Lake/Well Loop based HP as DHW preheat

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Hello All,

First, thanks to those who contributed earlier posts on the topic of
modeling a "Loop to Loop" heat pump with a "Lake/Well circulation loop.
Those were of great help in developing my model thus far.

At this point, I would like to try and incorporate a W-WHP tied to my
Lake/Well circ loop dedicated to DHW preheat. A separate circ pump runs
a loop from the W-WHP to a DHW preheat tank, reducing load on the DHW
boilers. The W-WHP is able to heat a limited flow rate of water to 110F
in the preheat tank, while the DHW tanks need the extra DHW boiler input
to be maintained 140F.

My problem has been the incompatibility between the DHW loop and the
Lake/Well loop. Then again, maybe preheat should be on a loop separate
from DHW.

Any ideas?


Eric Boxer, EIT

Boxer, Eric's picture
Joined: 2011-09-30
Reputation: 0

Hi Eric,

I'm going to try and remember this off the top of my head instead of
searching for an old project file. I think that you will need to have 3
circulation loops in your Plant side. a CHW, HW, and L/W Loop. The HW
side of the loop should be able to connect to the DHW. If it doesn't work
this smoothly, then you might have to have two HW loops. One you connect to
the DHW, and one you connect to your air-side systems.

That's my first guess. I would also suggest that you read through the
Loop-to-Loop chillers & Water-toWater chillers again in Volume 2 so that you
can identify how these equipment will supply DHW preheat...which can be done
in DOE2.

Sorry I can't offer you more details at this time.


Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

Dear eQUESTers

I am doing LEED-CS energy rating simulation. Part of the project is
residential type (hotel) and the HVAC system for baseline is PTAC while the
proposed system is FCU+DOAs. The Appendix G doesn't tell us to create the
PTAC baseline system with DOAS. But the question is how to set the OA value
to PTAC system in eQUEST? I think I should set the OA value in the
interface below, but how? Has anyone performed the PTAC simulation and Can
you tell me the details or can you give me an example you did?

Thanks a lot!

Yours Zhiren Zhou

cid:image001.png at 01CB991B.D66A79A0

zhiren zhou's picture
Joined: 2011-09-30
Reputation: 0

Dear Zhou,

OA can be inputed under the zone, which is conditioned by PTAC.

Referred to **, Section AIRSIDE HVAC, SYSTEM TYPE =
PTAC, page 272, you can see that OA control is not under AC system, and on
page 273 and 274 there is an example input for this system: *OA control is
under zone control*.

After setting, you can output OA hourly data to check it works or not.



grammy's picture
Joined: 2010-12-09
Reputation: 0