[Equest-users] Using Equipment Controls for 2 Pipe Loop with Heat Pump Chillers & Boilers

[Brian Fountain]

Hi Chris,

I have seen the same in 2.3 models.  The Equipment Controls in 2.3 do not work the same as in 2.2 and I have been unable to get a heating equipment control in 2.3 to lead with (or acknowledge) the heater/chillers.    I have had success with this strategy in 2.2.

I did share a bug report to the development team on this issue.

Brian

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Brian Fountain
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From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Chris Hadlock via Equest-users
Sent: Monday, August 14, 2023 12:16 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Using Equipment Controls for 2 Pipe Loop with Heat Pump Chillers & Boilers

CAUTION: This message originated from outside Smith + Andersen
________________________________
Has anyone successfully managed to control Heat Pump chillers and boilers serving a 2-pipe loop using Equipment Control sequencing?

I'm trying to model a sequence where my HP chillers will only run if the OAT is greater than 5F (this is a cold weather location). The sequence I'm trying to program is:
If OAT < 5F I want my boilers to run (HP chillers off)
If OAT > 5F I want my HP Chillers and boilers to run in sequence whereby my HP Chillers would have the highest priority and my boilers would only activate if the load exceeds the capacity of my HP Chillers.

I've tried to do this with Load Management (using OA Temperature Type) and Equipment Controls (to specify equipment priority based on my 2 OAT conditions).

I've read through the help files for Equipment Controls and Load Management and it seems to indicate that I should be able to model this...however I can't get it to work. The issue in a nutshell is that eQuest does not seem to recognize my Heat Pump chillers as a viable heating source for my 2 Pipe Loop.

I can run the model without any Equipment Control and it will run my HP Chillers to meet some of the heating load. Without Equipment Control specified, eQuest automatically sequences my HP Chillers & Boilers in the way that it feels is best to meet the load...which is not ideal because I only want to activate my HP chillers at an OAT above 5F and I would like to assign priority to my HP Chillers.

When I specify the Equipment Controls that way I think I should (see image below), eQuest will only run my boilers (and will never run my HP Chillers) to meet the heating load on the loop, even if my Heat Pump Chillers are specified as the highest priority equipment. I've tried specifying smaller capacity boilers that I know won't meet the entire load and still eQuest won't activate my Heat Pump Chillers.
[image.png]
If I remove the Boilers altogether from the Equipment Control (so that my HP Chillers are the only heating equipment), eQuest halts the simulation and says there is "no equipment enabled".

Anyone have experience with this that can help? Any thoughts/ideas would be appreciated.

Sincerely,

Chris
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