Skip navigation

Electrical Troubleshooting Quiz

Your facility has an outbuilding for security personnel (the guard shack)

Your facility has an outbuilding for security personnel (the guard shack). Though small, the guard shack has utilities run to it, including power and water. All incoming vehicles are stopped here at an electrically operated gate that only the guards can open. The guards check ID, enter the visitor information into the security system (shared via wireless LAN with the front desk and others), and issue visitor badges.

Last fall, the guards would occasionally complain about "static electricity," and now the complaints are more frequent and more severe. Instead of "static electricity," they speak of receiving an electrical shock.

What should you do to troubleshoot this problem?

Your first step is to look at the electrical supply to this building. Is it a subpanel? A common error with subpanels is to treat them as services. In fact, they are loads.

Instead of grounding a subpanel, bond its "grounding" bus to the main bonding jumper so undesired current has a low impedance path back to the source. The earth isn't a low impedance path; don't ground equipment on the load side. Load side grounding doesn't reduce touch potential, but it does create ground loops that circulate undesired current instead of providing it with a path back to the source.

If the shock problem is due to difference of potential, bonding per Art. 250, Part V will solve it. Cable leakage is another possibility, so conduct insulation resistance tests on the conductors entering the shack's panel.

TAGS: content
Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.