Excessive Heat Recovery Chiller Operation

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Couldn't find an answer in the archives so I thought I'd solicit the
experts.

Objective: I only want my HRC to recover waste heat when there's a call for
cooling.

Problem: I have more chiller operation in the winter than the summer. It
seems my HRC's are activating whenever there is a demand on the hot water
loop it's attached to.

Question: Does one have to specify equipment controls to get the HRC to
operate in the desired mode? If not, what else am I doing wrong here?

Anthony Hardman, PE

LEED AP BD&C

Anthony Hardman, PE
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Joined: 2011-09-30
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Anthony,

When modeling HRC's in eQUEST, I've found that by default, the chiller does
not operate without a load on the chilled water side.

I would suggest a few things to troubleshoot:

- Create an hourly report containing chilled water loop load, hot water loop
load, and assigned load to the HRC. Check to see if indeed there are hours
during which the chiller is operating with no call for cooling.

- Do you have other chillers besides the HRC? If so, you may be seeing more
HRC operation in the winter because eQUEST is selecting one of the other
chillers to run as the lead chiller during the higher load hours of the
summer. For example, say that the HRC is 200 tons and your other chiller is
400 tons. In the summer with a load of 350 tons, eQUEST may be choosing to
run the 400 ton chiller because it is a better match for the load, while in
the winter with a load of 200 tons, eQUEST may choose to run the 200 ton
HRC.

If you want the HRC to always be the lead, then you'll have to specify this
with equipment controls. I have not been able to successfully implement
anything other than a load-based control scheme for HRCs in eQUEST (which
may be all that you're after). Attempting to stage the chillers based on
outside air temperature or load in the HW loop, for example, causes eQUEST
to crash during run time for me (with no BDL errors). If you figure out how
to do this, I would love to know the secret. I prefer to stage HRCs based
on a combination of loop loads and outside air temperature, but I've never
been able to capture these savings in eQUEST.

Aaron

Couldn?t find an answer in the archives so I thought I?d solicit the
experts.

Objective: I only want my HRC to recover waste heat when there?s a call for
cooling.

Problem: I have more chiller operation in the winter than the summer. It
seems my HRC?s are activating whenever there is a demand on the hot water
loop it?s attached to.

Question: Does one have to specify equipment controls to get the HRC to
operate in the desired mode? If not, what else am I doing wrong here?

*Anthony Hardman, PE*

*LEED AP BD&C***

Aaron Powers2's picture
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Joined: 2011-09-30
Reputation: 0