What kinds of power issues can cause electronic loads to fail, and how can you find them at the distribution panel? Using your DMM, you can find two common culprits. Measure the phase-to-neutral voltages on the supply side of the panel. You are looking for:

  • Correct nominal voltage. Consult IEEE Recommended Practice for Electric Power Distribution for Industrial Plants (IEEE Red Book) for specific allowable voltage ranges.
  • Voltage balance. If the difference between any two measurements exceeds 2%, you have voltage imbalance. This causes premature motor failure and other problems.

If either problem exists, check at your service panels to start narrowing down the source of the problem. Now, repeat these measurements on the load side of each branch circuit breaker. If the problems exist on some circuits but not others, address the loads on the problem circuits.