Mcdonnell & Miller 260-1 1/2-30 Valve

The McDonnell & Miller 260-1 1/2-30 Valve (Part 182625) is a heavy-duty, diaphragm-operated relief valve engineered for large-scale hydronic heating systems and water storage tanks. Designed to meet the stringent requirements of ASME Boiler and Pressure Vessel Code Section IV, this valve features a robust cast iron body and a high-grade brass seat for reliable overpressure protection. With a factory-set relief pressure of 30 PSI and a high-capacity rating of 3,300,000 BTU/hr, it is purpose-built to handle thermal expansion and prevent critical failure in commercial boiler loops. The oversized diaphragm provides significant operating force to ensure positive opening even under fouling conditions, while the sealed spring chamber prevents sediment accumulation from interfering with the mechanical action. For professional contractors, the 1 1/2" NPT inlet and 2" NPT discharge configuration facilitates high-volume relief flow, effectively minimizing system hammering and protecting downstream components from excessive pressure spikes.

Key Benefits:

• ASME Section IV Certified: Ensures full compliance for commercial hot water boiler safety and pressure vessel protection.
• 3.3 Million BTU/hr Rating: Provides high-volume pressure relief capacity suitable for large-capacity hydronic systems.
• Anti-Clog Design: The sealed spring chamber protects the internal mechanism from scale and mineral buildup.
• Optimized Flow: Features a 2" NPT discharge to reduce backpressure and ensure rapid venting during overpressure conditions.
• High-Temperature Durability: Rated for system temperatures up to 250°F, maintaining integrity in high-demand heating applications.

Common Questions:

For optimal system safety, the 30 PSI relief valve should be manually tested by lifting the lever every 30 days during the heating season to ensure the seat is not seized and the discharge path is clear.

No, the Series 260 pressure relief valve must be installed in a vertical, upright position with the stem at the top to ensure the diaphragm and spring mechanism function according to technical specifications.

Continuous dripping is typically caused by sediment trapped on the brass seat or a thermal expansion tank that has lost its air charge, forcing the McDonnell & Miller safety valve to vent as system pressure approaches its 30 PSI limit.

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.