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:
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
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 |
- 1See 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
- 2Direct 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.
- 3These 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.
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:
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
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 |
- 1See 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
- 2Direct 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.
- 3These 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.
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:
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
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 |
- 1See 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
- 2Direct 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.
- 3These 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.
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:
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
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 |
- 1See 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
- 2Direct 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.
- 3These 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.
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 has a self-contained condenser built into the unit. Refrigerated casework with built-in condensers rejects 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. DOE has developed standards for refrigerated casework. Table 15 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 16 shows the performance requirements for walk-in refrigerators and freezers.
Table 15. Performance Rating Method for Commercial Refrigerators and Freezers
| Equipment Type | Application | Energy Use Limits k Wh/day | Test Procedure |
| Refrigerator with solid doors | 0.125 × V + 2.76 | ||
| Refrigerator with transparent doors | 0.172 × V + 4.77 | ||
| Freezers with solid doors | Holding temperature | 0.398 × V + 2.28 | AHRI 1200 |
| Freezers with transparent doors | 0.94 × V + 5.10 | ||
| Refrigerators/freezers with solid doors | 0.12 × V + 4.77 | ||
| Refrigerators/freezers with solid doors | 0.12 × V + 4.77 | ||
| Commercial refrigerators | Pulldown | 0.181 × V + 5.0 | |
| Note: V is the chiller or frozen compartment volume (ft3) as defined in Association of Home Appliance Manufacturers Standard HRF-1. |
Table 16. Performance Rating Method for Commercial Casework
| Equipment Class | 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 | |
| SVO.RC.M | Semivertical open | Remote condensing | Medium temperature | 1.01 × TDA + 3.18 | |
| HZO.RC.M | Horizontal open | Remote condensing | Medium temperature | 0.51 × TDA + 2.88 | |
| VOP.RC.L | Vertical open | Remote condensing | Low temperature | 2.84 × TDA + 6.85 | |
| HZO.RC.L | Horizontal open | Remote condensing | Low temperature | 0.68 × TDA + 6.88 | |
| VCT.RC.M | Vertical transparent door | Remote condensing | Medium temperature | 0.48 × TDA + 1.95 | |
| VCT.RC.L | Vertical transparent door | Remote condensing | Low temperature | 1.03 × TDA + 2.61 | |
| SOC.RC.M | Service over counter | Remote condensing | 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 | Self-contained | Medium temperature | 2.23 × TDA + 4.59 | |
| HZO.SC.M | Horizontal open | Self-contained | Medium temperature | 1.14 × TDA + 5.55 | AHRI 1200 |
| HZO.SC.L | Horizontal open | Self-contained | Low temperature | 2.63 × TDA + 7.08 | |
| VCT.SC.I | Vertical transparent door | Self-contained | Ice Cream | 1.63 × TDA + 3.29 | |
| VCS.SC.I | Vertical solid door | Self-contained | Ice Cream | 0.55 × V + 0.88 | |
| HCT.SC.I | Horizontal transparent door | Self-contained | 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 | Remote condensing | Ice Cream | 3.6 × TDA + 8.7 | |
| SVO.RC.I | Semivertical open | Remote condensing | Ice Cream | 3.6 × TDA + 8.7 | |
| HZO.RC.I | Horizontal open | Remote condensing | Ice Cream | 0.87 × TDA + 8.74 | |
| VCT.RC.I | Vertical transparent door | Remote condensing | Ice Cream | 1.2 × TDA + 3.05 | |
| HCT.RC.M | Horizontal transparent door | Remote condensing | Medium temperature | 0.39 × TDA + 0.13 | |
| HCT.RC.L | Horizontal transparent door | Remote condensing | Low temperature | 0.81 × TDA + 0.26 | |
| HCT.RC.I | Horizontal transparent door | Remote condensing | Ice Cream | 0.95 × TDA + 0.31 | |
| VCS.RC.M | Vertical solid door | Remote condensing | Medium temperature | 0.16 × V + 0.26 | |
| VCS.RC.L | Vertical solid door | Remote condensing | Low temperature | 0.33 × V + 0.54 | |
| VCS.RC.I | Vertical solid door | Remote condensing | Ice Cream | 0.39 × V + 0.63 | |
| HCS.RC.M | Horizontal solid door | Remote condensing | Medium temperature | 0.16 × V + 0.26 | |
| HCS.RC.L | Horizontal solid door | Remote condensing | Low temperature | 0.33 × V + 0.54 | |
| HCS.RC.I | Horizontal solid door | Remote condensing | Ice Cream | 0.39 × V + 0.63 | |
| SOC.RC.L | Service over counter | Remote condensing | Low temperature | 1.3 × TDA + 0.22 | |
| SOC.RC.I | Service over counter | Remote condensing | Ice Cream | 1.52 × TDA + 0.26 | AHRI 1200 |
| VOP.SC.L | Vertical open | Self-contained | Low temperature | 5.87 × TDA + 11.82 | |
| VOP.SC.I | Vertical open | Self-contained | Ice Cream | 7.45 × TDA + 15.02 | |
| SVO.SC.L | Semivertical open | Self-contained | Low temperature | 5.59 × TDA + 11.51 | |
| SVO.SC.I | Semivertical open | Self-contained | Ice Cream | 7.11 × TDA + 14.63 | |
| HZO.SC.I | Horizontal open | Self-contained | Ice Cream | 3.35 × TDA + 9.0 | |
| SOC.SC.I | Service over counter | Self-contained | Ice Cream | 2.13 × TDA + 0.36 | |
| HCS.SC.I | Horizontal solid door | Self-contained | 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
= low temperature [0°F], or I = ice cream temperature [15°F]). For example, “VOP.RC.M” refers to the
“vertical open, remote condensing.”
(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.
The PRM doesn’t include standard levels of performance for walk-in refrigerators and freezers. COMNET (COMNET 2017) default values for these are given in Table 17. 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 (4).
Where:
PWalk-in = 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 17 (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 (Frz) or refrigerator (Ref)
Table 17. Default Power for Walk-In Refrigerators and Freezers (W/ft²)
| 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 |
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 energy efficiency ratio (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.
| 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: · Modeling Defaults COMNET defaults. With this method, the methodology described above can be used for modeling walk-in refrigerators and freezers. Schedules are assumed to be continuous operation. · Performance rating method. 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). 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 another hourly simulation program with this capability. This method is not covered by this manual. · AHRI Rated Energy. Rated energy use in accordance to AHRI 1200. |
| Units | List (see above) |
| Input Restrictions |
When refrigeration equipment in the proposed design is rated in accordance with AHRI 1200, the rated energy use shall be modeled. For all other refrigeration equipment shall be modeled using actual equipment capacities and efficiencies using the performance rating method. If actual equipment capacities and efficiencies are not know, COMNET defaults can be used. |
| Baseline Building | If refrigeration equipment is listed in Table 15 and Table 16 of this manual, then the baseline building design shall be modeled according to Table 15 and Table 16. For refrigeration equipment not listed in either of these two tables, the baseline building shall be modeled to be the same as the proposed design. |
| Refrigeration Power | |
|---|---|
| Applicability | All buildings or spaces 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) or W/ft2 |
| Input Restrictions |
With the performance rating 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 Building |
When the performance rating method is used, refrigeration power for casework shall be determined from Table 15 and Table 16; the power for walk-in refrigerators and freezers shall be the same as the proposed design. However, variations of the power requirements, schedules, or control sequences of the refrigeration equipment modeled in the baseline building from those in the proposed design shall be allowed by the rating authority based upon documentation that the refrigeration equipment installed in the proposed design represents a significant verifiable departure from documented conventional practice. The burden of this documentation is to demonstrate that accepted conventional practice would result in Baseline Building refrigeration equipment different from that installed in the proposed design. Occupancy and occupancy schedules shall not be changed. NOTE: Any variation between proposed and baseline refrigeration power should be reported for rating authority approval and inspection. |
| Remote Condenser Fraction | |
|---|---|
| Applicability | All buildings that have commercial refrigeration for cold storage or display and use the DOE 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 and the heat gain fraction to the space through the condenser is zero. For combination systems, the value should be weighted according to 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 DOE 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 DOE performance rating method, the heat that is removed from the space is determined as follows:
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 DOE performance rating 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 zone. Other modeling techniques are acceptable as long as they are thermodynamically equivalent. |
| Units | Fraction |
| Input Restrictions |
None |
| Baseline Building |
Same as the proposed design |
| Refrigeration COP | |
|---|---|
| Applicability | All buildings that have commercial refrigeration for cold storage or display and use the DOE performance ratings methods |
| Definition |
The coefficient of performance (COP) 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 freezers1 |
| Baseline Building |
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 Building |
Same as the proposed design |
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:
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
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. |
- 1See 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
- 2Direct 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.
- 3These 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.
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:
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
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. |
- 1See 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
- 2Direct 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.
- 3These 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.