[Bldg-sim] eQuest: Ground Source Heat Pump + DHW + Glazing

Anthony Hardman Anthony at GeoEnergyServices.com
Tue Jan 8 08:50:21 PST 2008



Addressing your first question with eQuest is a difficult task.   First off,
if you don't have Climate Master's GSHP eQuest "expansion pack," get it
(http://www.climatemaster.com/index/equest).  It adds many GSHP modeling
functions, including DHW, which would accurately capture your DHW energy
requirements.  I think this still requires a dedicated HP to supply DHW.  


The real difficulty arises when you plan on using a single HP unit to supply
both radiant heating and DHW since there are no commercially available HP's
(that I'm aware of) that will operate the desuperheater option without a
call for radiant heating.  Obviously, in situations where no radiant heating
call exists, you run the risk of quickly exhausting your DHW supply (unless
you have auxiliary heating).  A practical solution to this involves using an
Indirect Hot Water tank as your radiant buffer tank.  Kudos if you can
figure out a way to model the latter!


Anthony Hardman

Mechanical Engineer

Geo-Energy Services


From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of gaurav mehta
Sent: Monday, January 07, 2008 1:30 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] eQuest: Ground Source Heat Pump + DHW + Glazing




I have two questions:


1. I am modeling a single family residential building in the pacific
Northwest with a Ground Source Heat Pump which apart from providing hot
water for the radiant slabs also provides heating for domestic hot water
(DHW). How does one model DHW in this situation? I have calculated the flow
rate (gpm) required for the house and have an annual schedule. I tried to
assign a process load to the Water Loop HP and when i modeled one case with
the process load and the the other without the process load the difference
in the pump energy does not confirm to the hand calculation. 


2. This question is independent of the first one (ie no process load
attached to the Water Loop HP). I modeled one case with double low e glazing
on all orientations and the other case had South facing glazing changed to
double clear and rest of orientations with the same double low e glazing.
Both the glazing types were modeled using the library method. The difference
in the results show a penalty of 2% in space heating for the case with South
facing glazing changed to double clear. Understandable, the building
configuration (amount of glazing + shading) is such that insulating property
of glazing provides more benefit than solar penetration. However, I also
note there is a penalty of 11% for the pump energy. There is no daylighting
and nothing different in the two models accept the South facing with
different glazing. There is no cooling modeled for the house as well and
hence no difference in that end use as well. I can understand some increase
in pump energy, but can anyone provide some insight as to why such an impact
on pump energy? 



I would greatly appreciate your response.






Sustainable Building Analyst,


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