McDonnell & Miller 157S-RBP-MD Combination Low Water Cut-Off & Pump Controller

The McDonnell & Miller 157S-RBP-MD (Part Number 176503) is a heavy-duty combination low water cut-off and pump controller engineered for reliable boiler protection and pump management in steam and hot water heating systems. Designed with advanced conductance-based sensing technology, this unit delivers precise water level detection and automatic pump control in a single, integrated package — reducing installation complexity and improving system reliability.

Key Features

• Combination low water cut-off and pump controller in one unit
• Snap acting SPDT (Single-Pole, Double-Throw) switch for positive, reliable switching action
• Maximum differential operation for optimized pump cycling and water level control
• Alternate tappings for flexible installation and piping configurations
• 2 integral conductance probes for accurate, dependable water level sensing
• RBP (Remote Blow-down Probe) design for easy maintenance and system servicing
• MD (Maximum Differential) configuration for extended pump run cycles

Product Benefits

• Protects boilers from low water damage by cutting off burner operation when water drops below safe levels
• Automates pump operation to maintain proper water levels without manual intervention
• Conductance probe technology eliminates mechanical float components, reducing wear and maintenance
• Alternate tappings provide installation versatility for a wide range of boiler configurations
• Snap acting switch ensures fast, decisive response to changing water level conditions

Applications

• Steam boiler low water protection
• Hot water boiler pump control
• Commercial and industrial hydronic heating systems
• Boiler rooms requiring combined cut-off and pump management in a single device

Product Details

• Brand: McDonnell & Miller (Xylem)
• Model: 157S-RBP-MD
• Part Number: 176503
• Switch Type: Snap Acting SPDT
• Operation: Maximum Differential
• Tappings: Alternate
• Probes: 2 Integral Conductance Probes