McDonnell & Miller 250-3/4-125 Valve

For veteran contractors managing high-demand hydronic systems, the McDonnell & Miller 250-3/4-125 Valve (Part Number 181825) is a critical safety component designed for over-pressure protection in large-scale boilers and pressure vessels. Built to meet the stringent requirements of ASME Boiler and Pressure Vessel Code, Section IV, this relief valve is engineered with a durable bronze body and seat to handle aggressive water conditions. It features a precise 125 PSI pressure set point and an exceptionally high discharge capacity of 2,535,000 BTU/hr, making it a reliable choice for commercial heating applications and large storage tanks.

The McDonnell & Miller 181825 utilizes an EPDM rubber diaphragm and seat disc to ensure a tight seal and consistent operation. A key technical advantage for technicians is its low differential pressure—only 3 PSI between opening and closing—which significantly minimizes hammering with flash steam and protects the system's structural integrity. With a 3/4" NPT threaded connection and a maximum operating temperature of 250°F, this ASME safety relief valve provides the heavy-duty performance required for complex hydronic heating systems where system failure is not an option.

• High BTU Capacity: Rated for 2,535,000 BTU/hr to support large commercial boilers and unfired pressure vessels.
• ASME Section IV Certified: Manufactured and tested to comply with industry-standard safety codes for pressure vessels.
• Reduced System Stress: Specifically engineered to minimize water hammer and vibration during discharge cycles.
• Durable Construction: Bronze body and EPDM soft goods provide long-term resistance to fouling and thermal fatigue.
• Reliable Reseating: Low 3 PSI differential ensures the valve closes efficiently once pressure is stabilized.

What is the maximum temperature rating for the McDonnell & Miller 181825?
This valve is rated for a maximum operating temperature of 250°F (121°C), making it suitable for high-temperature hydronic applications.

Can this relief valve be used for steam boiler applications?
The Series 250 is primarily designed for hot water heating systems and storage tanks. Always verify your specific boiler's requirements against the ASME Section IV parameters.

How does the low differential pressure benefit the installation?
The 3 PSI differential prevents the valve from "chattering" or cycling too rapidly, which protects the piping and reduces wear on the valve seat.

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.