Description
The Xylem-McDonnell & Miller 157S-MD is a heavy-duty combination low water cut-off and pump controller engineered to protect steam and hot water boilers from dangerous low-water conditions while simultaneously managing pump operation. Trusted by hydronic and steam heating professionals, this unit delivers reliable, code-compliant boiler protection in a single, compact device.
Product Overview
The 157S-MD integrates two critical boiler safety functions — low water cut-off protection and pump control — into one rugged assembly. The snap-acting SPDT (Single-Pole, Double-Throw) switch provides crisp, positive switching action for dependable cut-off response, while the maximum differential operation feature ensures the pump and burner circuits respond accurately to water level changes, reducing short-cycling and extending equipment life.
Key Features
- Combination low water cut-off and pump controller in a single unit
- Snap-acting SPDT switch for positive, reliable circuit switching
- Maximum differential operation minimizes short-cycling of burner and pump
- Designed for steam and hot water boiler applications
- Compact, integrated design simplifies installation and reduces wiring complexity
- Built to McDonnell & Miller’s industry-leading quality standards
- Part Number: 175412
Application
The 157S-MD is ideal for residential and light commercial boiler systems where both low water protection and pump control are required. By combining these functions, it reduces the number of components needed on the boiler, streamlines wiring, and ensures that the burner shuts down safely whenever water drops below the minimum safe operating level.
Why Choose McDonnell & Miller
McDonnell & Miller, a brand of Xylem, has been the industry standard in boiler water level controls for over a century. The 157S-MD continues that legacy with proven float-operated technology, durable construction, and dependable performance in demanding heating system environments.
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