A few days ago I received this post about a campground pedestal on my RVelectricity Facebook group, which was a real eye-opener for me and my gang of moderators and administrators.
We pulled into a sold-out campground last night after a long day of driving. Started getting set up, grabbed the multimeter to check power, got some interesting measurements:
G>L1 = 143v / G>L2 = 93v / G>N = 22v
N>L1 = 120v / N>L2 = 118v / N>G = 22v
L1>L2 = 238v
Called up to the park office to inform them. They sent someone over to check it out. While waiting, I took the time to double-check my cable and wiring in the RV to brace for the initial blame shift that tends to happen in these situations. Everything checked out.
Park guy arrives, I explain, then show, my findings. He is confused by the information. I asked if he knew the wiring of this pedestal. “All of these are new and the state just came through and inspected them with the boxes open.” I asked if we could pop the cover off and just see what the wiring looks like. He obliged. We removed the panel and the problem instantly presented itself to me. From the service panel into the pedestal there were only 3 wires: L1 / L2 / N
There was an additional local ground wire from pedestal to an earth grounding rod. The 50A, 30A, & 20A outlets were all grounded to the box itself.
So, just to prove that my Hughes EMS wasn’t the issue, I took the proper safety precautions, then plugged in power cable and flipped the pedestal breaker on. The Watchdog instantly alerted with error E6 – Line 2 Neutral Reverse. Its voltage readings were identical to mine.
Moral of the story. EDUCATE yourselves. Learn the proper way things should be. Learn how to read a meter and then use it ALWAYS. EVERY. TIME.
The owner stopped by this morning and we chatted about it. They are going to get it corrected. This is on older site and may have been this way for quite some time, I’m just the first one to have an issue. Which I will again reiterate. Use. Your. Meter. Not just your EMS.
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Back to me…
You can see that there are two black wires pulled into the box plus a yellow neutral. However, there’s no green or copper ground conductor (formally called the EGC or Equipment Grounding Conductor or Grounded Non-Current Carrying Conductor, if you look it up in NFPA 70, 1194 or 1192).
Now, if there was metallic conduit run between the service panel and the pedestal box, that could supply the EGC ground connection in many states, except for ones that have a lot of seismic activity (think California). However, in this case it appears they used non-metallic (PVC) conduit, so that’s not going to ground anything. So this pedestal still needs an EGC ground conductor wire to be safe.
There is an 8-gauge copper wire on the right side of the enclosure that goes down to a grounding rod that’s not in the picture. However, that DOES NOT ground the pedestal or your RV. As I’ve written dozens of times, that grounding rod is really there to help a lightning strike find its way deep into the earth before it can cause trouble. Because a grounding rod will typically have an earth impedance around 100 ohms in dry soil, it can never carry enough fault current to trip a circuit breaker if a short circuit occurs inside of your RV.
And without the ability to trip (clear) a circuit breaker rapidly during a shore-circuit event, your RV can easily develop a hot-skin potential of 40, 80 or even 120 volts. And touching anything metal on your RV while in contact with the wet ground can be deadly.
I am going to recommend one more test I pioneered that you should all perform after plugging into any campground or home outlet. You’ll want to check for a hot-skin voltage using a Non-Contact Voltage Tester like this Southwire 40150N. It not only tests for potential from 100 volts to 1,000 volts, it also includes a low-range button that can check for hot-skin potential as low as 12 volts.
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Here’s a quick video of me testing my micro-micro VW bus (I guess that would be a Pico-bus) for hot-skin voltage. Click the picture or HERE.
I think that doing a quick NCVT check for hot-skin voltage right after connecting to shore power is a great safey test that only takes a few seconds.
No matter what, be aware that if you feel ANY shock at all while touching an RV or appliance, that’s a hint there’s a voltage differential between it and whatever else you’re touching. And you need to investigate the problem IMMEDIATELY because it can easily become very dangerous.
For a deeper dive into RV ground troubleshooting principles, please read my 2-part Hot-Skin Testing Tutorial from last month.
Hot-Skin Voltage Testing Part 1
Hot-Skin Voltage Testing Part 2
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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When I do a hot skin test my minimum allowable voltage is <5vac. Anything over 48 volts will pierce the skin, so the test device isn’t sensitive enough to perform a proper hot skin test. There is NO substitute for using a multimeter set to AC voltage with the black lead connected to a good ground and the positive (red) lead making the contact on the RV.
BTW good call on finding out what was wrong with the pedestal.
I read your articles but I am not a electrician so for me to use anything other than my EMS would be absolute failure. I just have to trust that by plugging my EMS in and allowing it to run a diagnostic before plugging my trailer in will provide me with protection – as it has done on many occasions, with the campground thankfully being kind enough to move me or if possible to fix the problem. I will say I have learned to check my trailer for hot-skin by reading your articles.
I had the same thing happen in Santa Fe, the ground was completely open. The owner became enraged when I brought it up and yelled “first I’ve heard of it” and “nobody else has ever had a problem with it”. I am a licensed electrician and would have opened the box and helped them but the attitudes of both the owner and maintenance man were that I didn’t know what I was talking about and I could take it or leave it.
You could always report this to the AHJ (Authority Having Jurisdiction) which is typically the local electrical inspector. Since you’re a licensed electrician you should know how to contact them. Also, please send your contact info to email@example.com to discuss this further. I’m working on a grant to create a campground training program for maintenance crews.
Hi Mike, I did go online to see about reporting it to the Santa Fe planning and zoning dept but it seems they are quite busy and I debated whether or not they would actually care enough to do anything. There was no phone communication. Will email you.
Question: I have a EMS-PT50X. I thought/think that it would not allow the electricity to flow when L1 and L2 were so far apart in their values as was measured in your situation. Plus I understand it would do other diagnostics and I would get an error code(s). What is the reason for not trusting the EMS initially? Thanks for your expertise.
Just another reason not to buy an Airstream:)
Nothing on the outside of my 37 ft. 5th wheel is metal.
Actually, your bumper, hitch, tow vehicle, steps and door handles are all metal and bonded to the frame.
Hi Mr. Sokol,
So is the fix here to run a ground wire from the 50 amp receptacle to the wire that is grounding the pedestal to the ground rod?
No, it needs a ground conductor installed from the ground lug in the pedestal box all the way back to the campground service panel’s neutral/ground bonding point.
No, it needs a ground conductor run from the pedestal back to the service panel’s neutral/ground bonding point. This is also where the grounding rod connects to the service panel. Note that simply adding a grounding rod to a pedestal DOES NOT ground it since the earth impedance is way too high to allow enough current to flow that would trip a circuit breaker in a short circuit situation.
Mike, When looking at the pedestal panel I’m wondering is the pedestal considered a service or a branch circuit? If it is a service couldn’t they install an equipment grounding buss and main bonding jumper to make it perform correctly and be legal?
Negative, it’s considered to be a sub-panel just like in your home, not a separately derived service. It needs an EGC run all the way back to the service panel.
It is not a separately derived service so you can’t simply add a ground rod and create a local neutral/ground bond. That would be a code violation.
I don’t understand: “Use Your Meter. Not just your EMS.”
It seems like the EMS did its job–although the meter provided additional info.
This should have been your lead article!
I always use my Southwire NCVT on a pedestal. Perhaps a video on the simple use of the NCVT on the pedestal. The “beeps” on a 50 amp receptacle and the “beeps” on a 30 amp receptacle and the “beeps” on a 15/20 amp receptacle. Breaker on. Breaker off. The number of beeps vary on the 50 amp vs the 30 amp depending the hot and neutral. Just a hint for the beginners using the NCVT.