High boiler energy use compared to HW loop demand

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I have a situation where my boiler energy use (= 950 MBtu) is extremely high compared to the hot water loop demand = 550 MBtu. The modeled efficiency of the boiler is 80%...which should result in an estimated 690 MBtu of boiler energy use. Any ideas what could be going on here? Thanks.

Josh Doherty

Josh Doherty's picture
Joined: 2011-09-30
Reputation: 0

I have had the same problem when I let EQUEST automatically size the boiler for me. In my situation, EQUEST drastically oversized the boiler so it was running at 10% capacity 90% of the time. You can check to see if you have the same problem by looking at report PS-C to see what part load range your boiler is operating at. To fix the problem, first I manually set the capacity of the boiler, which helped a lot, but the program was still over estimating the energy consumption. Then, I created a custom performance curve using actual data for my boiler. That solved my problem.

Jeremy McClanathan's picture
Joined: 2011-09-30
Reputation: 200

If you are manually setting the boiler capacities -- you may also wish to
set the heating loop sizing to primary from the default secondary where it
is sized based on the coils etc.

bfountain's picture
Joined: 2011-09-30
Reputation: 201