURER MARKUP AND LIST PRICE MARKUP................................... 5­13

5.6 ENERGY CONSUMPTION MODEL

.......................................................................... 5­13

5.6.1 Screened­In Technologies.................................................................................. 5­14

5.6.2 Screened­In Technologies Not Considered in the Engineering Analysis.......... 5­14

5.6.2.1 Remote Lighting Ballast Location......................................................... 5­15

5.6.2.2 Evaporator Fan Motor Controllers......................................................... 5­15

5.6.2.3 Higher Efficiency Evaporator and Condenser Fan Blades

.................... 5­15

5.6.2.4 Improved or Thicker Insulation

............................................................. 5­16

5.6.2.5 Low Pressure Differential Evaporators.................................................. 5­16

5.6.2.6 Defrost Cycle Control............................................................................ 5­16

5.6.2.7 Defrost Mechanisms

.............................................................................. 5­17

5.6.3 Design Options................................................................................................... 5­17

5.6.3.1 Higher Efficiency Lighting and Ballasts................................................ 5­18

5.6.3.2 Higher Efficiency Evaporator Fan Motors

............................................ 5­19

5.6.3.3 Increased Evaporator Surface Area

....................................................... 5­20

5.6.3.4 Improved Doors

..................................................................................... 5­21

5.6.3.5 Higher Efficiency Condenser Fan Motors

............................................. 5­23

5.6.3.6 Increased Condenser Surface Area

........................................................ 5­23

5.6.3.7 Higher Efficiency Compressors............................................................. 5­24

5.6.4 Baseline Specifications

...................................................................................... 5­24

5.6.5 Non­Numerical Assumptions............................................................................. 5­25

5.6.6 Numerical Constants and Assumptions

............................................................. 5­27

5.6.7 Model Components............................................................................................ 5­28

5.6.7.1 Component Energy Consumption.......................................................... 5­29

5.6.7.2 Compressor Energy Consumption

......................................................... 5­30

5.6.7.3 Component Load Model

........................................................................ 5­31

5.6.7.4 Radiation Load Model

........................................................................... 5­31

5.6.7.5 Conduction Load Model

........................................................................ 5­32

5.6.7.6 Infiltration Load Model.......................................................................... 5­33

5.7 COST­EFFICIENCY CURVES

.................................................................................... 5­34

5.8 EXTENSION OF ANALYSIS TO LOW­SHIPMENT EQUIPMENT CLASSES

...... 5­51

5.8.1 Methodology...................................................................................................... 5­52

5.8.2 Correlations........................................................................................................ 5­53

5­i5.8.3 Results................................................................................................................ 5­54

5.9 SENSITIVITY ANALYSES

......................................................................................... 5­54

5.9.1 Material Price Sensitivity................................................................................... 5­55

5.9.2 Alternative Refrigerants..................................................................................... 5­56

5.10 RESULTS

...................................................................................................................... 5­56

REFERENCES

.......................................................................................................................... 5­57

LIST OF TABLES

Table 5.2.1 Shipment Data and Equipment Classes Analyzed.................................................... 5­3

Table 5.2.2 Equipment Classes Analyzed in the Engineering Analysis..................................... 5­4

Table 5.4.1 Major Manufacturing Processes

.............................................................................. 5­9

Table 5.4.2 Extension of Cost Model Estimates to Other Equipment Classes......................... 5­12

Table 5.6.1 Details for “Lighting for VOP, SVO, HZO, and SOC Equipment Families” Design

Option

............................................................................................................................... ......... 5­19

Table 5.6.2 Details for “Lighting for VCT Equipment Family” Design Option

...................... 5­19

Table 5.6.3 Details for “Evaporator Fan Motor” Design Option.............................................. 5­20

Table 5.6.4 Details for “Evaporator Coil” Design Option........................................................ 5­20

Table 5.6.5 Properties of Standard and Enhanced Evaporator Coil

......................................... 5­21

Table 5.6.6 Details for “Doors for VCT Equipment Family, Low Temperature” Design Option5­

22

Table 5.6.7 Details for “Doors for VCT Equipment Family, Medium Temperature” Design

Option

............................................................................................................................... ......... 5­22

Table 5.6.8 Details for “Doors for HCT Equipment Family, Ice­Cream Temperature” Design

Option

............................................................................................................................... ......... 5­22

Table 5.6.9 Details for “Doors for SOC Equipment Family, Medium Temperature” Design

Option

............................................................................................................................... ......... 5­23

Table 5.6.10 Details for “Increased Condenser Surface Area” Design Option........................ 5­23

Table 5.6.11 Properties of Standard and Enhanced Condenser Coil

......................................... 5­24

Table 5.6.12 Baseline Specifications........................................................................................ 5­25

Table 5.6.13 Energy Consumption Model Numerical Constants and Assumptions................. 5­28

Table 5.7.1 Figure, Table, and Page Numbers for Cost­Efficiency Results............................. 5­35

Table 5.7.2 Cost­Efficiency Data for the VCT.RC.L Equipment Class................................... 5­36

Table 5.7.3 Cost­Efficiency Data for the VOP.RC.M Equipment Class.................................. 5­37

Table 5.7.4 Cost­Efficiency Data for the SVO.RC.M Equipment Class.................................. 5­38

Table 5.7.5 Cost­Efficiency Data for the HZO.RC.L Equipment Class................................... 5­39

Table 5.7.6 Cost­Efficiency Data for the HZO.RC.M Equipment Class.................................. 5­40

Table 5.7.7 Cost­Efficiency Data for the VCT.RC.M Equipment Class.................................. 5­41

Table 5.7.8 Cost­Efficiency Data for the VOP.RC.L Equipment Class................................... 5­42

Table 5.7.9 Cost­Efficiency Data for the SOC.RC.M Equipment Class

.................................. 5­43

Table 5.7.10 Cost­Efficiency Data for the VOP.SC.M Equipment Class

................................ 5­44

Table 5.7.11 Cost­Efficiency Data for the SVO.SC.M Equipment Class

................................ 5­45

Table 5.7.12 Cost­Efficiency Data for the HZO.SC.L Equipment Class

................................. 5­46

Table 5.7.13 Cost­Efficiency Data for the HZO.SC.M Equipment Class

................................ 5­47

Table 5.7.14 Cost­Efficiency Data for the HCT.SC.I Equipment Class................................... 5­48

Table 5.7.15 Cost­Efficiency Data for the VCT.SC.I Equipment Class................................... 5­49

5­iiTable 5.7.16 Cost­Efficiency Data for the VCS.SC.I Equipment Class................................... 5­50

Table 5.8.1 Extension of Analyses to Low­Shipment Equipment Classes............................... 5­52

LIST OF FIGURES

Figure 5.3.1 Flow Diagram of Engineering Methodology

......................................................... 5­5

Figure 5.4.1 Components of Manufacturer Production Cost...................................................... 5­7

Figure 5.4.2 Manufacturer Production Cost Assessment Stages

................................................ 5­8

Figure 5.4.3 Part Count by Equipment Class and Subsystem................................................... 5­10

Figure 5.4.4 Weight by Equipment Class and Subsystem........................................................ 5­11

Figure 5.4.5 Manufacturer Production Cost by Equipment Class and Subsystem

................... 5­12

Figure 5.6.1 Components of the Energy Consumption Model

................................................. 5­29

Figure 5.7.1 Cost­Efficiency Curve for the VCT.RC.L Equipment Class

............................... 5­36

Figure 5.7.2 Cost­Efficiency Curve for the VOP.RC.M Equipment Class

.............................. 5­37

Figure 5.7.3 Cost­Efficiency Curves for the SVO.RC.M Equipment Class............................. 5­38

Figure 5.7.4 Cost­Efficiency Curves for the HZO.RC.L Equipment Class.............................. 5­39

Figure 5.7.5 Cost­Efficiency Curve for the HZO.RC.M Equipment Class

.............................. 5­40

Figure 5.7.6 Cost­Efficiency Curve for the VCT.RC.M Equipment Class

.............................. 5­41

Figure 5.7.7 Cost­Efficiency Curve for the VOP.RC.L Equipment Class

............................... 5­42

Figure 5.7.8 Cost­Efficiency Curve for the SOC.RC.M Equipment Class............................... 5­43

Figure 5.7.9 Cost­Efficiency Curve for the VOP.SC.M Equipment Class............................... 5­44

Figure 5.7.10 Cost­Efficiency Curve for the SVO.SC.M Equipment Class............................. 5­45

Figure 5.7.11 Cost­Efficiency Curve for the HZO.SC.L Equipment Class.............................. 5­46

Figure 5.7.12 Cost­Efficiency Curve for the HZO.SC.M Equipment Class............................. 5­47

Figure 5.7.13 Cost­Efficiency Curve for the HCT.SC.I Equipment Class............................... 5­48

Figure 5.7.14 Cost­Efficiency Curve for the VCT.SC.I Equipment Class............................... 5­49

Figure 5.7.15 Cost­Efficiency Curve for the VCS.SC.I Equipment Class

............................... 5­50

Figure 5.8.1 Extension of Analysis Using Correlations

........................................................... 5­51

Figure 5.8.2 Extension of Standard Level Using Correlations

................................................. 5­52

Figure 5.9.1 Material Price Sensitivity for the VOP.RC.M Equipment Class

......................... 5­55

5­iii5­ivCHAPTER 5. ENGINEERING ANALYSIS

5.1 INTRODUCTION

The engineering analysis establishes the relationship between manufacturer production

cost and energy consumption for the commercial refrigeration equipment (CRE) covered in this

rulemaking. This equipment includes commercial ice­cream freezers; self­contained commercial

refrigerators, commercial freezers, and commercial refrigerator­freezers without doors; and

remote condensing commercial refrigerators, commercial freezers, and commercial refrigeratorfreezers. The “cost­efficiency” relationship serves as the basis for cost/benefit calculations in

terms of individual customers, manufacturers, and the Nation. In determining this relationship,

the U.S. Department of Energy (DOE) estimates the increase in manufacturer production cost

(MPC) associated with technological changes that reduce the energy consumption of the baseline

models.

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

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

options from the screening analysis (chapter 4). 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

(both analytically derived and industry­supplied curves), and a manufacturer markup used to

convert MPC to manufacturer selling price (MSP). In the subsequent markups analysis (chapter

6), DOE determines customer prices by applying distribution markups, sales tax, and contractor

markups. After applying these markups, the data serve as inputs to the building energy­use and

end­use load characterization (chapter 7) and the life­cycle cost and payback period analyses

(chapter 8).

In this chapter, DOE discusses analyzed equipment classes, representative baseline units,

methodology used to develop MPC, methodology used to estimate energy consumption, costefficiency curves, methodology used to extend the analysis to low­shipment volume equipment

classes, sensitivity to material prices, and use of alternative refrigerants.

5.2 EQUIPMENT CLASSES ANALYZED

Because of the large number of equipment classes in this rulemaking, DOE did not

directly analyze all covered equipment classes in the engineering analysis. The shipment data

presented in the market and technology assessment (recreated in Table 5.2.1) was used to

prioritize the analysis by eliminating from direct examination those equipment classes that have

fewer than 100 annual shipments. The 14 remaining high­shipment volume equipment classes

5­1were directly analyzed. One additional equipment class, the VOP.RC.L equipment class, was

added after discussions with manufacturers. a

According to the Air­Conditioning and Refrigeration Institute (ARI) equipment

shipments data, these 15 equipment classes represent 98 percent of the shipments of covered

commercial refrigeration equipment. Table 5.2.2 shows the 15 equipment classes (out of 38

total) directly analyzed in the engineering analysis, organized by equipment family, condensing

unit type, and rating temperature.

a Product class designations consist of a combination (in sequential order separated by periods) of a product family

code (VOP=vertical open, SVO=semivertical open, HZO=horizontal open, VCT=vertical transparent doors,

VCS=vertical solid doors, HCT=horizontal transparent doors, HCS=horizontal solid doors, or SOC=service over

counter), an operating mode code (RC=remote condensing or SC=self­contained), and a rating temperature code

(M=medium temperature (38°F), L=low temperature (0°F), or I=ice­cream temperature (­15°F)). For example,

“VOP.RC.M” refers to the “vertical open, remote condensing, medium temperature” product class. See chapter 3,

market and technology assessment, for a more detailed explanation of the product class terminology.

5­2Table 5.2.1 Shipment Data and Equipment Classes Analyzed

Equipment Condensing Rating Equipment

Family Unit Type Temperature Class ARI Shipments**

Designation Designation Designation Designation*

M (38°F) VOP.RC.M 38743

RC L (0°F) VOP.RC.L† 0†

VOP I (­15°F) VOP.RC.I 0

M (38°F) VOP.SC.M 6512

SC L (0°F) VOP.SC.L 0

I (­15°F) VOP.SC.I 0

M (38°F) SVO.RC.M 29552

RC L (0°F) SVO.RC.L 0

SVO I (­15°F) SVO.RC.I 0

M (38°F) SVO.SC.M 9750

SC L (0°F) SVO.SC.L 0

I (­15°F) SVO.SC.I 0

M (38°F) HZO.RC.M 4541

RC L (0°F) HZO.RC.L 14278

HZO I (­15°F) HZO.RC.I 0

M (38°F) HZO.SC.M 838

SC L (0°F) HZO.SC.L 1738

I (­15°F) HZO.SC.I 0

M (38°F) VCT.RC.M 2767

RC L (0°F) VCT.RC.L 38483

VCT I (­15°F) VCT.RC.I 0

M (38°F) VCT.SC.M‡ 43374‡

SC L (0°F) VCT.SC.L‡ 2472‡

I (­15°F) VCT.SC.I 1898

M (38°F) VCS.RC.M 49

RC L (0°F) VCS.RC.L 2

VCS I (­15°F) VCS.RC.I 43

M (38°F) VCS.SC.M‡ 4‡

SC L (0°F) VCS.SC.L‡ 4202‡

I (­15°F) VCS.SC.I 470

M (38°F) HCT.RC.M 0

RC L (0°F) HCT.RC.L 15

HCT I (­15°F) HCT.RC.I 0

M (38°F) HCT.SC.M‡ 724‡

SC L (0°F) HCT.SC.L‡ 0‡

I (­15°F) HCT.SC.I 9056

M (38°F) HCS.RC.M 37

RC L (0°F) HCS.RC.L 0

HCS I (­15°F) HCS.RC.I 0

M (38°F) HCS.SC.M‡ 39761‡

SC L (0°F) HCS.SC.L‡ 4109‡

I (­15°F) HCS.SC.I 0

M (38°F) SOC.RC.M 9312

RC L (0°F) SOC.RC.L 9

SOC I (­15°F) SOC.RC.I 0

M (38°F) SOC.SC.M‡ 1108‡

SC L (0°F) SOC.SC.L‡ 0‡

I (­15°F) SOC.SC.I 0

* Equipment classes that DOE directly analyzed are shown in bold font.

**Source: ARI, No. 7 Exhibit B at p. 1.

† Based on discussions with manufacturers, the VOP.RC.L equipment class was added to the analysis.

‡ These equipment classes have standards established by EPACT 2005 and are therefore not covered under this

rulemaking.

5­3Table 5.2.2 Equipment Classes Analyzed in the Engineering Analysis

Equipment Remote Condensing Self­Contained

Family Medium Low Ice­Cream Medium Low Ice­Cream

Without

Doors VOP � � �

SVO � �

HZO � � � �

With

Doors VCT � � * �

VCS �

HCT �

HCS

SOC �

� Full analysis conducted.

* Shaded boxes indicate that these equipment classes have standards established by EPACT 2005 and are

therefore not considered in this rulemaking.

The engineering analysis considered only “refrigerators” (medium temperature),

“freezers” (low temperature), and “ice­cream freezers” (ice­cream temperature). DOE did not

focus on “refrigerator­freezers” (combinations of compartments at different temperatures)

because they have very limited shipment volumes. b Although DOE did not explicitly analyze

refrigerator­freezers in the engineering analysis, DOE assumed that the results of the refrigerator,

freezer, and ice­cream freezer analyses could be applied to refrigerator­freezers. Further, DOE

assumed that refrigerator­freezers have a similar cost­efficiency relationship, allowing standards

developed separately for refrigerators and freezers to be applied to refrigerator­freezers. In the

past, standards for refrigerator­freezers have been in the form of a normalization metric adjusted

for the additional energy consumption of the freezer (e.g., “adjusted volume”). While the size

constraints (i.e., cabinet sizes) may be different for the refrigerator and the refrigerator­freezer,

the technologies and design choices required to reduce energy consumption are usually similar.

Both of these equipment classes will realize essentially equivalent energy­consumption savings

from such improvements as higher efficiency compressors, improved evaporator coils, and other

designs and technologies.

5.3 METHODOLOGY OVERVIEW

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

this rulemaking, DOE is adopting an efficiency­level approach, supplemented by a design­option

approach. For the four equipment classes with the highest shipment volumes (VCT.RC.L,

VOP.RC.M, SVO.RC.M, and HZO.RC.L), DOE used industry­supplied cost­efficiency curves

developed using an efficiency­level approach in downstream analyses. These industry­supplied

curves are qualified using analytically derived curves developed by DOE using a design­option

approach. In addition, for the equipment classes where industry­supplied curves were not

b Shipments of refrigerator­freezers were not reported in the ARI shipment data.

5­4available, DOE used the analytically derived curves developed using a design­option approach in

the downstream analyses.

Figure 5.3.1 shows a flow diagram of that methodology and the corresponding sections in

this chapter, starting with models and sub­analyses on the left, and ending with results on the

right. The models developed in the engineering analysis are the cost model and the energyconsumption model. The sub­analyses are the markups analysis and the matched pair analysis.

The results of the engineering analysis are four qualified industry­supplied cost­efficiency

curves, 15 analytically derived cost­efficiency curves, and sensitivity analyses.

Cost Model

(section 5.4)

Energy

Consumption

Model

(section 5.6) 15 Analytically

Derived CostEfficiency

Curves

(CDEC versus

MPC) 4 IndustrySupplied Cost

Efficiency

Curves*

(CDEC versus

M L P )

Markups

Analysis

(section 5.5)

Matched

Pairs Analysis

(section 5.8) 4 Qualified

IndustrySupplied Cost

Efficiency

Curves*

(CDEC vs MSP)

( section 5.7)

11 Analytically

Derived CostEfficiency

Curves

(CDEC vs MSP)

( section 5.7)

Sensitivity

Analyses

( section 5.9) 15 Analytically

Derived CostEfficiency

Curves

(CDEC versus

MSP)

C D E C = Calculated Daily Energy Consumption

LIST = List price

MPC = Manufacturer Production Cost

MSP = Manufacturer Selling Price

* VCT.RC.L, VOP.RC.M, SVO.RC.M, HZO.RC.L

Figure 5.3.1 Flow Diagram of Engineering Methodology

DOE used the data submitted by ARI as the basis for the engineering analysis. ARI

submitted four cost­efficiency curves developed using an efficiency­level approach in the form

of calculated daily energy consumption (CDEC) versus manufacturer list price (MLP). These

“industry­supplied” curves were for the VCT.RC.L, VOP.RC.M, SVO.RC.M, and HZO.RC.L

equipment classes. As part of the markups analysis, DOE estimated the average industry

5­5discount from MLP to MSP (the list price discount). DOE used this discount to convert the

industry­supplied curves into the form of CDEC versus MSP.

DOE supplemented the industry­supplied curves with its own internally developed

curves. These “analytically derived” curves were developed using a design option analysis on

the selected equipment classes. In the markups analysis, DOE also developed a markup between

manufacturer production cost MPC and MSP. DOE used this markup to convert the MPC

(developed in the cost model) to MSP, for comparison to the industry­supplied curves.

As explained in section 5.2, some equipment classes have very low or no shipments and

were not included in the analysis. To develop standards for these equipment classes, DOE

explored the possibility of using analytical correlations to extend analyses from similar

equipment classes that were directly analyzed. For two of the 15 equipment classes that received

a direct analysis (HZO.RC.I and VCT.RC.I), DOE developed analytical correlations based on

market data (“matched pairs analysis”). For example, in lieu of the direct analysis, standards for

ice­cream freezers were developed based on an examination of their energy consumption relative

to freezers.

The primary results of the engineering analysis are a set of cost­efficiency curves, in the

form of MSP versus CDEC, for 15 equipment classes. For four of these equipment classes, the

primary cost­efficiency curves are the industry­supplied curves, qualified by the analytically

derived curves. For the remaining 11 equipment classes, the only curves available are those that

were analytically derived. The secondary results of the engineering analysis are two sensitivity

analyses. One of them is a sensitivity analysis of metal prices performed on the VOP.RC.M

cost­efficiency curve. The other is a sensitivity analysis of alternative refrigerants.

5.4 COST MODEL

A cost model was used to estimate the MPC of commercial refrigeration equipment. This

approach involved the disassembly of a unit from the VCT.SC.M equipment class, an analysis of

the materials and manufacturing processes, and the development of a parametric spreadsheet

model flexible enough to cover all equipment classes. The manufacturing cost model estimated

MPC and reported it in aggregated form to maintain confidentiality of sensitive cost data. DOE

obtained input from stakeholders on the MPC estimates and assumptions to confirm accuracy.

The cost model was applied directly to 7 of the 15 covered equipment classes, and the results

were extended to 6 of the remaining equipment classes. The cost of remaining two equipment

classes was estimated using available MLP information discounted to MPC.

5.4.1 Manufacturer Production Cost Estimates and Assumptions

Manufacturer production cost is the sum of direct labor, direct material and overhead

(including investment depreciation). Other non­production cost elements include selling, general

and administrative, research and development, and interest. Together these costs make up the

MPC as shown in Figure 5.4.1.

5­6Manufacturer Production

Cost (MPC)

Full Production Cost Non­Production Cost

Interest Research &

Development General &

Administrative Selling Overhead Direct

Material Direct

Labor

Figure 5.4.1 Components of Manufacturer Production Cost

The cost of specific models–or costs to individual manufacturers–will vary, depending on

elements such as the equipment’s precise characteristics, actual manufacturing processes, and the

equipment mix in the factory. There are also considerable differences in the levels of vertical

integration (companies with a large market share and/or revenue base tend to be more vertically

integrated than their smaller competitors) that affect cost structure and thus the cost of

equipment. Yet potentially all manufacturers buy at least some of their parts and/or subsystems

from outside vendors.

The CRE market features producers that span the range from mass­customized equipment

to tailored, “one­off” fabricators. Most equipment listed in catalogs use platforms that are then

customized to meet the particular needs of customers. Depending on the manufacturer and the

degree of customization, engineering costs can thus represent a significant portion of the MPC.

DOE made a number of simplifying assumptions to reflect common industry practice.

For example, DOE assumed that the cabinets for the VCT equipment family are made in­house,

but the entire door system (frames, doors, frame heaters, lights, ballasts, etc.) is purchased as an

assembled sub­system from a door­manufacturer. Further, DOE assumed that completed heat

exchanger assemblies, fan motors and blades, or compressor sleds for self­contained units are

also purchased as completed sub­systems that need to be integrated into the finished case.

Since there was only one equipment teardown from which to draw data regarding

manufacturing practices, DOE built a parametric model that allowed the scaling of most input

factors. The assumptions behind the model are based on published data by manufacturers,

general industry practice (based on site visits), manufacturer interviews, and previously

published DOE reports. DOE compared the model results to published unit data, list prices, and

stakeholders comments. For example, comparing listed shipping weights versus the calculated

weights for cabinets and doors was one way to verify the model’s predictions.

The lack of detailed teardowns for every equipment class and the varying degrees of

vertical integration in the industry make calculating representative investment requirements

difficult. Not only does the market share vary for each manufacturer across every equipment

class, the scale of operations also varies greatly. It is also quite likely that high­volume

manufacturers derive a cost advantage based on their purchasing volume for common raw

5­7materials and purchased parts alike. Lacking detailed data, no attempt was made to account for

low­ versus high­volume purchasing power.

Most design options evaluated for this study consisted of drop­in replacement purchased

parts that are more efficient than the parts currently used in baseline equipment. Hence, it is

unlikely that higher energy conservation standards would result in any stranded equipment,

tooling, or other capital assets–a theory confirmed during manufacturer interviews. Thus, DOE

assumed a simple markup, in addition to material and labor costs for all other direct and indirect

production costs, to determine the cost of goods sold (COGS) for each equipment class.

5.4.2 Structure of the Cost Model Spreadsheet

DOE used a detailed, component­focused manufacturing cost assessment methodology to

estimate the MPC of each equipment class analyzed in the cost model, taking into account, for

example, direct materials, direct labor, and factory overhead costs. Figure 5.4.2 shows the three

major steps in generating the MPC.

Figure 5.4.2 Manufacturer Production Cost Assessment Stages

The first step in the MPC assessment was the creation of a complete and structured bill of

materials (BOM) from the disassembly of a commercial refrigerator with transparent doors

(VCT.SC.M). The commercial refrigerator was dismantled, and each part was characterized

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

includes the costs for materials, components, and fasteners. Also, it provides estimates for the

cost of raw materials and purchased parts. Assumptions about the sourcing of parts and in­house

fabrication were based on industry experience, information in trade publications, and discussions

with manufacturers. DOE conducted interviews and plant visits with manufacturers to ensure

accuracy on methodology and pricing.

Following the development of a detailed BOM, the major manufacturing processes were

identified and developed for the spreadsheet model. These processes are listed in Table 5.4.1

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 the 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, a detailed summary was prepared for relevant components, subassemblies, and

processes.

5­8Table 5.4.1 Major Manufacturing Processes

Fabrication Finishing Assembly/Joining

Fixturing Washing Adhesive Bonding

Stamping/Pressing Powder Coating Spot Welding

Brake Forming De­burring Seam Welding

Cut and Shearing Polishing Inspecting & Testing

Insulating

5.4.3 Material Prices

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

from the American Metals Market. 1 The 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 five­year average of the Bureau of Labor Statistics Producer

Price Indices (PPIs) spanning 2002 to 2006 with an adjustment to 2006$. 2 DOE used the PPIs

for copper rolling, drawing and extruding, and steel mill products, and made the adjustments to

2006$ 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 five­year average in material prices from 2002­

2006, these drastic increases are normalized to some extent, to better represent long­term

material price averages. Because it is not clear if these material price trends will continue, a

sensitivity analysis was conducted to illustrate the effect of raw material price increases on the

cost of commercial refrigeration equipment (see section 5.9.1).

5.4.4 Results

DOE reported the cost model results as a basic case cost for seven analyzed equipment

classes: VCT.RC.L, VOP.RC.M, SVO.RC.M, HZO.RC.L, HCT.SC.I, HZO.SC.M, and

VCT.SC.I. The basic case cost is the cost of the structure and other features, but excludes all

components that relate to design options (such as fans, doors, and evaporator coils) and special

exterior materials (such as signage and other customer­specified options). Figure 5.4.3 through

Figure 5.4.5 show the part count, weight, and cost, respectively, for the seven equipment classes

directly analyzed in the cost model.

Figure 5.4.3 details the part count by equipment class, cabinet size, and sub­system. The

large number of cabinet parts is driven primarily by fasteners holding all the sheet metal parts

together. The distinction between inner, outer, and other cabinet parts represents DOE’s best

effort to disaggregate the various cabinet categories. “Other” can include some fascia and

structural elements that help to keep the inner and outer skins in alignment. The condenser and

evaporator descriptors attempt to capture all components outside the heat exchangers that are

related to condensers and evaporator circuits. The electrical section mainly captures the cost of

wiring for the ballasts.

5­90 200 400 600 800 1000 1200 1400 1600 1800 2000PartCount(#) Outer Cabinet

Inner Cabinet

Cabinet­Other

Wiring/Electric

Evaporator­Other

Condenser­Other

Fasteners

VCT.RC.L VOP.RC.M SVO.RC.M HZO.RC.L HCT.SC.I HZO.SC.M VCT.SC.I

Figure 5.4.3 Part Count by Equipment Class and Subsystem

Figure 5.4.4 summarizes the weight that each subsystem contributes to the overall weight

of baseline CRE units of different lengths. These calculated weights are for the basic case only

and do not incorporate the weight of doors or frames (in the VCT or VCS equipment families),

compressor sleds (for SC units), heat exchangers, or other design options. Thus, depending on

the equipment class, the weight reported here will be lighter compared to manufacturer­reported

shipping weights for completed units.

The weight of commercial refrigeration equipment is heavily influenced by the weight of

the inner, outer, and cabinet base assemblies. This equipment is built to withstand years of

abuse, and the shipping weights of the cabinets reflect this requirement. The degree to which a

design option adds weight and expense is largely driven by the subsystem. For example, the

design options include doors with two to three panes of glass. While adding coatings to the glass

may reduce the energy consumption without a weight impact, a design option calling for

additional panes will have a compounding effect of requiring stronger door hinges and frames.

5­100 200 400 600 800 1000 1200 1400Weight(lb) Outer Cabinet

Inner Cabinet

Insulation

Cabinet­Other

Wiring/Electric

Evaporator­Other

Condenser­Other

Fasteners

VCT.RC.L VOP.RC.M SVO.RC.M HZO.RC.L HCT.SC.I HZO.SC.M VCT.SC.I

Figure 5.4.4 Weight by Equipment Class and Subsystem

The actual MPC of this equipment is driven by the processes used to make them, the cost

of the underlying raw and purchased materials, and the labor required to assemble them into a

working commercial refrigerator. Figure 5.4.5 shows the MPC for the basic cases discussed in

this section.

When the costs are considered by percentage, the inner cavity assembly dominates the

overall cost. This is driven largely by the higher raw material costs; the manufacturing steps

required to form, shape, and paint these parts; and the time and effort required to assemble and

seal them.

Exterior parts that are not visible to the supermarket consumer tend to be made of

uncoated galvanized cold rolled steel, remain unpainted, and usually do not require nearly as

much work to be prepared for assembly. As expected, freestanding units like those in the

HZO.SC.M equipment class tend to have higher relative costs for their exterior cabinet

assemblies, as they have ten highly visible surfaces, as compared to units in the VCT.RC.L

equipment class with six surfaces.

5­110 500 1000 1500 2000 2500 3000Cost(US$) Outer Cabinet

Inner Cabinet

Insulation

Cabinet­Other

Wiring/Electric

Evaporator­Other

Condenser­Other

Fasteners

VCT.RC.L VOP.RC.M SVO.RC.M HZO.RC.L HCT.SC.I HZO.SC.M VCT.SC.I

Figure 5.4.5 Manufacturer Production Cost by Equipment Class and Subsystem

DOE developed basic case costs (as MPC) for seven equipment classes. As illustrated in

Table 5.4.2, these results were extended to six of the remaining equipment classes directly

analyzed in the engineering analysis. Because of the complexity of construction, the cost of the

remaining two equipment classes (SOC.RC.M and VOP.RC.L) was estimated using MLP

information from several manufacturers. DOE discounted the MLP values to MPC, and

subtracted the estimated costs of known components (fan motors, lighting, etc.) to arrive at a

basic case cost. These basic case costs (in the form of MPC) were incorporated into an

engineering spreadsheet, where the costs for various design options were added and markups

were applied.

Table 5.4.2 Extension of Cost Model Estimates to Other Equipment Classes

Developed in Cost Model Extended to

VCT.RC.L VCT.RC.M

VOP.RC.M VOP.SC.M

SVO.RC.M SVO.SC.M

HZO.RC.L HZO.RC.M

HCT.SC.I

­

HZO.SC.M HZO.SC.L

VCT.SC.I VCS.SC.I

5­125.5 MANUFACTURER MARKUP AND LIST PRICE MARKUP

At each stage of the distribution chain, manufacturers, wholesalers, and contractors apply

a markup to cover their operating costs and profit margins. In the engineering analysis, DOE

determined a manufacturer markup, and applied this markup to the MPC to arrive at the MSP.

Wholesaler, contractor, and other markups are determined in the markups analysis, chapter 6 of

the TSD.

The manufacturer markup is market­share­weighted average value for the industry. DOE

developed this markup by examining several major CRE manufacturers’ gross margin

information from annual reports and the Securities and Exchange Commission (SEC) 10­K

reports. The manufacturers analyzed by DOE account for approximately 80 percent of the CRE

market, and each of these companies is a subsidiary of a more diversified parent company that

manufactures equipment other than commercial refrigeration equipment. Because the 10­K

reports do not provide gross margin information at the subsidiary level, the estimated markups

represent the average markups that the parent company applies over its entire range of equipment

offerings.

DOE evaluated markups for the years between 2000 and 2005, inclusive. Then it

calculated the manufacturer markup as 100/(100

– average gross margin)

, where gross margin is

calculated as revenue

– cost of goods sold (COGS)

. To validate the information, DOE used

Internal Revenue Service industry statistics as a check on the data from the SEC 10­K's and

company annual reports. 4 The result of the analysis shows that the average manufacturer markup

within the industry is 1.39.

DOE estimated an industry list price markup, which is a markup on the MPC that gives

the MLP. DOE understands that manufacturers typically offer a discount off the MLP, which

depends on various factors such as the relationship with the customer, the volume and type of

equipment being purchased. For this estimate, DOE relied on information gathered on selfcontained commercial refrigeration equipment, since list price information is readily available

and typically published by manufacturers. A review of the data for self­contained equipment

shows that the list price markup is typically 2.0. During manufacturer interviews, some CRE

manufacturers agreed with the 2.0 markup estimate, while others stated the estimate was

somewhat high. DOE further verified the estimate by obtaining list price quotes from several

remote condensing equipment manufacturers. Because list price markup is highly uncertain and

depends on many factors, DOE applied the same estimated list price markup across each

equipment class to simplify the analysis. DOE compared the analytically derived cost­efficiency

curves to the industry­supplied cost­efficiency curves using the list price markup estimate (see

section 5.7 for these comparisons).

5.6 ENERGY CONSUMPTION MODEL

The energy consumption model is the second of two key analytical models used in

constructing cost­efficiency curves. This model estimates the CDEC of commercial refrigeration

equipment in kilowatt hours (kWh) at various performance levels using a design­options

approach. The model is specific to the types of equipment covered under this rulemaking

5­13(described in chapter 3, market and technology assessment), but is sufficiently generalized to

model the energy consumption of all covered equipment classes. DOE developed the energy

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

public on DOE’s website (http://www.eere.energy.gov/buildings/appliance_standards/

commercial_products.html). Appendix A provides instructions for using the spreadsheet.

For a given equipment class, the model estimates the daily energy consumption for the

baseline and the energy consumption of several levels of performance above the baseline. The

model is used to calculate each performance level separately. For the baseline level, a

corresponding cost is calculated using the cost model (described in section 5.4 above), and for

each level above the baseline, the cost increases of the various design options are used to

recalculate the cost.

5.6.1 Screened­In Technologies

The technology options that were analyzed (i.e., were not screened out as part of the

screening analysis, chapter 4) are as follows:

• higher efficiency lighting;

• higher efficiency lighting ballasts;

• remote lighting ballast location;

• higher efficiency evaporator fan motors;

• evaporator fan motor controllers;

• higher efficiency evaporator fan blades;

• increased evaporator surface area;

• low pressure differential evaporators;

• insulation increases or improvements;

• defrost mechanism;

• defrost cycle control;

• higher efficiency compressors (self­contained equipment only);

• increased condenser surface area (self­contained equipment only);

• higher efficiency condenser fan motors (self­contained equipment only); and

• higher efficiency condenser fan blades (self­contained equipment only).

5.6.2 Screened­In Technologies Not Considered in the Engineering Analysis

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

technologies that can be used to reduce the energy consumption of commercial refrigeration

equipment. In the screening analysis, DOE first narrowed this list down by eliminating from

consideration those technologies that can reduce annual energy consumption of commercial

refrigeration equipment but do not reduce CDEC. Then, from the remaining technologies, DOE

screened out those technologies that were not technologically feasible, were not practical to

manufacture, reduced equipment utility, or were considered unsafe.

The remaining list of screened­in technologies became one of the inputs to the

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

5­14technologies in the energy consumption model. These include location of remote lighting

ballasts, evaporator fan motor controllers, higher efficiency evaporator and condenser fan blades,

insulation increases or improvements, low pressure differential evaporators, defrost cycle

controls, and defrost mechanisms.

5.6.2.1 Remote Lighting Ballast Location

Relocation of fluorescent lamp ballasts outside the refrigerated space can reduce energy

consumption by lessening the refrigeration load on the compressor. However, for the majority of

commercial refrigeration equipment currently manufactured, ballasts are already located in

electrical trays outside of the refrigerated space, in either the base or top of the equipment. The

notable exceptions are the equipment classes in the VCT equipment family, where ballasts are

most often located on the interior of each door mullion.

Most commercial refrigeration equipment manufacturers purchase doors for VCT units

that are preassembled with the entire lighting system in place rather than configured for separate

ballasts. DOE believes that most commercial refrigeration equipment manufacturers choose

doors this way because it would be labor intensive and time consuming to relocate these ballasts

at the factory, and because of the additional cost and labor of wiring separate ballasts. In

addition, the potential energy savings are small, since modern electronic ballasts are very

efficient and typically contribute only a few watts each to the refrigeration load. Therefore, DOE

did not consider remote relocation of ballasts as a design option.

5.6.2.2 Evaporator Fan Motor Controllers

Evaporator fan motor controllers allow fan motors to run at variable speed, to match

changing conditions in the case. For evaporator fan motor controllers, there is some opportunity

for savings as the buildup and removal of frost creates differing pressure drops across the

evaporator coil. Theoretically, less fan power is required when the coil is free of frost.

Additionally, the coil would operate at a more stable temperature during the period of frost buildup. However, the effectiveness of the air curtain in equipment without doors is very sensitive to

changes in airflow, so fan motor controllers could disrupt the air curtain. The potential of

disturbance to the air curtain, which could lead to higher infiltration loads, does not warrant the

use of evaporator fan motor controllers in equipment without doors, even if there were some

reduction in fan energy use. In addition, DOE believes that savings from evaporator fan motor

controllers in all equipment types would be small. Therefore, DOE did not consider evaporator

fan motor controllers as a design option.

5.6.2.3 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 technology used in commercial

refrigeration equipment is 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 used, but did identify one alternative fan blade

technology that could potentially improve efficiency: tangential fan blades. Tangential fan

blades can produce a wide, even airflow, and have the potential to allow for increased saturated

5­15evaporator temperature (SET) through improved air distribution across the evaporator coil,

which would reduce compressor power. However, tangential fan blades in small sizes are

themselves 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.

5.6.2.4 Improved or Thicker Insulation

Increases in or improvements to insulation thickness reduce the heat load due to

conduction and thus reduce compressor power. Increases in the thickness of foam insulation are

problematic because they must either borrow volume from the refrigerated space or increase the

overall size of the equipment cabinet. Because the outer dimensions of commercial refrigeration

equipment are limited it is often not practical to increase the overall size of the cabinet (i.e., case

exterior dimensions are optimized for packing equipment into freight and shipping containers).

In addition, reducing the size of the refrigerated space would reduce the utility of the equipment.

Therefore, increasing the thickness of foam insulation is not practical. Furthermore, many

display cases do not have significant conduction loads, so insulation improvements do not offer

large energy savings.

Improvements to insulation material include better polyurethane foams and vacuum

panels. In consultation with insulation material manufacturers, DOE determined that there are

no significant differences in “grades” of insulation material, so most equipment manufacturers

are already using the best commercially available foam materials in their equipment. Vacuum

panels are an alternative form of insulation; however, they may degrade in performance in time

as small leaks develop. In addition, vacuum panels cannot be penetrated by fasteners, and do not

provide the rigidity of “foamed­in­place” panels that polyurethane insulation creates. Therefore,

DOE did not consider insulation thickness increases or improvements as a design option.

DOE did, however, consider improvements to the efficiency (e.g., thermal conductance)

of doors in the design options analysis. Higher efficiency doors reduce the overall heat gain to

the case by using better frame materials, more panes of glass and better (or more) insulation in

the doorframe.

5.6.2.5 Low Pressure Differential Evaporators

Low pressure differential evaporators reduce energy consumption by reducing the power

of evaporator fan motors. However, in space­constrained equipment such as commercial

refrigeration equipment, this reduction usually comes from a decrease in evaporator coil surface

area, which generally requires a lower SET to achieve the same discharge air temperature and

cooling potential. This, in turn, results in a reduction in compressor efficiency. Because of these

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

option.

5.6.2.6 Defrost Cycle Control

Defrost cycle control can reduce energy consumption by reducing the frequency and

duration of defrost periods. The majority of equipment currently manufactured already uses

partial defrost cycle control in the form of cycle termination control. However, defrost cycle

5­16initiation is still scheduled at regular intervals. Full defrost cycle control would involve a

method of detecting frost buildup and initiating defrost. As described in the market and

technology assessment (see chapter 3 of the TSD), this could be accomplished through an optical

sensor or sensing the temperature differential across the evaporator coil. However, both of these

methods are unreliable due to problems with fouling of the coil due to dust and other surface

contaminants. This becomes more of an issue as the display case ages. Because of these issues,

DOE did not consider defrost cycle control as a design option.

5.6.2.7 Defrost Mechanisms

Defrosting for medium temperature equipment is typically accomplished with off­cycle

defrost. Because off­cycle defrost uses no energy (and decreases compressor on­time) there is

no defrost design option capable of reducing defrost energy in cases that use off­cycle defrost.

Some medium temperature cases and all low temperature and ice­cream temperature cases use

supplemental heat for defrost. Commonly, electric resistance heating (electric defrost) is used in

these cases. An alternative to electric defrost in those cases that require supplemental defrost

heat is hot­gas defrost. Hot­gas defrost is most often used in remote condensing equipment and

involves the use of the hot compressor discharge gas to warm the evaporator from the refrigerant

side. The test procedure for commercial refrigeration equipment is not capable of quantifying

the energy expenditure of the compressor during a hot­gas defrost cycle. Therefore, DOE did

not consider it as a design option.

5.6.3 Design Options

After conducting the screening analysis and removing from consideration those

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

the energy consumption model. The design options used in the model are:

• higher efficiency lighting and ballasts for VOP, SVO, HZO, and SOC equipment

families (horizontal fixtures);

• higher efficiency lighting and ballasts for VCT equipment family (vertical fixtures);

• higher efficiency evaporator fan motors;

• increased evaporator surface area;

• improved doors for VCT equipment family, low temperature (hinged, 30 x 67

inches);

• improved doors for VCT equipment family, medium temperature (hinged, 30 x 67

inches);

• improved doors for HCT equipment family, ice­cream temperature (sliding, 18 x 20.5

inches);

• improved doors for SOC equipment family, medium temperature (sliding, 20 x 24

inches);

• higher efficiency condenser fan motors (for self­contained equipment only);

• increased condenser surface area (for self­contained equipment only); and

• higher efficiency compressors (for self­contained equipment only).

5­17Each design option has two to three technology levels, ranging from the minimum (worst

performing) to the maximum (best performing) technology. The design options and the

technology levels for each design option are described below.

5.6.3.1 Higher Efficiency Lighting and Ballasts

Lighting is an important characteristic of commercial refrigeration equipment because it

makes the product visible to the consumer. Lighting systems operate continuously and provide

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

reductions in total case energy consumption can be achieved both through a direct reduction in

electricity consumption by the lighting system, and a reduction of heat inside the case, thereby

reducing compressor work.

It is important that product illumination not degrade with higher design option levels, as

this would decrease the utility of the equipment. So, DOE made every effort to maintain

constant system light output among design options. This approach meant DOE had to consider

lighting as a system, rather than distinguishing lamps and ballasts as separate design options.

This approach becomes more important when considering light emitting diode (LED) lighting

systems, which don’t use ballasts, as fluorescent lighting systems do.

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

replace, the fixtures are more efficient at directing light onto the product. Although the total

lumen output of LED systems is lower than comparable fluorescent systems, the amount of light

incident on the product (illuminance) is roughly equivalent. Consultation with CRE

manufacturers, lighting manufacturers, and other technical experts indicated that current LED

technology provides product lighting that is adequate, and in most cases comparable to

fluorescent lighting.

To account for the variation in design between equipment families, DOE used two

lighting design options in the energy­consumption model. DOE used the “higher efficiency

lighting and ballasts for VOP, SVO, HZO, and SOC equipment families” design option for

lighting in a horizontal configuration, and “ higher efficiency lighting and ballasts for VCT

equipment family ” design option for the lighting in a vertical configuration. The VCS and HCS

equipment families do not require lighting because they are not designed to display food, while

the HCT equipment family typically does not have lighting because it relies on store ambient

lighting. Therefore, DOE did not consider lighting design options for these three equipment

families.

Because of the horizontal configuration of shelving and the linear nature of display­case

line­ups in the VOP, SVO, HZO, and SOC equipment families, fluorescent lighting is typically

installed with the bulb in a horizontal plane. Details for the “higher efficiency lighting and

ballasts for VOP, SVO, HZO, and SOC equipment families” design option are shown in Table

5.6.1. Remote condensing versions of these display cases are most often sold in 8­ and 12­foot

(ft) sections, using multiples of 4­ft fluorescent lamps to continuously light the entire width of

the case. Self­contained versions are commonly sold in 4­ft lengths, so that a single 4­ft

fluorescent lamp will light the full width of the case. Therefore, 4­ft lamps were specified for all

lighting systems in the horizontal configuration. Additionally, these lamps were required to have

5­18a color temperature of 3500 Kelvin (K), which is typical for this type of equipment. Fluorescent

T12 magnetic and electronic systems were not considered for the horizontal lighting because a

survey of existing equipment and discussions with manufacturers indicated that this technology

no longer is used in these equipment classes.

Table 5.6.1 Details for “Lighting for VOP, SVO, HZO, and SOC Equipment

Families” Design Option

Level Description Lamp

Type Lamp

Rated

Power

[watts

(W)] Lamp

Rated Light

Output

[Lumens] System

Efficacy

[Lumens/

W] System

Light

Output

[Lumens]

T8 4 ft, T8 Elec. F32T8 32.0 2850 85.0 2679

T8S 4 ft, “Super” T8 Elec. F32T8/HL 32.0 3100 91.4 2697

LED 4 ft, LED LED 4' 16.4 820 50.0 820

Because of the vertical configuration of the doors with the VCT equipment family,

fluorescent lamps are typically installed vertically behind the mullions between doors. Table

5.6.2 shows details for the “lighting for VCT equipment family” design option. Such lighting

systems typically consist of a single 5­ or 6­ft lamp and a single ballast per mullion and are

installed at each end of the case. All lighting systems in the vertical configuration were specified

to have 5­ or 6­ft lamps and a color temperature of 4100 K, which is typical for this equipment

family.

Table 5.6.2 Details for “Lighting for VCT Equipment Family” Design Option

Lamp Lamp Rated System System

Level Description Lamp Type Rated

Power Light

Output Efficacy

[Lumens Light

Output

[W] [Lumens] /W] [Lumens]

T12HO 6 ft, T12 HO Mag. F72T12/HO/SP 85.0 6550 64.9 5960

T8 5 ft, T8 Elec. F58T8/835 58.0 5400 93.1 5400

LED 5 ft, LED

­ 41.0 2050 50.0 2050

5.6.3.2 Higher Efficiency Evaporator Fan Motors

In conjunction with fan blades, fan motors are necessary for transferring heat from the

display case to the refrigerant and, in the case of self­contained equipment, rejecting heat from

the refrigerant into the ambient air. Fan motors are also responsible for maintaining product

temperatures and air curtains on open cases. They must operate virtually continuously, and

therefore use a significant amount of energy. As motor efficiency increases, reductions in total

case energy consumption are realized through a direct reduction both in electricity consumption

and waste heat inside the case, reducing compressor work.

Table 5.6.3 shows details for the evaporator fan motor design option. Currently, DOE

considers shaded­pole motors (SPM) as the minimum technology, permanent split capacitor

(PSC) motors as the mid­level technology, and brushless direct current (DC) or electronically

commutated motors (ECMs) as the maximum technology level. The motor efficiency levels

listed in Table 5.6.3 were taken from American National Standards Institute (ANSI)/ARI

5­19Standard 1200­2006 (ARI 1200), Performance Rating of Commercial Refrigerated Display

Merchandisers and Storage Cabinets

.

Table 5.6.3 Details for “Evaporator Fan Motor” Design Option

Rated Shaded­Pole Motor (SPM) Permanent Split Capacitor

(PSC) Motor Brushless DC Motor

(ECM)

Power

[W] Actual

Power

[W] Efficiency Actual

Power

[W] Efficiency Actual

Power

[W] Efficiency

15.0

9.0

6.0 75.0

45.0

30.0 20.0%

20.0%

20.0% 51.7

31.0

20.7 29.0%

29.0%

29.0% 22.7

13.6

9.1 66.0%

66.0%

66.0%

5.6.3.3 Increased Evaporator Surface Area

Evaporator coils are another component necessary for transferring heat from the display

case to the refrigerant. Table 5.6.4 shows details for the evaporator coil design option. In view

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

design option. For each level, DOE specified an overall UA­value c and a coil cost. The UAvalue 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

classes. In consultation with outside experts, DOE determined that the same coil improvements

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

Table 5.6.4 Details for “Evaporator Coil” Design Option

Level Description Normalized UA [­] Normalized Coil Cost

[$/Btu/hr]

EVAP1

EVAP2 Standard Coil

High­Performance Coil 1

1.667 $0.0358

$0.0500

The details of coil construction (shown in Table 5.6.5) were based on a baseline and

prototype high­performance coil evaluated in a study by Oak Ridge National Laboratory. 5 The

high­performance coil uses a combination of enhancements to the heat transfer surfaces that

increased its overall UA­value. These enhancements include higher fin pitch, rifled tubing, and

different tube spacing. In sum, these improvements allow the prototype coil to run at a SET that

is 6 degrees warmer than the baseline coil and maintain the same discharge air temperature

(30°F) and heat removal capacity (12,990 British Thermal Units per Hour (Btu/hr)).

The overall UA­value is the product of the overall heat transfer coefficient (Btu/h­ft 2 ­°F) and the total surface area

(ft 2 ) of the coil. This value can be derived from the total heat transfer rate of the coil (Btu/h) divided by the average

temperature difference between the discharge air and the saturated evaporator temperature (ΔT).

5­20 cTable 5.6.5 Properties of Standard and Enhanced Evaporator Coil

Property Standard Coil High­Performance Coil

Overall Width (in): 81 81

Overall Height (in): 7 5/8 7 1/2

Overall Depth (in): 12 13 9/16

Tube Rows per Circuit: 12 12

Number of Parallel Circuits: 4 6

Tubing Material: Copper Copper

Tubing Outer Diameter (in): 1/2 3/8

Tubing Wall Thickness (in): 0.012 0.012

Tubing Inner Surface: Smooth Rifled

Fin Material: Aluminum Aluminum

Fin Surface: Flat Flat

Fin Dimensions (in): 5.415 x 7.5 (5 front rows) 8.66 x 7.5 (all rows) 7.581 x7.5 (7 rear rows)

Fin Pitch (fins per inch): 2 (all rows) 3 (5 front rows)

4 (7 rear rows)

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 different sized coils and at different temperatures would result in

similar SET improvements.

5.6.3.4 Improved Doors

Transparent doors allow refrigerated products to be displayed to consumers while

keeping cold air inside of the display case. On freezers and some refrigerators, glass doors must

be heated to prevent frost from forming and rubber seals from freezing. These “anti­sweat”

heaters often run continuously and consume significant amounts of energy. Transparent doors

also allow heat to radiate into the display case and have a lower insulation value than solid walls.

Reductions in total case energy consumption can be achieved both by improving the overall

insulation value (U­factor) of the door, and by reducing the required anti­sweat heater power.

A wide variety of door types are used on the equipment covered in this rulemaking. Door

construction and performance can vary by equipment family as well as by operating temperature

of the case. To account for this variation, DOE developed four separate design options for the

different door types that are represented in the 15 equipment classes that were directly analyzed.

For all door design options, DOE estimated the thermal performance of the door (expressed as an

overall U­factor) using information about door construction from manufacturers and WINDOW

5 software, available from Lawrence Berkley National Laboratory. 6

Doors for the VCT equipment family operating at low temperature are of the hinged type

and are nominally 30 inches wide and 67 inches tall with three panes of glass. Table 5.6.6 shows

details of door thermal performance and anti­sweat heater requirements for this door type. DOE

considered two technology levels for this design option: the high­performance door that uses a

combination of low­emissivity coating, frame material, and inert fill­gas to achieve a reduced

overall U­factor; and a standard door.

5­21Table 5.6.6 Details for “Doors for VCT Equipment Family, Low Temperature”

Design Option

Level Description Overall U­Factor

[Btu/hr­ft­°F] Anti­Sweat Heater

Power [W/door]

DOOR1

DOOR2 Standard Door

High­Performance Door 0.547

0.276 160

60

Doors for the VCT equipment family operating at medium temperature are of the hinged

type and are nominally 30 inches wide and 67 inches tall with two panes of glass. Table 5.6.7

shows details of door thermal performance and anti­sweat heater requirements for this door type.

Two technology levels were considered for this design option. The high­performance door uses

a combination of low­emissivity coating, frame material, and inert fill­gas to achieve a reduced

overall U­factor compared to the standard door and elimination of anti­sweat heater power.

Table 5.6.7 Details for “Doors for VCT Equipment Family, Medium Temperature”

Design Option

Level Description Overall U­Factor

[Btu/hr­ft­°F] Anti­Sweat Heater

Power [W/door]

DOOR1

DOOR2 Standard Door

High­Performance Door 0.560

0.478 60

0

Doors for the HCT equipment family operating at ice­cream temperature (HCT.SC.I and

HCT.RC.I equipment class) are of the sliding type and are nominally 18 inches wide and 20.5

inches tall with one pane of glass. Table 5.6.8 shows details of door thermal performance and

anti­sweat heater requirements for this door type. DOE considered two technology levels for this

design option: a high­performance door that uses a combination of low­emissivity coating,

frame material, and an extra pane with inert fill­gas to achieve a reduced overall U­factor; and a

standard door. Typically, a high­performance door does not require anti­sweat heater power.

Table 5.6.8 Details for “Doors for HCT Equipment Family, Ice­Cream

Temperature” Design Option

Level Description Overall U­Factor

[Btu/hr­ft­°F] Anti­Sweat Heater

Power [W/door]

DOOR1

DOOR2 Standard Door

High­Performance Door 1.046

0.377 0

0

Doors for the SOC equipment family operating at medium temperature are of the sliding

type and are nominally 24 inches wide and 20 inches tall with 2 panes of glass. Table 5.6.9

shows details of door thermal performance and anti­sweat heater requirements for this door type.

DOE considered two technology levels for this design option: a high­performance door that uses

a combination of low­emissivity coating, frame material, and inert fill­gas to achieve a reduced

overall U­factor; and a standard door. Typically, a high­performance door does not require antisweat heater power.

5­22Table 5.6.9 Details for “Doors for SOC Equipment Family, Medium Temperature”

Design Option

Level Description Overall U­Factor

[Btu/hr­ft­°F] Anti­Sweat Heater

Power [W/door]

DOOR1

DOOR2 Standard Door

High­Performance Door 0.672

0.320 0

0

5.6.3.5 Higher Efficiency Condenser Fan Motors

The condenser fan motor design option applies only to those equipment classes that are

self­contained (SC). Details for the condenser fan motor design option are identical to those

shown in Table 5.6.3. As with evaporator fan motors, the SPM is the minimum technology

level, the PSC motor is the mid­technology, 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.

5.6.3.6 Increased Condenser Surface Area

Table 5.6.10 shows details for this design option, which only applies to self­contained

equipment classes. Details of coil construction are based on data provided from tear­downs by

Southern California Edison’s Refrigeration and Thermal Test Center (RTTC). 7 Based on

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

design option. For each level, DOE specified an overall UA­value and a coil cost. The UAvalue 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 selfcontained equipment classes. In consultation with outside experts, DOE determined that the

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

improvements.

Table 5.6.10 Details for “Increased Condenser Surface Area” Design Option

Level Description Normalized

UA [­] Normalized Coil Cost [$/Btu/h]

COND1

COND2 Standard Coil

High­Performance Coil 1

2.56 $0.0146

$0.0439

Details of coil construction are show in Table 5.6.11. The high­performance coil uses a

combination of enhancements to the heat transfer surfaces that increased its overall UA­value.

These enhancements include higher fin pitch, rifled tubing and different tube spacing. In sum,

these improvements allow the prototype coil to run at a saturated condenser temperature (SCT)

that is 10°F cooler than the baseline coil while maintaining the same heat rejection rate (1600

Btu/hr). Because compressor performance is directly related to SCT, reductions in total case

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

5­23Table 5.6.11 Properties of Standard and Enhanced Condenser Coil

Property Standard Coil High­Performance 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

5.6.3.7 Higher Efficiency Compressors

The compressor design option applies only to SC equipment classes. 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 single­speed hermetic compressor, and the maximum technology level is a highefficiency single­speed hermetic compressor. (See section 5.6.5 for a discussion of why

variable­speed 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 single­speed hermetic compressors from

several manufacturers over a range of capacities applicable to the covered equipment (1,500

­ 20,000 British thermal units per hour (Btu/h)). This data set was used to look up appropriately

sized compressors when developing each design­option curve (see section 5.6.7.2 for

information on the calculation of compressor energy consumption). Although several

compressor manufacturers produce high­efficiency compressors, little data are currently

available on their performance. Therefore, DOE approximated a set of high­efficiency

compressors by adjusting the power consumption of the standard compressors using a constant

multiplier. This multiplier was developed through consultation with experts and research

conducted by DOE (see section 5.6.5 for details on this multiplier).

5.6.4 Baseline Specifications

DOE defined baseline specifications (or case design 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 lowest technological level of each design option

(see section 5.6.3), the baseline specifications define the energy consumption and cost of the

typical minimum technology equipment on the market. Table 5.6.12 shows the specifications

and units that are defined for each equipment class.

5­24Table 5.6.12 Baseline Specifications

Specification Units

Case length ft

Case Gross Refrigerated Volume ft 3

Case Total Display Area ft 2

Number of Lamps in Conditioned Space #

Number of Lamps NOT in Conditioned Space #

Number of Ballasts in Conditioned Space #

Number of Ballasts NOT in Conditioned Space #

Evaporator Fan Nominal Rated Wattage W

Number of Evaporator Fans per Case #

Condenser Fan Nominal Rated Wattage W

Number of Condenser Fans per Case #

Defrost Mechanism Type [Off­Cycle, Electric, Manual] n/a

Defrost Time per Day hr

Defrost and Drain Heater Power W

Anti­Sweat Power Other Than Doors W

Condensate Pan Heater Power W

Average Case Temperature °F

Saturated Evaporator Temperature (SET) Nominal °F

Saturated Condenser Temperature (SCT) Nominal °F

Compressor Oversize Factor [>1] n/a

Nominal Insulation Thickness in

Wall Area ft 2

Number of Doors #

Single Door Area ft 2

Non­Door Glass Area ft 2

Case Interior Surface Area ft 2

Air­Curtain Height ft

Air­Curtain Angle From Vertical °

Defrost Melt Water lb/hr

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. This process created a representative unit for each equipment class with average

characteristics for physical parameters (e.g., volume, total display area), and minimum

performance of energy­consuming components (e.g., fans, lighting). Appendix B provides these

numerical specifications for each equipment class.

5.6.5 Non­Numerical Assumptions

In developing the energy consumption model, DOE made certain non­numerical

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

well as specific assumptions regarding load components and design options.

5­25DOE assumed that all conditions are based on new equipment tested in a controlledenvironment chamber subjected to ARI 1200, which references the ANSI/American Society of

Heating, Refrigerating and Air­Conditioning Engineers (ASHRAE) Standard 72­2005

(ASHRAE 72), Method of Testing Commercial Refrigerators and Freezers

. Manufacturers that

certify their equipment to comply with Federal standards will be required to test new units to this

test method, which specifies certain ambient temperature, humidity, light level, and other

requirements.

DOE assumed that there is no pull­down load associated with re­shelving products since

the test procedure does not address product re­shelving. Product re­shelving is the act of loading

new products into refrigerated display cases as existing products are sold. Typically, commercial

refrigeration equipment is not designed to pull down the temperature of warm products, but only

to display products that were already chilled or frozen in a refrigerated storage unit.

DOE also assumed that there are no pull­down loads associated with post­defrost periods.

During defrost periods, the compressor (or the flow of refrigerant for remote condensing cases)

is stopped and the coil is allowed to warm to a temperature above freezing (aided by electric

resistance heating in the case of electric defrosts). After the evaporator coil has been cleared of

frost, the merchandise in the case will typically have warmed several degrees. The merchandise

must be returned to normal operating temperature when the refrigeration cycle resumes, adding

an additional load to the condensing unit. Between equipment families and even within

equipment classes there is a large variation in defrost mechanism, defrost cycle time, temperature

recovery time, and product mass. Because of the uncertainty of these factors, DOE was not able

to accurately calculate the defrost pull­down load and, therefore, did not include it in the model.

Sample calculations show that this load may only account for 2 to 4 percent of the total

refrigeration load for a VOP.RC.M case, or roughly 1 to 2 percent of the total daily energy

consumption.

DOE did not consider hot­gas defrost as a design option for defrost mechanisms in

remote condensing cases (see chapter 4, screening analysis). During hot­gas defrost, hot

refrigerant from the compressor rack bypasses the condenser and expansion device and is piped

directly to the evaporator coil, melting the frost on the coil. The ASHRAE 72 test procedure

provides a method for measuring the total refrigeration load during steady­state conditions, and

does not capture the energy added to a display case during a hot­gas defrost cycle. Therefore,

DOE did not consider this technique.

DOE did not consider liquid suction heat exchangers (LSHX) as a design option (see

chapter 4, screening analysis). As with hot­gas defrost, the effects of LSHX cannot be measured

with the ASHRAE 72 test procedure.

DOE did not consider variable­speed compressors as a compressor design option.

Variable­speed compressors reduce energy consumption under real­world 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 single­speed compressor during part­load operation. The ASHRAE 72

test procedure prescribes steady­state conditions. Thus, a variable­speed compressor would be

5­26limited to single­speed operation, the resultant EER would be no better than a properly sized

single­speed compressor, and no appreciable energy savings would result. Similarly, under

ASHRAE 72, the performance of a high­efficiency variable­speed compressor would be

comparable to a high­efficiency single­speed compressor.

5.6.6 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 nonelectric loads. Details of these assumptions are shown in Table 5.6.13.

5­27Table 5.6.13 Energy Consumption Model Numerical Constants and Assumptions

Numerical Constants and Assumptions Number Source

Test Chamber Temperature [°F] 75 ASHRAE 72 8

Test Chamber Relative Humidity [%] 55 ASHRAE 72 8

Test Chamber Pressure [pounds per square

in (psi), absolute] 14.7 Assumed

Manufacturer Markup [$/$] 1.39 Publicly available corporate financial data

List Price Markup [$/$] 2.00 DOE estimate based on discussion with

manufacturers

Fraction of Anti­Sweat Heater Power Into

Case [W/W] 0.7 DOE estimate based on discussions with

manufacturers

Fraction of Lighting Power Into Case for

Lamps Outside of Air Curtain [W/W] 0.5 Electric Power Research Institute (EPRI),

Supermarket Simulation Tool (SST) v3.0 9

Lighting Operating Time Per Day [hr] 24 Assumed

Thermal Conductivity of Foam Insulation

[Btu­in/hr­ft 2 ­F] 0.125 Discussions with foam manufacturers;

Manufacturer data sheets

Convective Film Coefficient Inside Case

Walls [Btu/hr­ft 2 ­F] 4.00 Communication with Southern California Edison,

Refrigeration and Thermal Test Center (RTTC)

Convective Film Coefficient Outside Case

Walls [Btu/hr­ft 2 ­F] 1.46 Communication with RTTC

Overall U­Value of Single Pane Glass

[Btu/hr­ft 2 ­F] 1.059 Lawrence Berkeley National Laboratory

WINDOW 5 Software 6

Emissivity of Test Chamber Walls [­] 0.9 Communication with RTTC

Emissivity of Case Inner Walls [­] 0.9 Communication with RTTC

View Factor From Case Interior to Room

[­] 0.025 Communication with RTTC

Area of Test Chamber Walls [ft 2 ] 1000 Communication with RTTC

Case Interior Relative Humidity [%] 65 R. Faramarzi, Efficient Display Case

Refrigeration, ASHRAE Journal, November

1999 10

Evaporator Coil Overall Bypass Factor [%] 17 DOE estimate

High­Efficiency Compressor Cost

Premium 10% Arthur D. Little (ADL) 1996 11

High­Efficiency Compressor Power

Reduction 20% ADL 1996 11

5.6.7 Model Components

Figure 5.6.1 presents a schematic showing the components in the energy consumption

model. The model calculates energy consumption in two major subsections (expressed as

kilowatt hours per day (kWh/day)): compressor energy consumption, component energy

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

by each fan motor, lamp, defrost and drain heater, anti­sweat heater, and pan heater.

Compressor energy consumption is calculated from the total heat load (expressed as

Btu/h) and one of two compressor models: one version for remote condensing equipment, and

5­28one for self­contained equipment. The total heat load is a sum of the component load and the

non­electric load. The component load is a sum of the heat emitted by evaporator fan motors,

lighting, defrost heaters, drain heaters, and anti­sweat heaters inside and adjacent to the

refrigerated space (condenser fan motors and pan heaters are outside of the refrigerated space

and do not contribute to the component heat load). The non­electric load is the sum of the heat

contributed by radiation through glass and openings, heat conducted through walls and doors,

and warm air infiltration through openings.

Total Heat

Load

[Btu/h]

Component

Load

[Btu/h] Non­Electric

Load

[Btu/h]

Fan Motor

Heat Load

[Btu/h] L i g h t i n g H e a t

Load

[Btu/h] Defrost

Heater Load

[Btu/h] Anti­Sw eat

Heater Load

[Btu/h] Radiation

Load

[Btu/h] Conduction

Load

[Btu/h] Infiltration

Load

[Btu/h] Daily Energy

Consumption [kWh/day]

Component

Energy

C o n s u m p t i o n

[kWh/day]

Fan Motor

Energy

C o n s u m p t i o n

[kWh/day] Lighting

Energy

C o n s u m p t i o n

[kWh/day] Defrost

Energy

C o n s u m p t i o n

[kWh/day] Pan Heater

Energy

C o n s u m p t i o n

[kWh/day] Anti­Sw eat

Energy

C o n s u m p t i o n

[kWh/day] C o m p r e s s o r

Energy

C o n s u m p t i o n

[kWh/day]

C o m p r e s s o r M o d e l

(ARI 1200 or ARI 540)

Electric

Energy

Consumption

[kWh/day]

Heat Load

[Btu/h] Legend:

Figure 5.6.1 Components of the Energy Consumption Model

5.6.7.1 Component Energy Consumption

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

each fan motor, lamp, defrost and drain heater, anti­sweat heater, and pan heater.

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 a 24­hour period. (This calculation assumes that evaporator and condenser fans run

continuously when off­cycle defrost is used, and are turned off during defrost when electric

defrost is used).

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

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

period. (This calculation assumes that lighting operates continuously.)

5­29Defrost and drain heater energy consumption is calculated by summing the power draw

of each defrost heater and drain heater, and multiplying by the total time the case is in defrost

operation over a 24­hour period.

Anti­sweat energy consumption is calculated by summing the power draw of each antisweat heater, and multiplying by the total operating time of the heaters over a 24­hour period.

(This calculation assumes that anti­sweat heaters run continuously.)

Pan heater energy consumption is calculated by multiplying the power draw of each pan

heater by the total operating time of the heater over a 24­hour period. The total operating time is

calculated as the time it would take to evaporate all of the defrost melt water.

5.6.7.2 Compressor Energy Consumption

Compressor energy consumption (CEC) is calculated from the total heat load and one of

two compressor models: one version for remote condensing equipment and one for selfcontained equipment. Compressor energy consumption for remote condensing equipment is

calculated using default efficiency values from ARI 1200. Table 1 in ARI 1200 lists remote

condensing compressor EER in Btu/Wh, as a function of adjusted dew point temperature.

Adjusted dew point (ADP) temperature (°F) is calculated as:

ADP

= SET

– 2°F (for medium temperature)

ADP

= SET

– 3°F (for low/ice­cream temperature) Eq. 5.1

Eq. 5.2

where

SET is the saturated evaporator temperature (°F).

Once ADP is calculated, Table 1 in ARI 1200 is used to find the corresponding EER

value. The compressor energy consumption (kWh/day) is then calculated as:

CEC

= Q

tot x (24

­ t defrost ) / (EER x 1000) Eq. 5.3

where

Q

tot is the total heat load (Btu/hr), and

t defrost is the total defrost time in a 24 hour period (hr).

Compressor energy consumption for self­contained equipment is calculated by using the

compressor model described in section 6.4 of ARI Standard 540­2004 (ARI 540), Performance

Rating of Positive Displacement Refrigerant Compressors and Compressor Units

. This model is

based on a 10­coefficient 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

5­30determined given a SET and SCT. Using Equation 5.3 above, the compressor energy

consumption can be determined.

5.6.7.3 Component Load Model

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

defrost and drain heater, and anti­sweat heater inside and adjacent to the refrigerated space.

Each of these components creates waste heat that is rejected to the refrigerated space and must be

removed by the compressor.

It is 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 is eventually converted to heat as well.

For lamps inside the refrigerated space, it is assumed that all electrical energy consumed

by the lamps ends up as heat inside the space. For lamps that are outside the refrigerated space

(i.e., adjacent to the air curtain), it is assumed that 50 percent of the electrical energy consumed

by the lamps ends up as heat inside the space. For ballasts inside the refrigerated space, it is

assumed that all electrical energy consumed by the ballasts ends up as heat inside the space.

Ballasts outside the refrigerated space do not contribute any heat to the space.

Part of the electrical energy that is consumed by defrost heater coils is consumed by the

phase change of the melting frost. Over a 24­hour period, this total heat of melting is given by

Q

melt = m frost H f

, water Eq. 5.4

where

Q melt is the heat of melting (Btu/hr),

m

frost is the frost mass in a 24­hour period (lbs/hr), and

H

f,water is the heat of fusion of water (Btu/lb).

Of the energy consumed by defrost heaters, it is assumed that all the electrical energy,

other than what is used to melt the frost, ends up as heat inside the refrigerated space. For drain

heaters, it is assumed that all electrical energy ends up as heat inside the refrigerated space.

For anti­sweat heaters adjacent to the refrigerated space (frame, rail, glass, sill and air

grille heaters), it is assumed that on average, 70 percent of the electrical energy consumed by the

heaters ends up as heat inside the space.

5.6.7.4 Radiation Load Model

The radiation heat load model accounts for the gray­body radiation between the warm

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

refrigerated space. For cases without doors, the net radiation is given by:

5­31T 4

− 4 σ



# ( T

case 

# )

room Q

rad = Eq. 5.5 1

− ε 1 1

− ε

room case + +

ε A A F ε A

room room room case

− room case case

where

Q rad is the net radiation load (Btu/h),

σ is the Stefan­Boltzmann constant (Btu/h­ft 2 ­°F 4 ),

T

room is the temperature of the room walls (°F),

T

case is the temperature of the case inner walls (°F),

ε room is the emissivity of the room walls (dimensionless),

ε case is the emissivity of the case inner walls (dimensionless),

A

room is the area of the room walls (ft 2 ),

A

case is the area of the interior of the case (ft 2 ), and

F

case­room is the view factor from the case interior to the room walls

(dimensionless).

The wall temperatures of the case and the room are assumed to be in thermal equilibrium

with the air temperature in the case and the room, respectively. See Table 5.6.13 for numerical

constants pertaining to the radiation model.

For glass doors and other glass, the net radiation is incorporated into the overall U­value

of the door calculated by WINDOW 5 (see Table 5.6.6 through Table 5.6.9, and Table 5.6.13).

Within the WINDOW 5 program, the environmental conditions in the case and the room were

specified for cases at medium temperature, low temperature and ice­cream temperature. See

section 5.6.7.5 for a discussion of the calculation of the combined radiation and conduction loads

for glass doors and other glass.

5.6.7.5 Conduction Load Model

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

solid walls and doors, the conduction is given by:

T

− T

room case Q

cond = A

walls Eq. 5.6 1 d

ins 1

+ + h k h

o ins i

where

A walls is the area of the exterior of the case (ft 2 ),

h

o is the convective film coefficient on the outside of case walls (Btu/h­ft 2 ­°F),

h i is the convective film coefficient on the inside of case walls (Btu/h­ft 2 ­°F),

d

ins is the insulation thickness (in), and

k

ins is the insulation thermal conductivity (Btu­in/h­ft 2 ­°F).

5­32Because 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 5.6.13 for numerical constants pertaining to the

conduction model.

For glass doors and other glass, the conduction load is incorporated into the overall Ufactor of the door assembly or glass calculated by WINDOW 5 (see Table 5.6.6 through Table

5.6.9 and Table 5.6.13). The combined radiation and conduction load for glass doors and other

glass is calculated as:

Q

glass = U

overall A glass 

# ( T

room − T

case 

# ) Eq. 5.7

where

U overall is the overall U­factor, including convection and radiation (Btu/h­ft 2 ­°F),

and

A glass is the area of the glass (ft 2 ).

5.6.7.6 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 through display openings, door openings, and cracks. The

infiltration load is difficult to model because of the inherent complexity of the fluid phenomena

of infiltration and door­opening events. Therefore, DOE used empirical data for defrost melt

water to back­calculate the infiltration load. This approach was correlated using empirical data

for infiltration loads from several sources.

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 defrostmelt

m = Eq. 5.8

air 

# ( HR

− HR

case 

# ) ( 1

− CBF 

### )

room

where

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

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

HR

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

HR

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

CBF is the coil bypass factor (dimensionless).

5­33The 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 and data from the

Supermarket Simulation Tool (SST) were used to estimate the evaporator coil bypass factor. As

shown in Table 5.6.13, the coil bypass factor was determined to be 17 percent.

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 of the case. Using the mass flows of air and

water vapor, the infiltration load can be approximated using:

Q

inf = m air C dryair 

# ( T

room − T

case 

# )

+ m

vapor H

v H 2 Eq. 5.9

, O

where

Q inf is the infiltration load (Btu/h),

C

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

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

Hv ,H2O is the heat of vaporization of water.

5.7 COST­EFFICIENCY CURVES

The result of the engineering analysis is a set of cost­efficiency curves. DOE developed

15 curves representing the 15 directly analyzed equipment classes, using the baseline

specifications and design options described above (more details are also provided in appendix

B). The methodology for developing curves started with the determination of the baseline

energy consumption 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.

ARI created four industry­aggregated curves using an efficiency­level approach. ARI

presented these curves to DOE in the form of daily energy consumption and manufacturer list

price normalized by total display area (TDA). DOE applied the list price discount developed in

the markup section (see section 5.5 above) to the industry­supplied (IS) curves to arrive at a

TDA­normalized MSP.

The 15 cost­efficiency curves are shown in Figure 5.7.1 through Figure 5.7.15 and in

tabulated form in Table 5.7.2 through Table 5.7.16 in the form of TDA­normalized daily energy

consumption and MSP. Figure 5.7.1 through Figure 5.7.4 and Table 5.7.2 through Table 5.7.5

include the corresponding industry­supplied data for comparison. A list of the 15 analyzed

equipment classes and their corresponding figure, table, and page numbers is shown in Table

5.7.1. More detailed results, including the design options used at each design option level in the

analytically derived (AD) curves, are provided in appendix B.

5­34Table 5.7.1 Figure, Table, and Page Numbers for Cost­Efficiency Results

Equipment

Class Figure Table Page Number

VCT.RC.L* Figure 5.7.1 Table 5.7.2 5­36

VOP.RC.M* Figure 5.7.2 Table 5.7.3 5­37

SVO.RC.M* Figure 5.7.3 Table 5.7.4 5­38

HZO.RC.L* Figure 5.7.4 Table 5.7.5 5­39

HZO.RC.M Figure 5.7.5 Table 5.7.6 5­40

VCT.RC.M Figure 5.7.6 Table 5.7.7 5­41

VOP.RC.L Figure 5.7.7 Table 5.7.8 5­42

SOC.RC.M Figure 5.7.8 Table 5.7.9 5­43

VOP.SC.M Figure 5.7.9 Table 5.7.10 5­44

SVO.SC.M Figure 5.7.10 Table 5.7.11 5­45

HZO.SC.L Figure 5.7.11 Table 5.7.12 5­46

HZO.SC.M Figure 5.7.12 Table 5.7.13 5­47

HCT.SC.I Figure 5.7.13 Table 5.7.14 5­48

VCT.SC.I Figure 5.7.14 Table 5.7.15 5­49

VCS.SC.I** Figure 5.7.15 Table 5.7.16 5­50

* Shown with industry­supplied data.

** VCS equipment family is normalized by volume.

As stated above, DOE used the cost­efficiency curves from the engineering analysis as an

input to the life­cycle cost (LCC) analysis to determine the price of commercial refrigeration

equipment to the customer (see chapter 8). For the equipment classes with industry­supplied

curves, those curves were used in the LCC analysis (not the analytically derived curves). For all

other equipment classes, DOE used the analytically derived curves in the LCC analysis.

5­35Note: The industry­supplied curve was

converted to MSP using the list price

discount.

Figure 5.7.1 Cost­Efficiency Curve for the VCT.RC.L Equipment Class

Table 5.7.2 Cost­Efficiency Data for the VCT.RC.L Equipment Class

Industry­Supplied Data DOE Analytically derived Data

Efficiency

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ] Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

IS1 1.06 102.00

IS2 0.95 105.96

IS3 0.90 108.63

IS4 0.85 111.52

IS5 0.80 114.68

IS6 0.75 118.14

IS7 0.70 121.96

IS8 0.65 126.22

IS9 0.60 130.98

IS10 0.55 136.61 AD1 1.08 110.68

AD2 0.97 111.32

AD3 0.95 111.77

AD4 0.92 112.86

AD5 0.61 133.28

AD6 0.60 135.12

AD7 0.55 148.14

5­36Note: The industry­supplied curve was

converted to MSP using the list price

discount.

Figure 5.7.2 Cost­Efficiency Curve for the VOP.RC.M Equipment Class

Table 5.7.3 Cost­Efficiency Data for the VOP.RC.M Equipment Class

Industry­Supplied Data DOE Analytically derived Data

Efficiency

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ] Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

IS1 1.08 74.00

IS2 1.00 80.37

IS3 0.95 83.01

IS4 0.90 85.93

IS5 0.85 89.19

IS6 0.80 92.86

IS7 0.75 97.01

IS8 0.70 101.75

IS9 0.64 108.43 AD1 1.16 76.90

AD2 1.12 77.56

AD3 1.06 79.17

AD4 1.03 81.31

AD5 0.96 86.14

AD6 0.79 116.04

5­37Note: The industry­supplied curve was

converted to MSP using the list price

discount.

Figure 5.7.3 Cost­Efficiency Curves for the SVO.RC.M Equipment Class

Table 5.7.4 Cost­Efficiency Data for the SVO.RC.M Equipment Class

Industry­Supplied Data DOE Analytically derived Data

Efficiency

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ] Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

IS1 1.05 97.26

IS2 1.00 101.26

IS3 0.95 104.26

IS4 0.90 107.57

IS5 0.85 111.24

IS6 0.80 115.34

IS7 0.74 120.94 AD1 1.19 91.56

AD2 1.15 92.15

AD3 1.09 93.58

AD4 1.02 98.12

AD5 1.00 100.02

AD6 0.84 126.58

5­38Note: The industry­supplied curve was

converted to MSP using the list price

discount.

Figure 5.7.4 Cost­Efficiency Curves for the HZO.RC.L Equipment Class

Table 5.7.5 Cost­Efficiency Data for the HZO.RC.L Equipment Class

Industry­Supplied Data DOE Analytically derived Data

Efficiency

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ] Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

IS1 0.83 89.87

IS2 0.80 90.81

IS3 0.75 93.00

IS4 0.70 95.42

IS5 0.65 98.08

IS6 0.62 99.81 AD1 0.84 87.61

AD2 0.81 88.13

AD3 0.78 89.37

AD4 0.74 90.93

5­39Figure 5.7.5 Cost­Efficiency Curve for the HZO.RC.M Equipment Class

Table 5.7.6 Cost­Efficiency Data for the HZO.RC.M Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD1 0.16 85.26

AD2 0.14 85.78

AD3 0.11 87.01

AD4 0.10 87.66

5­40Figure 5.7.6 Cost­Efficiency Curve for the VCT.RC.M Equipment Class

Table 5.7.7 Cost­Efficiency Data for the VCT.RC.M Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD1 0.54 100.71

AD2 0.44 101.35

AD3 0.42 101.81

AD4 0.39 102.90

AD5 0.38 103.94

AD6 0.24 120.11

AD7 0.19 133.20

5­41Figure 5.7.7 Cost­Efficiency Curve for the VOP.RC.L Equipment Class

Table 5.7.8 Cost­Efficiency Data for the VOP.RC.L Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD1 2.93 148.57

AD2 2.79 150.42

AD3 2.61 154.89

AD4 2.47 161.50

AD5 2.46 162.35

AD6 2.39 174.24

5­42Figure 5.7.8 Cost­Efficiency Curve for the SOC.RC.M Equipment Class

Table 5.7.9 Cost­Efficiency Data for the SOC.RC.M Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD1 0.95 155.07

AD2 0.86 156.45

AD3 0.76 159.78

AD4 0.74 161.02

AD5 0.71 162.74

AD6 0.61 179.99

AD7 0.60 187.14

5­43Figure 5.7.9 Cost­Efficiency Curve for the VOP.SC.M Equipment Class

Table 5.7.10 Cost­Efficiency Data for the VOP.SC.M Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD1 2.55 163.26

AD2 2.51 167.35

AD3 2.28 168.14

AD4 2.23 169.33

AD5 2.18 171.23

AD6 2.07 176.40

AD7 2.02 179.27

AD8 1.98 181.62

AD9 1.84 198.49

AD10 1.65 229.68

5­44Figure 5.7.10 Cost­Efficiency Curve for the SVO.SC.M Equipment Class

Table 5.7.11 Cost­Efficiency Data for the SVO.SC.M Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD1 2.24 154.69

AD2 2.02 159.06

AD3 2.00 159.52

AD4 1.99 159.98

AD5 1.96 161.09

AD6 1.87 165.43

AD7 1.85 166.43

AD8 1.83 167.54

AD9 1.62 181.71

AD10 1.54 195.54

5­451

2

3

4

5

6

7

8 Figure 5.7.11 Cost­Efficiency Curve for the HZO.SC.L Equipment Class

Table 5.7.12 Cost­Efficiency Data for the HZO.SC.L Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD 2.05 172.43

AD 2.02 172.92

AD 1.80 176.43

AD 1.56 182.17

AD 1.53 183.36

AD 1.52 183.85

AD 1.33 195.30

AD 1.32 196.49

5­461

2

3

4

5

6

7

8 Figure 5.7.12 Cost­Efficiency Curve for the HZO.SC.M Equipment Class

Table 5.7.13 Cost­Efficiency Data for the HZO.SC.M Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD 0.78 135.81

AD 0.75 136.30

AD 0.64 139.10

AD 0.61 140.29

AD 0.59 140.78

AD 0.56 142.56

AD 0.54 143.75

AD 0.48 149.56

5­471

2

3

4

5

6 Figure 5.7.13 Cost­Efficiency Curve for the HCT.SC.I Equipment Class

Table 5.7.14 Cost­Efficiency Data for the HCT.SC.I Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD 1.63 217.21

AD 1.35 221.94

AD 1.28 223.16

AD 0.73 246.23

AD 0.61 252.41

AD 0.57 255.37

5­48Figure 5.7.14 Cost­Efficiency Curve for the VCT.SC.I Equipment Class

Table 5.7.15 Cost­Efficiency Data for the VCT.SC.I Equipment Class

DOE Analytically derived Data

Design

Option

Level TDANormalized

Daily Energy

Consumption

[kWh/day/ft 2 ] TDANormalized

Manufacturer

Selling Price

[$/ft 2 ]

AD1 1.58 134.21

AD2 1.44 134.90

AD3 1.39 135.34

AD4 1.24 137.34

AD5 1.19 138.41

AD6 1.17 138.71

AD7 1.13 140.75

AD8 0.77 160.76

AD9 0.76 161.48

AD10 0.69 168.13

AD11 0.63 182.32

5­491

2

3

4

5

6

7

8 Note: The VCS product family is

normalized by volume.

Figure 5.7.15 Cost­Efficiency Curve for the VCS.SC.I Equipment Class

Table 5.7.16 Cost­Efficiency Data for the VCS.SC.I Equipment Class

DOE Analytically derived Data

Design

Option

Level V­Normalized

Daily Energy

Consumption

[kWh/day/ft 3 ] V­Normalized

Manufacturer

Selling Price

[$/ft 3 ]

AD 0.274 34.36

AD 0.251 34.56

AD 0.217 35.20

AD 0.191 35.69

AD 0.186 35.82

AD 0.178 36.15

AD 0.173 36.47

AD 0.168 37.52

5­505.8 EXTENSION OF ANALYSIS TO LOW­SHIPMENT EQUIPMENT CLASSES

At this stage in the rulemaking, DOE did not analyze all covered equipment classes, but

focused on high­shipment equipment classes (see Table 5.2.2). To address low­shipment

equipment classes, DOE could either conduct a full technical analysis of these equipment classes

or develop correlations to extend analyses or standard levels in a subsequent phase of the

rulemaking. For now, DOE explored the approach of developing correlations by conducting a

“focused matched­pair analysis.” The correlations can be used to extend the analyses from the

high­shipment equipment classes that were directly analyzed to several lower­shipment

equipment classes.

The focused matched­pair analysis establishes a correlation between rating temperature

levels and energy consumption, which then allows DOE either to estimate the difference between

the cost­efficiency curve of one equipment class and the cost­efficiency curve of another

equipment class (see Figure 5.8.1) or, as an alternative, to estimate the difference between the

standard level equation of one equipment class and the standard level equation of another

equipment class (see Figure 5.8.2).IncrementalManufacturerProductionCost[$]

Low­Temp

Product Class Ice­Cream Temp

Product Class

CDEC/TDA

[kWh/day ft 2 ]

Figure 5.8.1 Extension of Analysis Using Correlations

5­51Ice­Cream Temp

Product Class

Low­Temp

Product Class

TDA [ft 2 ]CDEC[kWh/day]

Figure 5.8.2 Extension of Standard Level Using Correlations

To illustrate this approach, DOE extended the analyses of two low­temperature

equipment classes (HZO.RC.L and VCT.RC.L) to two ice­cream freezer equipment classes

(HZO.RC.I and VCT.RC.I) as an example. Then, DOE extended the analysis from a mediumtemperature equipment class (VOP.RC.M) to a low­temperature equipment class (VOP.RC.L) to

validate its matched­pair methodology. Since DOE conducted a full analysis on the VOP.RC.L

equipment class, the results of the extension were compared to the full analysis of that equipment

class as a validation. Table 5.8.1 below shows the equipment classes examined.

Table 5.8.1 Extension of Analyses to Low­Shipment Equipment Classes

Equipment Remote Condensing Self­Contained

Family Medium Low Ice­Cream Medium Low Ice­Cream

Without

Doors VOP

SVO

HZO �

�

� �

� Validation �

�

� �

VCT � � * �

With

Doors VCS

HCT

HCS �

�

SOC �

� Full analysis conducted.

* Shaded boxes indicate that these equipment classes have standards established by EPACT 2005 and are

therefore not considered in this rulemaking.

5.8.1 Methodology

DOE quantified the differences in energy consumption for matched pairs of equipment

classes that are very similar in features and dimensions, but have different operating

temperatures. Pairs of HZO.RC units and VCT.RC units were selected from several different

manufacturers for comparison. DOE selected identical units from a given manufacturer designed

to operate at multiple temperatures to isolate operating temperature as the only variable. The

HZO.RC unit analysis and the VCT.RC unit analysis compared units that operate at a low

temperature to units that operate at an ice­cream temperature, and the VOP.RC unit analysis

compared units that operate at a medium temperature to units that operate at a low temperature.

5­52DOE relied on catalog information from manufacturer specification sheets that provide

detailed information on features and dimensions for each CRE model, and allow calculation of

the daily energy consumption. Once it had selected the matched pairs, DOE entered the

pertinent data on operating conditions and features into a spreadsheet and used the methodology

in ARI 1200 to determine the CDEC for each unit. The CDEC values were normalized by TDA,

which allowed equipment of varying capacity to be compared on a unit display area basis.

DOE compared the CDEC/TDA values of each pair to determine the differential energy

consumption. The DAT for each pair of units was also compared to ensure they operated within

similar temperature ranges and were, therefore, comparable. Ideally, the comparisons would be

made in terms of the integrated average temperature (IAT), which is the temperature used to rate

CRE. Since the IAT is not given in the equipment data sheets, DAT was selected over SET as

the criterion for comparison because the DAT is closer to the IAT.

It should also be noted that while the medium­ and low­temperature equipment

considered in the matched­pairs analysis typically have an IAT at or near 38°F and 0°F,

respectively, the equipment data reported by manufacturers for “ice­cream” freezers does not

necessarily have an IAT of ­15°F. For the particular ice­cream freezers analyzed in this study,

the IAT is closer to ­10°F. This is because there is no consensus in the industry at this time

about what constitutes an ice­cream freezer. However, the results from these “ice­cream”

freezers can be extended to a temperature difference of 15°F by simple linear extrapolation.

Although there may be a difference in absolute costs between units in one equipment

class compared to units in another equipment class, the difference in incremental cost between

these equipment classes is not expected to be significant. In most cases, this is because similar

design options applied to either equipment class would cost about the same amount. Therefore,

when incremental costs are considered among similar equipment classes for the same design

options, there would be very little difference.

Because this is a simplified approach, there are several major assumptions. These

include: the incremental cost of a design option is constant among similar equipment classes, a

disregard for the energy­using features for cases to operate at various temperatures (e.g., multiple

air curtains and electric defrost for low­temperature cases), and the correlation between energy

use and DAT is a simple linear relationship. This simplified approach allows DOE to make a

rough estimate of the cost­efficiency relationship for low­shipment equipment classes, while

avoiding a time­consuming design options analysis.

5.8.2 Correlations

The results show that among the matched pairs examined, the VOP.RC.L units have on

average CDEC/TDA values that are 1.4 kWh/day/ft 2 higher and DAT values 37.5 ° F lower than

VOP.RC.M units. HZO.SC.I units have on average CDEC/TDA values 0.21 kWh/day/ft 2 higher

and DAT values 10.4 ° F lower than HZO.RC.L units. VCT.RC.I units have on average

CDEC/TDA values 0.051 kWh/day/ft 2 higher and DAT values 6.1 ° F lower than VCT.RC.L

units. The correlations developed are described in the following equations:

5­53VOP.RC.M to VOP.RC.L:

Δ CDEC / TDA

= 0.0371 Δ T Eq. 5.10

HZO.RC.L to HZO.RC.I:

Δ CDEC / TDA

= 0.0202 Δ T Eq. 5.11

VCT.RC.L to VCT.RC.I:

Δ CDEC / TDA

= 0.0083 Δ T Eq. 5.12

where

Δ CDEC / TDA is the difference in CDEC/TDA (kWh/day/ ft 2 ), and

Δ T is the difference in DAT ( ° F).

5.8.3 Results

The correlations established in the matched­pair analysis can be used to extend the full

analysis conducted on the high­shipment equipment classes that were analyzed in the

engineering analysis to other low­shipment equipment classes (see Figure 5.8.1). To do this, the

formulas described by correlations can be directly applied to the cost­efficiency curves based on

the difference in rating temperatures. For example, Equation 2 shows that the cost­efficiency

curve is shifted to the right by 0.303 kWh/day/ft 2 between HZO.RC.L and HZO.RC.I units (a

difference in rating temperature of 15 ° F).

Likewise, the correlations can also be used to extend the standard level equations (see

Figure 5.8.2). To do this, the correlations can be directly applied to the standard level equations

based on the difference in rating temperatures. For example, Equation 2 shows that the slope of

the standard level equation would be increased by 0.303 kWh/day/ft 2 between HZO.RC.L and

HZO.RC.I units (a difference in rating temperature of 15 ° F).

DOE validated this methodology by performing an extension of analysis on two related

equipment classes for which it had conducted a full analysis. DOE used Equation 2 to extend the

cost­efficiency curve for the VOP.RC.M equipment class to the VOP.RC.L equipment class,

then compared the results of the extension to results of the full design option analysis. Results

were within 9 percent.

5.9 SENSITIVITY ANALYSES

DOE conducted two sensitivity analyses. The first examined the sensitivity of the costefficiency curves to material prices. The second examined the sensitivity of standards to

alternative refrigerants.

5­545.9.1 Material Price Sensitivity

DOE conducted a sensitivity analysis on material prices to examine the effect of spikes in

commodity prices that the industry has experienced over the past few years. The sensitivity

compares the 5­year average prices for 2002­2006 (described in section 5.4.3) with the 5­year

high price for the same period (2006 is the year with the highest material prices during that 5­

year period). The results of this sensitivity analysis are presented in Figure 5.9.1 for the

VOP.RC.M equipment class, which has the highest shipment volume of all analyzed equipment

classes. Shown for comparison is the industry­supplied data for the VOP.RC.M equipment class.

In addition to adding about 15 percent to the overall cost of the equipment, the large

increase in copper prices dramatically raises the cost of the evaporator coil (roughly 50 percent

for both the baseline and enhanced evaporator coil). This increase in coil cost reduces the costeffectiveness of this design option, which can be seen as a change in the slope of the costefficiency curve between the third and fourth design option levels above the baseline. For this

equipment class, the 5­year average prices produce an analytically derived curve that more

closely matches the industry­supplied curve. Based on the assumption that the overall case cost

would increase by roughly 15% for other equipment classes, the 5­year average prices would

also provide a closer match than the 5­year high prices for the other industry­supplied curves

(Figure 5.7.1, Figure 5.7.3, and Figure 5.7.4).

Figure 5.9.1 Material Price Sensitivity for the VOP.RC.M Equipment Class

5­555.9.2 Alternative Refrigerants

In conducting an engineering analysis, DOE must consider the effects of regulatory

changes outside DOE’s statutory energy conservation standards rulemaking process that can

impact the manufacturers of the covered equipment. Some of these changes can also affect the

energy efficiency or energy consumption of the covered equipment. DOE identified such

external engineering issues that could impact the engineering analysis. The consideration of

these issues is closely related to the cumulative regulatory burden assessment that DOE carried

out as part of the manufacturer impact analysis.

Due to the phase­out of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons

(HCFCs), the commercial refrigeration industry must transition to non­ozone­depleting

refrigerants. As a result, the refrigeration industry is transitioning to hydrofluorocarbon­based

(HFC­based) refrigerants in its equipment. For the commercial refrigeration equipment covered

in this rulemaking, DOE understands that much of the industry has already been using HFCbased refrigerants for both remote condensing and self­contained equipment. Therefore, DOE

considered the effects of HFC­based refrigerants from the outset by using HFC refrigerants in its

analyses. For remote condensing equipment, the compressor efficiency values used in its

analysis are based on ARI 1200, which uses an HFC­based compressor rack with R­404a

refrigerant. Likewise for self­contained equipment, DOE’s analysis uses R­134a and R­404a,

both HFC­based refrigerants.

5.10 RESULTS

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

appendix B of this TSD.

5­56REFERENCES

1 American Metals Market. 2007. (Last accessed July 11, 2007.)

<http://www.amm.com/> The July 11, 2007, material from this website is available in

Docket # EE­2006­STD­0126. For more information, contact Brenda Edwards­Jones

at (202) 586­2945.

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

. 2007.

(Last accessed June 28, 2007.) <http://www.bls.gov/ppi/> The June 28, 2007, material

from this website is available in Docket # EE­2006­STD­0126. For more information,

contact Brenda Edwards­Jones at (202) 586­2945.

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

Implicit Price Deflator

. 2007. (Last accessed June 28, 2007.)

<https://bea.gov/bea/dn/nipaweb/TableView.asp#Mid> The June 28, 2007 material

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contact Brenda Edwards­Jones at (202) 586­2945.

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2007.) <http://windows.lbl.gov/software/window/window.html> The June 26, 2007

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. Southern California

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

Air­Conditioning Engineers. Standard 72­2005 : Method of Testing Commercial

Refrigerators and Freezers

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. 2007.

10 R. Faramarzi. Efficient Display Case Refrigeration. In ASHRAE Journal

. November

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5­5711 Arthur D. Little. Energy Savings Potential for Commercial Refrigeration Equipment

. 1996. Arthur D. Little. Cambridge, MA.

5­58