Heat recovery chiller

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I'm trying to model a hot water loop that's being heated entirely by a
heat recovery chiller (htrec) and supplying heating to a VAV system. I'd
like to utilize condenser heat prior to rejection to the dry coolers (I
have a large cooling load year around). The trouble is, even though it
appears like it is set up correctly, the system doesn't want to reject
ANY heat to the HW loop. When I just created the loop and ran a
simulation, eQuest gave me an error saying I had no primary heat source
on the HW loop. I tried adding a dummy boiler with virtually no
capacity, and that got rid of the error and allowed me to run, but I
still had no heat going to my HW loop.

Has anyone had success with this? When reading the DOE2.2 dictionary, it
appears this is exactly what the htrec chiller was designed to do, but
nothing I change makes any difference. If anyone's willing, I can send
you a copy of my input and pd2 files to look at.


Eric O'Neill

Eric O'Neill's picture
Joined: 2011-09-30
Reputation: 0


The information you provided is not quite enough to know what is going
on. I would check the run hours for your chiller to make sure it is
picking up part of the cooling load. Also, it's a bit strange that your
building needs no heat. If you want to send your input file, I can take
a look at it.

Sam Mason

Sam Mason's picture
Joined: 2011-09-30
Reputation: 0

Thanks for the response Xavier,

The cooling load is 24/7 and is located in an interior zone of a building located in a cold climate, so there are simultaneous heating and cooling periods. What I'm hoping to create is a system that will act much like a boiler, in that whenever the HW loop needs heat, the HTREC chiller runs and provides heat while cooling the chilled water loop. I added the HTREC chiller because it's supposed to be able to supply higher condensing water temperatures (which I need for my HW loops) than my other boilers are. The DOE2.2 documentation leads me to believe that this chiller would automatically sequence on whenever there is a heating load on the loop, but this doesn't seem to be the case. Even if I delete the HTREC chiller and make my other three chillers recover heat to the HW loop, none of them do.

The coils on the condensing loop are for the waterside economizer. There is more than sufficient heat for heat recovery (cooling load>>heating load), so I still need an economizer, although I want it to be secondary. I don't know if I can sequence that. My guess now after thinking about it is that the system is economizing whenever there is a heating load, so the chillers don't sequence on. Is there a way to make the chillers run if there is a load on the HW loop, but economize the remainder?


Eric O'Neill's picture
Joined: 2011-09-30
Reputation: 0

I was working on a similar problem a while ago. I was unable to find any way to control the heat recovery chiller operation based on the Hot Water Loop loads (chillers would only sequence on the chilled water loop load). I ended up going the route of manipulating hourly results data in a spreadsheet.

Good Luck, and if you do determine a way to accomplish this, please post to report.


Molly Curtz, P.E.

Molly Curtz's picture
Joined: 2011-09-30
Reputation: 0