Watts 0382820 Relief Valve

The Watts 0382820 (Model 740-1-50) is a high-capacity boiler pressure relief valve engineered specifically for large-scale commercial and industrial hot water heating systems. Designed with a 1-inch NPT inlet and outlet, this valve provides a fixed pressure setting of 50 PSI and features a massive steam discharge capacity of 1,899,000 BTU/hr. This model serves as a direct cross-reference for the Weil-McLain 511-546-950 and is frequently utilized in high-output hydronic installations where ASME Section IV compliance is mandatory. The expanded diaphragm construction prevents the spring and mechanical components from coming into contact with the media, effectively reducing the risk of corrosion and mineral buildup. For contractors performing retrofits or emergency maintenance, this ASME relief valve ensures reliable overpressure protection by utilizing a silicone disc for tight seating and a stainless steel spring for consistent set-point accuracy under thermal stress.

• High BTU Rating: Certified discharge capacity of 1,899,000 BTU/hr, suitable for high-demand commercial boilers.
• Superior Construction: Features a bronze body and EPDM diaphragm to isolate the internal spring from water-borne contaminants.
• Drop-in Replacement: Verified identical to Watts 382820 and Weil-McLain 511-546-950 for simplified field inventory.
• Wide Temperature Range: Rated for system temperatures up to 250°F (121°C) to handle extreme hydronic environments.
• Non-Stick Design: Incorporates a silicone seat to prevent the valve from sticking during long periods of inactivity.

What is the difference between the Watts 740 and 174A series?
The 740 series, including the 740-1-50, is designed for much higher BTU capacities than the 174A series. While both are used for hot water heating, the 740 series is the standard for heavy commercial boilers requiring massive discharge rates.

Is this relief valve compatible with glycol systems?
Yes, the EPDM and silicone internal components are compatible with standard propylene and ethylene glycol mixtures commonly found in closed-loop hydronic systems.

When should the 0382820 be replaced on a commercial boiler?
If you observe "weeping" at the atmospheric discharge or if the valve fails a manual lift test during annual inspections, the valve should be replaced to maintain HVAC safety compliance and prevent system pressure spikes.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.