[Equest-users] Question on a L2LHP with a Lake/Well GLHX

[Hall, Brendan]

I had a similar situation where I was trying to use multiple L2LHPs to
simulate a multistack system that used a geo loop for heat rejection per
the method that had been posted on the forum. The problem that I found
was that with the loop to loop chiller/heaters it is really hard to
determine how it is calculating the heating efficiency at part load
since there are only part load curves and EIR on the cooling side for
that type of equipment. Also, the heating performance seemed to get
worse as the ground source temperature increased (opposite of what you
would expect). I ended up using the regular heat pump system that has
both heating and cooling curves and EIR inputs. Two other things to
check are using the equipment controls/load management to force the heat
pump(s) to meet the heating load before the boiler and to normalize the
part load performance curves to what conditions the equipment was
selected for (most likely not ARI for a geo loop). Hope that helps. 

 

Brendan Hall, M.Sc.
Mechanical Engineer

 

karpinski
ENGINEERING
3135 Euclid Avenue
Cleveland, OH  44115
P  216.391.3700

F  216.391.0108
E  bhall at karpinskieng.com
W www.karpinskieng.com <http://www.karpinskieng.com/> 

 

________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
TaylorRoberts at Eaton.com
Sent: Monday, June 06, 2011 2:13 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Question on a L2LHP with a Lake/Well GLHX

 

Hello everyone,

 

I am trying to model a HVAC system that is composed of a central
geothermal system that uses a heater/chiller with back up boilers to
provide hot and chilled water to AHU for a VAV air-side system.
Following the advice I found on the archives from the Loop to Loop
Heatpump in eQuest discussion I modeled a system with a L2LHP that uses
a lake/well loop (see screen shot). I made sure to zero out the static
head for the GLHX and changed the max hot water temp in the hot water
loop to 130F to be compatible with a heatpump. I compared this system to
a basic chiller/boiler VAV system to see if it showed any signs of
improvement and the results have been very puzzling. The geothermal
system is using slightly less energy to cool but isn't providing any
heating to the system. Instead the boilers are providing all of the
heating. When I remove the boilers to make the L2LHP provide all of the
heating it is performing terribly using an enormous amount of
electricity to heat. Also, I assumed that there would be a pumping power
increase but the L2LHP is using about 3X the electricity as the
boiler/chiller system and this seems way too large. 

 

Has anyone had any luck modeling a system like this or has any ideas why
my L2LHP model is using more energy than a standard chiller/boiler
system? 

 

 

Taylor Roberts, EIT

Energy Solutions Intern

Energy Solutions Group

 

E M C Engineers, Inc.

Eaton's Electrical Services & Systems

970-208-7917

TaylorRoberts at Eaton.com

 

 

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