McDonnell & Miller 150S-HD Controller

The McDonnell & Miller 150S-HD (Part Number 173003) is a heavy-duty combination low water cut-off and pump controller head mechanism designed for industrial and commercial steam boiler applications. Operating at a maximum steam pressure of 150 PSI (10.5 kg/cm²), this unit serves as a precision-engineered OEM replacement head to restore critical water level management without replacing the entire float housing. This 150S series model utilizes a snap-acting SPDT switch mechanism to prevent rapid cycling and ensure positive electrical contact for both burner shut-off and feedwater pump activation. Forged for durability in high-temperature environments, the assembly features Monel bellows for superior corrosion resistance and a long service life under fluctuating thermal loads. Whether you are maintaining a process steam line or a primary heating plant, the 150S-HD head mechanism provides the reliable dual-terminal control required to protect equipment from dry-fire conditions while maintaining optimal operating levels.

Technical Benefits for Contractors

• Direct OEM Replacement: Seamlessly installs onto existing McDonnell & Miller 150 Series float chambers (Part #173003).
• Snap-Acting Contacts: High-quality SPDT switches eliminate terminal arcing and provide distinct signals for low water alarms and pump start/stop.
• Rigid Construction: Built with Monel bellows and high-performance internals to withstand corrosive condensate and high-pressure steam.
• Mechanical Reliability: Professional-grade weight and balance ensure the float-operated low water cut-off responds accurately to water level shifts.
• Versatile Application: Suitable for steam boilers, tanks, and receivers in commercial and industrial facilities.

Common Questions

Is this the complete unit or just the head mechanism?
This is the head mechanism only. It is designed to be bolted onto your existing housing, saving labor and material costs when the float chamber is still in good condition.

What is the difference between the 150 and 150S-HD?
The "S" designation refers to the snap-acting switch mechanism, which is more resistant to vibration and provides more reliable switching than older mercury-style or slow-moving versions.

Can I use this for a 150 PSI application?
Yes, the McDonnell & Miller 150S-HD is specifically rated for a maximum steam pressure of 150 PSI.

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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.