Maximum allowable working pressure. It is set by the design and construction code and the inspector's certificate, and the safety or relief valve must be set at or below it. Heating boilers have an MAWP of 15 psi on steam, and residential hot water boilers typically carry a 30 psi relief valve even when their MAWP is higher.
Nameplate says 30 psi MAWP and somebody put a 50 pound relief valve on it, that comes off before we fire it.
Also heard as
- maximum allowable working pressure
Related terms
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.
Heating boiler
A low-pressure boiler limited to 15 psi steam, or to 160 psi and 250 degrees F for hot water.
High limit
A safety control that shuts down the burner if pressure or temperature rises above the normal operating range.