Application Note

The contactor is the primary controller in a cooling

controls circuit. It is the switching device which activates

the compressor motor to pump refrigerant through the

system to provide cooling.

Contactors are used to break the power supply to the

compressor. Either 1 or 2 poles are needed for single

phase; 2 or 3 poles for 3 phase motors. Auxiliary

contacts may be used for interlock switching, fan loads

or crankcase heaters. If the contactor is selected with    

an adequate current rating, the condenser fan may also

be wired in parallel with the compressor. Then the

condenser fan is energized whenever the compressor

is powered.

• Check contactor operation by switching the

contactor from the system controls.

• Make sure that the pressure and overload controls

can break the system circuit to prevent contactor

operation, if necessary.

• Check electrical conductance of the contacts.

• Check the voltage source to the coil.