[Equest-users] GSHP supp. heat & unmet hours

[Nick Caton]

Christian/Matthew:

 

Here is a procedure I dug up in the past to verify whether the GLHE is
doing its job or not:

 

Here's an excerpt from an archived message - full text is here
<http://www.gard.com/ml/bldg-sim-archive/msg04366.html> :

Actually, the better way to watch the performance of a GLHE is to let
eQUEST output the hourly report of the GLHE outlet temperature, which is
the entering fluid temperature to the heat pump if the thermal loss from
the loop and the pump temperature rise can be ignored. As an example, to
output the hourly loads on GLHE, outlet temperature of GLHE, and the
undisturbed ground temperature, you can save following text as a short
inp file and add it to your input file by using the "Import files"
feature of eQUEST in the detailed mode. For advanced users, you can
directly define the hourly report in the detailed mode of eQUEST.

$ ---------------------------------------------------------
$              Hourly Reporting
$ ---------------------------------------------------------

"GHX" = REPORT-BLOCK    
   VARIABLE-TYPE    = "GLHX (VertWell-CM)"
   VARIABLE-LIST    = ( 1, 4, 5 )
   ..
"Hourly Report" = HOURLY-REPORT   
   LIBRARY-ENTRY "Hourly Report"
   ..
"Hourly Report 3" = HOURLY-REPORT   
   REPORT-SCHEDULE  = "Hourly Report Schedule"
   REPORT-BLOCK     = ( "GHX" )

Original credits to Xiaobing Liu, whose name you may recognize as a
fellow whose work has been pivotal with regard to modeling ground source
heat pumps.

 

In any case, if you'll do this and check out the hourly behavior of the
ground loop temperature over the year, it will probably be obvious if
your 30% unmet heating hours is due to an undersized field.

 

Best of luck!

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Matthew
W. Higgins
Sent: Friday, May 28, 2010 8:27 AM
To: cstalberg at naturalintelligence.us; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] GSHP supp. heat & unmet hours

 

It's very likely that your bore-field is undersized. Make sure that your
configuration is correct and that the multiplier against the bore
configuration results in the number of bores you have in the field.
Depth, conductivity, etc. also play a key role, but this is usually the
reason I come across.

 

Depending on the actual configuration of the field you may also want to
split the simulated field in two and have two GSHX fields to "draw"
from.

 

Matthew Higgins, ASHRAE-HBDP, LEED-AP

Energy Engineer

 

Bridgers & Paxton Consulting Engineers, Inc.

4600-C Montgomery Blvd. NE

Albuquerque, NM  87109

505-883-4111

505-888-1436  Fax

mwhiggins at bpce.com 

 

www.bpce.com

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
Christian Stalberg
Sent: Friday, May 28, 2010 6:52 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] GSHP supp. heat & unmet hours

 

I have a building using a GSHP with electric supplemental heating

and I'm getting almost 30% unmet heating hours. Any ideas why 

this could be occuring?

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