McDonnell & Miller 51-S Feeder

The McDonnell & Miller 51-S (Part Number 135600) is a heavy-duty mechanical water feeder designed specifically for high capacity steam and hot water boilers. Engineered for systems with a maximum vessel pressure of 35 PSI and a maximum water supply pressure of 100 PSI, this unit provides a reliable proportional feed action to maintain optimal water levels without the hunting common in electronic setups. It features 1" NPT connections for high-flow requirements and is typically utilized in commercial or industrial applications where cold water makeup is necessary. This float-operated feeder ensures continuous protection against low water conditions, making it a staple for contractors maintaining large-scale hydronic systems. The 51-S mechanical feeder is built for durability in demanding environments, offering a robust alternative to standard residential feeders when high-volume makeup water is required to keep the boiler operating within safe parameters.

• High-Capacity Performance: Optimized for boilers up to 35,000 sq. ft., providing the flow rate necessary for large commercial steam systems.
• Proportional Feed Action: Delivers precise water makeup by matching the feed rate to the boiler's actual demand, reducing thermal shock.
• Rugged Mechanical Reliability: The float-style mechanism operates without complex electronics, ensuring functional consistency in high-temperature environments.
• Standard 1" NPT Ports: Large diameter threaded connections simplify installation on high-flow equalization lines and water supply headers.
• Field Upgradeable: Compatible with optional No. 2 switches to add low water cut-off (LWCO) functionality if system requirements evolve.

Common Questions

If the valve remains open, first perform a broken union test. Debris or scale often becomes lodged in the valve seat or cartridge. Shut off the water supply, isolate the feeder, and inspect the internal strainer and valve assembly for sediment. Cleaning the cartridge usually restores the seal.

No, the McDonnell & Miller 135600 is strictly rated for low-pressure applications. The maximum vessel pressure is limited to 35 PSI. For high-pressure systems, you must select a feeder rated for the specific operating pressure of your vessel.

The standard 51-S is a mechanical water feeder only. While it can be field-configured with a No. 2 switch to provide LWCO protection, the base 135600 model focuses primarily on water level maintenance and proportional bypass feeding.

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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.