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McDonnell & Miller

Low Water Cut-Offs

McDonnell & Miller Low Water cut-offs are specially designed to protect steam and hot water boilers from the hazards of a low-water condition. In operation, they will interrupt the electrical current to the firing device if the water in the system drops below the boiler manufacturer’s minimum safe water level. Our low-water cut-offs also provide an additional circuit for a low-water alarm, should you desire to install one, for additional protection.

Water Feeders

McDonnell & Miller Boiler Water Feeders and Feeder Cut-Off Combinations are used to provide automatic operation, and to safeguard steam and hot water boilers against the hazards of a low-water condition. A feeder cut-off combination mechanically adds water as needed to maintain the required minimum water level, and electrically stops the firing device in case of an emergency.


The McDonnell & Miller line of boiler controls includes Test-N-Check valves and pressure-relief valves. Test-N-Check valves restrict water flow when the low-water cut-off’s blow-down valve is open. Pressure-relief valves protect against over pressure.

Flow Switches

Flow switches can make or break an electrical circuit when flow starts or when flow stops, and can be used to:

  • Actuate a signal when flow stops
  • Start a motor with flow
  • Shut off an alarm when flow is adequate
  • Stop a motor with no flow.  

McDonnell & Miller flow switches are equipped with either one or two SPDT switches. Liquid flow switches are for use on pipe sizes 1/2″ to 36″ NPT and air-flow switches are for installation in ducts 6″ or larger.