Refer to the VRF heat pump model section in the engineering reference for details on the transition from cooling only mode to heat recovery mode.
Check this checkbox if heat recovery is to enabled and the heat pump can independently cool and heat different zones. Otherwise the heat pump is only able to either cool or heat for any given time step.
All of the rest of the fields described below are only available when this checkbox is checked.
Tip: Refer to the VRF heat pump model section in the engineering reference for details on the transition from cooling only/heating only mode to heat recovery mode.
This field defines the minimum outdoor dry-bulb temperature allowed for heat recovery operation (in °C or °F). Below this temperature, heat recovery is disabled. This input must be greater than the larger of the minimum outdoor temperature in cooling or heating mode. This system may still operate in cooling or heating only mode when outdoor temperatures are below the minimum outdoor temperature in heat recovery mode.
This field defines the maximum outdoor dry-bulb temperature allowed for heat recovery operation (in °C or °F). Above this temperature, heat recovery is disabled. This input must be less than the smaller of the maximum outdoor temperature in cooling or heating mode. This system may still operate in cooling or heating only mode when outdoor temperatures are above the maximum outdoor temperature in heat recovery mode.
This field defines the fraction of cooling capacity available when the system transitions from cooling only operation to simultaneous cooling and heating. It is common for the cooling capacity to decrease before the system recovers. The default value is 0.5 which means that there is a 50% reduction in cooling capacity at the start of heat recovery mode. The system will recover according to the time constant entered in Heat recovery cooling capacity time constant. If the transition period is not to be modelled, this input field should be set to 1. This input is only used when the system changes from cooling only mode to heat recovery mode.
This field defines the cooling capacity time constant, in hours, used to model the time it takes for the system to change from cooling only operation to simultaneous cooling and heating. Total response time is defined as 5 time constants. If the transition period will not be modelled, the Initial heat recovery cooling capacity fraction field must be set to 1. This input is only used when the system changes from cooling only mode to heat recovery mode.
This field defines the fraction of cooling energy consumed when the system transitions from cooling only operation to simultaneous cooling and heating. It is common for the cooling energy to drop before the system recovers. The default value is 1 i.e. no change in energy at the start of heat recovery mode. If the transition period is not to be modelled, this field must be set to 1. This input is only used when the system changes from cooling only mode to heat recovery mode.
This field defines the cooling energy time constant, in hours, used to model the time it takes for the system to transition from cooling only operation to simultaneous cooling and heating. Total response time is defined as 5 time constants. The default value is 0.0. If the transition period is not to be modelled, the Initial heat recovery cooling capacity fraction field should be set to 1. This input is only used when the system changes from cooling only mode to heat recovery mode.
This curve defines the way cooling capacity modifier varies when heat recovery mode is active. This modifier is used as a multiplier for available cooling capacity, and when in heat recovery mode, it is usually less than 1. This curve is either a bi-quadratic equation using weighted average indoor temperature (i.e., the indoor terminal units weighted average inlet temperatures) and condenser entering air temperature as the independent variables or a cubic curve based on part-load ratio. This performance curve can be used to describe the cooling capacity modifier as either a constant (e.g., temperature or part-load ratio term coefficients are 0), a cooling modifier that varies with either indoor temperature and/or outdoor temperature, or part-load ratio (e.g., one or more temperature or part-load ratio term coefficients are 0), or varies with both indoor and outdoor temperatures or part-load ratio (e.g., all temperature or part-load ratio term coefficients are non-zero).
This modifier is applied only when heat recovery mode is active and when the system changes from cooling only mode to heat recovery mode.
This curve defines the way cooling energy modifier varies when heat recovery mode is active. This modifier is used as a multiplier for operating cooling energy, and when in heat recovery mode, it is usually greater than 1. This curve is a bi-quadratic equation using weighted average indoor temperature (i.e., the indoor terminal units weighted average inlet temperatures) and condenser entering air temperature as the independent variables. This performance curve can be used to describe the cooling energy modifier as either a constant (e.g., temperature term coefficients are 0), a cooling energy modifier that varies with indoor and/or outdoor temperatures (e.g., one or more temperature term coefficients are 0), or varies with both indoor and outdoor temperatures (e.g., temperature term coefficients are non-zero). This modifier is applied only when heat recovery mode is active.
This input is only used when the system changes from cooling only mode to heat recovery mode.
This field defines the fraction of heating capacity available when the system changes from heating only operation to simultaneous heating and cooling. It is common for the heating capacity to decrease before the system recovers. If this field is left blank, a default value of 0.5 is used (50% reduction in heating capacity at the start of heat recovery mode). The system will recover according to the time constant entered in Heat recovery heating capacity time constant below.
If the transition period will not be modelled, enter 1 here.
This input is only used when the system changes from heating only mode to heat recovery mode.
This field defines the heating capacity time constant, in hours, used to model the time it takes for the system to transition from cooling only operation to simultaneous cooling and heating. Total response time is defined as 5 time constants. If this field is left blank, a default value of 0.083 is used. If the transition period will not be modeled, the Initial Heat Recovery Heating Capacity Fraction field must be set to 1.
This input is only used when the system changes from heating only mode to heat recovery mode.
This field defines the fraction of heating energy consumed when the system changes from heating only operation to simultaneous heating and cooling. It is common for the heating energy to decrease before the system recovers. The default setting is 0.5 which means that there is 50% reduction in heating energy at the start of heat recovery mode. The system will recover according to the time constant entered in Heat recovery heating capacity time constant (above).
If the transition period is not to be modelled, this input should be set to 1.
This input is only used when the system changes from heating only mode to heat recovery mode.
This field defines the heating energy time constant, in hours, used to model the time it takes for the system to change from cooling only operation to simultaneous cooling and heating. Total response time is defined as 5 time constants. The default value is 0.0.
If the transition period is not to be modelled, the Initial heat recovery heating capacity fraction field must be set to 1.
This input is only used when the system changes from heating only mode to heat recovery mode.
This curve defines the heating capacity modifier when heat recovery mode is active. This modifier is used as a multiplier for available heating capacity, and when in heat recovery mode, this modifier is usually less than 1. This curve is a bi-quadratic equation using weighted average indoor temperature (i.e., the indoor terminal units weighted average inlet temperatures) and condenser entering air temperature as the independent variables. This performance curve can be used to describe the heating capacity modifier as either a constant (e.g., temperature term coefficients are 0), a heating modifier that varies with indoor and/or outdoor temperatures (e.g., one or more temperature term coefficients are 0), or varies with both indoor and outdoor temperatures (e.g., temperature term coefficients are non-zero).
This input is only used when the system changes from heating only mode to heat recovery mode.
This curve defines the heating energy modifier when heat recovery mode is active. This modifier is used as a multiplier for operating heating energy, and when in heat recovery mode, this modifier is usually greater than 1. This curve is a bi-quadratic equation using weighted average indoor temperature (i.e., the indoor terminal units weighted average inlet temperatures) and condenser entering air temperature as the independent variables. This performance curve can be used to describe the heating energy modifier as either a constant (e.g., temperature term coefficients are 0), a heating energy modifier that varies with indoor and/or outdoor temperatures (e.g., one or more temperature term coefficients are 0), or varies with both indoor and outdoor temperatures (e.g., temperature term coefficients are non-zero).
This modifier is applied only when heat recovery mode is active and when the system changes from heating only mode to heat recovery mode.