Oversized gas hydronic boiler

JPS

Is it possible to put a smaller gas burner in an oversized cast iron hydronic boiler. The boiler is 200,000 btu and should be 140,000. It's probably cheaper and easier just to get a new boiler, but this one is pretty sound.

Mike T., Swampeast MO

Have asked that question of numerous people.

Techs usually say "Sure", but their methods differ considerably...

Mfgrs generally say, "We don't recommend this."

Unknown

Mike...

I agree, but the way we say it is this: "It hasn't been tested and isn't listed and approved for that firing rate."

Usually the reason is the fear of dissolving a chimney; metal or masonry, and harming someone.

Noel

Jim Davis_3

Small burner in large boiler

It is easy to put a small peg in a large hole, but it will never be functional. Doing this can use 25%-40% more fuel. Resetting water temperature is the way to de-rate a boiler, furnace etc.

Unknown

That's not quite correct

Resetting water temperature will derate the radiation, but the boiler will still be fired at the original rate. If you don't use the full output of the boiler, it will still run short cycles.

A boiler has almost the same output at any temperature, within it's operating range.

Noel

Jim Davis_3

You are right, wrong terminology

The question that might be addressed is how many feet of radiation is there versus boiler. If you have a steam boiler with 200,000 BTU of radiators, can you heat those radiators effectively with a smaller boiler? Regardless, firing any equipment less than it is rated, seriously lowers it effective efficiency.

JPS

Oversized hydronic boiler

Thanks for the response. Sounds like the right boiler is the best option.