Chiller Name  
Applicability  All chillers 

Definition  A unique descriptor for each chiller 
Units  Text, unique 
Input Restrictions  User entry. Where applicable, this should match the tags that are used on the plans. 
Baseline Rules  Chillers are only designated when the baseline system is of type 7 (VAV with reheat) or 8 (VAV with PFP Boxes) (see Table G3.1.1B). 
Chiller Type  
Applicability  All chillers  

Definition  The type of chiller, either a vaporcompression chiller or an absorption chiller. Vapor compression chillers operate on the reverseRankine cycle, using mechanical energy to compress the refrigerant, and include:


Units  List (see above)  
Input Restrictions  As designed  
Baseline Rules 
The baseline building chiller is based on the design capacity of the proposed design as follows from ASHRAE 90.1 Appendix G:

Number of Identical Chiller Units  
Applicability  All chillers 

Definition  The number of identical units for staging. 
Units  None 
Input Restrictions  As designed. Default is 1. 
Baseline Rules  From [bookref id="typeandnumberofchillers"] above, there is one chiller if the cooling load is 300 tons or less and two equally sized chillers for loads between 300 and 600 tons. For loads above 600 tons, two or more chillers of equal size are used, with no chiller larger than 800 tons. 
Chiller Fuel  
Applicability  All chillers 

Definition  The fuel source for the chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed. 
Baseline Rules  Electricity 
Chiller Rated Capacity  
Applicability  All chillers 

Definition  The cooling capacity of a piece of heating equipment at rated conditions. 
Units  Btu/h or tons 
Input Restrictions  As designed. If unmet load hours are greater than 300, the chiller may have to be made larger. 
Baseline Rules  Determine loads for baseline building and oversize by 15%. 
Chiller Rated Efficiency  
Applicability  All chillers 

Definition  The Coefficient of Performance (COP) at ARI rated conditions. 
Units  Ratio 
Input Restrictions  As designed 
Baseline Rules  With the ASHRAE Standard 90.12007 baseline, use the minimum values of efficiency from either Table 6.8.1C for various types of chillers or the values from Tables 6.8.1H, 6.8.1I or 6.8.1J for centrifugal chillers. With the ASHRAE Standard 90.12001 baseline, use the minimum values of efficiency from either Table 6.2.1C for various types of chillers, or the values from Tables 6.2.1H, 6. 2.1I or 6. 2.1J for centrifugal chillers. 
Chiller Minimum Unloading Ratio  
Applicability  All chillers  

Definition 
The minimum unloading capacity of a chiller expressed as a fraction of the rated capacity. Below this level the chiller must cycle to meet the load.


Units  Percent (%)  
Input Restrictions  As designed. If the user does not employ the default values, supporting documentation is required.  
Baseline Rules  Use defaults listed above. 
Chiller Cooling Capacity Adjustment Curve  
Applicability  All chillers  

Definition 
A curve or group of curves or other functions that represent the available total cooling capacity as a function of evaporator and condenser conditions and perhaps other operating conditions. The default curves are given as follows: (6.8.21) $$ Q_{available} = CAP \_ FT \times Q_{rated}$$ For aircooled chillers: (6.8.22) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws}\right. ^2 + d \times t_{odb} + e \times \left. t_{odb}\right. ^2 + f \times t_{chws} \times t_{odb}$$ For watercooled chillers: (6.8.23) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws} \right. ^2 + d \times t_{cws} + e \times \left. t_{cws} \right. ^2 + f \times t_{chws} \times t_{cws}$$ where
Note: If an aircooled unit employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. [table title="Default Capacity Coefficients – Electric AirCooled Chillers" id="defaultcapacitycoefficients–electricaircooledchillers"]
[table title="Default Capacity Coefficients – Electric WaterCooled Chillers" id="defaultcapacitycoefficients–electricwatercooledchillers"]
[table title="Default Capacity Coefficients – Fuel & SteamSource WaterCooled Chillers" id="defaultcapacitycoefficients–fuel&steamsourcewatercooledchillers"]


Units  Data structure  
Input Restrictions  User may input curves, other appropriate functions, or use default curves. If the default curves are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Electric Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of an electric chiller as a function of evaporator conditions, condenser conditions and partload ratio. The default curves are given as follows: (6.8.24) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ EIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ aircooled \enspace EIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{odb} + \ e \times \left. t_{odb}\right. ^2+ \ f \times t_{chws} \times t_{odb}$$ $$ watercooled \enspace EIR\_FT = a + b \times t_{chws}+ c \times \left. t_{chws}\right. ^2 + d \times t_{cws} + e \times \left. t_{cws}\right. ^2+ f \times t_{chws} \times t_{cws}$$ $$P_{operating} = P_{rated} \times EIR\_FPLR \times EIR\_FT \times CAP\_FT $$ where
Note: If an aircooled chiller employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. [table title="Default Efficiency EIRFT Coefficients – AirCooled Chillers" id="defaultefficiencyeirftcoefficients–aircooledchillers"]
[table title="Default Efficiency EIRFT Coefficients – WaterCooled Chiller" id="defaultefficiencyeirftcoefficients–watercooledchiller"]
[table title="Default Efficiency EIRFPLR Coefficients – AirCooled Chillers" id="defaultefficiencyeirfplrcoefficients–aircooledchillers"]
[table title="Default Efficiency EIRFPLR Coefficients – WaterCooled Chillers" id="defaultefficiencyeirfplrcoefficients–watercooledchillers"]


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Fuel and Steam Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of a fuelfired or steam chiller as a function of evaporator conditions, condenser conditions, and partload ratio. The default curves are given as follows: (6.8.25) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{cws} + \ e \times \left. t_{cws}\right. ^2+ \ f \times t_{chws} \times t_{cws}$$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT \times CAP\_FT $$ Default Curves for DirectFired Double Effect Absorption Chillers (6.8.26) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT1 = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 $$ $$ FIR\_FT2 = d + e \times t_{cws} + \ f \times \left. t_{cws}\right. ^2 $$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT1 \times FIR\_FT2 \times CAP\_FT $$ The default curves for engine driven chillers are the same format as those for the SteamDriven Single and Double Effect Absorption Chillers but there are three sets of curves for different ranges of operation based on the engine speed. where
[table title="Default FIRFPLR coefficients – Fuel & SteamSource WaterCooled Absorption Chillers" id="defaultfirfplrcoefficients–fuel&steamsourcewatercooledabsorptionchillers"]
[table title="Default FIRFPLR coefficients – Engine Driven Chillers" id="defaultfirfplrcoefficients–enginedrivenchillers"]
[table title="Default FIRFT coefficients – Fuel & SteamSource WaterCooled Absorption Chillers" id="defaultfirftcoefficients–fuel&steamsourcewatercooledabsorptionchillers"]
[table title="Default FIRFT coefficients – Engine Driven Chillers" id="defaultfirftcoefficients–enginedrivenchillers"]


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Chilled Water Supply Temperature  
Applicability  All chillers 

Definition  The chilled water supply temperature of the chiller at design conditions 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Baseline Rules  The baseline chilled water supply temperature is set to 44°F. 
Chilled Water Return Temperature  
Applicability  All chillers 

Definition  The chilled water return temperature setpoint 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Baseline Rules  The baseline chilled water return temperature is set to 56°F. 
Chilled Water Supply Temperature Reset  
Applicability  All chillers 

Definition  The reset schedule for the chilled water supply temperature. The chilled water setpoint may be reset based on demand or outdoor air temperature. 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed. The default is [bookref id="chilledwatersupplytemperatureresetschedule"]. 
Baseline Rules 
The baseline chilled water supply temperature is reset from 44°F to 54°F based on outdoor air temperature as shown in the figure below. [figure title="Chilled Water Supply Temperature Reset Schedule" id="chilledwatersupplytemperatureresetschedule"][/figure] 
Condenser Type  
Applicability  All chillers 

Definition  The type of condenser for a chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed 
Baseline Rules  The baseline chiller is always assumed to have a watercooled condenser, although the chiller type will change depending on the design capacity. If the chiller size is less than 600 tons, the baseline chiller is a watercooled screw; if the capacity is greater than or equal to 600 tons, the baseline chiller is a watercooled centrifugal chiller. 
AirCooled Condenser Power  
Applicability  All chillers 

Definition  The energy usage of the condenser fan(s) at design conditions on an aircooled chiller. This unit should only be used for chillers composed of separate evaporator and condenser sections where the fan energy is not part of the chiller COP. 
Units  Kilowatts (kW) 
Input Restrictions  As designed. The user must enter data for remote aircooled condensing units. 
Baseline Rules  Not applicable, since all baseline chillers have watercooled condensers. 
Chiller Name  
Applicability  All chillers 

Definition  A unique descriptor for each chiller 
Units  Text, unique 
Input Restrictions  User entry. Where applicable, this should match the tags that are used on the plans. 
Baseline Rules  Chillers are only designated when the baseline system is of type 7 (VAV with reheat) or 8 (VAV with PFP Boxes) (see Table G3.1.1B). 
Chiller Type  
Applicability  All chillers  

Definition  The type of chiller, either a vaporcompression chiller or an absorption chiller. Vapor compression chillers operate on the reverseRankine cycle, using mechanical energy to compress the refrigerant, and include:


Units  List (see above)  
Input Restrictions  As designed  
Baseline Rules 
The baseline building chiller is based on the design capacity of the proposed design as follows from ASHRAE 90.1 Appendix G:

Number of Identical Chiller Units  
Applicability  All chillers 

Definition  The number of identical units for staging. 
Units  None 
Input Restrictions  As designed. Default is 1. 
Baseline Rules  From [bookref id="typeandnumberofchillers"] above, there is one chiller if the cooling load is 300 tons or less and two equally sized chillers for loads between 300 and 600 tons. For loads above 600 tons, two or more chillers of equal size are used, with no chiller larger than 800 tons. 
Chiller Fuel  
Applicability  All chillers 

Definition  The fuel source for the chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed. 
Baseline Rules  Electricity 
Chiller Rated Capacity  
Applicability  All chillers 

Definition  The cooling capacity of a piece of heating equipment at rated conditions. 
Units  Btu/h or tons 
Input Restrictions  As designed. If unmet load hours are greater than 300, the chiller may have to be made larger. 
Baseline Rules  Determine loads for baseline building and oversize by 15%. 
Chiller Rated Efficiency  
Applicability  All chillers 

Definition  The Coefficient of Performance (COP) at ARI rated conditions. 
Units  Ratio 
Input Restrictions  As designed 
Baseline Rules  With the ASHRAE Standard 90.12007 baseline, use the minimum values of efficiency from either Table 6.8.1C for various types of chillers or the values from Tables 6.8.1H, 6.8.1I or 6.8.1J for centrifugal chillers. 
Chiller Minimum Unloading Ratio  
Applicability  All chillers  

Definition 
The minimum unloading capacity of a chiller expressed as a fraction of the rated capacity. Below this level the chiller must cycle to meet the load.


Units  Percent (%)  
Input Restrictions  As designed. If the user does not employ the default values, supporting documentation is required.  
Baseline Rules  Use defaults listed above. 
Chiller Cooling Capacity Adjustment Curve  
Applicability  All chillers  

Definition 
A curve or group of curves or other functions that represent the available total cooling capacity as a function of evaporator and condenser conditions and perhaps other operating conditions. The default curves are given as follows: (6.8.21) $$ Q_{available} = CAP \_ FT \times Q_{rated}$$ For aircooled chillers: (6.8.22) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws}\right. ^2 + d \times t_{odb} + e \times \left. t_{odb}\right. ^2 + f \times t_{chws} \times t_{odb}$$ For watercooled chillers: (6.8.23) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws} \right. ^2 + d \times t_{cws} + e \times \left. t_{cws} \right. ^2 + f \times t_{chws} \times t_{cws}$$ where
Note: If an aircooled unit employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. [table title="Default Capacity Coefficients – Electric AirCooled Chillers" id="defaultcapacitycoefficients–electricaircooledchillers"]
[table title="Default Capacity Coefficients – Electric WaterCooled Chillers" id="defaultcapacitycoefficients–electricwatercooledchillers"]
[table title="Default Capacity Coefficients – Fuel & SteamSource WaterCooled Chillers" id="defaultcapacitycoefficients–fuel&steamsourcewatercooledchillers"]


Units  Data structure  
Input Restrictions  User may input curves, other appropriate functions, or use default curves. If the default curves are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Electric Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of an electric chiller as a function of evaporator conditions, condenser conditions and partload ratio. The default curves are given as follows: (6.8.24) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ EIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ aircooled \enspace EIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{odb} + \ e \times \left. t_{odb}\right. ^2+ \ f \times t_{chws} \times t_{odb}$$ $$ watercooled \enspace EIR\_FT = a + b \times t_{chws}+ c \times \left. t_{chws}\right. ^2 + d \times t_{cws} + e \times \left. t_{cws}\right. ^2+ f \times t_{chws} \times t_{cws}$$ $$P_{operating} = P_{rated} \times EIR\_FPLR \times EIR\_FT \times CAP\_FT $$ where
Note: If an aircooled chiller employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. [table title="Default Efficiency EIRFT Coefficients – AirCooled Chillers" id="defaultefficiencyeirftcoefficients–aircooledchillers"]
[table title="Default Efficiency EIRFT Coefficients – WaterCooled Chiller" id="defaultefficiencyeirftcoefficients–watercooledchiller"]
[table title="Default Efficiency EIRFPLR Coefficients – AirCooled Chillers" id="defaultefficiencyeirfplrcoefficients–aircooledchillers"]
[table title="Default Efficiency EIRFPLR Coefficients – WaterCooled Chillers" id="defaultefficiencyeirfplrcoefficients–watercooledchillers"]


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Fuel and Steam Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of a fuelfired or steam chiller as a function of evaporator conditions, condenser conditions, and partload ratio. The default curves are given as follows: (6.8.25) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{cws} + \ e \times \left. t_{cws}\right. ^2+ \ f \times t_{chws} \times t_{cws}$$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT \times CAP\_FT $$ Default Curves for DirectFired Double Effect Absorption Chillers (6.8.26) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT1 = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 $$ $$ FIR\_FT2 = d + e \times t_{cws} + \ f \times \left. t_{cws}\right. ^2 $$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT1 \times FIR\_FT2 \times CAP\_FT $$ The default curves for engine driven chillers are the same format as those for the SteamDriven Single and Double Effect Absorption Chillers but there are three sets of curves for different ranges of operation based on the engine speed. where
[table title="Default FIRFPLR coefficients – Fuel & SteamSource WaterCooled Absorption Chillers" id="defaultfirfplrcoefficients–fuel&steamsourcewatercooledabsorptionchillers"]
[table title="Default FIRFPLR coefficients – Engine Driven Chillers" id="defaultfirfplrcoefficients–enginedrivenchillers"]
[table title="Default FIRFT coefficients – Fuel & SteamSource WaterCooled Absorption Chillers" id="defaultfirftcoefficients–fuel&steamsourcewatercooledabsorptionchillers"]
[table title="Default FIRFT coefficients – Engine Driven Chillers" id="defaultfirftcoefficients–enginedrivenchillers"]


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Chilled Water Supply Temperature  
Applicability  All chillers 

Definition  The chilled water supply temperature of the chiller at design conditions 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Baseline Rules  The baseline chilled water supply temperature is set to 44°F. 
Chilled Water Return Temperature  
Applicability  All chillers 

Definition  The chilled water return temperature setpoint 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Baseline Rules  The baseline chilled water return temperature is set to 56°F. 
Chilled Water Supply Temperature Reset  
Applicability  All chillers 

Definition  The reset schedule for the chilled water supply temperature. The chilled water setpoint may be reset based on demand or outdoor air temperature. 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed. The default is [bookref id="chilledwatersupplytemperatureresetschedule"]. 
Baseline Rules 
The baseline chilled water supply temperature is reset from 44°F to 54°F based on outdoor air temperature as shown in the figure below. [figure title="Chilled Water Supply Temperature Reset Schedule" id="chilledwatersupplytemperatureresetschedule"][/figure] 
Condenser Type  
Applicability  All chillers 

Definition  The type of condenser for a chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed 
Baseline Rules  The baseline chiller is always assumed to have a watercooled condenser, although the chiller type will change depending on the design capacity. If the chiller size is less than 600 tons, the baseline chiller is a watercooled screw; if the capacity is greater than or equal to 600 tons, the baseline chiller is a watercooled centrifugal chiller. 
AirCooled Condenser Power  
Applicability  All chillers 

Definition  The energy usage of the condenser fan(s) at design conditions on an aircooled chiller. This unit should only be used for chillers composed of separate evaporator and condenser sections where the fan energy is not part of the chiller COP. 
Units  Kilowatts (kW) 
Input Restrictions  As designed. The user must enter data for remote aircooled condensing units. 
Baseline Rules  Not applicable, since all baseline chillers have watercooled condensers. 
Chiller Name  
Applicability  All chillers 

Definition  A unique descriptor for each chiller 
Units  Text, unique 
Input Restrictions  User entry. Where applicable, this should match the tags that are used on the plans. 
Baseline Rules  Chillers are only designated when the baseline system is of type 7 (VAV with reheat) or 8 (VAV with PFP Boxes) (see Table G3.1.1B). 
Chiller Type  
Applicability  All chillers  

Definition  The type of chiller, either a vaporcompression chiller or an absorption chiller. Vapor compression chillers operate on the reverseRankine cycle, using mechanical energy to compress the refrigerant, and include:


Units  List (see above)  
Input Restrictions  As designed  
Baseline Rules 
The baseline building chiller is based on the design capacity of the proposed design as follows from ASHRAE 90.1 Appendix G:
Table 6.8.21: Type and Number of Chillers

Number of Identical Chiller Units  
Applicability  All chillers 

Definition  The number of identical units for staging. 
Units  None 
Input Restrictions  As designed. Default is 1. 
Baseline Rules  From Table 7.8.21 above, there is one chiller if the cooling load is 300 tons or less and two equally sized chillers for loads between 300 and 600 tons. For loads above 600 tons, two or more chillers of equal size are used, with no chiller larger than 800 tons. 
Chiller Fuel  
Applicability  All chillers 

Definition  The fuel source for the chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed. 
Baseline Rules  Electricity 
Chiller Rated Capacity  
Applicability  All chillers 

Definition  The cooling capacity of a piece of heating equipment at rated conditions. 
Units  Btu/h or tons 
Input Restrictions  As designed. If unmet load hours are greater than 300, the chiller may have to be made larger. 
Baseline Rules  Determine loads for baseline building and oversize by 15%. 
Chiller Rated Efficiency  
Applicability  All chillers 

Definition  The Coefficient of Performance (COP) at ARI rated conditions. 
Units  Ratio 
Input Restrictions  As designed 
Baseline Rules  With the ASHRAE Standard 90.12007 baseline, use the minimum values of efficiency from either Table 6.8.1C for various types of chillers or the values from Tables 6.8.1H, 6.8.1I or 6.8.1J for centrifugal chillers. 
Chiller Minimum Unloading Ratio  
Applicability  All chillers  

Definition 
The minimum unloading capacity of a chiller expressed as a fraction of the rated capacity. Below this level the chiller must cycle to meet the load.


Units  Percent (%)  
Input Restrictions  As designed. If the user does not employ the default values, supporting documentation is required.  
Baseline Rules  Use defaults listed above. 
Chiller Cooling Capacity Adjustment Curve  
Applicability  All chillers  

Definition 
A curve or group of curves or other functions that represent the available total cooling capacity as a function of evaporator and condenser conditions and perhaps other operating conditions. The default curves are given as follows: (6.8.21) $$ Q_{available} = CAP \_ FT \times Q_{rated}$$ For aircooled chillers: (6.8.22) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws}\right. ^2 + d \times t_{odb} + e \times \left. t_{odb}\right. ^2 + f \times t_{chws} \times t_{odb}$$ For watercooled chillers: (6.8.23) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws} \right. ^2 + d \times t_{cws} + e \times \left. t_{cws} \right. ^2 + f \times t_{chws} \times t_{cws}$$ where
Note: If an aircooled unit employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit.
Table 6.8.23: Default Capacity Coefficients – Electric AirCooled Chillers
Table 6.8.24: Default Capacity Coefficients – Electric WaterCooled Chillers
Table 6.8.25: Default Capacity Coefficients – Fuel & SteamSource WaterCooled Chillers


Units  Data structure  
Input Restrictions  User may input curves, other appropriate functions, or use default curves. If the default curves are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Electric Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of an electric chiller as a function of evaporator conditions, condenser conditions and partload ratio. The default curves are given as follows: (6.8.24) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ EIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ aircooled \enspace EIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{odb} + \ e \times \left. t_{odb}\right. ^2+ \ f \times t_{chws} \times t_{odb}$$ $$ watercooled \enspace EIR\_FT = a + b \times t_{chws}+ c \times \left. t_{chws}\right. ^2 + d \times t_{cws} + e \times \left. t_{cws}\right. ^2+ f \times t_{chws} \times t_{cws}$$ $$P_{operating} = P_{rated} \times EIR\_FPLR \times EIR\_FT \times CAP\_FT $$ where
Note: If an aircooled chiller employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit.
Table 6.8.26: Default Efficiency EIRFT Coefficients – AirCooled Chillers
Table 6.8.27: Default Efficiency EIRFT Coefficients – WaterCooled Chiller
Table 6.8.28: Default Efficiency EIRFPLR Coefficients – AirCooled Chillers
Table 6.8.29: Default Efficiency EIRFPLR Coefficients – WaterCooled Chillers


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Fuel and Steam Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of a fuelfired or steam chiller as a function of evaporator conditions, condenser conditions, and partload ratio. The default curves are given as follows: (6.8.25) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{cws} + \ e \times \left. t_{cws}\right. ^2+ \ f \times t_{chws} \times t_{cws}$$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT \times CAP\_FT $$ Default Curves for DirectFired Double Effect Absorption Chillers (6.8.26) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT1 = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 $$ $$ FIR\_FT2 = d + e \times t_{cws} + \ f \times \left. t_{cws}\right. ^2 $$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT1 \times FIR\_FT2 \times CAP\_FT $$ The default curves for engine driven chillers are the same format as those for the SteamDriven Single and Double Effect Absorption Chillers but there are three sets of curves for different ranges of operation based on the engine speed. where
Table 6.8.210: Default FIRFPLR coefficients – Fuel & SteamSource WaterCooled Absorption Chillers
Table 6.8.211: Default FIRFPLR coefficients – Engine Driven Chillers
Table 6.8.212: Default FIRFT coefficients – Fuel & SteamSource WaterCooled Absorption Chillers
Table 6.8.213: Default FIRFT coefficients – Engine Driven Chillers


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required.  
Baseline Rules  Use default curves. 
Chilled Water Supply Temperature  
Applicability  All chillers 

Definition  The chilled water supply temperature of the chiller at design conditions 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Baseline Rules  The baseline chilled water supply temperature is set to 44°F. 
Chilled Water Return Temperature  
Applicability  All chillers 

Definition  The chilled water return temperature setpoint 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Baseline Rules  The baseline chilled water return temperature is set to 56°F. 
Chilled Water Supply Temperature Reset  
Applicability  All chillers 

Definition  The reset schedule for the chilled water supply temperature. The chilled water setpoint may be reset based on demand or outdoor air temperature. 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed. The default is Figure 6.8.21. 
Baseline Rules 
The baseline chilled water supply temperature is reset from 44°F to 54°F based on outdoor air temperature as shown in the figure below.
Figure 6.8.21: Chilled Water Supply Temperature Reset Schedule 
Condenser Type  
Applicability  All chillers 

Definition  The type of condenser for a chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed 
Baseline Rules  The baseline chiller is always assumed to have a watercooled condenser, although the chiller type will change depending on the design capacity. If the chiller size is less than 600 tons, the baseline chiller is a watercooled screw; if the capacity is greater than or equal to 600 tons, the baseline chiller is a watercooled centrifugal chiller. 
AirCooled Condenser Power  
Applicability  All chillers 

Definition  The energy usage of the condenser fan(s) at design conditions on an aircooled chiller. This unit should only be used for chillers composed of separate evaporator and condenser sections where the fan energy is not part of the chiller COP. 
Units  Kilowatts (kW) 
Input Restrictions  As designed. The user must enter data for remote aircooled condensing units. 
Baseline Rules  Not applicable, since all baseline chillers have watercooled condensers. 
Chiller Name 


Applicability 
All chillers 
Definition 
A unique descriptor for each chiller 
Units 
Text, unique 
Input Restrictions 
User entry. Where applicable, this should match the tags that are used on the plans. 
Baseline Rules 
Baseline HVAC systems 7, 8, 11, 12, and 13 have chillers. 
Chiller Type 


Applicability 
All chillers 

Definition 
The type of chiller, either a vaporcompression chiller or an absorption chiller.


Units 
List (see above) 

Input Restrictions 
As designed 

Baseline Rules 
The baseline building chiller is based on the baseline building peak cooling load, as follows: Table 3.8.21: Chiller Type

Number of Identical Chiller Units 


Applicability 
All chillers 
Definition 
The number of identical units for staging. 
Units 
Unitless integer 
Input Restrictions 
As designed. Default is 1. 
Baseline Rules 
There is one chiller if the cooling load is 300 tons or less and two equally sized chillers for loads between 300 and 600 tons. For loads above 600 tons, two or more chillers of equal size are used, with no chiller larger than 800 tons. See Table 3.8.21. 
Chiller Fuel 


Applicability 
All chillers 

Definition 
The fuel source for the chiller. The choices are:


Units 
List (see above) This input is restricted, based on the choice of Chiller Type, according to the following rules: Table 3.8.22: Chiller Fuel


Input Restrictions 
As designed. 

Baseline Rules 
Electricity 
Chiller Rated Capacity 


Applicability 
All chillers 
Definition 
The cooling capacity of a piece of heating equipment at rated conditions. 
Units 
Btu/h or tons 
Input Restrictions 
As designed. If unmet load hours are greater than 300, the chiller may have to be made larger. 
Baseline Rules 
Determine loads for baseline building and oversize by 15%. 
Chiller Rated Efficiency 


Applicability 
All chillers 

Definition 
The efficiency of the chiller expressed as EER for air cooled chillers, kW/ton for water cooled, positive displacement chillers, and COP for fuelfired and heat driven chillers. COP is also sometimes used for electric chillers. The applicable test procedure is AHRI Standard 550/590. The test conditions for the full load (FL) rating are summarized below:
Chillers are also rated at part load conditions known as IPLV (integrated part load value). The IPLV is the weighted average of the chiller efficiency at 100%, 75%, 50% and 25%. The corresponding weights for these partload conditions are are 17%, 39%, 33%, and 11%. 

Units 
kW/ton, EER or COP, depending on chiller type 

Input Restrictions 
As designed, but chillers must meet minimum efficiency standards 

Baseline Rules 
The baseline chiller efficiencies are as follows: Table 3.8.23: Baseline Chiller Rated Efficiency

Chiller Minimum Unloading Ratio 


Applicability 
All chillers 

Definition 
The minimum unloading capacity of a chiller expressed as a fraction of the rated capacity. Below this level the chiller must cycle to meet the load. The following are default values for various types of chillers Table 3.8.24: Baseline Chiller Minimum Unloading Ratio


Units 
Percent (%) 

Input Restrictions 
As designed. If the user does not employ the default values, supporting documentation is required. 

Baseline Rules 
The baseline HVAC chiller will be either a screw or centrifugal. Use the defaults for these chiller types from the above table: 15% for screw and 10% for centrifugal. 
Chiller Cooling Capacity Adjustment Curve 


Applicability 
All chillers 

Definition 
A curve or group of curves or other functions that represent the available total cooling capacity as a function of evaporator and condenser conditions and perhaps other operating conditions. The default curves are given as follows: (Equation 3.8.21) $$Q_{available} = CAP\_FT \times Q_{rated}$$ For aircooled chillers: (Equation 3.8.22) $$CAP\_FT = a + b \cdot t_{chws} + c \cdot t_{chws}^{2} + d \cdot t_{odb} + e \cdot t_{odb}^{2} +f \cdot t_{chws} \cdot t_{odb}$$ For watercooled chillers: (Equation 3.8.23) $$CAP\_FT = a + b \cdot t_{chws} + c \cdot t_{chws}^{2} + d \cdot t_{cws} + e \cdot t_{cws}^{2} +f \cdot t_{chws} \cdot t_{cws}$$ where
Note: If an aircooled unit employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. 

Units 
Data structure 

Input Restrictions 
User may input curves, other appropriate functions, or use default curves. If the default curves are overridden, supporting documentation is required. 

Baseline Rules 
Use default equations and coefficients for the baseline chillers.. 
Electric Chiller Cooling Efficiency Adjustment Curves 


Applicability 
All chillers 

Definition 
A curve or group of curves that varies the cooling efficiency of an electric chiller as a function of evaporator conditions, condenser conditions and partload ratio. Note that for variablespeed chillers, the partload cooling efficiency curve is a function of both partload ratio and leaving condenser water temperature. The default curves are given as follows: (Equation 3.8.24) $$PLR = \frac{Q_{operating}}{Q_{available}(t_{chws},t_{cws/odb})}$$ $$EIR\_FPLR = a + b \cdot PLR + c \cdot PLR^{2}$$ Variable speed $$EIR\_FPLR = a + b \cdot PLR + c \cdot PLR^{2} + d \cdot t_{cws} + e \cdot t_{cws}^{2} + f \cdot PLR \cdot t_{cws} + g \cdot PLR^{3} + h \cdot t_{cws}^{3} + i \cdot PLR^{2} \cdot t_{cws} + j \cdot PLR \cdot t_{cws}^{2}$$ Air cooled $$EIR\_FT = a + b \cdot t_{chws} + c \cdot t_{chws}^{2} + d \cdot t_{odb} + e \cdot t_{odb}^{2} + f \cdot t_{chws}\cdot t_{odb} $$ Water cooled $$EIR\_FT = a + b \cdot t_{chws} + c \cdot t_{chws}^{2} + d \cdot t_{cws} + e \cdot t_{cws}^{2} + f \cdot t_{chws}\cdot t_{cws} $$ Where
Note: If an aircooled chiller employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. 

Units 
Data structure 

Input Restrictions 
User may input curves or use default curves. If defaults are overridden, supporting documentation is required. 

Baseline Rules 
Use default equations and coefficients for the baseline HVAC chillers. 
Fuel and Steam Chiller Cooling Efficiency Adjustment Curves 


Applicability 
All chillers 

Definition 
A curve or group of curves that varies the cooling efficiency of a fuelfired or steam chiller as a function of evaporator conditions, condenser conditions, and partload ratio. The default curves are given as follows: Default Curves for SteamDriven Single and Double Effect Absorption Chillers (Equation 3.8.25) $$PLR = \frac{Q_{operating}}{Q_{available}(t_{chws},t_{cws/odb})}$$ $$FIR\_FPLR = a + b \cdot PLR + c \cdot PLR^{2}$$ $$FIR\_FT = a + b \cdot t_{chws} + c \cdot t_{chws}^{2} + d \cdot t_{cws} + e \cdot t_{cws}^{2} + f \cdot t_{chws} \cdot t_{cws}$$ Default Curves for DirectFired Double Effect Absorption Chillers (Equation 3.8.26) $$PLR = \frac{Q_{operating}}{Q_{available}(t_{chws},t_{cws/odb})}$$ $$FIR\_FPLR = a + b \cdot PLR + c \cdot PLR^{2}$$ $$FIR\_FT1 = a + b \cdot t_{chws} + c \cdot t_{chws}^{2}$$ $$FIR\_FT2 = d + e \cdot t_{cws} + f \cdot t_{cws}^{2}$$ $$Fuel_{partload} = Fuel_{rated} \cdot FIR\_FPLR \cdot FIR1\_FT1 \cdot FIR1\_FT2 \cdot CAP\_FT$$ The default curves for engine driven chillers are the same format as those for the SteamDriven Single and Double Effect Absorption Chillers but there are three sets of curves for different ranges of operation based on the engine speed. where


Units 
Data structure 

Input Restrictions 
User may input curves or use default curves. If defaults are overridden, supporting documentation is required. 

Baseline Rules 
Not applicable. The baseline HVAC system has electric chillers. 
Chilled Water Supply Temperature 


Applicability 
All chillers 
Definition 
The chilled water supply temperature of the chiller at design conditions 
Units 
Degrees Fahrenheit (°F) 
Input Restrictions 
As designed 
Baseline Rules 
The baseline chilled water supply temperature is set to 44°F. 
Chilled Water Return Temperature 


Applicability 
All chillers 
Definition 
The chilled water return temperature setpoint 
Units 
Degrees Fahrenheit (°F) 
Input Restrictions 
As designed 
Baseline Rules 
The baseline chilled water return temperature is set to 56°F. 
Chilled Supply Temperature Control Type 


Applicability 
All chillers 
Definition 
The method by which the chilled water setpoint temperature is reset. The chilled water setpoint may be reset based on demand or outdoor air temperature. 
Units 
List: demand or outdoor air temperature 
Input Restrictions 
As designed 
Baseline Rules 
Outdoor air temperature 
Chilled Water Supply Temperature Reset 


Applicability 
All chillers 
Definition 
The reset schedule for the chilled water supply temperature. The chilled water setpoint may be reset based on demand or outdoor air temperature. 
Units 
Data structure 
Input Restrictions 
As designed. The default to reset based on outdoor air temperature as follows:

Baseline Rules 
The baseline chilled water supply temperature reset uses the defaults. However, if the baseline chilledwater system serves a computer room HVAC system, the supply chilledwater temperature shall be reset higher based on the HVAC system requiring the most cooling; i.e., the chilledwater setpoint is reset higher until one cooling coil valve is nearly wide open. The maximum reset chilledwater supply temperature shall be 54°F. Temperature reset is not required for systems served by purchased chilled water. 
Condenser Type 


Applicability 
All chillers 
Definition 
The type of condenser for a chiller. The choices are:
Aircooled chillers use air to cool the condenser coils. Watercooled chillers use cold water to cool the condenser and additionally need either a cooling tower or a local source of cold water. Evaporativelycooled chillers are similar to aircooled chillers, except they use a water mist to cool the condenser coil which makes them more efficient. 
Units 
List (see above) 
Input Restrictions 
As designed 
Baseline Rules 
The baseline chiller is always assumed to have a watercooled condenser, although the chiller type will change depending on the design capacity. 
AirCooled Condenser Power 


Applicability 
All chillers with aircooled condensers where fan energy is not part of the COP. 
Definition 
The energy usage of the condenser fan(s) at design conditions on an aircooled chiller. This unit should only be used for chillers composed of separate evaporator and condenser sections where the fan energy is not part of the chiller COP. 
Units 
Kilowatts (kW) 
Input Restrictions 
As designed. The user must enter data for remote aircooled condensing units. 
Baseline Rules 
Not applicable, since all baseline chillers have watercooled condensers. 
Chiller Name  
Applicability  All chillers 

Definition  A unique descriptor for each chiller 
Units  Text, unique 
Input Restrictions  User entry. Where applicable, this should match the tags that are used on the plans. 
Chiller Type  
Applicability  All chillers  

Definition  The type of chiller, either a vaporcompression chiller or an absorption chiller. Vapor compression chillers operate on the reverseRankine cycle, using mechanical energy to compress the refrigerant, and include:


Units  List (see above)  
Input Restrictions  As designed  
Baseline Rules 
The baseline building chiller is based on the design capacity of the proposed design as follows from ASHRAE 90.1 Appendix G:

Number of Identical Chiller Units  
Applicability  All chillers 

Definition  The number of identical units for staging. 
Units  None 
Input Restrictions  As designed. Default is 1. 
Chiller Fuel  
Applicability  All chillers 

Definition  The fuel source for the chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed. 
Chiller Rated Capacity  
Applicability  All chillers 

Definition  The cooling capacity of a piece of heating equipment at rated conditions. 
Units  Btu/h or tons 
Input Restrictions  As designed. If unmet load hours are greater than 300, the chiller may have to be made larger. 
Chiller Rated Efficiency  
Applicability  All chillers 

Definition  The Coefficient of Performance (COP) at ARI rated conditions. 
Units  Ratio 
Input Restrictions  As designed 
Chiller Minimum Unloading Ratio  
Applicability  All chillers  

Definition 
The minimum unloading capacity of a chiller expressed as a fraction of the rated capacity. Below this level the chiller must cycle to meet the load.


Units  Percent (%)  
Input Restrictions  As designed. If the user does not employ the default values, supporting documentation is required. 
Chiller Cooling Capacity Adjustment Curve  
Applicability  All chillers  

Definition 
A curve or group of curves or other functions that represent the available total cooling capacity as a function of evaporator and condenser conditions and perhaps other operating conditions. The default curves are given as follows: (6.8.21) $$ Q_{available} = CAP \_ FT \times Q_{rated}$$ For aircooled chillers: (6.8.22) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws}\right. ^2 + d \times t_{odb} + e \times \left. t_{odb}\right. ^2 + f \times t_{chws} \times t_{odb}$$ For watercooled chillers: (6.8.23) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws} \right. ^2 + d \times t_{cws} + e \times \left. t_{cws} \right. ^2 + f \times t_{chws} \times t_{cws}$$ where
Note: If an aircooled unit employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. [table title="Default Capacity Coefficients – Electric AirCooled Chillers" id="defaultcapacitycoefficients–electricaircooledchillers"]
[table title="Default Capacity Coefficients – Electric WaterCooled Chillers" id="defaultcapacitycoefficients–electricwatercooledchillers"]
[table title="Default Capacity Coefficients – Fuel & SteamSource WaterCooled Chillers" id="defaultcapacitycoefficients–fuel&steamsourcewatercooledchillers"]


Units  Data structure  
Input Restrictions  User may input curves, other appropriate functions, or use default curves. If the default curves are overridden, supporting documentation is required. 
Electric Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of an electric chiller as a function of evaporator conditions, condenser conditions and partload ratio. The default curves are given as follows: (6.8.24) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ EIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ aircooled \enspace EIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{odb} + \ e \times \left. t_{odb}\right. ^2+ \ f \times t_{chws} \times t_{odb}$$ $$ watercooled \enspace EIR\_FT = a + b \times t_{chws}+ c \times \left. t_{chws}\right. ^2 + d \times t_{cws} + e \times \left. t_{cws}\right. ^2+ f \times t_{chws} \times t_{cws}$$ $$P_{operating} = P_{rated} \times EIR\_FPLR \times EIR\_FT \times CAP\_FT $$ where
Note: If an aircooled chiller employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. [table title="Default Efficiency EIRFT Coefficients – AirCooled Chillers" id="defaultefficiencyeirftcoefficients–aircooledchillers"]
[table title="Default Efficiency EIRFT Coefficients – WaterCooled Chiller" id="defaultefficiencyeirftcoefficients–watercooledchiller"]
[table title="Default Efficiency EIRFPLR Coefficients – AirCooled Chillers" id="defaultefficiencyeirfplrcoefficients–aircooledchillers"]
[table title="Default Efficiency EIRFPLR Coefficients – WaterCooled Chillers" id="defaultefficiencyeirfplrcoefficients–watercooledchillers"]


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required. 
Fuel and Steam Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of a fuelfired or steam chiller as a function of evaporator conditions, condenser conditions, and partload ratio. The default curves are given as follows: (6.8.25) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{cws} + \ e \times \left. t_{cws}\right. ^2+ \ f \times t_{chws} \times t_{cws}$$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT \times CAP\_FT $$ Default Curves for DirectFired Double Effect Absorption Chillers (6.8.26) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT1 = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 $$ $$ FIR\_FT2 = d + e \times t_{cws} + \ f \times \left. t_{cws}\right. ^2 $$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT1 \times FIR\_FT2 \times CAP\_FT $$ The default curves for engine driven chillers are the same format as those for the SteamDriven Single and Double Effect Absorption Chillers but there are three sets of curves for different ranges of operation based on the engine speed. where
[table title="Default FIRFPLR coefficients – Fuel & SteamSource WaterCooled Absorption Chillers" id="defaultfirfplrcoefficients–fuel&steamsourcewatercooledabsorptionchillers"]
[table title="Default FIRFPLR coefficients – Engine Driven Chillers" id="defaultfirfplrcoefficients–enginedrivenchillers"]
[table title="Default FIRFT coefficients – Fuel & SteamSource WaterCooled Absorption Chillers" id="defaultfirftcoefficients–fuel&steamsourcewatercooledabsorptionchillers"]
[table title="Default FIRFT coefficients – Engine Driven Chillers" id="defaultfirftcoefficients–enginedrivenchillers"]


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required. 
Chilled Water Supply Temperature  
Applicability  All chillers 

Definition  The chilled water supply temperature of the chiller at design conditions 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Chilled Water Return Temperature  
Applicability  All chillers 

Definition  The chilled water return temperature setpoint 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Chilled Water Supply Temperature Reset  
Applicability  All chillers 

Definition  The reset schedule for the chilled water supply temperature. The chilled water setpoint may be reset based on demand or outdoor air temperature. 
Units  Degrees Fahrenheit (°F) 
Input Restrictions 
As designed. The default is [bookref id="chilledwatersupplytemperatureresetschedule"]. [figure title="Chilled Water Supply Temperature Reset Schedule" id="chilledwatersupplytemperatureresetschedule"][/figure] 
Condenser Type  
Applicability  All chillers 

Definition  The type of condenser for a chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed 
AirCooled Condenser Power  
Applicability  All chillers 

Definition  The energy usage of the condenser fan(s) at design conditions on an aircooled chiller. This unit should only be used for chillers composed of separate evaporator and condenser sections where the fan energy is not part of the chiller COP. 
Units  Kilowatts (kW) 
Input Restrictions  As designed. The user must enter data for remote aircooled condensing units. 
Chiller Name  
Applicability  All chillers 

Definition  A unique descriptor for each chiller 
Units  Text, unique 
Input Restrictions  User entry. Where applicable, this should match the tags that are used on the plans. 
Chiller Type  
Applicability  All chillers  

Definition  The type of chiller, either a vaporcompression chiller or an absorption chiller. Vapor compression chillers operate on the reverseRankine cycle, using mechanical energy to compress the refrigerant, and include:


Units  List (see above)  
Input Restrictions  As designed  
Baseline Rules 
The baseline building chiller is based on the design capacity of the proposed design as follows from ASHRAE 90.1 Appendix G:

Number of Identical Chiller Units  
Applicability  All chillers 

Definition  The number of identical units for staging. 
Units  None 
Input Restrictions  As designed. Default is 1. 
Chiller Fuel  
Applicability  All chillers 

Definition  The fuel source for the chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed. 
Chiller Rated Capacity  
Applicability  All chillers 

Definition  The cooling capacity of a piece of heating equipment at rated conditions. 
Units  Btu/h or tons 
Input Restrictions  As designed. If unmet load hours are greater than 300, the chiller may have to be made larger. 
Chiller Rated Efficiency  
Applicability  All chillers 

Definition  The Coefficient of Performance (COP) at ARI rated conditions. 
Units  Ratio 
Input Restrictions  As designed 
Chiller Minimum Unloading Ratio  
Applicability  All chillers  

Definition 
The minimum unloading capacity of a chiller expressed as a fraction of the rated capacity. Below this level the chiller must cycle to meet the load.


Units  Percent (%)  
Input Restrictions  As designed. If the user does not employ the default values, supporting documentation is required. 
Chiller Cooling Capacity Adjustment Curve  
Applicability  All chillers  

Definition 
A curve or group of curves or other functions that represent the available total cooling capacity as a function of evaporator and condenser conditions and perhaps other operating conditions. The default curves are given as follows: (6.8.21) $$ Q_{available} = CAP \_ FT \times Q_{rated}$$ For aircooled chillers: (6.8.22) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws}\right. ^2 + d \times t_{odb} + e \times \left. t_{odb}\right. ^2 + f \times t_{chws} \times t_{odb}$$ For watercooled chillers: (6.8.23) $$ CAP \_FT = a + b \times t_{chws} + c \times \left. t_{chws} \right. ^2 + d \times t_{cws} + e \times \left. t_{cws} \right. ^2 + f \times t_{chws} \times t_{cws}$$ where
Note: If an aircooled unit employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. [table title="Default Capacity Coefficients – Electric AirCooled Chillers" id="defaultcapacitycoefficients–electricaircooledchillers"]
[table title="Default Capacity Coefficients – Electric WaterCooled Chillers" id="defaultcapacitycoefficients–electricwatercooledchillers"]
[table title="Default Capacity Coefficients – Fuel & SteamSource WaterCooled Chillers" id="defaultcapacitycoefficients–fuel&steamsourcewatercooledchillers"]


Units  Data structure  
Input Restrictions  User may input curves, other appropriate functions, or use default curves. If the default curves are overridden, supporting documentation is required. 
Electric Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of an electric chiller as a function of evaporator conditions, condenser conditions and partload ratio. The default curves are given as follows: (6.8.24) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ EIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ aircooled \enspace EIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{odb} + \ e \times \left. t_{odb}\right. ^2+ \ f \times t_{chws} \times t_{odb}$$ $$ watercooled \enspace EIR\_FT = a + b \times t_{chws}+ c \times \left. t_{chws}\right. ^2 + d \times t_{cws} + e \times \left. t_{cws}\right. ^2+ f \times t_{chws} \times t_{cws}$$ $$P_{operating} = P_{rated} \times EIR\_FPLR \times EIR\_FT \times CAP\_FT $$ where
Note: If an aircooled chiller employs an evaporative condenser, t_{odb} is the effective drybulb temperature of the air leaving the evaporative cooling unit. [table title="Default Efficiency EIRFT Coefficients – AirCooled Chillers" id="defaultefficiencyeirftcoefficients–aircooledchillers"]
[table title="Default Efficiency EIRFT Coefficients – WaterCooled Chiller" id="defaultefficiencyeirftcoefficients–watercooledchiller"]
[table title="Default Efficiency EIRFPLR Coefficients – AirCooled Chillers" id="defaultefficiencyeirfplrcoefficients–aircooledchillers"]
[table title="Default Efficiency EIRFPLR Coefficients – WaterCooled Chillers" id="defaultefficiencyeirfplrcoefficients–watercooledchillers"]


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required. 
Fuel and Steam Chiller Cooling Efficiency Adjustment Curves  
Applicability  All chillers  

Definition 
A curve or group of curves that varies the cooling efficiency of a fuelfired or steam chiller as a function of evaporator conditions, condenser conditions, and partload ratio. The default curves are given as follows: (6.8.25) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 + \ d \times t_{cws} + \ e \times \left. t_{cws}\right. ^2+ \ f \times t_{chws} \times t_{cws}$$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT \times CAP\_FT $$ Default Curves for DirectFired Double Effect Absorption Chillers (6.8.26) $$ PLR = \frac {Q_{operating}}{Q_{available}\left ( t_{chws} , t_{cws/odb}\right )}$$ $$ FIR\_FPLR = a + b \times PLR + c \times PLR^2$$ $$ FIR\_FT1 = a + \ b \times t_{chws}+ \ c \times \left. t_{chws}\right. ^2 $$ $$ FIR\_FT2 = d + e \times t_{cws} + \ f \times \left. t_{cws}\right. ^2 $$ $$Fuel_{partload} = Fuel_{rated} \times FIR\_FPLR \times FIR\_FT1 \times FIR\_FT2 \times CAP\_FT $$ The default curves for engine driven chillers are the same format as those for the SteamDriven Single and Double Effect Absorption Chillers but there are three sets of curves for different ranges of operation based on the engine speed. where
[table title="Default FIRFPLR coefficients – Fuel & SteamSource WaterCooled Absorption Chillers" id="defaultfirfplrcoefficients–fuel&steamsourcewatercooledabsorptionchillers"]
[table title="Default FIRFPLR coefficients – Engine Driven Chillers" id="defaultfirfplrcoefficients–enginedrivenchillers"]
[table title="Default FIRFT coefficients – Fuel & SteamSource WaterCooled Absorption Chillers" id="defaultfirftcoefficients–fuel&steamsourcewatercooledabsorptionchillers"]
[table title="Default FIRFT coefficients – Engine Driven Chillers" id="defaultfirftcoefficients–enginedrivenchillers"]


Units  Data structure  
Input Restrictions  User may input curves or use default curves. If defaults are overridden, supporting documentation is required. 
Chilled Water Supply Temperature  
Applicability  All chillers 

Definition  The chilled water supply temperature of the chiller at design conditions 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Chilled Water Return Temperature  
Applicability  All chillers 

Definition  The chilled water return temperature setpoint 
Units  Degrees Fahrenheit (°F) 
Input Restrictions  As designed 
Chilled Water Supply Temperature Reset  
Applicability  All chillers 

Definition  The reset schedule for the chilled water supply temperature. The chilled water setpoint may be reset based on demand or outdoor air temperature. 
Units  Degrees Fahrenheit (°F) 
Input Restrictions 
As designed. The default is [bookref id="chilledwatersupplytemperatureresetschedule"]. [figure title="Chilled Water Supply Temperature Reset Schedule" id="chilledwatersupplytemperatureresetschedule"][/figure] 
Condenser Type  
Applicability  All chillers 

Definition  The type of condenser for a chiller. The choices are:

Units  List (see above) 
Input Restrictions  As designed 
AirCooled Condenser Power  
Applicability  All chillers 

Definition  The energy usage of the condenser fan(s) at design conditions on an aircooled chiller. This unit should only be used for chillers composed of separate evaporator and condenser sections where the fan energy is not part of the chiller COP. 
Units  Kilowatts (kW) 
Input Restrictions  As designed. The user must enter data for remote aircooled condensing units. 