Test an Overload Relay
This equipment operates at high voltages. Use extreme caution, observe all warnings,
and follow all safety procedures. Failure to observe safety precautions may result in
injury or death to personnel.
The overload relays are wired to the contactor output terminals. Verify that the contactors
are operating correctly before testing the overload relays.
1. Ensure the P-1 pump, P-3 pump, or P-4 pump, as applicable, has been switched on at the PLC and is
in a position to be operating.
2. Open the PLC enclosure and locate the overload relay (Figure 21, Item 42) to be tested.
3. Press the overload reset button (Figure 21, Item 43). If resetting the overload corrects the
malfunction, determine the cause of the overload.
4. Use a voltmeter to test for voltage between the two control terminals (Figure 21, Item 44) on the
relay. There should be 0 VAC between these two points. Test between each control terminal and
ground. There should be 120 VAC between each terminal and ground.
5. Use a voltmeter to test for voltage between the T-1 terminal (Figure 21, Item 45) on the contactor
(Figure 21, Item 37) and the L1 terminal (Figure 21, Item 46) on the relay (Figure 21, Item 42).
There should be 0 VAC between these two points.
6. Replace an inoperative overload relay.
7. Close the PLC enclosure and monitor for normal operation.