3.4.6 Commercial Refrigeration Equipment

Commercial refrigeration does not need to be modeled for calculation of tax deductions.

Commercial refrigeration equipment includes the following:

  • Walk-in refrigerators
  • Walk-in freezers
  • Refrigerated casework

The 2008 California energy efficiency standards include refrigerated warehouses for the first time and there are plans to include walk-in refrigerators and freezers in the next update for 2011. ASHRAE has expanded the scope for Standard 90.1 to include more process energy, including commercial refrigeration. The building energy efficiency standards generally do not address commercial refrigeration, however, a recent USDOE standard scheduled to become effective in 2012 does address some of the equipment.

Walk-in refrigerators and freezers typically have remote condensers. Some refrigerated casework has remote condensers, while some have a self-contained condenser built into the unit. Refrigerated casework with built-in condensers reject heat directly to the space while remote condensers reject heat in the remote location, typically on the roof or behind the building.

Refrigerated casework can be further classified by the purpose, the type of doors and, when there are no doors, the configuration: horizontal, vertical or semi-vertical. USDOE has developed standards for refrigerated casework. [bookref id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"] shows these classifications along with the standard level of performance, expressed in kWh/d, which depends on the class of equipment, the total display area, and the volume of the casework.

[table title="USDOE Requirements for Refrigerated Casework (kWh/d)" id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"]

Table I-1- Standard Levels For Commercial Refrigeration Equipment

Equipment class 2 Standard level * **
(kWh/day)***
Equipment class Standard level * **
(kWh/day)
VOP.RC.M 0.82 x TDA + 4.07 VCT.RC.I 0.66 x TDA + 3.05
SVO.RC.M 0.83 x TDA + 3.18 HCT.RC.M 0.16 x TDA + 0.13
HZO.RC.M 0.35 x TDA + 2.88 HCT.RC.L 0.34 x TDA + 0.26
VOP.RC.L 2.27 x TDA + 6.85 HCT.RC.I 0.4 x TDA + 0.31
HZO.RC.L 0.57 x TDA + 6.88 VCS.RC.M 0.11 x V + 0.26
VCT.RC.M 0.22 x TDA + 1.95 VCS.RC.L 0.23 x V + 0.54
VCT.RC.L 0.56 x TDA + 2.61 VCS.RC.I 0.27 x V + 0.63
SOC.RC.M 0.51 x TDA + 0.11 HCS.RC.M 0.11 x V + 0.26
VOP.SC.M 1.74 x TDA + 4.71 HCS.RC.L 0.23 x V + 0.54
SVO.SC.M 1.73 x TDA + 4.59 HCS.RC.I 0.27 x V + 0.63
HZO.SC.M 0.77 x TDA + 5.55 SOC.RC.L 1.08 x TDA + 0.22
HZO.SC.L 1.92 x TDA + 7.08 SOC.RC.I 1.26 x TDA + 0.26
VCT.SC.I 0.67 x TDA + 3.29 VOP.SC.L 4.37 x TDA + 11.82
VCS.SC.I 0.38 x V + 0.88 VOP.SC.I 5.55 x TDA + 15.02
HCT.SC.I 0.56 x TDA + 0.43 SVO.SC.L 4.34 x TDA + 11.51
SVO.RC.L 2.27 x TDA + 6.85 SVO.SC.I 5.52 x TDA + 14.63
VOP.RC.I 2.89 x TDA + 8.7 HZO.SC.I 2.44 x TDA + 9.
SVO.RC.I 2.89 x TDA + 8.7 SOC.SC.I 1.76 x TDA + 0.36
HZO.RC.I 0.72 x TDA + 8.74 HCS.SC.I 0.38 x V + 0.88

*TDA is the total display area of the case, as measured in the Air-Conditioning and Refrigeration Institute (ARI) Standard 1200-2006, Appendix D.

** V is the volume of the case, as measured in ARI Standard 1200-2006, Appendix C.

***Kilowatt hours per day.

2For this rulemaking, equipment class designations consist of a combination (in sequential order separated by periods) of : (1) An equipment 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); (2) an operating mode code (RC=remote condensing or SC=self contained); and (3) a rating temperature code (M=medium temperature (38º F), L=low temperature (0ºF), or I=ice-cream temperature (-15ºF)). For example, "VOP.RC.M" refers to the "vertical open, remote condensing, medium temperature" equipment class. See discussion in section V.A.2 and chapter 3 of the TSD, market and technology assessment, for a more detailed explanation of the equipment class terminology. See table IV-2 for a list of the equipment classes by category.

Walk-in refrigerators and freezers are not covered by the USDOE standards and test procedures. COMNET default values for these are given in [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]. These values are expressed in W/ft² of refrigerator or freezer area. This power is assumed to occur continuously. Some walk-ins have glass display doors on one side so that products can be loaded from the back. Glass display doors increase the power requirements of walk-ins. Additional power is added when glass display doors are present. The total power for walk-in refrigerators and freezers is given in Equation (6.4.6-1).

(6.4.6-1)

$$ P_{Walk-in} = \left ( A_{Ref} \cdot PD_{Ref} + N_{Ref} \cdot D_{Ref} \right )+\left ( A_{Frz} \cdot PD_{Frz} + N_{Frz} \cdot D_{Frz} \right ) $$

Where

PWalk-in is the estimated power density for the walk-in refrigerator or freezer in (W)
Axxx the area of the walk-in refrigerator or freezer (ft²)
Nxxx the number of glass display doors (unitless)
PDxxx the power density of the walk-in refrigerator or freezer taken from [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"] (W/ft²)
Dxxx the power associated with a glass display door for a walk-in refrigerator or freezer (W/door)
xxx subscript indicating a walk-in freezer or refrigerator (Ref or Frz)

[table title="Default Power for Walk-In Refrigerators and Freezers (W/ft²)" id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]
Source: These values are determined using the procedures of the Heatcraft Engineering Manual, Commercial Refrigeration Cooling and Freezing Load Calculations and Reference Guide, August 2006. The EER is assumed to be 12.39 for refrigerators and 6.33 for Freezers. The specific efficiency is assumed to be 70 for refrigerators and 50 for freezers. Operating temperature is assumed to be 35 F for refrigerators and -10 F for freezers.

Floor  Area Refrigerator Freezer
100 ft²  or less 8.0 16.0
101 ft² to 250 ft² 6.0 12.0
251 ft² to 450 ft² 5.0 9.5
451 ft² to 650 ft² 4.5 8.0
651 ft² to 800 ft² 4.0 7.0
801 ft² to 1,000 ft² 3.5 6.5
More than 1,000 ft² 3.0 6.0
Additional Power for each Glass Display Door 105 325
Note:
Refrigeration Modeling Method
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition

The method used to estimate refrigeration energy and to model the thermal interaction with the space where casework is located. Three methods are included in this manual:

  • COMNET defaults. With this method, the power density values provided in Appendix B, Table 61 are used; schedules are assumed to be continuous operation.
  • USDOE performance ratings. With this method, the energy modeler takes inventory of the refrigerated casework in the rated building and sums the rated energy use (typically in kWh/day). Walk-in refrigerators and freezers shall use the defaults from Equation (6.4.6-1) and the values from [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]. All refrigeration equipment is then assumed to operate continuously. 
  • Explicit refrigeration model. With this method, all components of the refrigeration system are explicitly modeled in DOE-2.2R or other hourly simulation program with this capability.2 

The remaining building descriptors in this section apply to buildings that use either the COMNET defaults or the USDOE performance ratings.

Units List (see above)
Input Restrictions None
Baseline Rules Method used to model the proposed design shall be used for the baseline building. Note that credit is offered only when the USDOE performance ratings method is used.
Refrigeration Power
Applicability All buildings that have commercial refrigeration for cold storage or display and do not use the explicit refrigeration model
Definition Commercial refrigeration power is the average power for all commercial refrigeration equipment, assuming constant year-round operation. Equipment includes walk-in refrigerators and freezers, open refrigerated casework, and closed refrigerated casework. It does not include residential type refrigerators used in kitchenettes or refrigerated vending machines. These are covered under receptacle power.
Units Kilowatts (kW)
Input Restrictions With the COMNET defaults method, the values in Appendix B, Table 6 are prescribed. These values are multiplied times the floor area of the rated building to estimate the refrigeration power. With the USDOE performance ratings method, refrigeration power is estimated by summing the kWh/day for all the refrigeration equipment in the space and dividing by 24 hours. The refrigeration power for walk-in refrigerators and freezers is added to this value.
Baseline Rules Refrigeration power is the same as the proposed design when the COMNET defaults are used. When the USDOE performance ratings method is used, refrigeration power for casework shall be determined from [bookref id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"]; the power for walk-in refrigerators and freezers shall be the same as the proposed design.
Remote Condenser Fraction
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition

The fraction of condenser heat that is rejected to the outdoors. For self-contained refrigeration casework, this value will be zero. For remote condenser systems, this value is 1.0. For combination systems, the value should be weighted according refrigeration capacity.

For refrigeration with self contained condensers and compressors, the heat that is removed from the space is equal to the heat that is rejected to the space, since the evaporator and condenser are both located in the same space. There may be some latent cooling associated with operation of the equipment, but this may be ignored with the COMNET defaults or USDOE performance ratings methods. The operation of self-contained refrigeration units may be approximated by adding a continuously operating electric load to the space that is equal to the energy consumption of the refrigeration units. Self-contained refrigeration units add heat to the space that must be removed by the HVAC system.

When the condenser is remotely located, heat is removed from the space but rejected outdoors. In this case, the refrigeration equipment functions in a manner similar to a continuously running split system air conditioner. Some heat is added to the space for the evaporator fan, the anti-fog heaters and other auxiliary energy uses, but refrigeration systems with remote condensers remove more heat from the space where they are located than they add. The HVAC system must compensate for this imbalance.

For remotely located condensers using the COMNET defaults or USDOE performance ratings methods, the heat that is removed from the space is determined as follows:

(6.4.6-2)

$$ Q = \Big [ \left ( 1 - F \right ) \times kW - \left ( F \times kW \times COP \right ) \Big ] \times 3.413 $$Where

Q The rate of heat removal from the space due to the continuous operation of the refrigeration system (kBtu/h). A negative number means that heat is being removed from the space; a positive number means that heat is being added.

kW
The power of the refrigeration system determined by using the COMNET defaults or the USDOE performance ratings method (kW)
F The remote condenser fraction (see building descriptor below) (unitless)
COP The coefficient of performance of the refrigeration system (unitless)

The simple approach outlined above assumes that there is no latent cooling associated with the refrigeration system. The heat addition or removal resulting from the above equation can be modeled in a number of ways, to accommodate the variety of calculation engines available. It can be scheduled if the engine can accommodate a heat removal schedule. It can be modeled as a separate, constantly running air conditioner, if the engine can accommodate two cooling systems serving the same thermal block. Other modeling techniques are acceptable as long as they are thermodynamically equivalent.

Units Fraction
Input Restrictions None
Baseline Rules Same as the proposed design
Refrigeration COP
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition The coefficient of performance of the refrigeration system. This is used only to determine the heat removed or added to the space, not to determine the refrigeration power or energy.
Units Fraction
Input Restrictions This value is prescribed to be 3.6 for refrigerators and 1.8 for freezers.3
Baseline Rules Same as the proposed design
Refrigeration Schedule
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition The schedule of operation for commercial refrigeration equipment. This is used to convert refrigeration power to energy use.
Units Data structure: schedule, fractional
Input Restrictions Continuous operation is prescribed.
Baseline Rules Same as the proposed design
  • 1. See Table C-43, p. 146 of NREL/TP-550-41956, Methodology for Modeling Building Energy Performance across the Commercial Sector, Technical Report, Appendix C, March 2008. The values in this report were taken from Table 8-3 of the California Commercial End-Use Survey, Consultants Report, March 2006, CEC-400-2006-005
  • 2. Direct modeling of refrigeration equipment in buildings is not broadly supported by energy simulation programs. The simulation program that is used in most energy analysis of refrigeration equipment is DOE-2.2R, which is a proprietary and limited release version of the DOE-2.2 simulation engine used by EQuest. EnergyPlus also has refrigeration modeling capabilities. These software applications allow the user to define the configuration of equipment and to specify the performance characteristics of each piece of equipment. These applications can also account for the interaction of the equipment with the temperature and humidity of the space where it is located. The complexity and variation of input for these models makes it very difficult to specify baseline conditions. For this reason, credit for efficient refrigeration systems is not offered in COMNET Phase I when explicit refrigeration models are used.
  • 3. These values are consistent with the assumptions for the default values for walk-ins, which assume an EER of 12.39 for refrigerators and 6.33 for freezers.
90.1-2007

Commercial refrigeration equipment includes the following:

  • Walk-in refrigerators
  • Walk-in freezers
  • Refrigerated casework

The 2008 California energy efficiency standards include refrigerated warehouses for the first time and there are plans to include walk-in refrigerators and freezers in the next update for 2011. ASHRAE has expanded the scope for Standard 90.1 to include more process energy, including commercial refrigeration. The building energy efficiency standards generally do not address commercial refrigeration, however, a recent USDOE standard scheduled to become effective in 2012 does address some of the equipment.

Walk-in refrigerators and freezers typically have remote condensers. Some refrigerated casework has remote condensers, while some have a self-contained condenser built into the unit. Refrigerated casework with built-in condensers reject heat directly to the space while remote condensers reject heat in the remote location, typically on the roof or behind the building.

Refrigerated casework can be further classified by the purpose, the type of doors and, when there are no doors, the configuration: horizontal, vertical or semi-vertical. USDOE has developed standards for refrigerated casework. [bookref id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"] shows these classifications along with the standard level of performance, expressed in kWh/d, which depends on the class of equipment, the total display area, and the volume of the casework.

[table title="USDOE Requirements for Refrigerated Casework (kWh/d)" id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"]

Table I-1- Standard Levels For Commercial Refrigeration Equipment

Equipment class 2 Standard level * **
(kWh/day)***
Equipment class Standard level * **
(kWh/day)
VOP.RC.M 0.82 x TDA + 4.07 VCT.RC.I 0.66 x TDA + 3.05
SVO.RC.M 0.83 x TDA + 3.18 HCT.RC.M 0.16 x TDA + 0.13
HZO.RC.M 0.35 x TDA + 2.88 HCT.RC.L 0.34 x TDA + 0.26
VOP.RC.L 2.27 x TDA + 6.85 HCT.RC.I 0.4 x TDA + 0.31
HZO.RC.L 0.57 x TDA + 6.88 VCS.RC.M 0.11 x V + 0.26
VCT.RC.M 0.22 x TDA + 1.95 VCS.RC.L 0.23 x V + 0.54
VCT.RC.L 0.56 x TDA + 2.61 VCS.RC.I 0.27 x V + 0.63
SOC.RC.M 0.51 x TDA + 0.11 HCS.RC.M 0.11 x V + 0.26
VOP.SC.M 1.74 x TDA + 4.71 HCS.RC.L 0.23 x V + 0.54
SVO.SC.M 1.73 x TDA + 4.59 HCS.RC.I 0.27 x V + 0.63
HZO.SC.M 0.77 x TDA + 5.55 SOC.RC.L 1.08 x TDA + 0.22
HZO.SC.L 1.92 x TDA + 7.08 SOC.RC.I 1.26 x TDA + 0.26
VCT.SC.I 0.67 x TDA + 3.29 VOP.SC.L 4.37 x TDA + 11.82
VCS.SC.I 0.38 x V + 0.88 VOP.SC.I 5.55 x TDA + 15.02
HCT.SC.I 0.56 x TDA + 0.43 SVO.SC.L 4.34 x TDA + 11.51
SVO.RC.L 2.27 x TDA + 6.85 SVO.SC.I 5.52 x TDA + 14.63
VOP.RC.I 2.89 x TDA + 8.7 HZO.SC.I 2.44 x TDA + 9.
SVO.RC.I 2.89 x TDA + 8.7 SOC.SC.I 1.76 x TDA + 0.36
HZO.RC.I 0.72 x TDA + 8.74 HCS.SC.I 0.38 x V + 0.88

*TDA is the total display area of the case, as measured in the Air-Conditioning and Refrigeration Institute (ARI) Standard 1200-2006, Appendix D.

** V is the volume of the case, as measured in ARI Standard 1200-2006, Appendix C.

***Kilowatt hours per day.

2For this rulemaking, equipment class designations consist of a combination (in sequential order separated by periods) of : (1) An equipment 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); (2) an operating mode code (RC=remote condensing or SC=self contained); and (3) a rating temperature code (M=medium temperature (38º F), L=low temperature (0ºF), or I=ice-cream temperature (-15ºF)). For example, "VOP.RC.M" refers to the "vertical open, remote condensing, medium temperature" equipment class. See discussion in section V.A.2 and chapter 3 of the TSD, market and technology assessment, for a more detailed explanation of the equipment class terminology. See table IV-2 for a list of the equipment classes by category.

Walk-in refrigerators and freezers are not covered by the USDOE standards and test procedures. COMNET default values for these are given in [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]. These values are expressed in W/ft² of refrigerator or freezer area. This power is assumed to occur continuously. Some walk-ins have glass display doors on one side so that products can be loaded from the back. Glass display doors increase the power requirements of walk-ins. Additional power is added when glass display doors are present. The total power for walk-in refrigerators and freezers is given in Equation (6.4.6-1).

(6.4.6-1)

$$ P_{Walk-in} = \left ( A_{Ref} \cdot PD_{Ref} + N_{Ref} \cdot D_{Ref} \right )+\left ( A_{Frz} \cdot PD_{Frz} + N_{Frz} \cdot D_{Frz} \right ) $$

Where

PWalk-in is the estimated power density for the walk-in refrigerator or freezer in (W)
Axxx the area of the walk-in refrigerator or freezer (ft²)
Nxxx the number of glass display doors (unitless)
PDxxx the power density of the walk-in refrigerator or freezer taken from [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"] (W/ft²)
Dxxx the power associated with a glass display door for a walk-in refrigerator or freezer (W/door)
xxx subscript indicating a walk-in freezer or refrigerator (Ref or Frz)

[table title="Default Power for Walk-In Refrigerators and Freezers (W/ft²)" id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]
Source: These values are determined using the procedures of the Heatcraft Engineering Manual, Commercial Refrigeration Cooling and Freezing Load Calculations and Reference Guide, August 2006. The EER is assumed to be 12.39 for refrigerators and 6.33 for Freezers. The specific efficiency is assumed to be 70 for refrigerators and 50 for freezers. Operating temperature is assumed to be 35 F for refrigerators and -10 F for freezers.

Floor  Area Refrigerator Freezer
100 ft²  or less 8.0 16.0
101 ft² to 250 ft² 6.0 12.0
251 ft² to 450 ft² 5.0 9.5
451 ft² to 650 ft² 4.5 8.0
651 ft² to 800 ft² 4.0 7.0
801 ft² to 1,000 ft² 3.5 6.5
More than 1,000 ft² 3.0 6.0
Additional Power for each Glass Display Door 105 325
Note:
Refrigeration Modeling Method
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition

The method used to estimate refrigeration energy and to model the thermal interaction with the space where casework is located. Three methods are included in this manual:

  • COMNET defaults. With this method, the power density values provided in Appendix B, Table 61 are used; schedules are assumed to be continuous operation.
  • USDOE performance ratings. With this method, the energy modeler takes inventory of the refrigerated casework in the rated building and sums the rated energy use (typically in kWh/day). Walk-in refrigerators and freezers shall use the defaults from Equation (6.4.6-1) and the values from [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]. All refrigeration equipment is then assumed to operate continuously. 
  • Explicit refrigeration model. With this method, all components of the refrigeration system are explicitly modeled in DOE-2.2R or other hourly simulation program with this capability.2 

The remaining building descriptors in this section apply to buildings that use either the COMNET defaults or the USDOE performance ratings.

Units List (see above)
Input Restrictions None
Baseline Rules Method used to model the proposed design shall be used for the baseline building. Note that credit is offered only when the USDOE performance ratings method is used.
Refrigeration Power
Applicability All buildings that have commercial refrigeration for cold storage or display and do not use the explicit refrigeration model
Definition Commercial refrigeration power is the average power for all commercial refrigeration equipment, assuming constant year-round operation. Equipment includes walk-in refrigerators and freezers, open refrigerated casework, and closed refrigerated casework. It does not include residential type refrigerators used in kitchenettes or refrigerated vending machines. These are covered under receptacle power.
Units Kilowatts (kW)
Input Restrictions With the COMNET defaults method, the values in Appendix B, Table 6 are prescribed. These values are multiplied times the floor area of the rated building to estimate the refrigeration power. With the USDOE performance ratings method, refrigeration power is estimated by summing the kWh/day for all the refrigeration equipment in the space and dividing by 24 hours. The refrigeration power for walk-in refrigerators and freezers is added to this value.
Baseline Rules Refrigeration power is the same as the proposed design when the COMNET defaults are used. When the USDOE performance ratings method is used, refrigeration power for casework shall be determined from [bookref id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"]; the power for walk-in refrigerators and freezers shall be the same as the proposed design.
Remote Condenser Fraction
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition

The fraction of condenser heat that is rejected to the outdoors. For self-contained refrigeration casework, this value will be zero. For remote condenser systems, this value is 1.0. For combination systems, the value should be weighted according refrigeration capacity.

For refrigeration with self contained condensers and compressors, the heat that is removed from the space is equal to the heat that is rejected to the space, since the evaporator and condenser are both located in the same space. There may be some latent cooling associated with operation of the equipment, but this may be ignored with the COMNET defaults or USDOE performance ratings methods. The operation of self-contained refrigeration units may be approximated by adding a continuously operating electric load to the space that is equal to the energy consumption of the refrigeration units. Self-contained refrigeration units add heat to the space that must be removed by the HVAC system.

When the condenser is remotely located, heat is removed from the space but rejected outdoors. In this case, the refrigeration equipment functions in a manner similar to a continuously running split system air conditioner. Some heat is added to the space for the evaporator fan, the anti-fog heaters and other auxiliary energy uses, but refrigeration systems with remote condensers remove more heat from the space where they are located than they add. The HVAC system must compensate for this imbalance.

For remotely located condensers using the COMNET defaults or USDOE performance ratings methods, the heat that is removed from the space is determined as follows:

(6.4.6-2)

$$ Q = \Big [ \left ( 1 - F \right ) \times kW - \left ( F \times kW \times COP \right ) \Big ] \times 3.413 $$Where

Q The rate of heat removal from the space due to the continuous operation of the refrigeration system (kBtu/h). A negative number means that heat is being removed from the space; a positive number means that heat is being added.

kW
The power of the refrigeration system determined by using the COMNET defaults or the USDOE performance ratings method (kW)
F The remote condenser fraction (see building descriptor below) (unitless)
COP The coefficient of performance of the refrigeration system (unitless)

The simple approach outlined above assumes that there is no latent cooling associated with the refrigeration system. The heat addition or removal resulting from the above equation can be modeled in a number of ways, to accommodate the variety of calculation engines available. It can be scheduled if the engine can accommodate a heat removal schedule. It can be modeled as a separate, constantly running air conditioner, if the engine can accommodate two cooling systems serving the same thermal block. Other modeling techniques are acceptable as long as they are thermodynamically equivalent.

Units Fraction
Input Restrictions None
Baseline Rules Same as the proposed design
Refrigeration COP
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition The coefficient of performance of the refrigeration system. This is used only to determine the heat removed or added to the space, not to determine the refrigeration power or energy.
Units Fraction
Input Restrictions This value is prescribed to be 3.6 for refrigerators and 1.8 for freezers.3
Baseline Rules Same as the proposed design
Refrigeration Schedule
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition The schedule of operation for commercial refrigeration equipment. This is used to convert refrigeration power to energy use.
Units Data structure: schedule, fractional
Input Restrictions Continuous operation is prescribed.
Baseline Rules Same as the proposed design
  • 1. See Table C-43, p. 146 of NREL/TP-550-41956, Methodology for Modeling Building Energy Performance across the Commercial Sector, Technical Report, Appendix C, March 2008. The values in this report were taken from Table 8-3 of the California Commercial End-Use Survey, Consultants Report, March 2006, CEC-400-2006-005
  • 2. Direct modeling of refrigeration equipment in buildings is not broadly supported by energy simulation programs. The simulation program that is used in most energy analysis of refrigeration equipment is DOE-2.2R, which is a proprietary and limited release version of the DOE-2.2 simulation engine used by EQuest. EnergyPlus also has refrigeration modeling capabilities. These software applications allow the user to define the configuration of equipment and to specify the performance characteristics of each piece of equipment. These applications can also account for the interaction of the equipment with the temperature and humidity of the space where it is located. The complexity and variation of input for these models makes it very difficult to specify baseline conditions. For this reason, credit for efficient refrigeration systems is not offered in COMNET Phase I when explicit refrigeration models are used.
  • 3. These values are consistent with the assumptions for the default values for walk-ins, which assume an EER of 12.39 for refrigerators and 6.33 for freezers.
90.1-2010

Commercial refrigeration equipment includes the following:

  • Walk-in refrigerators
  • Walk-in freezers
  • Refrigerated casework

The 2008 California energy efficiency standards include refrigerated warehouses for the first time and there are plans to include walk-in refrigerators and freezers in the next update for 2011. ASHRAE has expanded the scope for Standard 90.1 to include more process energy, including commercial refrigeration. The building energy efficiency standards generally do not address commercial refrigeration, however, a recent USDOE standard scheduled to become effective in 2012 does address some of the equipment.

Walk-in refrigerators and freezers typically have remote condensers. Some refrigerated casework has remote condensers, while some have a self-contained condenser built into the unit. Refrigerated casework with built-in condensers reject heat directly to the space while remote condensers reject heat in the remote location, typically on the roof or behind the building.

Refrigerated casework can be further classified by the purpose, the type of doors and, when there are no doors, the configuration: horizontal, vertical or semi-vertical. USDOE has developed standards for refrigerated casework. Table 6.4.6-1 shows these classifications along with the standard level of performance, expressed in kWh/d, which depends on the class of equipment, the total display area, and the volume of the casework.

Table 6.4.6-1: USDOE Requirements for Refrigerated Casework (kWh/d)

Table I-1- Standard Levels For Commercial Refrigeration Equipment

Equipment class 2 Standard level * **
(kWh/day)***
Equipment class Standard level * **
(kWh/day)
VOP.RC.M 0.82 x TDA + 4.07 VCT.RC.I 0.66 x TDA + 3.05
SVO.RC.M 0.83 x TDA + 3.18 HCT.RC.M 0.16 x TDA + 0.13
HZO.RC.M 0.35 x TDA + 2.88 HCT.RC.L 0.34 x TDA + 0.26
VOP.RC.L 2.27 x TDA + 6.85 HCT.RC.I 0.4 x TDA + 0.31
HZO.RC.L 0.57 x TDA + 6.88 VCS.RC.M 0.11 x V + 0.26
VCT.RC.M 0.22 x TDA + 1.95 VCS.RC.L 0.23 x V + 0.54
VCT.RC.L 0.56 x TDA + 2.61 VCS.RC.I 0.27 x V + 0.63
SOC.RC.M 0.51 x TDA + 0.11 HCS.RC.M 0.11 x V + 0.26
VOP.SC.M 1.74 x TDA + 4.71 HCS.RC.L 0.23 x V + 0.54
SVO.SC.M 1.73 x TDA + 4.59 HCS.RC.I 0.27 x V + 0.63
HZO.SC.M 0.77 x TDA + 5.55 SOC.RC.L 1.08 x TDA + 0.22
HZO.SC.L 1.92 x TDA + 7.08 SOC.RC.I 1.26 x TDA + 0.26
VCT.SC.I 0.67 x TDA + 3.29 VOP.SC.L 4.37 x TDA + 11.82
VCS.SC.I 0.38 x V + 0.88 VOP.SC.I 5.55 x TDA + 15.02
HCT.SC.I 0.56 x TDA + 0.43 SVO.SC.L 4.34 x TDA + 11.51
SVO.RC.L 2.27 x TDA + 6.85 SVO.SC.I 5.52 x TDA + 14.63
VOP.RC.I 2.89 x TDA + 8.7 HZO.SC.I 2.44 x TDA + 9.
SVO.RC.I 2.89 x TDA + 8.7 SOC.SC.I 1.76 x TDA + 0.36
HZO.RC.I 0.72 x TDA + 8.74 HCS.SC.I 0.38 x V + 0.88

*TDA is the total display area of the case, as measured in the Air-Conditioning and Refrigeration Institute (ARI) Standard 1200-2006, Appendix D.

** V is the volume of the case, as measured in ARI Standard 1200-2006, Appendix C.

***Kilowatt hours per day.

2For this rulemaking, equipment class designations consist of a combination (in sequential order separated by periods) of : (1) An equipment 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); (2) an operating mode code (RC=remote condensing or SC=self contained); and (3) a rating temperature code (M=medium temperature (38º F), L=low temperature (0ºF), or I=ice-cream temperature (-15ºF)). For example, "VOP.RC.M" refers to the "vertical open, remote condensing, medium temperature" equipment class. See discussion in section V.A.2 and chapter 3 of the TSD, market and technology assessment, for a more detailed explanation of the equipment class terminology. See table IV-2 for a list of the equipment classes by category.

Walk-in refrigerators and freezers are not covered by the USDOE standards and test procedures. COMNET default values for these are given in Table 6.4.6-2. These values are expressed in W/ft² of refrigerator or freezer area. This power is assumed to occur continuously. Some walk-ins have glass display doors on one side so that products can be loaded from the back. Glass display doors increase the power requirements of walk-ins. Additional power is added when glass display doors are present. The total power for walk-in refrigerators and freezers is given in Equation (6.4.6-1).

(6.4.6-1)

$$ P_{Walk-in} = \left ( A_{Ref} \cdot PD_{Ref} + N_{Ref} \cdot D_{Ref} \right )+\left ( A_{Frz} \cdot PD_{Frz} + N_{Frz} \cdot D_{Frz} \right ) $$

Where

PWalk-in is the estimated power density for the walk-in refrigerator or freezer in (W)
Axxx the area of the walk-in refrigerator or freezer (ft²)
Nxxx the number of glass display doors (unitless)
PDxxx the power density of the walk-in refrigerator or freezer taken from Table 6.4.6-2 (W/ft²)
Dxxx the power associated with a glass display door for a walk-in refrigerator or freezer (W/door)
xxx subscript indicating a walk-in freezer or refrigerator (Ref or Frz)

Table 6.4.6-2: Default Power for Walk-In Refrigerators and Freezers (W/ft²)
Source: These values are determined using the procedures of the Heatcraft Engineering Manual, Commercial Refrigeration Cooling and Freezing Load Calculations and Reference Guide, August 2006. The EER is assumed to be 12.39 for refrigerators and 6.33 for Freezers. The specific efficiency is assumed to be 70 for refrigerators and 50 for freezers. Operating temperature is assumed to be 35 F for refrigerators and -10 F for freezers.

Floor  Area Refrigerator Freezer
100 ft²  or less 8.0 16.0
101 ft² to 250 ft² 6.0 12.0
251 ft² to 450 ft² 5.0 9.5
451 ft² to 650 ft² 4.5 8.0
651 ft² to 800 ft² 4.0 7.0
801 ft² to 1,000 ft² 3.5 6.5
More than 1,000 ft² 3.0 6.0
Additional Power for each Glass Display Door 105 325
Note:
Refrigeration Modeling Method
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition

The method used to estimate refrigeration energy and to model the thermal interaction with the space where casework is located. Three methods are included in this manual:

  • COMNET defaults. With this method, the power density values provided in Appendix B, Table 61 are used; schedules are assumed to be continuous operation.
  • USDOE performance ratings. With this method, the energy modeler takes inventory of the refrigerated casework in the rated building and sums the rated energy use (typically in kWh/day). Walk-in refrigerators and freezers shall use the defaults from Equation (6.4.6-1) and the values from Table 6.4.6-2. All refrigeration equipment is then assumed to operate continuously. 
  • Explicit refrigeration model. With this method, all components of the refrigeration system are explicitly modeled in DOE-2.2R or other hourly simulation program with this capability.2 

The remaining building descriptors in this section apply to buildings that use either the COMNET defaults or the USDOE performance ratings.

Units List (see above)
Input Restrictions None
Baseline Rules Method used to model the proposed design shall be used for the baseline building. Note that credit is offered only when the USDOE performance ratings method is used.
Refrigeration Power
Applicability All buildings that have commercial refrigeration for cold storage or display and do not use the explicit refrigeration model
Definition Commercial refrigeration power is the average power for all commercial refrigeration equipment, assuming constant year-round operation. Equipment includes walk-in refrigerators and freezers, open refrigerated casework, and closed refrigerated casework. It does not include residential type refrigerators used in kitchenettes or refrigerated vending machines. These are covered under receptacle power.
Units Kilowatts (kW)
Input Restrictions With the COMNET defaults method, the values in Appendix B, Table 6 are prescribed. These values are multiplied times the floor area of the rated building to estimate the refrigeration power. With the USDOE performance ratings method, refrigeration power is estimated by summing the kWh/day for all the refrigeration equipment in the space and dividing by 24 hours. The refrigeration power for walk-in refrigerators and freezers is added to this value.
Baseline Rules Refrigeration power is the same as the proposed design when the COMNET defaults are used. When the USDOE performance ratings method is used, refrigeration power for casework shall be determined from Table 6.4.6-1; the power for walk-in refrigerators and freezers shall be the same as the proposed design.
Remote Condenser Fraction
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition

The fraction of condenser heat that is rejected to the outdoors. For self-contained refrigeration casework, this value will be zero. For remote condenser systems, this value is 1.0. For combination systems, the value should be weighted according refrigeration capacity.

For refrigeration with self contained condensers and compressors, the heat that is removed from the space is equal to the heat that is rejected to the space, since the evaporator and condenser are both located in the same space. There may be some latent cooling associated with operation of the equipment, but this may be ignored with the COMNET defaults or USDOE performance ratings methods. The operation of self-contained refrigeration units may be approximated by adding a continuously operating electric load to the space that is equal to the energy consumption of the refrigeration units. Self-contained refrigeration units add heat to the space that must be removed by the HVAC system.

When the condenser is remotely located, heat is removed from the space but rejected outdoors. In this case, the refrigeration equipment functions in a manner similar to a continuously running split system air conditioner. Some heat is added to the space for the evaporator fan, the anti-fog heaters and other auxiliary energy uses, but refrigeration systems with remote condensers remove more heat from the space where they are located than they add. The HVAC system must compensate for this imbalance.

For remotely located condensers using the COMNET defaults or USDOE performance ratings methods, the heat that is removed from the space is determined as follows:

(6.4.6-2)

$$ Q = \Big [ \left ( 1 - F \right ) \times kW - \left ( F \times kW \times COP \right ) \Big ] \times 3.413 $$Where

Q The rate of heat removal from the space due to the continuous operation of the refrigeration system (kBtu/h). A negative number means that heat is being removed from the space; a positive number means that heat is being added.

kW
The power of the refrigeration system determined by using the COMNET defaults or the USDOE performance ratings method (kW)
F The remote condenser fraction (see building descriptor below) (unitless)
COP The coefficient of performance of the refrigeration system (unitless)

The simple approach outlined above assumes that there is no latent cooling associated with the refrigeration system. The heat addition or removal resulting from the above equation can be modeled in a number of ways, to accommodate the variety of calculation engines available. It can be scheduled if the engine can accommodate a heat removal schedule. It can be modeled as a separate, constantly running air conditioner, if the engine can accommodate two cooling systems serving the same thermal block. Other modeling techniques are acceptable as long as they are thermodynamically equivalent.

Units Fraction
Input Restrictions None
Baseline Rules Same as the proposed design
Refrigeration COP
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition The coefficient of performance of the refrigeration system. This is used only to determine the heat removed or added to the space, not to determine the refrigeration power or energy.
Units Fraction
Input Restrictions This value is prescribed to be 3.6 for refrigerators and 1.8 for freezers.3
Baseline Rules Same as the proposed design
Refrigeration Schedule
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition The schedule of operation for commercial refrigeration equipment. This is used to convert refrigeration power to energy use.
Units Data structure: schedule, fractional
Input Restrictions Continuous operation is prescribed.
Baseline Rules Same as the proposed design
  • 1. See Table C-43, p. 146 of NREL/TP-550-41956, Methodology for Modeling Building Energy Performance across the Commercial Sector, Technical Report, Appendix C, March 2008. The values in this report were taken from Table 8-3 of the California Commercial End-Use Survey, Consultants Report, March 2006, CEC-400-2006-005
  • 2. Direct modeling of refrigeration equipment in buildings is not broadly supported by energy simulation programs. The simulation program that is used in most energy analysis of refrigeration equipment is DOE-2.2R, which is a proprietary and limited release version of the DOE-2.2 simulation engine used by EQuest. EnergyPlus also has refrigeration modeling capabilities. These software applications allow the user to define the configuration of equipment and to specify the performance characteristics of each piece of equipment. These applications can also account for the interaction of the equipment with the temperature and humidity of the space where it is located. The complexity and variation of input for these models makes it very difficult to specify baseline conditions. For this reason, credit for efficient refrigeration systems is not offered in COMNET Phase I when explicit refrigeration models are used.
  • 3. These values are consistent with the assumptions for the default values for walk-ins, which assume an EER of 12.39 for refrigerators and 6.33 for freezers.
90.1-2016 BM

Commercial refrigeration equipment includes the following:

  • Walk-in refrigerators
  • Walk-in freezers
  • Refrigerated casework

Walk-in refrigerators and freezers typically have remote condensers. Some refrigerated casework has remote condensers, while some have a self-contained condenser built into the unit. Refrigerated casework with built-in condensers reject heat directly to the space while remote condensers reject heat in the remote location, typically on the roof or behind the building. This is an important modeling distinction.

Refrigerated casework can be further classified by the purpose, the type of doors and, when there are no doors, the configuration: horizontal, vertical or semi-vertical. USDOE has developed standards for refrigerated casework. Table 3.4.6-1 shows these classifications along with the standard level of performance, expressed in kWh/d, which depends on the class of equipment and the total display area or volume of the casework.

Table 3.4.6-1: USDOE Requirements for Commercial Refrigerators and Freezers

Equipment Type

Application

Energy Use Limits (kWh/day)

Test Procedure

Refrigerator with solid doors

Holding temperature

0.125 × V + 2.76

AHRI 1200

Refrigerator with transparent doors

0.172 × V + 4.77

Freezers with solid doors

0.398 × V + 2.28

Freezers with transparent doors

0.94 × V + 5.10

Refrigerators/freezers with solid doors

0.12 × V + 4.77

Commercial refrigerators

Pulldown

0.181 × V + 5.01

V is the chiller or frozen compartment volume (ft3) as defined in Association of Home Appliance Manufacturers Standard HRF-1.

 

Table 3.4.6-2: USDOE Requirements for Refrigerated Casework (kWh/d)

Equipment Classa

Family Code

Operating Mode

Rating Temperature

Energy Use Limits,b,c

kWh/day

Test Procedure

VOP.RC.M

Vertical open

Remote condensing

Medium temperature

1.01 × TDA + 4.07

AHRI 1200

SVO.RC.M

Semivertical open

Medium temperature

1.01 × TDA + 3.18

HZO.RC.M

Horizontal open

Medium temperature

0.51 × TDA + 2.88

VOP.RC.L

Vertical open

Low temperature

2.84 × TDA + 6.85

HZO.RC.L

Horizontal open

Low temperature

0.68 × TDA + 6.88

VCT.RC.M

Vertical transparent door

Medium temperature

0.48 × TDA + 1.95

VCT.RC.L

Vertical transparent door

Low temperature

1.03 × TDA + 2.61

SOC.RC.M

Service over counter

Medium temperature

0.62 × TDA + 0.11

 VOP.SC.M

Vertical open

Self contained

Medium temperature

2.34 × TDA + 4.71

 SVO.SC.M

Semivertical open

Medium temperature

2.23 × TDA + 4.59

HZO.SC.M

Horizontal open

Medium temperature

1.14 × TDA + 5.55

HZO.SC.L

Horizontal open

Low temperature

2.63 × TDA + 7.08

VCT.SC.I

Vertical transparent door

Ice cream

1.63 × TDA + 3.29

VCS.SC.I

Vertical solid door

Ice cream

0.55 × V + 0.88

HCT.SC.I

Horizontal transparent door

Ice cream

1.33 × TDA + 0.43

SVO.RC.L

Semivertical open

Remote condensing

Low temperature

2.84 × TDA + 6.85

VOP.RC.I

Vertical open

Ice cream

3.6 × TDA + 8.7

SVO.RC.I

Semivertical open

Ice cream

3.6 × TDA + 8.7

HZO.RC.I

Horizontal open

Ice cream

0.87 × TDA + 8.74

VCT.RC.I

Vertical transparent door

Ice cream

1.2 × TDA + 3.05

HCT.RC.M

Horizontal transparent door

Remote condensing

Medium temperature

0.39 × TDA + 0.13

AHRI 1200

HCT.RC.L

Horizontal transparent door

Low temperature

0.81 × TDA + 0.26

HCT.RC.I

 Horizontal transparent door

Ice cream

0.95 × TDA + 0.31

VCS.RC.M

 Vertical solid door

Medium temperature

0.16 × V + 0.26

VCS.RC.L

Vertical solid door

Low temperature

0.33 × V + 0.54

VCS.RC.I

Vertical  solid door

Ice cream

0.39 × V + 0.63

HCS.RC.M

Horizontal solid door

Medium temperature

0.16 × V + 0.26

HCS.RC.L

Horizontal solid door

Low temperature

0.33 × V + 0.54

HCS.RC.I

Horizontal solid door

Ice cream

0.39 × V + 0.63

SOC.RC.L

Service over counter

Low temperature

1.3 × TDA + 0.22

SOC.RC.I

Service over counter

Ice cream

1.52 × TDA + 0.26

VOP.SC.L

Vertical open

Self contained

Low temperature

5.87 × TDA + 11.82

VOP.SC.I

Vertical open

Ice cream

7.45 × TDA + 15.02

SVO.SC.L

Semivertical open

Low temperature

5.59 × TDA + 11.51

SVO.SC.I

Semivertical open

Ice cream

7.11 × TDA + 14.63

HZO.SC.I

Horizontal open Service

Ice cream

3.35 × TDA + 9.0

SOC.SC.I

over counter

Ice cream

2.13 × TDA + 0.36

HCS.SC.I

Horizontal solid door

Ice cream

0.55 × V + 0.88

a.   Equipment class designations consist of a combination (in sequential order separated by periods [AAA].[BB].[C]) of the following: (AAA) An equipment 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, and SOC = service over counter); (BB) An operating mode code (RC = remote condensing and SC = self contained); and (C) A rating temperature code (M = medium temperature [38°F], L = lowtemperature [0°F], or I = ice cream temperature [15°F]). For example, “VOP.RC.M” refers to the “vertical open, remote condensing, medium temperature” equipment class.

b.   V is the volume of the case (ft3) as measured in AHRI Standard 1200, Appendix C.

c. TDA is the total display area of the case (ft2) as measured in AHRI Standard 1200, Appendix D.

 

Walk-in refrigerators and freezers are not covered by the USDOE standards and test procedures. COMNET default values for these are given in Table 3.4.6-2. These values are expressed in W/ft² of refrigerator or freezer area. This power is assumed to occur continuously. Some walk-ins have glass display doors on one side so that products can be loaded from the back. Glass display doors increase the power requirements of walk-ins. Additional power is added when glass display doors are present. The total power for walk-in refrigerators and freezers is given in Equation 3.4.6-1.

(Equation 3.4.6-1)

$$P_{Walk-in}=\left ( A_{Ref}\cdot PD_{Ref}+N_{Ref}\cdot D_{Ref} \right )+\left ( A_{Frz}\cdot PD_{Frz}+N_{Frz}\cdot D_{Frz} \right )$$

Where

PWalk-in

is the estimated power density for the walk-in refrigerator or freezer in (W)

Axxx

the area of the walk-in refrigerator or freezer (ft²)

Nxxx

the number of glass display doors (unitless)

PDxxx

the power density of the walk-in refrigerator or freezer taken from Table 3.4.6-2 (W/ft²)

Dxxx

the power associated with a glass display door for a walk-in refrigerator or freezer (W/door)

xxx

subscript indicating a walk-in freezer or refrigerator (Ref or Frz)

Table 3.4.6-3: Default Power for Walk-In Refrigerators and Freezers (W/ft²)

Source: These values are determined using the procedures of the Heatcraft Engineering Manual, Commercial Refrigeration Cooling and Freezing Load Calculations and Reference Guide, August 2006. The EER is assumed to be 12.39 for refrigerators and 6.33 for Freezers. The specific efficiency is assumed to be 70 for refrigerators and 50 for freezers. Operating temperature is assumed to be 35 F for refrigerators and -10 F for freezers.

Floor  Area

Refrigerator

Freezer

100 ft²  or less

8.0

16.0

101 ft² to 250 ft²

6.0

12.0

251 ft² to 450 ft²

5.0

9.5

451 ft² to 650 ft²

4.5

8.0

651 ft² to 800 ft²

4.0

7.0

801 ft² to 1,000 ft²

3.5

6.5

More than 1,000 ft²

3.0

6.0

Additional Power for each Glass Display Door

105

325

Note:

 

Refrigeration Modeling Method

Applicability

All buildings that have commercial refrigeration for cold storage or display

Definition

The method used to estimate refrigeration energy and to model the thermal interaction with the space where casework is located. Three methods are included in this manual:

  • COMNET defaults. With this method, the power density values provided in Appendix B are used; schedules are assumed to be continuous operation.1
  • USDOE performance ratings. With this method, the energy modeler takes inventory of the refrigerated casework in the rated building and sums the rated energy use (typically in kWh/day). Walk-in refrigerators and freezers shall use the defaults from Equation 3.4.6-1 and the values from Table 3.4.6-2. All refrigeration equipment is then assumed to operate continuously. 
  • Explicit refrigeration model. With this method, all components of the refrigeration system are explicitly modeled in DOE-2.2R or other hourly simulation program with this capability.2 

The remaining building descriptors in this section apply to buildings that use either the COMNET defaults or the USDOE performance ratings.

Units

List (see above)

Input Restrictions

None

Baseline Rules

Method used to model the proposed design shall be used for the baseline building. Note that credit is offered only when the USDOE performance ratings method is used.

 

Refrigeration Power

Applicability

All buildings that have commercial refrigeration for cold storage or display and do not use the explicit refrigeration model

Definition

Commercial refrigeration power is the average power for all commercial refrigeration equipment, assuming constant year-round operation. Equipment includes walk-in refrigerators and freezers, open refrigerated casework, and closed refrigerated casework. It does not include residential type refrigerators used in kitchenettes or refrigerated vending machines. These are covered under receptacle power.

Units

Kilowatts (kW)

Input Restrictions

With the COMNET defaults method, the values in Appendix B are prescribed. These values are multiplied times the floor area of the rated building if the whole building categories are used or the floor area of the space if the space-by-space classifications are used. to estimate the refrigeration power. With the USDOE performance ratings method, refrigeration power is estimated by summing the kWh/day for all the refrigeration equipment in the space and dividing by 24 hours. The refrigeration power for walk-in refrigerators and freezers is added to this value.

Baseline Rules

Refrigeration power is the same as the proposed design when the COMNET defaults are used. When the USDOE performance ratings method is used, the baseline refrigeration power for casework shall be determined from Table 3.4.6-1; the power for walk-in refrigerators and freezers shall be the same as the proposed design.

 

Remote Condenser Fraction

Applicability

All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods

Definition

The fraction of condenser heat that is rejected to the outdoors. For self-contained refrigeration casework, this value will be zero. For remote condenser systems, this value is 1.0. For combination systems, the value should be weighted according refrigeration capacity.

For refrigeration with self contained condensers and compressors, the heat that is removed from the space is equal to the heat that is rejected to the space, since the evaporator and condenser are both located in the same space. There may be some latent cooling associated with operation of the equipment, but this may be ignored with the COMNET defaults or USDOE performance ratings methods. The operation of self-contained refrigeration units may be approximated by adding a continuously operating electric load to the space that is equal to the energy consumption of the refrigeration units. Self-contained refrigeration units add heat to the space that must be removed by the HVAC system.

When the condenser is remotely located, heat is removed from the space but rejected outdoors. In this case, the refrigeration equipment functions in a manner similar to a continuously running split system air conditioner. Some heat is added to the space for the evaporator fan, the anti-fog heaters and other auxiliary energy uses, but refrigeration systems with remote condensers remove more heat from the space where they are located than they add. The HVAC system must compensate for this imbalance.

For remotely located condensers using the COMNET defaults or USDOE performance ratings methods, the heat that is removed from the space is determined as follows:

(Equation 3.4.6-2)

$$A=\left [ \left ( 1-F \right )\cdot kW-\left ( F\cdot kW \cdot COP \right ) \right ]\cdot 3412$$

Where

Q

The rate of heat removal from the space due to the continuous operation of the refrigeration system (kBtu/h). A negative number means that heat is being removed from the space; a positive number means that heat is being added.


kW

The power of the refrigeration system determined by using the COMNET defaults or the USDOE performance ratings method (kW)

F

The remote condenser fraction (see building descriptor below) (unitless)

COP

The coefficient of performance of the refrigeration system (unitless)

The simple approach outlined above assumes that there is no latent cooling associated with the refrigeration system. The heat addition or removal resulting from the above equation can be modeled in a number of ways, to accommodate the variety of calculation engines available. It can be scheduled if the engine can accommodate a heat removal schedule. It can be modeled as a separate, constantly running air conditioner, if the engine can accommodate two cooling systems serving the same thermal block. Other modeling techniques are acceptable as long as they are thermodynamically equivalent.

Units

Fraction

Input Restrictions

None

Baseline Rules

Same as the proposed design

 

Refrigeration COP

Applicability

All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods

Definition

The coefficient of performance of the refrigeration system. This is used only to determine the heat removed or added to the space, not to determine the refrigeration power or energy.

Units

Fraction

Input Restrictions

This value is prescribed to be 3.6 for refrigerators and 1.8 for freezers.3

Baseline Rules

Same as the proposed design

 

Refrigeration Schedule

Applicability

All buildings that have commercial refrigeration for cold storage or display

Definition

The schedule of operation for commercial refrigeration equipment. This is used to convert refrigeration power to energy use.

Units

Data structure: schedule, fractional

Input Restrictions

Continuous operation is prescribed.

Baseline Rules

Same as the proposed design

 

  • 1. See Table C-43, p. 146 of NREL/TP-550-41956, Methodology for Modeling Building Energy Performance across the Commercial Sector, Technical Report, Appendix C, March 2008. The values in this report were taken from Table 8-3 of the California Commercial End-Use Survey, Consultants Report, March 2006, CEC-400-2006-005
  • 2. Direct modeling of refrigeration equipment in buildings is not broadly supported by energy simulation programs. The simulation program that is used in most energy analysis of refrigeration equipment is DOE-2.2R, which is a proprietary and limited release version of the DOE-2.2 simulation engine used by EQuest. EnergyPlus also has refrigeration modeling capabilities. These software applications allow the user to define the configuration of equipment and to specify the performance characteristics of each piece of equipment. These applications can also account for the interaction of the equipment with the temperature and humidity of the space where it is located. The complexity and variation of input for these models makes it very difficult to specify baseline conditions. For this reason, credit for efficient refrigeration systems is not offered in COMNET Phase I when explicit refrigeration models are used.
  • 3. These values are consistent with the assumptions for the default values for walk-ins, which assume an EER of 12.39 for refrigerators and 6.33 for freezers.
Building EQ

Commercial refrigeration equipment includes the following:

  • Walk-in refrigerators
  • Walk-in freezers
  • Refrigerated casework

The 2008 California energy efficiency standards include refrigerated warehouses for the first time and there are plans to include walk-in refrigerators and freezers in the next update for 2011. ASHRAE has expanded the scope for Standard 90.1 to include more process energy, including commercial refrigeration. The building energy efficiency standards generally do not address commercial refrigeration, however, a recent USDOE standard scheduled to become effective in 2012 does address some of the equipment.

Walk-in refrigerators and freezers typically have remote condensers. Some refrigerated casework has remote condensers, while some have a self-contained condenser built into the unit. Refrigerated casework with built-in condensers reject heat directly to the space while remote condensers reject heat in the remote location, typically on the roof or behind the building.

Refrigerated casework can be further classified by the purpose, the type of doors and, when there are no doors, the configuration: horizontal, vertical or semi-vertical. USDOE has developed standards for refrigerated casework. [bookref id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"] shows these classifications along with the standard level of performance, expressed in kWh/d, which depends on the class of equipment, the total display area, and the volume of the casework.

[table title="USDOE Requirements for Refrigerated Casework (kWh/d)" id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"]

Table I-1- Standard Levels For Commercial Refrigeration Equipment

Equipment class 2 Standard level * **
(kWh/day)***
Equipment class Standard level * **
(kWh/day)
VOP.RC.M 0.82 x TDA + 4.07 VCT.RC.I 0.66 x TDA + 3.05
SVO.RC.M 0.83 x TDA + 3.18 HCT.RC.M 0.16 x TDA + 0.13
HZO.RC.M 0.35 x TDA + 2.88 HCT.RC.L 0.34 x TDA + 0.26
VOP.RC.L 2.27 x TDA + 6.85 HCT.RC.I 0.4 x TDA + 0.31
HZO.RC.L 0.57 x TDA + 6.88 VCS.RC.M 0.11 x V + 0.26
VCT.RC.M 0.22 x TDA + 1.95 VCS.RC.L 0.23 x V + 0.54
VCT.RC.L 0.56 x TDA + 2.61 VCS.RC.I 0.27 x V + 0.63
SOC.RC.M 0.51 x TDA + 0.11 HCS.RC.M 0.11 x V + 0.26
VOP.SC.M 1.74 x TDA + 4.71 HCS.RC.L 0.23 x V + 0.54
SVO.SC.M 1.73 x TDA + 4.59 HCS.RC.I 0.27 x V + 0.63
HZO.SC.M 0.77 x TDA + 5.55 SOC.RC.L 1.08 x TDA + 0.22
HZO.SC.L 1.92 x TDA + 7.08 SOC.RC.I 1.26 x TDA + 0.26
VCT.SC.I 0.67 x TDA + 3.29 VOP.SC.L 4.37 x TDA + 11.82
VCS.SC.I 0.38 x V + 0.88 VOP.SC.I 5.55 x TDA + 15.02
HCT.SC.I 0.56 x TDA + 0.43 SVO.SC.L 4.34 x TDA + 11.51
SVO.RC.L 2.27 x TDA + 6.85 SVO.SC.I 5.52 x TDA + 14.63
VOP.RC.I 2.89 x TDA + 8.7 HZO.SC.I 2.44 x TDA + 9.
SVO.RC.I 2.89 x TDA + 8.7 SOC.SC.I 1.76 x TDA + 0.36
HZO.RC.I 0.72 x TDA + 8.74 HCS.SC.I 0.38 x V + 0.88

*TDA is the total display area of the case, as measured in the Air-Conditioning and Refrigeration Institute (ARI) Standard 1200-2006, Appendix D.

** V is the volume of the case, as measured in ARI Standard 1200-2006, Appendix C.

***Kilowatt hours per day.

2For this rulemaking, equipment class designations consist of a combination (in sequential order separated by periods) of : (1) An equipment 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); (2) an operating mode code (RC=remote condensing or SC=self contained); and (3) a rating temperature code (M=medium temperature (38º F), L=low temperature (0ºF), or I=ice-cream temperature (-15ºF)). For example, "VOP.RC.M" refers to the "vertical open, remote condensing, medium temperature" equipment class. See discussion in section V.A.2 and chapter 3 of the TSD, market and technology assessment, for a more detailed explanation of the equipment class terminology. See table IV-2 for a list of the equipment classes by category.

Walk-in refrigerators and freezers are not covered by the USDOE standards and test procedures. COMNET default values for these are given in [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]. These values are expressed in W/ft² of refrigerator or freezer area. This power is assumed to occur continuously. Some walk-ins have glass display doors on one side so that products can be loaded from the back. Glass display doors increase the power requirements of walk-ins. Additional power is added when glass display doors are present. The total power for walk-in refrigerators and freezers is given in Equation (6.4.6-1).

(6.4.6-1)

$$ P_{Walk-in} = \left ( A_{Ref} \cdot PD_{Ref} + N_{Ref} \cdot D_{Ref} \right )+\left ( A_{Frz} \cdot PD_{Frz} + N_{Frz} \cdot D_{Frz} \right ) $$

Where

PWalk-in is the estimated power density for the walk-in refrigerator or freezer in (W)
Axxx the area of the walk-in refrigerator or freezer (ft²)
Nxxx the number of glass display doors (unitless)
PDxxx the power density of the walk-in refrigerator or freezer taken from [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"] (W/ft²)
Dxxx the power associated with a glass display door for a walk-in refrigerator or freezer (W/door)
xxx subscript indicating a walk-in freezer or refrigerator (Ref or Frz)

[table title="Default Power for Walk-In Refrigerators and Freezers (W/ft²)" id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]
Source: These values are determined using the procedures of the Heatcraft Engineering Manual, Commercial Refrigeration Cooling and Freezing Load Calculations and Reference Guide, August 2006. The EER is assumed to be 12.39 for refrigerators and 6.33 for Freezers. The specific efficiency is assumed to be 70 for refrigerators and 50 for freezers. Operating temperature is assumed to be 35 F for refrigerators and -10 F for freezers.

Floor  Area Refrigerator Freezer
100 ft²  or less 8.0 16.0
101 ft² to 250 ft² 6.0 12.0
251 ft² to 450 ft² 5.0 9.5
451 ft² to 650 ft² 4.5 8.0
651 ft² to 800 ft² 4.0 7.0
801 ft² to 1,000 ft² 3.5 6.5
More than 1,000 ft² 3.0 6.0
Additional Power for each Glass Display Door 105 325
Note:
Refrigeration Modeling Method
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition

The method used to estimate refrigeration energy and to model the thermal interaction with the space where casework is located. Three methods are included in this manual:

  • COMNET defaults. With this method, the power density values provided in Appendix B, Table 61 are used; schedules are assumed to be continuous operation.
  • USDOE performance ratings. With this method, the energy modeler takes inventory of the refrigerated casework in the rated building and sums the rated energy use (typically in kWh/day). Walk-in refrigerators and freezers shall use the defaults from Equation (6.4.6-1) and the values from [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]. All refrigeration equipment is then assumed to operate continuously. 
  • Explicit refrigeration model. With this method, all components of the refrigeration system are explicitly modeled in DOE-2.2R or other hourly simulation program with this capability.2 

The remaining building descriptors in this section apply to buildings that use either the COMNET defaults or the USDOE performance ratings.

Units List (see above)
Input Restrictions None
Refrigeration Power
Applicability All buildings that have commercial refrigeration for cold storage or display and do not use the explicit refrigeration model
Definition Commercial refrigeration power is the average power for all commercial refrigeration equipment, assuming constant year-round operation. Equipment includes walk-in refrigerators and freezers, open refrigerated casework, and closed refrigerated casework. It does not include residential type refrigerators used in kitchenettes or refrigerated vending machines. These are covered under receptacle power.
Units Kilowatts (kW)
Input Restrictions With the COMNET defaults method, the values in Appendix B, Table 6 are prescribed. These values are multiplied times the floor area of the rated building to estimate the refrigeration power. With the USDOE performance ratings method, refrigeration power is estimated by summing the kWh/day for all the refrigeration equipment in the space and dividing by 24 hours. The refrigeration power for walk-in refrigerators and freezers is added to this value.
Remote Condenser Fraction
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition

The fraction of condenser heat that is rejected to the outdoors. For self-contained refrigeration casework, this value will be zero. For remote condenser systems, this value is 1.0. For combination systems, the value should be weighted according refrigeration capacity.

For refrigeration with self contained condensers and compressors, the heat that is removed from the space is equal to the heat that is rejected to the space, since the evaporator and condenser are both located in the same space. There may be some latent cooling associated with operation of the equipment, but this may be ignored with the COMNET defaults or USDOE performance ratings methods. The operation of self-contained refrigeration units may be approximated by adding a continuously operating electric load to the space that is equal to the energy consumption of the refrigeration units. Self-contained refrigeration units add heat to the space that must be removed by the HVAC system.

When the condenser is remotely located, heat is removed from the space but rejected outdoors. In this case, the refrigeration equipment functions in a manner similar to a continuously running split system air conditioner. Some heat is added to the space for the evaporator fan, the anti-fog heaters and other auxiliary energy uses, but refrigeration systems with remote condensers remove more heat from the space where they are located than they add. The HVAC system must compensate for this imbalance.

For remotely located condensers using the COMNET defaults or USDOE performance ratings methods, the heat that is removed from the space is determined as follows:

(6.4.6-2)

$$ Q = \Big [ \left ( 1 - F \right ) \times kW - \left ( F \times kW \times COP \right ) \Big ] \times 3.413 $$Where

Q The rate of heat removal from the space due to the continuous operation of the refrigeration system (kBtu/h). A negative number means that heat is being removed from the space; a positive number means that heat is being added.

kW
The power of the refrigeration system determined by using the COMNET defaults or the USDOE performance ratings method (kW)
F The remote condenser fraction (see building descriptor below) (unitless)
COP The coefficient of performance of the refrigeration system (unitless)

The simple approach outlined above assumes that there is no latent cooling associated with the refrigeration system. The heat addition or removal resulting from the above equation can be modeled in a number of ways, to accommodate the variety of calculation engines available. It can be scheduled if the engine can accommodate a heat removal schedule. It can be modeled as a separate, constantly running air conditioner, if the engine can accommodate two cooling systems serving the same thermal block. Other modeling techniques are acceptable as long as they are thermodynamically equivalent.

Units Fraction
Input Restrictions None
Refrigeration COP
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition The coefficient of performance of the refrigeration system. This is used only to determine the heat removed or added to the space, not to determine the refrigeration power or energy.
Units Fraction
Input Restrictions This value is prescribed to be 3.6 for refrigerators and 1.8 for freezers.3
Refrigeration Schedule
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition The schedule of operation for commercial refrigeration equipment. This is used to convert refrigeration power to energy use.
Units Data structure: schedule, fractional
Input Restrictions Continuous operation is prescribed.
  • 1. See Table C-43, p. 146 of NREL/TP-550-41956, Methodology for Modeling Building Energy Performance across the Commercial Sector, Technical Report, Appendix C, March 2008. The values in this report were taken from Table 8-3 of the California Commercial End-Use Survey, Consultants Report, March 2006, CEC-400-2006-005
  • 2. Direct modeling of refrigeration equipment in buildings is not broadly supported by energy simulation programs. The simulation program that is used in most energy analysis of refrigeration equipment is DOE-2.2R, which is a proprietary and limited release version of the DOE-2.2 simulation engine used by EQuest. EnergyPlus also has refrigeration modeling capabilities. These software applications allow the user to define the configuration of equipment and to specify the performance characteristics of each piece of equipment. These applications can also account for the interaction of the equipment with the temperature and humidity of the space where it is located. The complexity and variation of input for these models makes it very difficult to specify baseline conditions. For this reason, credit for efficient refrigeration systems is not offered in COMNET Phase I when explicit refrigeration models are used.
  • 3. These values are consistent with the assumptions for the default values for walk-ins, which assume an EER of 12.39 for refrigerators and 6.33 for freezers.
Energy Star

Commercial refrigeration equipment includes the following:

  • Walk-in refrigerators
  • Walk-in freezers
  • Refrigerated casework

The 2008 California energy efficiency standards include refrigerated warehouses for the first time and there are plans to include walk-in refrigerators and freezers in the next update for 2011. ASHRAE has expanded the scope for Standard 90.1 to include more process energy, including commercial refrigeration. The building energy efficiency standards generally do not address commercial refrigeration, however, a recent USDOE standard scheduled to become effective in 2012 does address some of the equipment.

Walk-in refrigerators and freezers typically have remote condensers. Some refrigerated casework has remote condensers, while some have a self-contained condenser built into the unit. Refrigerated casework with built-in condensers reject heat directly to the space while remote condensers reject heat in the remote location, typically on the roof or behind the building.

Refrigerated casework can be further classified by the purpose, the type of doors and, when there are no doors, the configuration: horizontal, vertical or semi-vertical. USDOE has developed standards for refrigerated casework. [bookref id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"] shows these classifications along with the standard level of performance, expressed in kWh/d, which depends on the class of equipment, the total display area, and the volume of the casework.

[table title="USDOE Requirements for Refrigerated Casework (kWh/d)" id="USDOE-requirements-for-refrigerated-casework-(kWh/d)"]

Table I-1- Standard Levels For Commercial Refrigeration Equipment

Equipment class 2 Standard level * **
(kWh/day)***
Equipment class Standard level * **
(kWh/day)
VOP.RC.M 0.82 x TDA + 4.07 VCT.RC.I 0.66 x TDA + 3.05
SVO.RC.M 0.83 x TDA + 3.18 HCT.RC.M 0.16 x TDA + 0.13
HZO.RC.M 0.35 x TDA + 2.88 HCT.RC.L 0.34 x TDA + 0.26
VOP.RC.L 2.27 x TDA + 6.85 HCT.RC.I 0.4 x TDA + 0.31
HZO.RC.L 0.57 x TDA + 6.88 VCS.RC.M 0.11 x V + 0.26
VCT.RC.M 0.22 x TDA + 1.95 VCS.RC.L 0.23 x V + 0.54
VCT.RC.L 0.56 x TDA + 2.61 VCS.RC.I 0.27 x V + 0.63
SOC.RC.M 0.51 x TDA + 0.11 HCS.RC.M 0.11 x V + 0.26
VOP.SC.M 1.74 x TDA + 4.71 HCS.RC.L 0.23 x V + 0.54
SVO.SC.M 1.73 x TDA + 4.59 HCS.RC.I 0.27 x V + 0.63
HZO.SC.M 0.77 x TDA + 5.55 SOC.RC.L 1.08 x TDA + 0.22
HZO.SC.L 1.92 x TDA + 7.08 SOC.RC.I 1.26 x TDA + 0.26
VCT.SC.I 0.67 x TDA + 3.29 VOP.SC.L 4.37 x TDA + 11.82
VCS.SC.I 0.38 x V + 0.88 VOP.SC.I 5.55 x TDA + 15.02
HCT.SC.I 0.56 x TDA + 0.43 SVO.SC.L 4.34 x TDA + 11.51
SVO.RC.L 2.27 x TDA + 6.85 SVO.SC.I 5.52 x TDA + 14.63
VOP.RC.I 2.89 x TDA + 8.7 HZO.SC.I 2.44 x TDA + 9.
SVO.RC.I 2.89 x TDA + 8.7 SOC.SC.I 1.76 x TDA + 0.36
HZO.RC.I 0.72 x TDA + 8.74 HCS.SC.I 0.38 x V + 0.88

*TDA is the total display area of the case, as measured in the Air-Conditioning and Refrigeration Institute (ARI) Standard 1200-2006, Appendix D.

** V is the volume of the case, as measured in ARI Standard 1200-2006, Appendix C.

***Kilowatt hours per day.

2For this rulemaking, equipment class designations consist of a combination (in sequential order separated by periods) of : (1) An equipment 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); (2) an operating mode code (RC=remote condensing or SC=self contained); and (3) a rating temperature code (M=medium temperature (38º F), L=low temperature (0ºF), or I=ice-cream temperature (-15ºF)). For example, "VOP.RC.M" refers to the "vertical open, remote condensing, medium temperature" equipment class. See discussion in section V.A.2 and chapter 3 of the TSD, market and technology assessment, for a more detailed explanation of the equipment class terminology. See table IV-2 for a list of the equipment classes by category.

Walk-in refrigerators and freezers are not covered by the USDOE standards and test procedures. COMNET default values for these are given in [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]. These values are expressed in W/ft² of refrigerator or freezer area. This power is assumed to occur continuously. Some walk-ins have glass display doors on one side so that products can be loaded from the back. Glass display doors increase the power requirements of walk-ins. Additional power is added when glass display doors are present. The total power for walk-in refrigerators and freezers is given in Equation (6.4.6-1).

(6.4.6-1)

$$ P_{Walk-in} = \left ( A_{Ref} \cdot PD_{Ref} + N_{Ref} \cdot D_{Ref} \right )+\left ( A_{Frz} \cdot PD_{Frz} + N_{Frz} \cdot D_{Frz} \right ) $$

Where

PWalk-in is the estimated power density for the walk-in refrigerator or freezer in (W)
Axxx the area of the walk-in refrigerator or freezer (ft²)
Nxxx the number of glass display doors (unitless)
PDxxx the power density of the walk-in refrigerator or freezer taken from [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"] (W/ft²)
Dxxx the power associated with a glass display door for a walk-in refrigerator or freezer (W/door)
xxx subscript indicating a walk-in freezer or refrigerator (Ref or Frz)

[table title="Default Power for Walk-In Refrigerators and Freezers (W/ft²)" id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]
Source: These values are determined using the procedures of the Heatcraft Engineering Manual, Commercial Refrigeration Cooling and Freezing Load Calculations and Reference Guide, August 2006. The EER is assumed to be 12.39 for refrigerators and 6.33 for Freezers. The specific efficiency is assumed to be 70 for refrigerators and 50 for freezers. Operating temperature is assumed to be 35 F for refrigerators and -10 F for freezers.

Floor  Area Refrigerator Freezer
100 ft²  or less 8.0 16.0
101 ft² to 250 ft² 6.0 12.0
251 ft² to 450 ft² 5.0 9.5
451 ft² to 650 ft² 4.5 8.0
651 ft² to 800 ft² 4.0 7.0
801 ft² to 1,000 ft² 3.5 6.5
More than 1,000 ft² 3.0 6.0
Additional Power for each Glass Display Door 105 325
Note:
Refrigeration Modeling Method
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition

The method used to estimate refrigeration energy and to model the thermal interaction with the space where casework is located. Three methods are included in this manual:

  • COMNET defaults. With this method, the power density values provided in Appendix B, Table 61 are used; schedules are assumed to be continuous operation.
  • USDOE performance ratings. With this method, the energy modeler takes inventory of the refrigerated casework in the rated building and sums the rated energy use (typically in kWh/day). Walk-in refrigerators and freezers shall use the defaults from Equation (6.4.6-1) and the values from [bookref id="default-power-for-walk-in-refrigerators-and-freezers-(W/ft²)"]. All refrigeration equipment is then assumed to operate continuously. 
  • Explicit refrigeration model. With this method, all components of the refrigeration system are explicitly modeled in DOE-2.2R or other hourly simulation program with this capability.2 

The remaining building descriptors in this section apply to buildings that use either the COMNET defaults or the USDOE performance ratings.

Units List (see above)
Input Restrictions None
Refrigeration Power
Applicability All buildings that have commercial refrigeration for cold storage or display and do not use the explicit refrigeration model
Definition Commercial refrigeration power is the average power for all commercial refrigeration equipment, assuming constant year-round operation. Equipment includes walk-in refrigerators and freezers, open refrigerated casework, and closed refrigerated casework. It does not include residential type refrigerators used in kitchenettes or refrigerated vending machines. These are covered under receptacle power.
Units Kilowatts (kW)
Input Restrictions With the COMNET defaults method, the values in Appendix B, Table 6 are prescribed. These values are multiplied times the floor area of the rated building to estimate the refrigeration power. With the USDOE performance ratings method, refrigeration power is estimated by summing the kWh/day for all the refrigeration equipment in the space and dividing by 24 hours. The refrigeration power for walk-in refrigerators and freezers is added to this value.
Remote Condenser Fraction
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition

The fraction of condenser heat that is rejected to the outdoors. For self-contained refrigeration casework, this value will be zero. For remote condenser systems, this value is 1.0. For combination systems, the value should be weighted according refrigeration capacity.

For refrigeration with self contained condensers and compressors, the heat that is removed from the space is equal to the heat that is rejected to the space, since the evaporator and condenser are both located in the same space. There may be some latent cooling associated with operation of the equipment, but this may be ignored with the COMNET defaults or USDOE performance ratings methods. The operation of self-contained refrigeration units may be approximated by adding a continuously operating electric load to the space that is equal to the energy consumption of the refrigeration units. Self-contained refrigeration units add heat to the space that must be removed by the HVAC system.

When the condenser is remotely located, heat is removed from the space but rejected outdoors. In this case, the refrigeration equipment functions in a manner similar to a continuously running split system air conditioner. Some heat is added to the space for the evaporator fan, the anti-fog heaters and other auxiliary energy uses, but refrigeration systems with remote condensers remove more heat from the space where they are located than they add. The HVAC system must compensate for this imbalance.

For remotely located condensers using the COMNET defaults or USDOE performance ratings methods, the heat that is removed from the space is determined as follows:

(6.4.6-2)

$$ Q = \Big [ \left ( 1 - F \right ) \times kW - \left ( F \times kW \times COP \right ) \Big ] \times 3.413 $$Where

Q The rate of heat removal from the space due to the continuous operation of the refrigeration system (kBtu/h). A negative number means that heat is being removed from the space; a positive number means that heat is being added.

kW
The power of the refrigeration system determined by using the COMNET defaults or the USDOE performance ratings method (kW)
F The remote condenser fraction (see building descriptor below) (unitless)
COP The coefficient of performance of the refrigeration system (unitless)

The simple approach outlined above assumes that there is no latent cooling associated with the refrigeration system. The heat addition or removal resulting from the above equation can be modeled in a number of ways, to accommodate the variety of calculation engines available. It can be scheduled if the engine can accommodate a heat removal schedule. It can be modeled as a separate, constantly running air conditioner, if the engine can accommodate two cooling systems serving the same thermal block. Other modeling techniques are acceptable as long as they are thermodynamically equivalent.

Units Fraction
Input Restrictions None
Refrigeration COP
Applicability All buildings that have commercial refrigeration for cold storage or display and use the COMNET defaults or USDOE performance ratings methods
Definition The coefficient of performance of the refrigeration system. This is used only to determine the heat removed or added to the space, not to determine the refrigeration power or energy.
Units Fraction
Input Restrictions This value is prescribed to be 3.6 for refrigerators and 1.8 for freezers.3
Refrigeration Schedule
Applicability All buildings that have commercial refrigeration for cold storage or display
Definition The schedule of operation for commercial refrigeration equipment. This is used to convert refrigeration power to energy use.
Units Data structure: schedule, fractional
Input Restrictions Continuous operation is prescribed.
  • 1. See Table C-43, p. 146 of NREL/TP-550-41956, Methodology for Modeling Building Energy Performance across the Commercial Sector, Technical Report, Appendix C, March 2008. The values in this report were taken from Table 8-3 of the California Commercial End-Use Survey, Consultants Report, March 2006, CEC-400-2006-005
  • 2. Direct modeling of refrigeration equipment in buildings is not broadly supported by energy simulation programs. The simulation program that is used in most energy analysis of refrigeration equipment is DOE-2.2R, which is a proprietary and limited release version of the DOE-2.2 simulation engine used by EQuest. EnergyPlus also has refrigeration modeling capabilities. These software applications allow the user to define the configuration of equipment and to specify the performance characteristics of each piece of equipment. These applications can also account for the interaction of the equipment with the temperature and humidity of the space where it is located. The complexity and variation of input for these models makes it very difficult to specify baseline conditions. For this reason, credit for efficient refrigeration systems is not offered in COMNET Phase I when explicit refrigeration models are used.
  • 3. These values are consistent with the assumptions for the default values for walk-ins, which assume an EER of 12.39 for refrigerators and 6.33 for freezers.