Contactor Coils and Long Control Circuit Cable Runs

In the last issue we spoke of contactor coil characteristics and how both high and low voltage could cause coil burn-out. We also described how a typical three-phase pump panel and a Franklin deluxe control box have both a main power circuit and a separate control circuit.

In this issue we will discuss circumstances which can result in contactor coil burn-out or the failure of the contactor to dropout (shut off the motor) even though the control switch has opened. The Figure to the right shows a contactor and control circuit for a single-phase unit, although this condition could affect either a single- or three-phase contactor. Note that in the example there is more than 300 feet of wire between the contactor and the control circuit switch. Again the control switch could be a pressure switch, float switch, time clock, or other control device(s). Continue reading