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

[Chris Hadlock]

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: 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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