Is there a way to model split inverted heat pump unit (ductless) with multiple indoor units? I know the PTHP is a single zone system but what if it is connected to multiple indoor units, how to model this scenario then?
To connect one outdoor unit to multiple indoor units, take a look at the Variable Refrigerant Flow Equipment objects. You will need to use the following:
AirConditioner:VariableRefrigerantFlow - this is the outdoor unit
ZoneTerminalUnitList - this is a list of indoor units. The outdoor unit will reference this list so that it knows which indoor units it is connected to.
ZoneHVAC:TerminalUnit:VariableRefrigerantFlow - this is the indoor unit, and is used instead of the PTHP.
Coil:Cooling:DX:VariableRefrigerantFlow and Coil:Heating:DX:VariableRefrigerantFlow - these are the variable refrigerant cooling and heating coils. Each ZoneHVAC:TerminalUnit:VariableRefrigerantFlow will need one cooling and one heating coil.
The example file: "DOASDXCOIL_wADPBFMethod.idf" shows an implementation of these objects.
@kwalkerman: Thanks for your answer but in PTHP we only have ZoneHVAC:PackagedTerminalHeatPump, which accommodates coils, fans etc. and we don't have specifically indoor and outdoor units. If I replace ZoneHVAC:TerminalUnit:VariableRefrigerantFlow with ZoneHVAC:PackagedTerminalHeatPump, then what will be outdoor unit for PTHP?
with ZoneHVAC:PackagedTerminalHeatPump, the performance of the outdoor unit is integrated into directly into the ZoneHVAC unit. There is no separate outdoor unit.
@kwalkerman: Sorry if I misunderstood it. Are you suggesting that I should use VRF system and then using multiple terminal units instead of PTHP (as PTHP is limited to one indoor unit i.e. ZoneHVAC:PackagedTerminalHeatPump)?
@Waseem: yes. Use the VRF system with multiple ZoneHVAC:TerminalUnit:VariableRefrigerantFlow units.
@kwalkerman, what type of fan do you use for this? 1) Fan:OnOff doesn't seem to work (if using curves, power is always zero because speed ratio is zero) 2) Fan:VariableVolume is not compatible with AirConditioner:VariableRefrigerantFlow 3) Fan:ConstantVolume won't turn off during hours of no operation (I believe)
@Eric Wilson - I have used Fan:OnOff sucessfully with both ZoneHVAC:PackagedTerminalHeatPump and ZoneHVAC:TerminalUnit:VariableRefrigerantFlow. When you say that Fan:OnOff doesn't show any energy use due to curves - what curves are you referring to?
@kwalkerman, Fan:OnOff has the option to reference fan power and efficiency curves. If I try using the curves, the output is always zero because the VRF speed ratio is zero. I assume you're not using these curves to modify the fan power or efficiency.
@Eric Wilson - I do not usually use those curves with Fan:OnOff - if you are getting 0 fan energy use with those curves and VRF, sounds like an issue you need to report to the development team.
I think it depends if the muliple indoor units are all in the same thermal zone or not. If they are in different zones, then this is VRF. If they are all in the same zone then it is just one big PTHP and you would just ignore the fact that there are really multiple indoor units. You can also model with just a single zone terminal unit using the VRF system, as for a mini-split.
I think you can just put your heat pumps in an AHU and then connect them up to the zones with a VAVnoreheat or singleductuncontrolled, depending on whether it is a variable air flow or constant air flow system.
Annie
this would still be one indoor unit and one outdoor unit, but you would be able to supply multiple zones with the one unit.
Asked: 2015-07-01 08:26:16 -0500
Seen: 755 times
Last updated: Jul 01 '15
