Gas Fitter Practice Test

What should the relief valve for a residential low-pressure hot water boiler system be set to?

1. 14.7 psia

2. 15 psia

3. 30 psig

4. 30 psia

The correct answer is: 30 psig

The relief valve for a residential low-pressure hot water boiler system is typically set to a pressure of 30 psig. This setting is established to ensure that the system can safely handle the expansion of water as it heats, preventing excessive pressure buildup that could lead to boiler failure or dangerous conditions. In a low-pressure system, the National Board of Boiler and Pressure Vessel Inspectors and industry standards generally dictate that relief valves should be designed to open at pressures that exceed the maximum allowable pressure of the system, which, for residential hot water boilers, often aligns with the 30 psig mark. Setting the relief valve to this pressure allows it to effectively relieve excess pressure, ensuring that the boiler can operate safely and efficiently without risking damage or hazards associated with overpressure situations.