McDonnell & Miller 339800 Arm Assembly

The McDonnell & Miller 339800 is a precision-engineered SA25-5 Arm Assembly specifically designed for the 25A Series make-up water feeders. As a veteran technician knows, maintaining the mechanical linkage between the float and the valve assembly is critical for ensuring accurate water level regulation in residential and commercial boiler systems. This replacement float arm serves as a direct OEM component for Series 25-A controls, restoring the necessary leverage and stroke to the valve mechanism. Constructed with industrial-grade materials, the MM339800 is built to withstand the constant cycling and thermal stresses inherent in hydronic heating applications. By utilizing this genuine McDonnell & Miller arm assembly, contractors can ensure seamless float arm compatibility and prevent the diagnostic errors or improper feeding issues associated with worn or aftermarket linkages. Whether you are performing routine maintenance or a full system overhaul, this assembly is the standard for maintaining the integrity of boiler water level controls.

• Direct OEM Replacement: Engineered specifically for the 25A Series to ensure perfect mechanical alignment.
• Industrial-Grade Construction: Designed to resist corrosion and vibration in high-demand HVACR environments.
• Precision Calibration: Maintains the exact leverage ratio required for accurate make-up water feeder operation.
• Reduced Downtime: Simplified installation process allows for quick field swaps during service calls.

Is the SA25-5 compatible with other McDonnell & Miller series?
This specific arm assembly is engineered for the 25A Series; always verify your model number against the manufacturer’s service parts catalog to ensure proper fitment.

Does this assembly include the float or valve?
The 339800 is the arm assembly only. If your float or valve seat is compromised, those components must be sourced separately to restore full functionality.

What are the signs that a float arm assembly needs replacement?
Technicians should look for mechanical binding, significant corrosion at pivot points, or a bent profile that prevents the valve from seating or opening fully.

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.