gb142 boiler replacement question

shawn laverty

I would like some information or thoughts on a question.
MY question is we are looking at a gas hot water boiler replacement which feeds misc cast iron rediators and some runtal heaters. The existing boiler has a 3' main coming off of it and runs the length of the building. So I would like to install a gb142 boiler does anyone know if i will have a problem with the water capacity in the pipes in the building or will i have to install 2 boilers The btu load will handle the building just need some ideas or if you have any experiance on this situation.

Thank you

Brad White

Water capacity is not heating capacity

especially in a system with constant circulation. Once that water is warmed up, BTU's in should equal BTU's out.

shawn laverty

The piping the have is a 2 pipe system 1 feed 1 return.
tee's coming off at radiators. what if it was not piped constant circulation. The gb has a primary loop

Brad White

If it is not constant circulation

you may wait a while for the heat to get to your radiators from a cold-start condition. In actual practice, if it is cold out the system will be running more often so you will be starting from a pre-warmed condition. Really not a big operational deal but it should not be a factor in sizing the system either.

The "longer wait from a cold start" is not the worst thing because the piping will store the heat after the boiler shuts off. Good outdoor reset mitigates this effect which can cause over-heating. TRV's on the radiators are a very good thing too. They account for rooms with a lot of sun or where you may want them cooler such as bedrooms.

The only thing a second boiler would do for you is to shorten the warm-up time and give you a spare should one go down.

The boiler should be sized to a calculated heat loss only.