This report just in from the Stray Voltage Patrol…. It describes an SVP member feeling a shock from the call box at the campground gate. This was an extremely dangerous situation that was identified and reported by an SVP member before anyone was injured or killed.
Describe what you discovered:
When I came through the gate and touched the call box, I felt a good shock. I pressed the call button, it was OK. Went back to RV and got my NCVT and went back to check. Box was hot (stray voltage). Reported it to night security.
Campground response to your report:
Security guard immediately called maintenance person. He told me that gate had been worked on Tuesday 9/11. He thanked me for reporting problem.
SVP Badge #22
Why did this happen?
Well, everything metal that is in any way connected to electrical power is supposed to be bonded (grounded) to the incoming ground wire (the EGC or Equipment Grounding Conductor) at the service panel. That’s to ensure that any accidental contact of the metal object to a hot wire won’t create a hot-skin/stray-voltage condition.
There have been a few recent electrocutions (deaths by electrical shock) of high school students touching the chain link fence at a football field. An extension cord had been wrapped around the fence and the cord insulation worn through enough to allow contact of the hot wire with the metal of the fence. That was a deadly condition since a student standing on the damp ground and touching the now-electrified fence created a fault current path though their own body, which was enough to kill them. Touching anything electrified while you’re standing on the ground is a recipe for electrocution.
In the case of the campground call box that was found with a stray voltage, the box must not have been properly bonded to the incoming ground wire, which allowed the metal box to develop a stray voltage. The NFPA 70 (National Electrical Code) requires that any outlet or control boxes are bonded to the ground wire, for exactly this type of scenario. Then if there’s any internal contact between the electrical power hot wire and the metal of the box, the EGC ground wire will create a large fault current back to the neutral bonding point in the incoming electrical service panel, which will trip the circuit breaker quickly.
Note that simply “earthing” the fence or call button box via a ground rod or fence post is not an actual “neutral-ground bond” since its impedance to earth will be too high to create a fault current of high enough amperage to trip the circuit breaker feeding it.
This was a great save by SVP Badge #22 (you know who you are). That’s because the next person stopping by to push the button might have been standing in a puddle of water with wet hands. If that was the case, then they could have been electrocuted and I would be writing a very different kind of article.
Again, as I’ve written hundreds of times before in this newsletter and dozens of other forums – NEVER ACCEPT FEELING A SHOCK! If you do feel even a tingle, that means that the electrical grounding system has somehow failed and there’s a stray voltage on the item you’re touching. And the next time you or someone else touches it with wet hands and feet, instead of a tingle it could be a deadly shock. So report all such incidents immediately and make sure they’re followed up on.
So this week, SVP Badge #22 gets my Hero of the Day award. Well done!
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.