McDonnell & Miller 21 Water Feeder

The McDonnell & Miller Series 21 Water Feeder (Part Number 126400) is a heavy-duty, float-operated make-up water feeder engineered specifically for boiler receiver tanks and condensate return systems. This mechanical unit facilitates proportional feed action, ensuring a consistent water level without the abrupt surges associated with solenoid-based systems. By utilizing a direct-mount design with a 6-bolt 5 3/4" bolt circle, this feeder installs directly onto the tank flange, eliminating the need for complex equalizing connections and reducing potential leak points in the boiler feed system.

Constructed with a robust soft-seat valve and an integral strainer, the Series 21 provides a positive seal against supply pressures up to 150 PSI. It is rated for a maximum vessel pressure of 35 PSI and an inlet water temperature of 120°F. For contractors and technicians, the 3/4" NPT threaded connection and 4-3/4" copper float ensure long-term reliability in commercial and industrial steam boiler applications where accurate water inventory is critical for pump protection and system stability.

Key Benefits for the Contractor

• Simplified Installation: The direct-mount flange allows for mounting at the 1/3 level of the tank with no external equalizing lines required.
• Enhanced Sealing: Features a high-grade soft seat and elastomer sealing disc to prevent "creeping" water levels and ensure closure against high supply pressure.
• Debris Protection: Includes an integrated strainer assembly with a removable drainage plug for easy maintenance and protection of the internal valve components.
• Durable Construction: Built with brass and stainless steel internal components to resist corrosion in harsh condensate environments.
• Reliable Water Control: The proportional feed mechanism gradually adds water to match system demand, maintaining optimal boiler water level stability.

Common Questions

Can the Series 21 be used on high-pressure steam boilers?
While the water supply pressure can reach 150 PSI, the vessel (tank) pressure must not exceed 35 PSI. This unit is specifically designed for receiver tanks, not high-pressure boiler shells.

Does this unit require an electrical connection?
No, the McDonnell & Miller 126400 is an entirely mechanical, float-operated feeder and does not require a power source or low water cut-off signal to operate.

How do I service the internal strainer?
The strainer housing is located at the inlet and features a removable plug. Periodic maintenance involves closing the water supply and clearing the basket to prevent flow restrictions.

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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.