McDonnell & Miller 310437 Float and Gasket

The McDonnell & Miller 310437 (Model Number FLT-51-05) is a high-precision replacement float and gasket kit engineered specifically for the Series 51 and Series 551-S mechanical water feeders. This kit is a critical component for maintaining the integrity of low water cut-off (LWCO) systems and ensuring accurate boiler water level control. Featuring a durable stainless steel float and a high-performance F-26 gasket (304200), this assembly is designed to withstand the thermal stresses of steam and hydronic heating applications. It provides direct compatibility for Series 51-2, 51S-2, and 3155 controls, addressing common failure points such as waterlogged floats or compromised flange seals that can lead to hazardous dry-fire conditions.

Installation of the FLT-51-05 float kit requires technical precision to ensure a leak-proof seal. Technicians should thoroughly clean the head casting and die-casting surfaces before seating the new gasket. When reassembling, utilize an alternating star pattern to torque the head bolts to the manufacturer-specified 35–40 ft./lbs. This HVAC replacement part is essential for contractors performing annual boiler maintenance or repairing combination water feeders where the existing float has lost buoyancy or the bellows engagement has drifted.

• Direct OEM Compatibility: Specifically sized for McDonnell & Miller 51 Series and 551-S make-up water feeders to ensure precise switch actuation.
• Complete Professional Kit: Includes the 310437 float and the required F-26 flange gasket for a comprehensive field repair.
• Optimized System Safety: Restores reliable liquid level control functionality, preventing short-cycling and protecting the heat exchanger from low-water events.
• Rugged Construction: Built to handle the corrosive environment of commercial steam boiler systems without premature degradation.

• Which specific McDonnell & Miller models use the 310437 kit? This kit is used with the Series 51, 51-2, 51-S, 51S-2, 551-S, and 3155 series controls.
• Does this include the bellows assembly? No, this kit includes the float ball and the flange gasket only. If the bellows are leaking, a separate BA-51-05 assembly may be required.
• How do I verify if my float needs replacement? If the float feels heavy or you hear liquid splashing inside, the seal has been compromised and it must be replaced to maintain proper buoyancy.

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.