The Series 150 and 150S controls and their various models are float actuated controls that make or break contacts as the water level in the boiler moves up or down. They can be used on boilers of any pressure (150psi maximum) and steaming capacity.

Snap switch versions were introduced in September 1996 because mercury is becoming more expensive each year and is considered an environmentally hazardous material. Current suppliers of mercury switches are indicating they want to cease production in the future, so McDonnell & Miller must be prepared for that eventuality. Mercury switch units will continue to be built for the foreseeable future.

A reliable and rugged control, the 150 has been the mainstay of McDonnell & Miller’s product family for almost 50 years.