[Equest-users] Heat Pump Heating Undersized

[Brian Goldsmith]

Ya I looked at all that, seemed to be fine. It seems like whenever I change my system from single zone package to variable air volume this problem comes up. I just changed the system type and left everything else the same.

Brian Goldsmith
Brian.Goldsmith at atce.com<mailto:Brian.Goldsmith at atce.com>
direct  408.487.1217

________________________________
From: Joe Fleming [mailto:joe at thespinnakergroupinc.com]
Sent: Thursday, April 07, 2011 12:14 PM
To: Brian Goldsmith; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Heat Pump Heating Undersized

Usually scheduling (fan, available heating and t-stat don't coincide every hour of every day), airflow (too low), SAT (too low), or multiple zones on one unit.
Usually...

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Brian Goldsmith
Sent: Thursday, April 07, 2011 2:24 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Heat Pump Heating Undersized

I'm having trouble with the heating in my heat pump. I modeled a Packaged VAV (PVAVS) with HEAT-SOURCE= Heat Pump and ZONE-HEAT-SOURCE= Not Installed. Set HEAT-SET-T to 120F, DESIGN-HEAT-T to 70F, and did not specify auxiliary heat. I get the message that my zone has insufficient heating capability. Looking at SS-A, is says the maximum heating load is only -10.1 KBTU/HR. Looking at SS-P, the report says my heating capacity is -47.8 KBTU/HR. So why do I have 563 underheated hours? Does it have something to do with the system type? I tried ZONE-HEAT-SOURCE= Heat pump and tried HEAT-SIZING-RATIO= 5, just to see if either one would do anything, although I didn't really expect them to. Also tried electric supplemental heat, which comes out to -31.715 KBTU/HR. My design supply flow is 1913 CFM, and the outside air flow is 252 CFM. The design supply flow is the same for both the heating and cooling performance summaries. Should this be the case? Thanks for any help.

Brian Goldsmith, LEED(r) AP
Design Engineer
[cid:image001.jpg at 01CBF528.BFF91460]
97 E. Brokaw Road, No 300
San Jose, CA 95112
main    408.487.1200
direct  408.487.1217
www.atce.com<http://www.atce.com/>

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