Courtesy of Tony Moscioni: (Canada)
Trade Safety Advisory


Manual motor controllers have been installed as disconnect switches on rooftop-type air-conditioning units and for other applications. Used as disconnect switches, some manual motor controllers may expose workers to electric shock.

Some manual motor controllers may look like proper disconnects, but have not been certified to a CSA standard as a "disconnect device." Such switches are certified for stop/start operation only and when used as a "disconnect device" could fail, leaving one or more phases live after the switch is opened.

Some manual motor controller switches have also been found installed backwards, causing power to be ON when the switch enclosure indicates OFF.

Manual motor controllers installed as disconnect switches on rooftop air-conditioning units should be replaced with an approved disconnect device certified by CSA International or another accredited certification body. In future, controllers marked as "suitable for motor disconnect" will be available.

Before starting work on electrical components, always lock out (and tag) the power supply using a CSA-certified disconnect device. Then test for power to ensure that components are de-energized.

Refrigeration/Air-Conditioning Trade and ECAO/IBEW Electrical Trade Labour-Management Health and Safety Committees

Electrical Safety Authority [ESA]

CSA International, 178 Rexdale Blvd., Toronto, Ontario M9W 1R3

Construction Safety Association of Ontario, 1-800-781-2726 [CSAO]