[Bldg-sim] eQUEST GSHP Unmet Load Hours

[Jon Evans]

Robby,

 

This is a typical, real world issue with heat pumps.  We typically advise
owners not to use an aggressive night setback (more than 2 or 3 degrees)
because of this exact problem.  We usually have a control sequence put in
place that limits the night setback if the outdoor air temperature falls
below a certain level (say 30 degF). Can you apply for a variance under the
local building code? If this is how the building will be operated in real
life with a 15 degree setback, you will probably get too cold complaints
from the occupants.

 

One way around the modeling problem would be to use perimeter baseboard in
the model.  I would set it to electric, and schedule the baseboard to only
to be available during the morning warm-up period.  It shouldn’t add too
much energy into you model and will eliminate most of your unmet load hours.

 

Good luck!

 

Jon Evans, PE

 

Sustainable Engineering Group LLC

431 Charmany Drive Suite 102

Madison, WI 53719

 

Tel: (608) 231 9664

Fax: (608) 231 9665

 

E-mail: jevans at sustaineng.com 

Web: www.sustaineng.com <http://www.sustaineng.com/> 

 

  _____  

From: Robby Oylear [mailto:robbyo at rushingco.com] 
Sent: Thursday, May 22, 2008 10:13 AM
To: bldg-sim at onebuilding.org
Subject: [Bldg-sim] eQUEST GSHP Unmet Load Hours

 

Hi everyone,

 

I’m trying to model a ground source heat pump system in eQUEST using a Water
Loop Heat Pump system attached to a ground source heat exchanger.  The
system seems to work fine during occupied hour but it just can’t meet
morning warm-up loads.  I’m doing a systems energy analysis for our local
energy code compliance and there is a mandatory night setback of 55 °F from
70 °F in heating.  During winter months the system doesn’t seem to be able
to jump from 55 °F to 70 °F space temperature in less than 1-2 hours.  I’ve
double checked the fan schedules and the system is allowed to come on during
this time.  

 

Does anyone have any suggestions for getting the system to meet these unmet
load hours?  

 

Robby Oylear

Mechanical Engineer

direct: 206.788.4571

cell: 206.354.2721

 <http://www.rushingco.com> www.rushingco.com



 

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