I think the capacities of boiler is sized based on non-coincident condition as default.

Min-Hwan Yang, LEED AP

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.