Watts 0274428 3/4 In Bronze Boiler Pressure Relief Valve, 30 psi, Threaded Female Connections

The Watts 174A model 0274428 is factory set to relieve at 30 psi. That is the standard setting for a residential or light commercial hot water heating boiler, where the system operates below 30 psi. If your boiler nameplate lists a maximum allowable working pressure above 30 psi and you want the valve set higher, the 174A series covers a 30 to 150 psi range in other settings.

Both ends are 3/4 inch female NPT. Inlet and outlet are the same size, so it threads onto a 3/4 inch male tapping on the boiler and takes a 3/4 inch male-threaded discharge pipe on the outlet. No adapters or unions come with the valve, so plan on a close nipple at the boiler and pipe for the discharge line.

The 0274428 has a steam discharge capacity of 650,000 BTU per hour. Match that against the gross output (not input) on your boiler nameplate: the relief valve capacity must equal or exceed it. For most residential and small commercial hot water boilers 650,000 BTU/hr is well above the requirement. If your boiler output is higher, you need a larger capacity valve, not this one.

No on both counts. The 174A 0274428 is set for 30 psi on a hot water heating boiler. A low pressure steam boiler needs a steam safety valve set at 15 psi or less, and a potable water heater needs a T and P valve with a temperature probe. Use the 0274428 only where the spec calls for a pressure-only boiler relief valve.

Yes, it has a manual test lever. Maintenance staff can lift it to verify the valve is free and not seized with scale, which is the routine annual check on a boiler relief valve. Lift it only when the boiler is at normal operating temperature and have the discharge line piped to a safe termination first.

Bronze body. That is the standard material for boiler relief valves on closed hydronic loops, and it holds up to the hot water and mild dissolved oxygen you get in a heating system better than plated steel. The valve is made in the United States.