Xylem-McDonnell & Miller 157S-M Combination Low Water Cut-Off & Pump Controller (175402)

Description

The Xylem-McDonnell & Miller 157S-M (Part Number 175402) is a combination low water cut-off and pump controller engineered to protect steam and hot water boilers from the hazards of low water conditions. Featuring a snap-acting manual reset SPDT (Single-Pole, Double-Throw) switch, this control provides reliable boiler protection by shutting down the burner when water drops below a safe operating level — and requires a deliberate manual reset before the system can resume operation, adding an important layer of safety accountability.

McDonnell & Miller, a trusted name in hydronic and steam boiler controls for over a century, designed the 157S-M for straightforward installation and dependable long-term performance in commercial and residential boiler applications.

Key Features

• Combination low water cut-off and pump controller in a single unit
• Snap-acting manual reset SPDT switch for positive, reliable switching action
• Manual reset design requires deliberate operator intervention before restart — enhancing boiler safety
• Float-operated mechanism provides accurate water level sensing
• Suitable for steam and hot water boiler applications
• Side-mounted installation for easy integration into boiler piping
• Durable cast iron body construction for long service life

Product Specifications

• Part Number: 175402
• SKU: 157S-M
• Switch Type: SPDT (Single-Pole, Double-Throw), Snap-Acting
• Reset Type: Manual Reset
• Function: Low Water Cut-Off / Pump Controller (Combination)
• Brand: Xylem-McDonnell & Miller

Applications

• Steam boilers requiring low water protection and pump control
• Hot water boilers in commercial and residential heating systems
• Hydronic heating systems requiring automatic pump sequencing
• Installations where manual reset capability is required by code or preference

Why Choose the McDonnell & Miller 157S-M?

The 157S-M combines two critical boiler safety functions — low water cut-off and pump control — into one compact, reliable unit. The snap-acting SPDT switch ensures clean, positive switching without hesitation, while the manual reset feature prevents automatic restart after a low water event, protecting both the boiler and building occupants. Backed by Xylem’s engineering expertise and McDonnell & Miller’s century-long legacy in boiler controls, this unit delivers the dependability that HVAC professionals and building engineers demand.