5-1 CHA P TER 5. ENGINEERING ANALYSIS

TABLE OF CONTENTS

5.1 INTRODUCTION ........................................................................................................... 5-3 5.2 METHODOLOGY OVERVIEW .................................................................................... 5-3 5.3 COST MODEL ................................................................................................................ 5-4 5.3.1 Manufacturer Production Cost Estimates ............................................................ 5-4 5.3.2 Structure of the Cost Model Spreadsheet............................................................. 5-5 5.3.3 Material Prices ..................................................................................................... 5-6 5.3.4 Results.................................................................................................................. 5-6 5.4 MANUFACTURER MARKUP ...................................................................................... 5-6 5.5 ENERGY CONSUMPTION MODEL ............................................................................ 5-7 5.5.1 Screened-In Technologies.................................................................................... 5-7 5.5.2 Screened-In Technologies Not Considered in the Engineering Analysis............ 5-8 5.5.2.1 Higher Efficiency Evaporator and Condenser Fan Blades ...................... 5-8 5.5.2.2 Low-Pressure Differential Evaporators ................................................... 5-8 5.5.2.3 Defrost Mechanisms ................................................................................ 5-9 5.5.3 Design Options..................................................................................................... 5-9 5.5.3.1 Higher Efficiency Lighting and Ballasts.................................................. 5-9 5.5.3.2 Higher Efficiency Evaporator Fan Motors ............................................ 5-11 5.5.3.3 Evaporator Fan Controls........................................................................ 5-11 5.5.3.4 Improved Evaporator Design................................................................. 5-12 5.5.3.5 Insulation Increases or Improvements ................................................... 5-13 5.5.3.6 Improved Glass Pack ............................................................................. 5-14 5.5.3.7 Higher Efficiency Condenser Fan Motors ............................................. 5-14 5.5.3.8 Increased Condenser Surface Area ........................................................ 5-15 5.5.3.9 Higher Efficiency Compressors............................................................. 5-16 5.5.4 Baseline Specifications ...................................................................................... 5-16 5.5.5 Non-Numerical Assumptions............................................................................. 5-19 5.5.6 Numerical Constants and Assumptions ............................................................. 5-19 5.5.7 Model Components............................................................................................ 5-20 5.5.7.1 Component Energy Consumption.......................................................... 5-21 5.5.7.2 Compressor Energy Consumption ......................................................... 5-22 5.5.7.3 Component Load Model ........................................................................ 5-22 5.5.7.4 Radiation Load Model ........................................................................... 5-22 5.5.7.5 Conduction Load Model ........................................................................ 5-22 5.5.7.6 Infiltration Load Model.......................................................................... 5-23 5.6 COST-EFFICIENCY CURVES .................................................................................... 5-24 5.7 SENSITIVITY ANALYSES ......................................................................................... 5-32 5.7.1 Material Price Sensitivity................................................................................... 5-32 5.7.2 Alternative Refrigerants..................................................................................... 5-33 5.8 RESULTS ...................................................................................................................... 5-34 REFERENCES .......................................................................................................................... 5-355-2 LIS T OF TABLES
Table 5.3.1 Major Manufacturing Processes .............................................................................. 5-6 Table 5.3.2 Calculated Base Case Costs..................................................................................... 5-6 Table 5.5.1 Details for “Class A Lighting” Design Option ...................................................... 5-10 Table 5.5.2 Details for “Class B Lighting” Design Option ...................................................... 5-11 Table 5.5.3 Details for “Evaporator Fan Motor” Design Option.............................................. 5-11 Table 5.5.4 Details for “Improved Class A Evaporator Coil” Design Option.......................... 5-12 Table 5.5.5 Details for “Improved Class B Evaporator Coil” Design Option.......................... 5-12 Table 5.5.6 Properties of Standard and Enhanced Class B Evaporator Coil ............................ 5-13 Table 5.5.7 Properties of Standard and Enhanced Class A Evaporator Coil............................ 5-13 Table 5.5.8 Details for “Improved Glass Pack” Design Option ............................................... 5-14 Table 5.5.9 Details for “Improved Glass Pack” Design Option ............................................... 5-14 Table 5.5.10 Details for “Improved Class A Condenser Coil” Design Option ........................ 5-15 Table 5.5.11 Details for “Improved Class B Condenser Coil” Design Option......................... 5-15 Table 5.5.12 Properties of Standard and Enhanced Class A Condenser Coil............................ 5-16 Table 5.5.13 Properties of Standard and Enhanced Class B Condenser Coil............................ 5-16 Table 5.5.14 Baseline Specifications........................................................................................ 5-17 Table 5.5.15 Class A Equipment Class Baseline Specifications .............................................. 5-18 Table 5.5.16 Class B Equipment Class Baseline Specifications .............................................. 5-18 Table 5.5.17 Energy Consumption Model Numerical Constants and Assumptions................. 5-20 Table 5.5.18 Engineering Constants ......................................................................................... 5-20 Table 5.6.1 Cost-Efficiency Data for the Small-Size Class A Equipment Class...................... 5-26 Table 5.6.2 Cost-Efficiency Data for the Medium-Size Class A Equipment Class ................. 5-27 Table 5.6.3 Cost-Efficiency Data for the Large-Size Class A Equipment Class...................... 5-28 Table 5.6.4 Cost-Efficiency Data for the Small-Size Class B Equipment Class...................... 5-29 Table 5.6.5 Cost-Efficiency Data for the Medium-Size Class B Equipment Class.................. 5-30 Table 5.6.6 Cost-Efficiency Data for the Large-Size Class B Equipment Class...................... 5-31

LIST OF FIGURES
Figure 5.3.1 Components of Manufacturer Production Cost...................................................... 5-4 Figure 5.3.2 Manufacturer Production Cost Assessment Stages ................................................ 5-5 Figure 5.5.1 Components of the Energy Consumption Model ................................................. 5-21 Figure 5.6.1 Cost-Efficiency Curves for the Small-Size Class A Equipment Class................. 5-26 Figure 5.6.2 Cost-Efficiency Curve for the Medium-Size Class A Equipment Class.............. 5-27 Figure 5.6.3 Cost-Efficiency Curves for the Large-Size Class A Equipment Class................. 5-28 Figure 5.6.4 Cost-Efficiency Curve for the Small-Size Class B Equipment Class .................. 5-29 Figure 5.6.5 Cost-Efficiency Curve for the Medium-Size Class B Equipment Class .............. 5-30 Figure 5.6.6 Cost-Efficiency Curve for the Large-Size Class B Equipment Class .................. 5-31 Figure 5.7.1 Material Price Sensitivity for the Medium-Size Class A Machine ...................... 5-32 Figure 5.7.2 Material Price Sensitivity for the Medium-Size Class B Machine....................... 5-335-3 CHA P TER 5. ENGINEERING ANALYSIS

5.1 INTRODUCTION
The engineering analysis establishes the relationship between manufacturer selling price (MSP) and daily energy consumption (DEC), measured in kilowatt hours per day (kWh/day), for the refrigerated beverage vending machines covered in this rulemaking. This cost-efficiency relationship serves as the basis for cost/benefit calculations for individual customers, manufacturers, and the Nation. In determining this relationship, the U.S. Department of Energy (DOE) estimates the increase in manufacturerproduction cost (MPC) associated with technological changes that reduce the energy consumption of the baseline models, then converts each MPC to MSP by applying a multiplier to determine the manufacturer markup.
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 in the TSD) and technology options from the screening analysis (chapter 4 in the TSD). Additional inputsinclude 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 cost-efficiency curves and a manufacturer markup multiplier used to convert MPC to MSP. In the subsequent markups analysis (chapter 6 in the TSD), DOE determines customer prices by applying distribution markups, sales tax, and contractor markups. After applying these markups,the data serve as inputs to the energy use characterization (chapter 7 in the TSD) and the lifecycle cost and payback period analyses (chapter 8 in the TSD).
In this chapter, DOE discusses representative baseline units, methodology used todevelop MPC, markups to MSP, methodology used to estimate energy consumption, costefficiency curves, sensitivity to material prices, and use of alternative refrigerants.

5.2 METHODOLOGY OVERVIEW
This section describes the analytical methodology used in the engineering analysis. In this rulemaking, DOE is adopting a design-option approach, which calculates the incremental costs of adding specific design options to a baseline model. For each equipment class, DOE analyzed three different machine sizes to assess how energy use varies with size. A small-, medium-, and large-sized machine was picked for Class A and Class B machines based on equipment offerings currently on the market. See chapter 3 of the TSD for a detailed description of the Class A and Class B equipment classes and section 5.5.4 below for additional detail on the different size machines analyzed.
For each equipment class and size, DOE developed a core case cost using a manufacturing cost model. The core case cost is the MPC of the structure, walls, doors, shelving and fascia of the case, but does not include the cost of any energy-using components. DOE developed pricing for each design option and added the design option pricing to the core case costs to arrive at total MPC for each equipment class and size. DOE also calculated the impact5-4

of e a ch design option on DEC using an energy consumption model. DOE then conducted a markups analysis to translate MPC to MSP.
The primary results of the engineering analysis are a set of cost-efficiency curves, in the form of MSP versus DEC, for three sizes of each equipment class. The secondary results of the engineering analysis are two sensitivity analyses: a sensitivity of MSP to the price of metal a sensitivity of DEC to the use of alternative refrigerants.

5.3 COST MODEL
The cost model is the first of two key analytical models used in constructing costefficiency curves. A cost model was used to estimate the core case cost of a refrigerated beverage vending machine. This cost model was adapted from a cost model developed for DOE’s rulemaking on commercial refrigeration equipment (CRE). a The approach for CRE inv o lved the disassembly of a self-contained refrigerator, an analysis of the materials and manufacturing processes, and the development of a parametric spreadsheet model. DOE modified the CRE model for refrigerated beverage vending machines using input from stakeholders on beverage vending machine MPC estimates and assumptions to confirm accuracy. DOE believes this approach is acceptable given the similarities in materials and manufacturing processes between commercial refrigeration equipment and beverage vending machines.

5.3.1 Manufacturer Production Cost Estimates
Manufacturer production cost is the sum of direct labor, direct material, and overhead

(including investment depreciation) costs. Non-production cost elements, which are otherwise related to MPC, include sales, general and administrative, research and development, and interest. Altogether, these costs make up the MPC shown in
Figure 5.3.1.

a See http://www.eere.energy.gov/buildings/appliance_standards/commercial_products.html for further detail on and valida tion of the CRE cost model. Manufacturer Production Cost

Full Production Cost Non-Production Cost

Interest Research& Development Costs General &Administrative Costs Sales Costs Overhead Direct Material Direct Labor5-5 Fig u re 5.3.1 Components of Manufacturer Production Cost
The cost of specific models

 or cost to an individual manufacturer to produce a refrigerated beverage vending machine

 will vary depending on the equipment’s precise design and features, actual manufacturing processes, the equipment mix in the factory, and other production factors. There are also considerable differences in the levels of vertical integration that affect cost structure and thus the cost of equipment. That is to say, companies with a large market share and/or revenue base tend to be more vertically integrated than their smaller competitors. Yet, potentially all manufacturers buy at least some of their parts and/or subsystems from outside vendors.

5.3.2 Structure of the Cost Model Spreadsheet
DOE used a detailed, component-focused 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 5.3.2 shows the three major steps in generating the MPC.

Figure 5.3.2 Manufacturer Production Cost Assessment Stages
The first step in the MPC assessment was creating a complete and structured bill of materials (BOM) from the disassembly of a commercial refrigerator with transparent doors. The commercial refrigerator was dismantled, and each part was characterized according to weight, manufacturing processes, dimensions, material, and quantity. The BOM includes the costs of materials, components, and fasteners. It also estimates the cost of raw materials and purchased parts. DOE based assumptions about the sourcing of parts and in-house fabrication on industry experience, information in trade publications, and discussions with manufacturers. During the BVM rulemaking, DOE’s contractors conducted interviews and plant visits with manufacturers to ensure accuracy of the BVM model’s methodology and pricing. DOE accounted for equipment designs pertaining to BVMs by interviewing manufacturers and visiting plants, and then made appropriate changes to the BVM cost model.
After developing a detailed BOM, DOE identified the major manufacturing processes, listed in Table 5.3.1, and developed a spreadsheet model. DOE estimated fabrication process cycle times and entered them into the BOM. For this analysis, $24.00 per hour was used as the average fully burdened labor rate based on typical annual wages and benefits of industry employees. In the final step of the cost assessment, DOE estimated assembly times and Raw Mater i als Bill of Materials Fabrication Processes Assembly Processes Finished Materials

Purchased Parts5-6

ass o ciated direct labor costs. Once the cost estimate for each unit was finalized, DOE prepared a detailed summary of relevant components, subassemblies, and processes.
Table 5.3.1 Major Manufacturing Processes Fabrication Finishing Assembly/Joining Fixturing Washing Adhesive Bonding Stamping/Pressing Powder Coating Spot Welding Brake Forming De-burring Seam Welding Cut and Shearing Polishing Inspecting & Testing Insulating

5.3.3 Material Prices
DOE determined the cost of raw materials by using prices for copper, steel, and aluminum from the American Metals Market. 1 Prices for rifled and unrifled copper tubing were obtai ned directly from a tubing manufacturer. DOE noted that there have been drastic fluctuations in metal prices over the last few years. To account for these large fluctuations, DOE used prices of metals that reflect a 5-year average of the Bureau of Labor Statistics Producer Price Indices (PPIs) spanning 2002 to 2006 with an adjustment to 2007$. 2 DOE used the PPIs for s teel mill products and copper rolling, drawing, and extruding, and adjusted to 2007$ using the gross domestic product implicit price deflator. 3

Betw een 2003 and 2006, the price of steel rose over 60 percent and the price of copper over 140 percent. Because DOE used a 5-year average in material prices from 2002 to 2006, these drastic increases are somewhat normalized to better represent long-term material price averages. Because it is not clear if these material price trends will continue, DOE conducted a sensitivity analysis to illustrate the effect of raw material price increases on the cost of beverage vending machines (see section 5.7.1 below).

5.3.4 Results
Core costs, defined as MPC minus the cost of design options, were calculated for three sizes of each equipment class. Table 5.3.2 displays these results.

Table 5.3.2 Calculated Core Case Costs Equipment Class 12- O unce Can Capacity Size Designation Calculated Core Cost $ Class A 270 Small 1,449 Class A 350 Medium 1,758 Class A 410 Large 1,906 Class B 450 Small 1,159 Class B 650 Medium 1,330 Class B 800 Large 1,382

5.4 MANUFACTURER MARKUP5-7

At e a ch stage of the distribution chain, manufacturers, wholesalers, and distributors 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 for each equipment class. Wholesaler, distributor, and other markups are determined in the markups analysis (see chapter 6 of the TSD).
The manufacturer markup is a market-share-weighted average value for the industry. DOE developed this markup by examining several BVM manufacturers’ gross margin information from annual reports and Securities and Exchange Commission 10-K reports. The manufacturers analyzed by DOE account for approximately 70 percent of the BVM market, and each of these companies is a subsidiary of a more diversified parent company that manufactures equipment other than beverage vending machines. Because the 10-K 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 2001 through 2006, calculating the manufacturer markup as 100/(100 – average gross margin), where average gross margin is calculated as revenue – cost of goods sold. To validate the information, DOE reviewed its assumptions with BVM manufacturers. During interviews (see chapter 12 of the TSD), BVM manufacturers stated that many manufacturers generate revenue and profit by providing other goods and services, and their margins for beverage vending machines are lower than their company-wide margin. Taking this information into consideration, DOE is using an industry-wide manufacturer markup of 1.03 in the engineering analysis.

5.5 ENERGY CONSUMPTION MODEL
The energy consumption model is the second of two key analytical models used in constructing cost-efficiency curves. This model estimates the DEC of refrigerated beverage vending machines in kWh/day at various performance levels using a design-options approach. DOE developed the energy consumption model as a Microsoft Excel spreadsheet and is making the model available to the public on DOE’s website at http://www.eere.energy.gov/buildings/appliance_standards/commercial_products.html. Appendix A of the TSD provides instructions for using the spreadsheet.
For a given equipment class, the model estimates the DEC for the baseline and the DEC of several levels of performance above the baseline. The model calculates energy consumption at each performance level separately. DOE selected ENERGY STAR Tier 1 as the baseline level for each equipment class and machine size. 4 For the baseline level, DOE calculated a

cor r esponding MPC using the cost model (described in section 5.3 above). For each level above the baseline, DOE used the cost increases of the various design options to recalculate the MPC.

5.5.1 Screened-In Technologies
In the market and technology assessment (chapter 3 of the TSD), DOE defined an initial list of technologies that can be used to reduce the energy consumption of refrigerated beverage vending machines. DOE then analyzed the following technology options:5-8

• hig h er efficiency lighting

• higher efficiency lighting ballasts

• higher efficiency evaporator fan motors

• evaporator fan motor controllers

• higher efficiency evaporator fan blades

• improved evaporator design

• low-pressure differential evaporators

• insulation increases or improvements

• defrost mechanism

• improved glass pack (only for Class A machines)

• higher efficiency condenser fan motors

• higher efficiency condenser fan blades

• improved condenser design

• higher efficiency compressors

5.5.2 Screened-In Technologies Not Considered in the Engineering Analysis
In the screening analysis (chapter 4 of the TSD), DOE narrowed this list by eliminating those technologies that can reduce annual energy consumption of refrigerated beverage vending machines but do not reduce DEC. DOE then screened out those technologies that were not feasible, were not practical to manufacture, reduced equipment utility, or were considered unsafe.
The remaining list of screened-in technologies became an input to the engineering analysis. However, for reasons noted below, DOE did not incorporate all of these technologies in the energy consumption model. These include higher efficiency evaporator and condenser fan blades, low-pressure differential evaporators, and defrost mechanisms.

5.5.2.1 Higher Efficiency Evaporator and Condenser Fan Blades
Higher efficiency evaporator and condenser fan blades reduce motor shaft power requirements by moving air more efficiently. Current BVM designs use stamped sheet metal or plastic axial fan blades. These fan blades are lightweight and inexpensive. DOE was not able to identify any axial fan blade technology that is significantly more efficient than what is currently being used, but did identify one alternative fan blade technology that might improve efficiency: tangential fan blades. These blades can produce a wide, even airflow, and have the potential to increase saturated evaporator temperature (SET) through improved air distribution across the evaporator coil, which would reduce compressor power. However, tangential fan blades are small and less efficient at moving air, and thus require greater motor shaft power. Because of these competing effects, DOE did not consider tangential fan blades as a design option.

5.5.2.2 Low-Pressure Differential Evaporators
Low-pressure differential evaporators reduce energy consumption by reducing the power required by evaporator fan motors. However, in space-constrained equipment, such as beverage vending machines, this reduction usually comes from a decrease in evaporator coil surface area,5-9

whi c h generally requires a lower SET to achieve the same discharge air temperature and cooling potential. This, in turn, reduces compressor efficiency. Because of these competing effects, DOE did not consider low-pressure differential evaporators as a design option.

5.5.2.3 Defrost Mechanisms
Defrosting for refrigerated beverage vending machines is typically accomplished with off-cycle defrost. Because off-cycle defrost uses no energy (and decreases compressor on-time), there is no defrost mechanism to reduce defrost energy consumption. Therefore, DOE did not consider it as a design option.

5.5.3 Design Options
After conducting the screening analysis and removing from consideration those technologies described above, the following technologies were implemented as design options in the energy consumption model:

• higher efficiency lighting and ballasts (a combination of the first two design options listed above)

• higher efficiency evaporator fan motors

• evaporator fan motor controllers

• improved evaporator design

• insulation increases or improvements

• improved glass pack (for Class A machines)

• higher efficiency condenser fan motors

• improved condenser design

• higher efficiency compressors
Each design option has two to four technology levels, ranging from the worst performing to the best performing technology. The design options and the technology levels for each design option are described below.

5.5.3.1 Higher Efficiency Lighting and Ballasts
Lighting is an important characteristic of refrigerated beverage vending machines: it makes the product visible to the consumer in Class A machines and provides product advertising for Class B machines. Lighting systems typically operate continuously and provide an opportunity for significant energy savings. As lighting system efficiency increases, total energy consumption can be decreased by reducing the lighting system’s electricity consumption and the heat inside the refrigerated volume of Class A machines, which reduces the work of the compressor. For Class B machines, increasing lighting system efficiency only reduces direct energy consumption, because lamps and ballasts are placed outside the refrigerated space.
It is important that machine (in the case of Class B machines) or vended product (in the case of Class A machines) illumination not degrade with higher design option levels, because this would decrease equipment utility. Therefore, DOE made every effort to maintain constant5-10

sys t em light output among the lighting design options. This approach meant that DOE had to consider lighting as a system, rather than distinguishing lamps and ballasts as separate design options. This approach 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 used with LEDs direct light more efficiently. Although the total lumen output of LED systems is lower than that of comparable fluorescent systems, the amount of light incident on a surface (illuminance) is roughly equivalent. BVM manufacturers, lighting manufacturers, and other technical experts indicated that current LED technology provides adequate product lighting for Class A machines, and in most cases is comparable to fluorescent lighting. For Class B machines, DOE originally believed that LED technology would be adequate, but BVM manufacturers indicated that they were still exploring LED technology, despite the lower lumen outputs.
To account for variations in design between equipment classes, DOE used two lighting design options in the energy-consumption model. The first was for Class A machines and the second was for Class B machines.
Class A machines illuminate the beverage containers being vended. Lamps must be sized to fit within the refrigerated space. DOE used 4-foot fluorescent lamps, based on the size of machines currently on the market. DOE started with a minimum technology of T12 fluorescent lamps and magnetic ballasts, but today is using a baseline of T8 fluorescent lamps with electronic ballasts, based on market data and conversations with manufacturers of refrigerated BVMs. Additionally, these lamps were required to have a color rendering index (CRI) of approximately 80, which is typical for this type of equipment.
Table 5.5.1 Performance Details for “Class A Lighting” Design Option

Level Description Lamp Type Lam p Rated Power [watts (W)] Lamp

Rated Light Output [Lumens] System

Efficacy [Lumens/ W] System

Light Output [Lumens] T12 4-ft T12, Magnetic F34T12 34.0 2,650 68.6 2,332 T8 4-ft T8, Electric F32T8 32.0 2,850 85.0 2,679
T8S 4-ft “Super” T8,

Electric F32T8/HL 32.0 3,100 91.4 2,697 LED 4-ft LED 4-ft LED 27.2 1,360 50.0 1,360 Traditionally, Class B machines use 5- or 6-foot, high-output (HO) T12 fluorescent lamps and magnetic ballasts to attract as much attention to the machine as possible and to signal that the machine was functioning. DOE used this configuration as the minimum technology option. However, with the introduction of the ENERGY STAR qualified machines, BVM manufacturers have moved to T8 fluorescent lamps, and DOE used this as the baseline. Some beverage vending machine customers dictate certain size fluorescent lamps (to reduce the number of lamp types that lighting repair personnel carry on their trucks). As a result, DOE used a 4-foot and a 2-foot T8 lamp to replace a 6-foot T12 lamp. These lamps were also required to have a CRI of approximately 80, which is typical for this type of equipment.5-11

Tab l e 5.5.2 Performance Details for “Class B Lighting” Design Option

Level Description Lamp Type Lam p Rated Power [W] Lamp Rated

Light Output [Lumens] System

Efficacy [Lumens /W] System

Light Output [Lumens]
T12HO 6-ft., T12 HO

Magnetic F72T12/

HO/SP 85.0 6,550 64.9 5,960

T8 2-ft. T8 & 4–ft. T8

Electric F17T8 &

F32T8 49.0 4,250 90.4 3,910

LED 6-ft. LED - 34.0 1,700 50.0 1,700

5.5.3.2 Higher Efficiency Evaporator Fan Motors
In conjunction with fan blades, fan motors are necessary to transfer heat from the refrigerated space to the refrigerant. In most situations they operate nearly continuously, and therefore use a significant amount of energy. As motor efficiency increases, energy consumption decreases due to a direct reduction in electricity consumption and waste heat inside the refrigerated space.
Table 5.5.3 shows details for the evaporator fan motor design option. Currently, DOE considers shaded-pole motors (SPM) as the minimum technology, permanent split capacitor (PSC) motors as the mid-level technology, and brushless direct current (DC) or electronically commutated motors (ECMs) as the maximum technology. The motor efficiencies listed in Table 5.5.3 are from Energy Savings Potential for Commercial Refrigeration Equipment , prepared by Arthur D. Little in 1996. 5

Tabl e 5.5.3 Performance Details for “Evaporator Fan Motor” Design Option

Shaded-Pole Motor (SPM) Per m anent Split Capacitor (PSC) Motor Brushless DC Motor (ECM) Rated Power [W] Actual

Power [W] Efficiency Actual Power [W] Efficiency Actual Power [W] Efficiency

15.0 75.0 20.0% 33 45.5% 20.5 73.2% 9.0 53.0 17.0% 21 42.9% 12.5 72.0% 6.0 40.0 15.0% 15 40.0% 8.5 70.6%

5.5.3.3 Evaporator Fan Controls
Beverage vending machine manufacturers typically design evaporator fans to operate continuously. Circulating warm air through the case during compressor off-times prevents the evaporator coil from icing over. However, manufacturers indicated during interviews that under typical conditions, the evaporator fan is not required to run during all compressor off-times to keep the coils ice-free. Because of this, DOE developed a design option with controls to turn offthe evaporator fan during compressor off-time and a period of fan operation to accomplish offcycle defrost. Based on discussions with outside experts and beverage vending machine manufacturers, DOE estimated that a total of 1.5 hours of off-cycle defrost operation would be required during a 24-hour period. To assess the total cost of this design option, DOE took into account the additional cost of parts, engineering, and increased labor for assembly.5-12

5.5.3 .4 I mproved Evaporator Design
Evaporator coils are another component necessary to transfer heat from the refrigerated space to the refrigerant. Table 5.5.4 and
Table 5.5.5 show details for the evaporator coil design option. Based on available information, DOE considered a minimum and a maximum technology level for this design option. DOE analyzed different evaporator coils given the differences in design load between Class A and Class B machines. For each level, DOE specified an overall UA-value b and a coil

cos t . The UA-value is normalized to the standard coil, and the coil cost is normalized to the heat removal capacity of the coil. This allowed DOE to apply these details of coil design across all equipment sizes. In consultation with outside experts, DOE determined that the same coil improvements applied to different-sized coils would result in similar performance improvements.
Table 5.5.4 Performance Details for “Improved Class A Evaporator Coil” Design Option

Level Description Normalized UA [-] Norm alized Coil Cost [$/Btu/h] FEV1 Standard Coil 1 $0.0058 FEV2 High-Performance Coil 1.605 $0.0125
Table 5.5.5 Performance Details for “Improved Class B Evaporator Coil” Design Option

Level Description Normalized UA [-] Norm alized Coil Cost [$/Btu/h] ZEV1 Standard Coil 1 $0.0066 ZEV2 High-Performance Coil 1.646 $0.0143
The details of coil construction (shown in Table 5.5.6 and Table 5.5.7) were based on a baseline and prototype high-performance coil evaluated in a study by the Refrigeration and Thermal Test Center (RTTC) at Southern California Edison. 6 The high-performance coil uses a comb ination of enhancements to the heat transfer surfaces that increased its overall UA-value. These enhancements include a slightly higher fin pitch and different fin material. In summary, these changes result in an increased UA-value and increased coil cost. The increase in UA-value leads to an increase in the coil SET. Because compressor performance is directly related to SET, reductions in total case energy consumption are realized through an improved energy efficiency ratio (EER) at the condensing unit. In consultation with outside experts, DOE determined that the same coil improvements applied to differently sized coils at different temperatures would result in similar UA-value improvements.

b The overall UA-value is the product of the overall heat transfer coefficient (British thermal units per hour (Btu/h)- ft 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 log mean temperature difference of the air and refrigerant flows (∆T LM ).5-13

Tab l e 5.5.6 Properties of Standard and Enhanced Class B Evaporator Coil

Property Sta n dard Coil High-Performance Coil Overall Width (in) 24 24 Overall Height (in) 6 6 Overall Depth (in) 3 3 Tube Rows per Circuit 15 15 Number of Parallel Circuits 1 1 Tubing Material Copper Copper Tubing Outer Diameter (in) 3/8 3/8 Tubing Wall Thickness (in) 0.012 0.012 Tubing Inner Surface Smooth Smooth Fin Material Aluminum Copper Fin Surface Flat Wavy Fin Dimensions (in) 3 x 6 3 x 6 Fin Pitch (fins per inch) 6 7
Table 5.5.7 Properties of Standard and Enhanced Class A Evaporator Coil

Property Stan dard Coil High-Performance Coil Overall Width (in) 12 12 Overall Height (in) 8 8 Overall Depth (in) 3 3 Tube Rows per Circuit 28 28 Number of Parallel Circuits 1 1 Tubing Material Copper Copper Tubing Outer Diameter (in) 3/8 3/8 Tubing Wall Thickness (in) 0.012 0.012 Tubing Inner Surface Smooth Smooth Fin Material Aluminum Copper Fin Surface Flat Wavy Fin Dimensions (in) 3 x 8 3 x 8 Fin Pitch (fins per inch) 7 8

5.5.3.5 Insulation Increases or Improvements
Increasing or improving insulation decreases the conduction load, which reduces compressor energy consumption. DOE looked at two different methods of reducing the conduction load. The first method was a 1/8-inch increase in insulation thickness in all insulated panels. DOE assumed this addition required the machine to expand outward rather than inward, because an expansion inward would likely reduce the capacity to store canned or bottled beverages. DOE also accounted for the increased core case costs (due to the larger shell), design time, and fixture retooling.
The second method DOE explored was changing the insulation material. Currently, beverage vending machines use foamed-in-place polyurethane as the primary insulation material. After discussions with insulation manufacturers, industry experts, and BVM manufacturers, DOE concluded that there are no significant variations among different polyurethane foams and blowing agents. Thus, DOE did not consider improvements in polyurethane foams or blowing agents. DOE also did not consider vacuum panels because they cannot provide the structural support of foamed-in-place designs, and cannot accept the bolts and fasteners typically used on the skins and frame that house the insulation. However, DOE did consider aerogels as a5-14

rep l acement for foamed-in-place polyurethane. DOE considered an open cell, silica-based aerogel that comes in an expansion pack and is expanded to fit the insulation cavity.

5.5.3.6 Improved Glass Pack
An improved glass pack design option only applies to Class A machines. Improvements to the glass pack (a prefabricated assembly of glass sheets, coatings, framing, and fill gas) result in less heat transfer to the refrigerated volume by radiation and conduction. This reduces the heat load on the refrigerant and hence the compressor load, thus reducing compressor energy consumption. The glass pack can be improved several ways, including adding panes of glass, adding low- emissivity (low-E) coating, changing from air fill to argon fill, and changing from an aluminum frame to a vinyl frame. Rather than examine each variation as an individual design option, DOE looked at three different option packages, shown in Table 5.5.8.
The design options shown in Table 5.5.8 were then entered into WINDOW 5.2 7 to yield U-v a lues c that account for heat transfer due to radiation and conduction at each of the test cond itions set forth in American National Standards Institutue (ANSI)/American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) Standard 32.1–2004, Methods of Testing for Rating Vending Machines for Bottled, Canned, and Other Sealed Beverages

. 8 Table 5.5.9 catalogs the resulting U-values.

Tabl e 5.5.8 Performance Details for “Improved Glass Pack” Design Option Variable Base line Enhanced Super Enhanced Frame Material Aluminum Aluminum Vinyl Number of Panes 2 2 3 Glass Type: Panel 1 Clear Clear Clear Glass Type: Panel 2 Clear Low-E Low-E Glass Type: Panel 3 - - Clear Gas Fill Air Argon Argon
Table 5.5.9 Performance Details for “Improved Glass Pack” Design Option

Level Desc ription Overall U-Factor at the ASHRAE 32.1 75 ° F Test Condition [Btu/h-ft-°F] Overall U-Factor at the ASHRAE 32.1 90 ° F Test Condition [Btu/h-ft-°F] DOOR 1 Baseline 0.704 0.717 DOOR 2 Enhanced 0.447 0.455 DOOR 3 Super-Enhanced 0.292 0.298

5.5.3.7 Higher Efficiency Condenser Fan Motors
Performance details for the condenser fan motor design option are identical to those shown in Table 5.5.3. As with evaporator fan motors, the SPM is the minimum technology level, the PSC motor is the mid-level technology, and the DC motor or ECM is the maximum technology level. Because condenser fan motors are outside the refrigerated space, efficiency

c U-value is a measure of air-to-air heat transmission (loss or gain) due to thermal conductance and the difference in indoo r and outdoor temperatures.5-15

imp r ovements only impact the direct electrical consumption of the motors and not the total case heat load.

5.5.3.8 Increased Condenser Surface Area
Condenser coils reject heat from the refrigerant to the ambient air. Based on available information, DOE considered both minimum and maximum technology levels for this design option. For each level, DOE specified an overall UA-value and a coil cost, shown in Table 5.5.10 and Table 5.5.11. The UA-value is normalized to the standard coil, and the coil cost is normalized to the heat removal capacity of the coil. This allowed DOE to apply these details of coil design across all equipment sizes. In consultation with outside experts, DOE determined that the same coil improvements applied to different-sized coils would result in similar performance improvements.
Table 5.5.10 Performance Details for “Improved Class A Condenser Coil” Design Option

Level Des c ription Normalized UA [-] Normalized Coil

Cost [$/Btu/h] FCO1 Standard Coil 1 $0.006 FCO2 High-Performance Coil 1.74 $0.015
Table 5.5.11 Performance Details for “Improved Class B Condenser Coil” Design Option

Level Desc ription Normalized UA [-] Normalized Coil

Cost [$/Btu/h] ZCO1 Standard Coil 1 $0.006 ZCO2 High-Performance Coil 1.67 $0.019 As previously mentioned, details of coil construction (shown in Table 5.5.12 and Table 5.5.13) were based on a baseline and prototype high-performance coil evaluated in a study by RTTC. The high-performance coil uses a combination of enhancements to the heat transfer surfaces that increased its overall UA-value. These enhancements include higher fin pitch and different fin material. In sum, these improvements give the prototype coil a higher UA-value, allowing the coil to run at a saturated condenser temperature (SCT) cooler than the baseline coil while maintaining the same heat rejection rate. DOE did not consider rifled tubing because the refrigerant flow rates in beverage vending machines are typically not high enough to trigger turbulent flow. Because compressor performance is directly related to SCT, reductions in total case energy consumption are realized through an improved EER at the condensing unit.5-16

Tab l e 5.5.12 Properties of Standard and Enhanced Class A Condenser Coil

Property Sta n dard Coil High-Performance Coil Overall Width (in) 21 21 Overall Height (in) 10 10 Overall Depth (in) 4 4 Tube Rows per Circuit 36 36 Number of Parallel Circuits 1 1 Tubing Material Copper Copper Tubing Outer Diameter (in) 3/8 3/8 Tubing Wall Thickness (in) 0.012 in 0.012 in Tubing Inner Surface Smooth Smooth Fin Material Aluminum Copper Fin Surface Flat Wavy Fin Pitch (fins per inch) 4 5
Table 5.5.13 Properties of Standard and Enhanced Class B Condenser Coil

Property Stan dard Coil High-Performance Coil Overall Width (in) 12.5 24 Overall Height (in) 10 10 Overall Depth (in) 2.25 3 Tube Rows per Circuit 28 16 Number of Parallel Circuits 3 2 Tubing Material Copper Copper Tubing Outer Diameter (in) 3/8 3/8 Tubing Wall Thickness (in) 0.012 in 0.012 in Tubing Inner Surface Smooth Rifled Fin Material Aluminum Aluminum Fin Surface Flat Flat Fin Pitch (fins per inch) 6 7

5.5.3.9 Higher Efficiency Compressors
In consultation with compressor manufacturers and external technical experts, DOE determined that two levels of technology were applicable for the compressor design option. The minimum technology level is a standard single-speed hermetic compressor, and the maximum technology level is a high-efficiency single-speed hermetic compressor (see chapter 4 of the TSD for a discussion of why variable-speed compressors were not considered). Reductions in total case energy consumption are realized through a reduction in compressor power consumption.
DOE collected performance data for standard single-speed hermetic compressors from several manufacturers over a range of capacities applicable to the covered equipment (1,000 – 4,000 Btu/h). This data set was used to look up appropriately sized compressors when developing each design-option curve (see section 5.5.7.2 below for information on the calculation of compressor energy consumption). Although several compressor manufacturers produce high-efficiency compressors, little data are currently available on their performance. Therefore, DOE approximated a set of high-efficiency compressors by adjusting the power consumption of the standard compressors using a constant multiplier. DOE developed this multiplier through research and consultation with experts.

5.5.4 Baseline Specifications5-17

DOE d e fined baseline specifications for each equipment class. These specifications include dimensions, numbers of components, temperatures, nominal power ratings, and other case features that are necessary to calculate the energy consumption of each equipment class. In conjunction with the lowest technological level of each design option (see section 5.5.3 above),the baseline specifications define the energy consumption and cost of the typical lowestefficiency equipment on the market. DOE also provided details on minimum technology options for design options that are typically below the efficiency of currently available equipment. DOE did this because a small portion of the market does not meet the voluntary ENERGY STAR Tier 1 level. Table 5.5.14 below shows the specifications and units that are defined for each equipment class.
Table 5.5.14 Baseline Specifications Specification Unit s Refrigerated Volume ft 3 Number of Lamps in Refrigerated Volume - Number of Lamps not in Refrigerated Volume - Number of Ballasts in Refrigerated Volume - Number of Ballasts not in Refrigerated Volume - Evaporator Fan Nominal Rated Wattage W (Watts) Number of Evaporator Fans - Condenser Fan Nominal Rated Wattage W Number of Condenser Fans - Average Refrigerated Volume Temperature F (Fahrenheit) Nominal SET F Nominal SCT F Nominal Discharge Air Temperature (DAT) F Nominal Compressor Sizing Btu/h Solid Wall Area (including the door for Class B Machines) ft 2 Glass Area ft 2 Baseline Air Infiltration lb/hour Load from Electronic Components (bill changers, LED displays, etc.) kWh DOE established baseline specifications for each of the equipment classes modeled in the engineering analysis by reviewing available manufacturer data, selecting several representative units from available manufacturer data, and then aggregating the physical characteristics of the selected units. The baseline specifications were chosen so that the baseline machines met ENERGY STAR’s Tier 1 criteria (see chapter 3 of the TSD for further details on the criteria). This process created a representative unit for each equipment class with average characteristics for physical parameters (e.g., volume, wall area), and typical performance for energy-consuming components (e.g., fans, lighting). Table 5.5.15 and Table 5.5.16 show the results for each equipment class and size. Table 5.5.15 and Table 5.5.16 also include the 12-oz. can capacity of each size machine, for reference.5-18

Tab l e 5.5.15 Class A Equipment Class Baseline Specifications Specification Sma ll Medium Large Refrigerated Volume [ft 3 ] 19 3 1 35 12 oz. Can Capacity [#] 270 350 410 Number of Lamps in Refrigerated Volume [#] 2 2 2 Number of Lamps not in Refrigerated Volume [#] 0 0 0 Number of Ballasts in Refrigerated Volume [#] 0 0 0 Number of Ballasts not in Refrigerated Volume [#] 1 1 1 Evaporator Fan Nominal Rated Wattage [W] 9 9 9 Number of Evaporator Fans [#] 1 1 1 Condenser Fan Nominal Rated Wattage [W] 9 9 9 Number of Condenser Fans [#] 1 1 1 Average Refrigerated Volume Temperature [F] 36 36 36 Nominal SET [F] 8 8 8 Nominal SCT [F] 95 95 95 Nominal Discharge Air Temperature (DAT) [F] 19 19 19 Nominal Compressor Sizing [Btu/h] 2,400 2,900 2,900 Solid Wall Area (including the door for Class B Machines) [ft 2 ] 34 46 51 Glass Area [ft 2 ] 8 9 11 Baseline Air Infiltration [lb/hour] 5 9 10 Load from Electronic components (bill changers, LED displays, etc.) [kWh] 0.45 0.45 0.45

Table 5.5.16 Class B Equipment Class Baseline Specifications Specification Small Medium Large Refrigerated Volume [ft 3 ] 19 2 4 31 12 oz. Can Capacity [#] 450 650 800 Number of Lamps in Refrigerated Volume [#] 0 0 0 Number of Lamps not in Refrigerated Volume [#] 2 2 2 Number of Ballasts in Refrigerated Volume [#] 0 0 0 Number of Ballasts not in Refrigerated Volume [#] 1 1 1 Evaporator Fan Nominal Rated Wattage [W] 9 9 9 Number of Evaporator Fans [#] 2 2 2 Condenser Fan Nominal Rated Wattage [W] 9 9 9 Number of Condenser Fans [#] 1 1 1 Average Refrigerated Volume Temperature [F] 39 39 39 Nominal SET [F] 12 12 12 Nominal SCT [F] 98 98 98 Nominal Discharge Air Temperature (DAT) [F] 27 27 27 Nominal Compressor Sizing [Btu/h] 2,300 2,400 2,400 Solid Wall Area (including the door for Class B Machines) [ft 2 ] 45 56 62 Glass Area [ft 2 ] 0 0 0 Baseline Air Infiltration [lb/hour] 10.3 13 17 Load from Electronic components (bill changers, LED displays, etc.) [kWh] 0.2 0.2 0.25-19

5.5.5 N o n-Numerical Assumptions
In developing the energy consumption model, DOE made certain non-numerical assumptions concerning the analysis. These include general assumptions about the analysis as well as specific assumptions about load components and design options.
DOE assumed that all conditions are based on new equipment tested in a controlledenvironment chamber and subjected to the methods of testing and rating in ANSI/ASHRAE Standard 32.1–2004. Manufacturers that certify their equipment to comply with Federal standards will be required to test new units using this method, which specifies ambient temperature, humidity, light level, and other requirements.
DOE did not consider variable-speed compressors as a compressor design option. Variable-speed compressors reduce energy consumption under real-world conditions by matching their capacity to the refrigeration load, which can change due to variation in ambient conditions and product loading. This eliminates the inefficiencies that occur due to mismatched capacity and load in a single-speed compressor during part-load operation. The ANSI/ASHRAE Standard 32.1-2004 test procedure prescribes steady-state conditions. Thus, a variable-speed compressor would be limited to single-speed operation and the resulting EER would be no better than that of a properly sized single-speed compressor. Similarly, under ANSI/ASHRAE 32.1– 2004, the performance of a high-efficiency variable-speed compressor would be comparable to a high-efficiency single-speed compressor.
Because baseline models must meet ENERGY STAR’s Tier 1 criteria, DOE assumed that Class B machines meet the Tier 1 criteria when tested at the ANSI/ASHRAE Standard 32.1-2004 required 90°F test condition, and Class A machines meet the Tier 1 criteria when tested at the ASHRAE Standard 32.1-2004 required 75°F test condition.

5.5.6 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 ambientconditions, financial assumptions, and parameters necessary to calculate the component and nonelectric loads. Details of these assumptions are shown in Table 5.5.17 and Table 5.5.18 below.5-20

Tab l e 5.5.17 Energy Consumption Model Numerical Constants and Assumptions Numerical Constants and Assumptions Value Sou r ce Test Chamber Temperature [°F] 75 or 90 ASHRAE Standard 32.1-2004 Test Chamber Relative Humidity [%] 45 or 65 ASHRAE Standard 32.1-2004 Test Chamber Pressure [pounds per square in (psi), absolute] 14.7 Assumed
Manufacturer Markup [$/$] 1.03 Publicly available corporate financial data; discussions with manufacturers. List Price Markup [$/$] 2.00 Assumed Lighting Operating Time Per Day [hr] 24 Assumed based upon ASHRAE Standard 32.1- 2004
Evaporator Fan(s) Run Time Per Day [hr] 24 or less, Less than 24 hours if the evaporator fan motor control option is selected, based on discussions with manufacturers Off-cycle defrost time per day if Evaporator Fan Control is Enabled [hr] 1.5 Assumed
R Value of Foam Insulation [ft2F·h/Btu·in] 8 Discussions with foam manufacturers; manufacturer data sheets R Value of Aerogel Insulation [ft2·°F·h/Btu·in] 10 Discussions with aerogel manufacturers
Convective Film Coefficient Inside Case Walls With Evap Fan On [Btu/h-ft 2 -F] 4.00 Communication with RTTC
Convective Film Coefficient Inside Case Walls With Evap Fan Off[Btu/h-ft 2 -F] 1.00 ASHRAE Handbook–Fundamentals 2005
Convective Film Coefficient Outside Case Walls [Btu/h-ft 2 -F] 1.46 Communication with RTTC Evaporator Coil Overall Bypass Factor [%] 17 DOE estimate Density of Air @ Test Temperature [lb/ft 3 ] 0.07 3 or 0.071 ASHRAE Handbook–Fundamentals 2005 High-Efficiency Compressor Cost Premium 6% Interviews with compressor manufacturers High-Efficiency Compressor Power Reduction 3% Interviews with compressor manufacturers

Electricity Cost [$/kWh] 0.08 Commercial Building Energy Consumption Survey (CBECS), Energy Information Administration (EIA), average commercial price in 2004
Table 5.5.18 Engineering Constants Numerical Constants and Assumptions Number Sour ce Specific Heat of Air @ Test Conditions [Btu/lb-R] 0.24 Thermodynamics by Cengel and Boles, 4th edition, 2002 Latent Heat of Vaporization of Water/Water Vapor @ Test Temp [Btu/lb] 1050 or 1044 Thermodynamics by Cengel and Boles, 4th edition, 2002 Latent Heat of Fusion of Water/Ice [Btu/lb] 143.5 ASHRAE Handbook–Fundamentals 2005 Conversion from Watts to Btu/h [Btu/h-W] 3.415179 ASHRAE Handbook–Fundamentals 2005

5.5.7 Model Components
Figure 5.5.1 shows the components of the energy consumption model. The model calculates DEC in two major subsections: component energy consumption and compressor energy consumption. Component energy consumption is the sum of electrical energy directly5-21

con s umed by each fan motor and lamp. Compressor energy consumption is calculated from the total heat load (expressed as Btu/h).
The total heat load is the sum of the component load and the non-electric load. The component load is a sum of the heat emitted by evaporator fan motors and lighting inside the refrigerated space. (Condenser fan motors are outside the refrigerated space and do not contribute to the component heat load.) The non-electric load is the sum of the heat contributed by radiation through glass (for Class A machines), heat conducted through walls and doors, and warm air infiltration.

Figure 5.5.1 Components of the Energy Consumption Model

5.5.7.1 Component Energy Consumption
Component energy consumption is the sum of electrical energy directly consumed by each fan motor and lamp.
Fan motor energy consumption is calculated by summing the power draw of each evaporator and condenser fan motor, and multiplying the total motor power by the total running time over 24 hours. This analysis assumed condenser fans only run when the compressor is on. The evaporator fan is assumed to run 24 hours a day, unless the evaporator fan motor control option is selected. In this case, the evaporator fan motor is off during compressor off-cycle times except for defrost periods. Total Heat Load [Btu/h]

Component Load [Btu/h] Non-Electric Load [Btu/h]

Fan Motor Heat Load [Btu/h] Lighting Heat

Load [Btu/h] Radiation

Load [Btu/h] Conduction

Load [Btu/h] Infiltration

Load [Btu/h] Daily Energy Consumption [kWh/day]

Compressor Energy Consumption [kWh/day]
Compressor Model

(ARI 540)

Electric Energy Consumption [kWh/day]

Heat Load [Btu/h] Legend: Component Energy Consumption [kWh/day]

Fan Motor Energy Consumption [kWh/day] Lighting

Energy Consumption [kWh/day]5-22

Lig h ting 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 24-hour period.

5.5.7.2 Compressor Energy Consumption
DOE calculated compressor energy consumption (CEC) using the compressor model described in section 6.4 of Air-Conditioning and Refrigeration Institute (ARI) Standard 540- 2004, Performance Rating of Positive Displacement Refrigerant Compressors and Compressor Units . This model is based on a 10-coefficient polynomial derived from empirical compressor performance data for power, mass flow, current, and efficiency. The coefficients are derived for each of these parameters as a function of SET and SCT. Compressor coefficients, or tabulated empirical data (from which coefficients can be derived), are available from compressor manufacturers. Similar to the method used for remote condensing equipment, the EER of any compressor can be determined given the SET and SCT.

5.5.7.3 Component Load Model
The component load is the sum of the heat emitted by each evaporator fan motor and lamps inside the refrigerated volume. This waste heat must be removed by the compressor.
DOE assumed that all electrical energy consumed by the evaporator fan motors ends up as heat inside the refrigerated space. In any electric motor, irreversibilities in the motor windings, bearings, and other mechanical components convert much of the input electrical energy into heat. The rest of the energy is converted to moving air inside the case. This moving air is slowed by friction and eventually converted to heat as well.
DOE assumed that all electrical energy consumed by lamps and ballasts inside the refrigerated space ends up as heat inside that space. DOE also assumed that none of the electrical energy consumed by lamps and ballasts outside the refrigerated space ends up as heat inside that space. (Note that having ballasts inside the refrigerated space is not typical of current beverage vending machine designs, but DOE wished to consider the possibility in the model.)

5.5.7.4 Radiation Load Model
The radiation heat load model accounts for the gray-body radiation between the warm surfaces of the surrounding environment (the test chamber) and the cold inner surfaces of the refrigerated space through the glass doors of Class A machines. The net radiation is incorporated into the overall U-value of the door calculated by WINDOW 5.2 (see Table 5.5.9 above for the U-values calculated). Within the WINDOW 5.2 program, the environmental conditions in the refrigerated volume and the test chamber were specified to match the two test conditions defined in ASHRAE Standard 32.1-2004. See section 5.5.7.5 below for a discussion of the calculation of the combined radiation and conduction loads for glass doors and other glass.

5.5.7.5 Conduction Load Model5-23

The c o nduction load model accounts for the heat conducted through walls and doors. For solid walls and doors, the conduction load is given by:

Q A T T

h d k h cond walls room case

o ins

ins i = −

+ + 1 1 Eq. 5.1

where

A walls is the area of the exterior of the refrigerated volume (ft 2 ), h o is the convective film coefficient on the outside of refrigerated volume walls (Btu/h-ft 2 -°F), h i is the convective film coefficient on the inside of refrigerated walls (Btu/h-ft 2 -°F), d ins is the insulation thickness (in), and k ins is the insulation thermal conductivity (Btu-in/h-ft 2 -°F).

Bec a use 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 5.5.17 above for numerical constants pertaining to the conduction model.
For glass doors, the conduction load is incorporated into the overall U-factor of the door assembly or glass calculated by WINDOW 5.2 (see Table 5.5.9 above for the U-values calculated). The combined radiation and conduction load for glass doors and other glass is calculated as: 

# ( )

Q U A T T glass overall glass room case = − Eq. 5.2

where

U overall is the overall U-factor, including convection and radiation (Btu/h-ft 2 -°F), and A glass is the area of the glass (ft 2 ).

5.5.7.6 I nfiltration Load Model
The infiltration load model accounts for the heat that is added to a display case when warm, moist air enters the case (primarily through leaks and vend doors). The infiltration load is difficult to model because of the inherent complexity of the fluid phenomena of infiltration. Therefore, DOE used empirical data for defrost melt water to back-calculate the infiltration load. This approach was correlated using empirical data for infiltration loads provided by Southern California Edison’s RTTC from beverage vending machine testing.
Ambient room air infiltrated into the refrigerated space contributes to the load in two ways: a sensible load in the form of the heat contained in the dry air, and a latent load in the form of water vapor in the air that condenses on cold surfaces. Assuming the amount of condensation on the coil—and thus the amount of defrost melt water—is correlated to the amount of water that enters the case through infiltration, the defrost melt water mass flow can be5-24

use d 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 m HR HR CBF air defr ostmelt

room case =

− −

1 Eq. 5.3

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 roo m i s the humidity ratio of the ambient air in the room (dimensionless), HR case i s the humidity ratio of the air inside the case (dimensionless), and CBF is the coil bypass factor (dimensionless).
The coil bypass factor is a measure of the fraction of air in the case that is never influenced by the evaporator coil (or a measure of the fraction of air that does not deposit its moisture onto the evaporator coil). This factor allows the infiltration calculation to be correlated to empirical data. Communication with Southern California Edison’s RTTC was used to estimate the evaporator coil bypass factor. As shown in Table 5.5.17 above, the coil bypass factor was estimated to be 17 percent.
Once the air flow rates were calculated, they were entered into DOE’s model. The mass flow of water vapor into the case is the mass flow of air multiplied by the difference of humidity ratios inside and outside the case. Using the mass flows of air and water vapor, the infiltration load can be approximated using:



# ( ) Q m C T T m H

air dryair room case vapor v H O inf , = − + 2 Eq. 5.4

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.

5.6 COS T-EFFICIENCY CURVES
The result of the engineering analysis is a set of cost-efficiency curves. DOE developed six curves representing the two equipment classes and three different size machines in each equipment class using the baseline specifications and design options described above. The method for developing curves started with determining the baseline energy consumption (chosen to be ENERGY STAR Tier 1) and manufacturer production cost. Above the baseline, design options were implemented in order of lowest to highest payback, and only one design option was5-25

imp l emented at each design option level. Design options were implemented until all technologies were at a maximum level.
The six cost-efficiency curves are shown in Figure 5.6.1 through Figure 5.6.6 below and in tabular form in Table 5.6.1 through Table 5.6.6 below in the form of DEC versus MSP. More detailed results, including the design options used at each design option level, are provided in appendix B. The cost-efficiency curves were calculated at the 75°F test condition of ASHRAE Standard 32.1-2004.
As stated above, DOE used the cost-efficiency curves from the engineering analysis as an input to the life-cycle cost (LCC) analysis to determine the price of beverage vending machines to the customer (see chapter 8 of the TSD).5-26 $1,500 $1,600 $1,700 $1,800 $1,900 $2,000 $2,100 $2,200 $2,300 $2,400

3.0 3.5 4.0 4.5 5.0 5.5 6.0



### Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.6.1 Cost-Efficiency Curves for the Small-Size Class A Equipment Class

Table 5.6.1 Cost-Efficiency Data for the Small-Size Class A Equipment Class

Efficiency Lev e l Daily Energy

Consumption [kWh/day] Manufacturer

Selling Price [$]

1 5.80 1,684.50 2 5.56 1,688.87 3 5.21 1,700.65 4 4.76 1,717.19 5 4.60 1,724.48 6 4.41 1,735.04 7 4.34 1,739.80 8 4.16 1,762.79 9 4.12 1,773.35 10 4.07 1,788.00 11 3.88 1,890.09 12 3.76 1,972.75 13 3.71 2,320.215-27 $1,900 $2,000 $2,100 $2, 200 $2, 300 $2,400 $2,500 $2,600 $2,700 $2,800 $2,900

3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0



### Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.6.2 Cost-Efficiency Curve for the Medium-Size Class A Equipment Class

Table 5.6.2 Cost-Efficiency Data for the Medium-Size Class A Equipment Class

Efficiency Lev e l Daily Energy

Consumption [kWh/day] Manufacturer

Selling Price [$]

1 6.36 2,028.10 2 6.12 2,032.48 3 5.76 2,044.26 4 5.30 2,064.24 5 5.13 2,071.53 6 4.95 2,082.09 7 4.86 2,087.71 8 4.63 2,115.49 9 4.59 2,126.05 10 4.52 2,143.79 11 4.32 2,258.65 12 4.19 2,341.31 13 4.14 2,815.255-28 $2,100 $2,300 $2,500 $2,700 $2,900 $3,100 $3,300

3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0



### Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.6.3 Cost-Efficiency Curves for the Large-Size Class A Equipment Class

Table 5.6.3 Cost-Efficiency Data for the Large-Size Class A Equipment Class

Efficiency Lev e l Daily Energy

Consumption [kWh/day] Manufacturer

Selling Price [$]

1 6.72 2,190.22 2 6.46 2,194.60 3 6.11 2,206.38 4 5.60 2,226.36 5 5.44 2,233.66 6 5.25 2,244.21 7 5.16 2,249.84 8 4.91 2,277.62 9 4.86 2,288.17 10 4.78 2,306.94 11 4.53 2,447.32 12 4.41 2,529.99 13 4.34 3,054.385-29 $1,300 $1, 4 00 $1,500 $1,600 $1,700 $1,800 $1,900 $2,000 $2,100

3.0 3.5 4.0 4.5 5.0 5.5 6.0



### Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.6.4 Cost-Efficiency Curve for the Small-Size Class B Equipment Class

Table 5.6.4 Cost-Efficiency Data for the Small-Size Class B Equipment Class

Efficiency Lev e l Daily Energy

Consumption [kWh/day] Manufacturer

Selling Price [$]

1 5.49 1,370.33 2 4.70 1,382.11 3 4.55 1,386.49 4 4.18 1,407.60 5 4.13 1,411.93 6 3.93 1,430.10 7 3.48 1,507.20 8 3.42 1,519.79 9 3.28 1,551.23 10 3.26 1,561.79 11 3.21 2,026.005-30 $1,500 $1,600 $1,700 $1,800 $1,900 $2,000 $2,100 $2,200 $2,300 $2,400

3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5



### Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.6.5 Cost-Efficiency Curve for the Medium-Size Class B Equipment Class

Table 5.6.5 Cost-Efficiency Data for the Medium-Size Class B Equipment Class

Efficiency Lev e l Daily Energy

Consumption [kWh/day] Manufacturer

Selling Price [$]

1 6.02 1,554.94 2 5.25 1,566.72 3 5.07 1,571.09 4 4.65 1,590.05 5 4.32 1,611.17 6 4.26 1,615.93 7 4.18 1,693.03 8 3.74 1,707.68 9 3.58 1,740.48 10 3.55 1,751.04 11 3.49 2,327.485-31 $1,500 $1, 6 00 $1,700 $1,800 $1,900 $2,000 $2,100 $2,200 $2,300 $2,400 $2,500

3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0



### Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.6.6 Cost-Efficiency Curve for the Large-Size Class B Equipment Class

Table 5.6.6 Cost-Efficiency Data for the Large-Size Class B Equipment Class

Efficiency Lev e l Daily Energy

Consumption [kWh/day] Manufacturer

Selling Price [$]

1 6.43 1,608.50 2 5.70 1,620.28 3 5.49 1,624.65 4 5.01 1,643.61 5 4.66 1,664.73 6 4.60 1,669.49 7 4.51 1,746.59 8 4.32 1,779.39 9 3.88 1,795.07 10 3.84 1,805.63 11 3.78 2,446.245-32

5.7 SE N SITIVITY ANALYSES
DOE conducted two sensitivity analyses. The first examined the sensitivity of the costefficiency curves to material prices. The second examined the sensitivity of performance levels to the use of alternative refrigerants.

5.7.1 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 analysis compares the 5-year average prices for 2002–2006 (described in section 5.3.3) with the 5-year high price for the same period (2006 having the highest material prices ). The results of this sensitivity analysis are presented in Figure 5.7.1 below for the medium-size Class A machine, and Figure 5.7.2 below for the medium-size Class B machine.
The most noticeable impact is a 6-percent increase in the Class B machine price and a 3- percent increase in the Class A machine price. Also, the high material prices increased coil costs by roughly 50 percent because of the large increases in copper costs. As a result, design option ordering changed because coil improvements became less cost-effective.

1900 2100 2300 2500 2700 2900 3100

4.0 4.5 5.0 5.5 6.0 6.5 

### Daily Energy Consumption [kWh/Day]Manufacturer Selling Price [$] 

### 2002-2006 (5-Yr Avg)

2006 Prices (5-Yr High)

Figure 5.7.1 Material Price Sensitivity for the Medium-Size Class A Machine5-33 1400 1600 1800 2000 2200 2400 2600

3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5



### Daily Energy Consumption [kWh/Day]Manufacturer Selling Price [$] 

### 2002-2006 (5-Yr Avg)

2006 Prices (5-Yr High)

Figure 5.7.2 Material Price Sensitivity for the Medium-Size Class B Machine

5.7.2 Al ternative Refrigerants
In conducting an engineering analysis, DOE considers the effects of regulatory changes outside DOE’s statutory energy conservation standards rulemaking process that can affect the manufacturers of the covered equipment. Some of these changes can also affect the energy efficiency or energy consumption of that equipment. DOE identified such external engineering issues that could affect the engineering analysis. These issues are closely related to the cumulative regulatory burden assessment that DOE conducted as part of the manufacturer impact analysis (see chapter 12 of the TSD).
Due to the phaseout of chlorofluorocarbons and hydrochlorofluorocarbons, the beverage vending machine industry must transition to non-ozone-depleting refrigerants. As a result, the industry is transitioning to hydrofluorocarbon-based (HFC-based) refrigerants in its equipment. Much of the beverage vending machine industry is already using HFC-based refrigerants, particularly R-134a. Therefore, DOE assumed from the outset that manufacturers would continue to use HFC-based refrigerants in their equipment.
However, some countries where BVM manufacturers sell their equipment and the BVM customers in those countries might try to shift away from HFC-based refrigerants. Based on conversations with beverage vending machine manufacturers and industry experts, DOE examined two classes of non-HFC refrigerants: hydrocarbon-based refrigerants and carbon dioxide (CO 2) .5-34

Hyd r ocarbon-based refrigerants, such as butane and propane, are the first alternative. These are extremely volatile and are not currently feasible because of safety risks. If the refrigerant leaked, it could ignite and cause personal and property damage. Because of this, DOE did not conduct a cost sensitivity analysis on hydrocarbon-based refrigerants.
The second alternative, CO 2 , does not have the volatility issues of hydrocarbons, but does req u ire design changes from HFC-based refrigerant systems. CO 2 operates at a higher pressure, so di fferent materials or material thicknesses must be used for coils and compressors. However, components do not currently exist in sizes appropriate for beverage vending machines. Thus, DOE was not able to conduct a cost sensitivity analysis on CO 2 -based systems.

5.8 RE S ULTS
DOE presents more detailed results and supporting data for the engineering analysis in appendix B of this TSD.** DRAFT **

5-35 REF E RENCES

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

2 U.S. Department of Labor, Bureau of Labor Statistics, Producer Price Indices , htt p ://www.bls.gov/ppi/.

3 U.S. Department of Commerce, Bureau Economic Analysis, Gross Domestic Product Implicit Price Deflator , https://bea.gov/bea/dn/nipaweb/TableView.asp#Mid.

4 Environmental Protection Agency and U.S. Department of Energy’s ENERGY STAR prog ram, http://www.energystar.gov.

5 Arthur D. Little, Ener

gy Savings Potential for Commercial Refrigeration Equipment , June 1996.

6 Southern California Edison, Next Generation Vending Machine, 2006 ACEEE Summer Study on Energy Efficiency in Buildings.

7 Lawrence Berkley National Laboratory, Wind ow 5.0 , available at http://windows.lbl.gov/software/window/window.html.

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

- conditioning Engineers, 2004. Standard 32.1-2004: Methods of Testing for Rating Vending Machine for Bottled, Canned, and Other Sealed Beverages

.