When Circuit Boards are Toast, Part 10

Previously, we said a neutral-ground (N-G) bond might be upstream of the receptacle where measurements indicate the existence of the bond. We also said that if you didn't find it at the supply panel to check the other equipment on that panel. Fixing this in an efficient manner will require some scheduled downtime. Using the panel directory, you can probably identify the connected loads; however, verify with current drawings. Then, ensure the wiring for each circuit is properly and accurately labeled.

Arrange to do the work when production shuts down for lunch, between shifts, or at some other time the affected production manager agrees will minimize interruption of production. The amount of time required will depend on how many circuits are on that panel.

You will need two people: one at the receptacle to measure N-G, and one at the panel to disconnect and reconnect loads.

  1. Open each breaker, and then open the panel main.
  2. Disconnect the wiring at each breaker except the one supplying the control panel receptacle.
  3. Connect one circuit, close the breaker. Close the main. Note whether measurement at the control pane receptacle shows an N-G bond or not.
  4. Disconnect. Open the breaker. Repeat this and the preceding step for all other breakers.
  5. Reconnect all breakers. Close them one at a time.
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