McDonnell & Miller 42S Boiler Low Water Cut-Off/Pump Controller

The McDonnell & Miller 42S Boiler Low Water Cut-Off/Pump Controller is a trusted boiler low water cutoff and pump controller designed to protect boilers from dry firing and brittle operation.

This versatile unit combines protective low-water control with pump management for steam and water media across residential, commercial, and industrial applications. It features a 1 inch threaded port for easy integration, a SPST snap action switch for precise signaling, and broad electrical compatibility, including 120/240 VAC inputs up to 345 VA. The 42S supports a wide range of operating currents and includes a dedicated alarm circuit for safety. Built to meet safety standards (UL, CSA, FM), it delivers reliable performance in demanding environments with a 50 PSI pressure rating.

• Port Connection: 1 inch threaded
• Switch Type: SPST Snap Action
• Dimensions: 12-1/4 in W x 8-7/8 in H
• Current Rating (Full Load): 7.4 A @ 120 V; 3.7 A @ 240 V
• Locked Rotor Current: 44.4 A @ 120 V; 22.2 A @ 240 V
• Alarm Circuit: 1 A @ 120 V; 1/2 A @ 240 V
• Input Supply Rating: 120/240 VAC, 345 VA
• Media Handled: Steam, Water
• Applications: Residential, Commercial, Industrial
• Standards: UL, CSA, FM
• Pressure Rating: 50 PSI