Built in the 50's, nameplate is wore out, I do have install manual MN. ou-2650. It apprears to have been manufactered by US Radiator Corporation. Any help is appreciated.
Rule of thumb. Count the burners, each burner equals 20,000 BTU's. But don't tell anyone that's an old trade secret.
u either have to clock the gas meter or measure the main burner orifice's along with the gas pressure,,this is something that a tech would normally do,,if u are looking to replace the boiler u would have to do a heat loss on the house and that would tell u what size boiler u would need
