Oversized Boiler -- Question

wanttolearn

Hi-

I have a steam radiator system in my house.  A year ago, I did an oil to gas conversion, where I replaced my old boiler with a modern Peerless gas boiler.

My house was built in the 1920s and measures approx. 5200 sq. ft. on three floors.

I had obtained quotes from several reputable plumbers, and most of them had sized the new boiler at 345,000 BTU.  One of the plumbers told me that according to his measurement, the boiler should be larger, at 450,000 BTU.  Because his price was competitve with all the others, I assumed that bigger is better and I went with the 450,000 BTU boiler, figuring I am getting a bigger boiler for the same amount of money.

Based on what I have read on this website, this is a HUGE boiler for a house of my size.  My question now is this:  Are my monthly gas bills significantly higher because of this mistake?  If so, is there a way to quantify how much I am overpaying each month in gas bills as a result of having a boiler that is too large?  I am located on Long Island, NY and my heating bills have been approx. $1,000 per month for December and January.

A couple of observations to help you respond:  I have NOT observed the boiler to be short cycling.  On a typical day the steam turns on once every two hours, the heating cycle last approx. 20 to 30 mins and then the burner shuts off again until the next cycle starts. 

I know this is a vague question I am asking, but I am quite upset about this issue and I want to get an idea for how much lower my heating bills would be if I had a correctly sized boiler.

Any help would be greatly appreciated. 

Mike Kusiak_2

Need more info

How does the rating of your boiler compare to the EDR of the installed radiation? Without knowing the EDR, you really can't say that the boiler is oversized or properly sized. A steam boiler is not specified by the size of the house or heat loss, but by the amount of radiation present to condense the steam.



In a previous posting, you mentioned that you had a Peerless 64-09 boiler rated at 460,000 BTU input, and a net steam rating of 1146 sq ft of steam EDR. If you have radiators totalling 1146 sq ft EDR or more, then the boiler is not oversized.



So until you calculate the total EDR of all your radiators, you cannot definitively say your boiler is oversized. You mentioned that the boiler normally runs a 30 minute thermostat cycle without ever reaching the pressuretrol limit. This would tend to indicate that the boiler is not grossly oversized, and in fact may be properly sized for the amount of radiation you have.

Mark N

Oversized?

The bigger boiler consumes 30% more fuel than the smaller boiler. But Mike is right maybe the bigger boiler is the correct size. The last 2 months my gas bills have been about $250. My house is 1/4 the size of your home, my boiler is 1/4 the size of your boiler, and my bill was 1/4 the size of your bill.