The default 'Cooling/Heating Energy Input Ratio Modifier Function of Low Part Load Ratio' curves created from the AirConditionerVariableRefrigerantFlow constructor have 'min value of x' field set to 0.5, which is higher than the VRF input of 'Minimum Heat Pump Part-Load Ratio'. AFAIK the OS default curves have not changed, but since this is now causing a fatal error, EnergyPlus likely changed its error handling around this object. The fix for that issue is to set curve's min value equal to the Minimum Heat Pump Part-Load Ratio.
Additionally, when specifying a VRF with Condenser Type = 'WaterCooled', the performance curves that have condenser entering temperatures as an independent variable should be constructed with respect to entering water temperatures. Currently, OpenStudio default curves don't make this distinction and are all relative to Outdoor Air Wetbulb temperatures. This PR includes a new Curves module for creating and converting curve coefficients, and water-source VRF curve coefficients obtained from Trane Trace equipment library. The gbxml hvac translator will now create and apply these curves when the gbXML indicates that the VRF condenser type is water cooled. The condenser water loop created to serve the WSVRF unit has also been modified to add a boiler and Dual Temperature SPM to better model the heat source/sink primary equipment.
Fixes https://github.com/NREL/gbxml-to-openstudio/issues/122
The default 'Cooling/Heating Energy Input Ratio Modifier Function of Low Part Load Ratio' curves created from the AirConditionerVariableRefrigerantFlow constructor have 'min value of x' field set to 0.5, which is higher than the VRF input of 'Minimum Heat Pump Part-Load Ratio'. AFAIK the OS default curves have not changed, but since this is now causing a fatal error, EnergyPlus likely changed its error handling around this object. The fix for that issue is to set curve's min value equal to the Minimum Heat Pump Part-Load Ratio.
Additionally, when specifying a VRF with Condenser Type = 'WaterCooled', the performance curves that have condenser entering temperatures as an independent variable should be constructed with respect to entering water temperatures. Currently, OpenStudio default curves don't make this distinction and are all relative to Outdoor Air Wetbulb temperatures. This PR includes a new Curves module for creating and converting curve coefficients, and water-source VRF curve coefficients obtained from Trane Trace equipment library. The gbxml hvac translator will now create and apply these curves when the gbXML indicates that the VRF condenser type is water cooled. The condenser water loop created to serve the WSVRF unit has also been modified to add a boiler and Dual Temperature SPM to better model the heat source/sink primary equipment.