Description
Overview
The Xylem-McDonnell & Miller 150S-M-MD-HD is a combination low water cut-off and pump controller engineered for reliable boiler protection in steam heating systems. This head mechanism-only unit features a snap-acting manual reset SPDT (Single-Pole, Double-Throw) switch with maximum differential operation, providing precise water level control and automatic pump management to safeguard boilers from dangerous low-water conditions.
Key Features
- Combination low water cut-off and pump controller in a single unit
- Snap-acting SPDT switch for reliable, positive switching action
- Manual reset design — requires deliberate operator reset after a low-water event for added safety
- Maximum differential operation for optimized pump cycling and water level control
- Head mechanism only — designed for installation on compatible McDonnell & Miller bodies
- Trusted McDonnell & Miller engineering backed by Xylem quality standards
How It Works
The 150S-M-MD-HD monitors boiler water level continuously. When water drops below the safe operating level, the snap-acting SPDT switch opens the burner circuit and shuts down the boiler. The manual reset feature prevents automatic restart, requiring a technician to inspect and resolve the root cause before returning the system to service. The pump controller function cycles the feed pump to maintain proper water levels within the maximum differential range, reducing short-cycling and extending equipment life.
Applications
- Steam boilers in commercial and residential heating systems
- Hydronic and steam heating applications requiring low water protection
- Boiler rooms requiring code-compliant low water cut-off protection
- Replacement head mechanism for compatible McDonnell & Miller 150S-series bodies
Why Choose the 150S-M-MD-HD
McDonnell & Miller, a brand under Xylem, has been the industry standard in boiler low water cut-off protection for decades. The 150S-M-MD-HD delivers the combination of pump control and burner safety in one compact head mechanism, simplifying installation and reducing the number of components required. The manual reset SPDT switch ensures that no low-water event goes unaddressed, protecting your boiler investment and maintaining system safety compliance.
