Each section is a hollow casting with water passages and flue passages; sections are joined by push nipples or gaskets and pulled together with tie rods, so size is set by section count and they can be carried down a basement stair in pieces. Cast iron resists corrosion well but cracks under thermal shock, and non-condensing models need return water kept hot enough, usually above about 130 degrees F on gas, so flue gas does not condense inside them.
Cast iron sectional boiler, seven sections, number three's cracked and leaking onto the burners.
Also heard as
- sectional boiler
- cast iron boiler
- CI boiler
Related terms
Heating boiler
A low-pressure boiler limited to 15 psi steam, or to 160 psi and 250 degrees F for hot water.
Thermal shock
Damaging stress from a sudden temperature change in boiler metal, such as cold water hitting hot iron.
Condensing boiler
A boiler designed to cool flue gas below its dew point so water vapor condenses and gives up its latent heat.
Sweating
Flue gas moisture condensing on the cold fireside of a boiler during startup and dripping into the combustion chamber.