These limits separate heating boilers from power boilers, which carry stricter construction, inspection and attendance rules. Heating boilers serve space heating and domestic hot water in homes, schools, offices and hospitals, and include cast iron sectional, steel firetube, copper and condensing designs. In many jurisdictions they need periodic inspection but not a licensed operator on site.
It's a heating boiler, 15 psi max, so the low-pressure license covers it, the plant's high-pressure units are another story.
Low-pressure does not mean low risk; a 15 psi steam boiler holds enough energy to level a basement if it fails.
Also heard as
- low-pressure boiler
- Section IV boiler
Related terms
MAWP
Maximum allowable working pressure: the highest pressure a boiler is approved to operate at, stamped on its nameplate.
Safety valve
The spring-loaded valve on a steam boiler that pops fully open to vent steam before pressure exceeds the boiler's rating.
Relief valve
The pressure-relief valve on a hot water boiler, rated in Btu per hour and set at or below the boiler's maximum pressure.
Cast iron sectional boiler
A boiler built from cast iron sections joined in a row, used widely for residential and commercial heating.