McDonnell & Miller 150S-M-MD-HD HEAD

The McDonnell & Miller 150S-M-MD-HD serves as a direct replacement low water cut-off head assembly for the 150S series combination pump controllers. Designed specifically for high-pressure steam boiler applications, this heavy-duty unit manages a maximum operating pressure of 150 psi (10.5 kg/cm²). This specific model features a manual reset mechanism, which is critical for meeting safety codes in commercial boiler rooms where a manual restart is required following a low water condition. The internal switch mechanism utilizes high-quality mercury-free snap switches to ensure precise electrical contact and long-term reliability in high-vibration environments. When replacing the head assembly on a 150S-M-MD, you are restoring the primary pump control and low water cut-off functions without needing to pull the entire body from the piping, significantly reducing downtime. Technical specifications remain consistent with McDonnell & Miller 172810 factory standards, ensuring exact bolt-on compatibility and seamless integration with existing float chambers.

Key Benefits for Contractors

• Direct OEM Replacement: The 172810 head assembly drops directly onto existing 150S series bodies for efficient field repairs.
• Manual Reset Safety: Integrated manual reset button prevents automatic boiler firing until a technician can verify water levels.
• Mercury-Free Switches: Features updated snap-action switches for consistent differential control and reliable high-voltage switching.
• High-Pressure Rating: Engineered to withstand steam boiler pressures up to 150 psi, ideal for commercial and industrial process steam.
• Streamlined Maintenance: Replacing only the low water cut-off head preserves the integrity of the original float chamber piping.

Common Technical Questions

How do I test the manual reset function on the 150S-M-MD-HD?
After a low water condition is simulated or occurs, the water level must be restored to the "Normal" operating range before the manual reset button on the head assembly can be depressed to restore power to the burner circuit.

Is the 150S-M-MD-HD head compatible with non-MD bodies?
This head is specifically designed for the MD (Maximum Durability) series. While many McDonnell & Miller components share footprints, always verify the specific pump controller replacement part number to ensure the internal float linkages align correctly.

Does this assembly include the gasket?
Standard replacement heads typically require a new head gasket to ensure a steam-tight seal; it is best practice to replace the gasket whenever the head assembly is removed from the bowl.

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.