[Equest-users] Heat Pump Heating Undersized

Joe Fleming joe at thespinnakergroupinc.com
Thu Apr 7 12:13:40 PDT 2011


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, LEEDR AP

Design Engineer



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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