A heat pump has diminishing capacity as the outdoor temperature becomes lower. This is the reason that supplemental heating coils are needed in some situations. You may be able to increase the Sizing:Parameters or Sizing:Zone Heating Sizing Factor to make your heat pump larger and reduced unmet load hours.
The Building Performance Team
James V. Dirkes II, P.E., BEMP , LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Energy Partners
Sent: Monday, August 15, 2011 11:12 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Split-air conditioning system
Dear James,
The room is simulated in a place with cold climate and the minimum temperature goes down to 9degree.
The system is autosized so why E+ doesn't size the system bigger to keep the room warm?
Thanks.
Regards
Chun
From: Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Monday, 15 August 2011 8:58 PM
Subject: RE: [EnergyPlus_Support] Split-air conditioning system
It sounds like you DID disable the supplemental heating!
· No gas consumption
· Not enough heating during an additional 150 hours
Perhaps the model is showing you the actual results of a colder room.
Consider adding a report variable for the room temperature in order to see how cold the room becomes.
The Building Performance Team
James V. Dirkes II, P.E., BEMP , LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of energy.partners
Sent: Monday, August 15, 2011 2:47 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Split-air conditioning system
Hi,
I am trying to set up a split-air conditioning system (DX single speed cooling, DX single speed heating and Air-to-air Heat pump). The size of the system is autosized. I have also set up gas heating as the supplemental heating. In reality some split systems don't have supplemental heating. I have tried to "turn off" this function by input the "Maximum Outdoor Dry-Bulb Temperature for Supplemental Heating" (under AirLoopHVAC:UnitaryHeatPump:AirToAir)to -10 degree. The gas heating consumption drop to zero but the "Time Set Point Not Met During Occupied Heating" increase from 50 to 230 hours which would be unacceptable. Could anyone give me some advice on how to disable the supplemental heating?
Thank you very much.
Regards.
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