Forum Discussion

tim_rohrer's avatar
tim_rohrer
Explorer
Aug 13, 2017

RV "Hot Skin" and GFCI?

Yesterday I discovered I had the troubling “hot skin” condition. After some troubleshooting and testing of different configurations, I determined I could only resolve the hot skin condition by physically disconnecting the RV power cord from the pedestal. Our cord is old and even the power input on the side of our RV shows wear so I purchased a brand new cord and power input.

Before connecting the new cord (I haven’t swapped out the power inputs), I used my multimeter to confirm the power at the pedestal was good. I then connected the new cord but did not energize the 50A circuit. The hot skin condition returned. Here is where it gets interesting.

I decided to test the 30A and 20A circuits at the pedestal using the multimeter; both circuits were off and I had not touched them since we arrived at this campground a few days ago. I flipped on the 30A breaker and tested voltages with the multimeter. No issues. I then flipped the 20A breaker and noted the GFCI plug was tripped. I reset it, and flipped the breaker. On a whim, I checked the RV and the hot skin condition was GONE. I have since tripped the GFCI and turned off the 20A breaker, but the hot skin condition has not returned.

So, especially for any electricians out there, what the heck happened? How could a pedestal be wired such that clearing a probably-blown GFCI (on a different circuit) could have led to this? And why didn’t the EMS system in my coach pick up the problem?

Thanks in advance.

Tim
  • time2roll's avatar
    time2roll
    Nomad
    Aug 13, 2017
    What EMS do you have? Model number?
    Did you use a regular 3 light tester to check the pedestal and the RV?
  • BB_TX's avatar
    BB_TX
    Nomad
    Aug 13, 2017
    You need to verify that ground at the pedastal is good. Then verify that ground is good all the way from the pedastal thru your power cord and to the RV frame. If you have good ground connection from the frame to a good solid ground at the pedastal and the pedastal ground is confirmed good, you should not have hot skin.

    If it comes and goes you may have a loose/bad ground connection somewhere.
  • tim_rohrer's avatar
    tim_rohrer
    Explorer
    Aug 13, 2017
    time2roll wrote:
    What EMS do you have? Model number?
    Did you use a regular 3 light tester to check the pedestal and the RV?


    A Progressive Industries EMS-HW50. In the interest of full disclosure, my EMS has an issue and PI is sending me a new circuit card. However, I understood this issue only affected the display on the remote. However, I'll be sending them a description of what transpired yesterday and finding out their thoughts.

    I used a multimeter as described below.
  • tim_rohrer's avatar
    tim_rohrer
    Explorer
    Aug 13, 2017
    BB_TX wrote:
    You need to verify that ground at the pedastal is good. Then verify that ground is good all the way from the pedastal thru your power cord and to the RV frame. If you have good ground connection from the frame to a good solid ground at the pedastal and the pedastal ground is confirmed good, you should not have hot skin.

    If it comes and goes you may have a loose/bad ground connection somewhere.


    Should I go so far as to interpret your post as saying the blown GFCI, unenergized, was not screwing up the ground at the pedestal?

    Are you thinking I may not actually have the hot skin resolved?

    The tests I did with the multimeter involved going around the diamond and testing ground to neutral. I got zero for the latter, and ~120V for each of the ground to X/Y. I was also able to show 245-250 between the hots, but I had a little trouble getting my smallish probes to get metal on the hots.

    Thanks.

    Tim
  • enblethen's avatar
    enblethen
    Nomad
    Aug 13, 2017
    There seems to be an open in the ground in the pedestal wiring. When you energize the GFCI receptacle, a ground path is made possibly through the neutral of the 120 volt 15/20 amp circuit.
  • tim_rohrer's avatar
    tim_rohrer
    Explorer
    Aug 13, 2017
    enblethen wrote:
    There seems to be an open in the ground in the pedestal wiring. When you energize the GFCI receptacle, a ground path is made possibly through the neutral of the 120 volt 15/20 amp circuit.


    Thanks, Chief.

    One place I'm scratching my head though. Now, when I change the status of the GFCI or its associated breaker, the hot skin doesn't return.

    In a properly wired pedestal, aren't the 50A and the 20A/30A supposed to be totally separate? Or, I guess they would share a common earth ground?
  • time2roll's avatar
    time2roll
    Nomad
    Aug 13, 2017
    Not really separate as there is a common Hot(2), Neutral and Ground to feed the string or row in the campground.

    So you will have a common Neutral Bus and Ground Bus where all are connected.
    The main hots will feed the breaker bus.

    There are not separate wires for each connection going back to the main panel.
  • tim_rohrer's avatar
    tim_rohrer
    Explorer
    Aug 13, 2017
    time2roll wrote:
    Not really separate as there is a common Hot(2), Neutral and Ground to feed the string or row in the campground.

    So you will have a common Neutral Bus and Ground Bus where all are connected.
    The main hots will feed the breaker bus.

    There are not separate wires for each connection going back to the main panel.


    That makes sense. I recall reading some time ago that "properly wired" campground pedestals will have two service feeds, one dedicated to the 50A and another to the 20A/30A breakers. However, I can easily see where most installers wouldn't do that unless the code specifically required it. In the case of this pedestal, the breakers do all appear to be on the same bus.

    Knowing that, I'm still trying to figure out why the GFCI (or potentially the 30A breaker) would (or could) cause an open ground situation leading to the hot skin, and why that wouldn't show up when testing the grounds.

    Am I misunderstanding something?

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