[Equest-users] WSHP System with PS-H Report Circulation Loop Overload

Nicholas Caton ncaton at catonenergy.com
Wed Jan 27 10:46:44 PST 2016

Hi Kathryn,

I can’t answer without digging in myself, but I *think* if you follow along
with the textual description of PLANT simulation in the DOE2 engineers
manual (I’d attach, but don’t have my library handy atm – it’s out there in
google!), leveraging your intimacy with the project-at-hand as a working
example, you might come up with a better understanding of exactly what that
“overload” figure is in isolation.  There’s a bulleted list somewhere in
there that explains the order in which various parts of your model are
considered before the remaining loop loads (for any loop type) are labeled

A separate shot in the dark from the hip:  It may be possible the reason
“net peak + overload peak =/= total peak” could have to do with one or more
heatpumps on the loop operating in the reverse direction during the peak
hour… maybe… or not… =)



*Nick Caton, P.E.*

  Senior Energy Engineer
  Energy and Sustainability Services
  North America Operations
  Schneider Electric

D  913.564.6361
M  785.410.3317
E  nicholas.caton at schneider-electric.com
F  913.564.6380

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States


*Please consider the environment before printing this e-mail

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *Kathryn Kerns
*Sent:* Friday, January 22, 2016 2:10 PM
*To:* equest-users at lists.onebuilding.org
*Subject:* [Equest-users] WSHP System with PS-H Report Circulation Loop

Everyone, I made an energy model of a building being served by water source
heat pumps attached to a typical water loop with a fluid cooler and a
boiler. I let eQuest size all the equipment including the boiler and water
source heat pumps. The PS-H Water Loop report showed the following:

Notice that in January, the peak heating load is -991.9 kbtu/hr, the peak
net load is -576.1 kbtu/hr, and the peak over load is -355.6 kbtu/hr.
eQuest sized the water loop boiler to be -576.1 kbtu/hr. I believe these
numbers are correct and the boiler size is correct but I cannot find an
explanation in a document telling me how net load and over load is
calculated and what they mean. I can explain how eQuest develops the heat
load, but not the other two loads. I know a typical hot water coil system
has heat load peaks equal to net load peaks and the over loads are usually
zero. I am pretty sure the over load value is related to the heat pump COP,
but I would like to be able to point to a written piece of documentation
explaining this. Anybody know where to look?


P.S. the energy model ran successfully with less than 10 heating hours out
of throttling range.

*Kathryn Kerns*

*Systems Specialist*

*BCE* *Engineers, Inc.*

*| Ph: 253.922.0446 | Fx: 253.922.0896 |*
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