[Bldg-sim] GSHP EIR Part Load Curve

David S Eldridge DSE at grummanbutkus.com
Tue May 20 07:31:20 PDT 2008


Two things could be throwing off your comparison.

Not knowing what your baseline heating system is, the ground source heat pump will have a lower heating energy usage compared to conventional systems at the building line (electricity used at some COP compared to 80%-90% boiler/furnace or electric resistance heat at 100%).  Relative costs of each depending on your location.

Also the VAV system may have reheat where the zonal system will only be providing heat to meet the loads.

David


________________________________
From: bldg-sim-bounces at lists.onebuilding.org [bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Tony Kriel [tkriel at sustaineng.com]
Sent: Tuesday, May 20, 2008 8:45 AM
To: bldg-sim at lists.onebuilding.org; equest-users at lists.onebuilding.org
Subject: [Bldg-sim] GSHP EIR Part Load Curve

SIM List,

We are modeling a GSHP system in eQuest.  After selecting the options in the wizard and running the model we noticed that the space heating was quite a bit lower when compared to a VAV system for the same project.

We then went into detailed mode and started to look into what performance curves the heat pumps had defaulted.  It seemed that the default part load curve (HEAT-EIR-FPLR) that eQuest selected, seemed very aggressive.  It is my understanding that the heat pumps cycle on and off when needed, and when they cycle on and off they operate at 100%.  So, should the part load curve be changed to be 100%, (ie it shouldn’t have a part load curve)?  Or should we be looking at something else.

Thanks,

Tony Kriel
Mechanical Engineer
Sustainable Engineering Group, LLC.
431 Charmany Drive, Suite 102
Madison, WI 53719

Phone:  (608) 231-9664 ext. 16
Fax:  (608) 231-9665
E-mail:  tkriel at sustaineng.com<mailto:tkriel at sustaineng.com>
Web:  www.sustaineng.com<http://www.sustaineng.com>




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