Checking Three Phase Line Voltage

Ensure the control panel disconnect is OFF.  Turn off all motor load circuit breakers (AB 140Ms), turn off all other circuit breakers, and pull open all fused terminal blocks.

Using a voltmeter or multimeter, check for short circuits to earth ground from each wire above and below the disconnect.  Then test for short circuits between each line above and below the disconnect. (L1-L2, L1-L3 and L2-L3).

Double-check to make sure the panel has an appropriately sized incoming earth ground wire.  Using the multimeter, check for conductivity for all ground points, the main metal enclosure, and the door.  This is for safety and must not be skipped.

Turn on the power feeder circuit to the control panel.

Measure the input line-to-line voltages at the top of the control panel disconnect and record. This is done by measuring between the three (3) combinations of input terminals. (L1-L2, L1-L3 and L2-L3).

Incoming Voltages L1-L2                  _, L1-L3                   , L2-L3________

Turn on the control panel rotary disconnect with the panel door closed and latched.  Now open the powered-up panel using the small pinhole release button on the side of the disconnect handle.

Measure the input line-to-line voltages at the bottom of the control panel disconnect and record. This is done by measuring between the three (3) combinations of input terminals. (L1-L2, L1-L3 and L2-L3).

Feeder Voltages L1-L2                     _, L1-L3                   , L2-L3________

Turn on one 140M circuit breaker at a time.  If powering a VFD, make sure the VFD powers on.  Then power on each circuit breaker one at a time, ensuring after that the correct circuit powers on.  If the voltage steps down to 120VAC or 24VDC, check the correct voltage readings directly passed the transformer or power supply with a voltmeter or multimeter.

Push in each fused terminal block one at a time, ensuring the correct devices power up, respectively.

Actuate each output and flag each input one and a time, verifying the field wiring and device are working correctly (if possible).

You can now start your control panel and loads.

Note – If any load motor rotates backwards, switch any two (2) connections at the load (ensure you follow lockout-tagout rules supplied by your company or safety director).