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Pressure and Temperature gauge on hot water or hydronic heating boilers: this gauge displays the heating boiler internal pressure and temperature.
Typical pressure for a residential boiler serving a two story home would show 12 psi cold, and less than 30 psi hot. Over 30 psi boiler pressure will cause the pressure relief valve to open.
Typical operating temperature settings on a boiler call for a Low temperature (boiler cut-in) between 120 and 160 °F.
Typical operating temperatures on a hydronic boiler call for a high temperature (boiler cuts off) of 180-200 °F.
Over 200 degrees F. we're at risk of spilling at the pressure temperature relief valve.
Typical operating temperature observed at the gauge will be below the high, and can be as low as nighttime room temperature in non-heating season if no tankless coil is in use.
The temperature/pressure gauge may help in checking for normal conditions before and during boiler operation.
However the boiler pressure or temperature gauge can be wrong!
This boiler pressure and temperature gauge shows a typical in-boiler pressure of under 20 psi, and a temperature of about 190 °F. (The boiler had just cut off on a heating cycle.)