In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Size boiler by Measured heat load, "Manual J" or Designed Heat Load?
I'm considering a new boiler. I'm trying to come to come to an agreement with myself on the right size.
I did a heat load based on our fuel use over January and some of February last year using the method here
. That came to about 137MBH ( Details of calculation
Then I did a heat load based on the size of the cast-iron radiators in the house, and that came to about 288 MBH (Details of calculation
The heating system has 4 zones and there's an indirect domestic hot water. One zone is the garage, and one is spare rooms over the garage. Both of those are rarely heated over 40F. Is it crazy to size a new boiler based on measured heat usage, even though it's significantly lower than the design load implied by the size of the radiators?
FWIW, the current boiler is 413 MBH DOE. I'm pretty sure that's too big in any case!
Also, a guy from a supply house came to do a "Manual J" for me. I put that Manual J in quotes, because I don't get to see the results, just the sales recommendation. But he recommended a Burnham MPO-IQ231 - 203K BTU.
Obviously I'll be getting a tech to work with to do this right, but I like to be able to have an informed discussion when I'm getting quotes, so any advice would be appreciated.