• VW's-Travels
    92
    This post may not make much sense unless you have some knowledge as to how electrical distribution systems are wired, at least here in the US.
    Here’s what I came across:
    From the main service a three conductor direct burial type cable was used to feed the RV type power pedestals. So, two ‘hot’ conductors and a neutral.
    Each RV pedestal had a ground rod driven which was connected to the ground bar in the pedestal.
    Although the (US) National Electrical Code now requires that a grounding conductor be installed along with the feeders it wasn’t required when this park was originally wired so long as each pedestal was considered its own ‘service’. That requires that neutral and ground are bonded together. Or in other words electrically connected with either a screw or bonding jumper from the neutral bar to the cabinet or ground bar.
    None of the bonding jumpers had been installed in any of park RV pedestals. Curiously enough, the factory-supplied jumpers and screws were still in their packages, neatly tucked under the neutral bars.
    So what happens in this case if there is a short between hot and ground in an RV where the circuit isn’t protected by GFCI? Answer: Nothing. The trailer frame becomes energized. – No breakers trip.
    I took some ohm readings between ground and neutral at various points around the park and was getting anywhere between 12 Ω and 75 Ω.
    If we do the math: 120V / 12 Ω = 10 Amps. So a 20 Amp breaker just sees a 10 Amp load – Not a short circuit.
    Interesting to note that RV voltage testers/protectors aren’t looking for resistance/impedance issues.
  • Ray
    1.2k
    Wow, that seems a little scary. I didn't realize there were parks wired like that.
  • VW's-Travels
    92
    Given that you have to go all the way back through the bond at the main service to the neutral tap on the transformer to read any voltage at all, I don't quite understand how it is possible to measure any current/voltage flow at all through, say 100 meters of 'dirt'. Especially with a 9-volt battery in a meter.
    But that's the part that has me scratching my head since hot to "ground" reads 120V at the pedestals.
    To prove I wasn't BSing the park owner about the issue, I connected a wire from a breaker to a ground bar and turned the breaker on. It didn't trip.
  • Ray
    1.2k
    To prove I wasn't BSing the park owner about the issue, I connected a wire from a breaker to a ground bar and turned the breaker on. It didn't trip.VW's-Travels

    It would be interesting to measure the amperage on that wire with a clamp-on meter.
bold
italic
underline
strike
code
quote
ulist
image
url
mention
reveal
youtube
tweet
Add a Comment