Could this be shocking?

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uwireme

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Cottonwood, CA
Got a call someone got a shock when kneeling on the wet ground at an RV park.

Could the grass growing around hot lugs cause about 50 volts when touching the wet ground?

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I would not suspect the grass. I would be looking for a bad wire somewhere. Take some voltage readings with power turned on and off, loads on and off. I'm not one of these guys that hollars "MEGGER" every time but this would be a good one.
 
I have done a voltage and amp test to to see if its drawing amps when there is no load connected and nothing, but that was after I removed the grass

I was never able to simulate the 50 volts.... only the park host was able to see 50 volts from the earth to the RV pedestal
 
uwireme said:
I have done a voltage and amp test to to see if its drawing amps when there is no load connected and nothing, but that was after I removed the grass

I was never able to simulate the 50 volts.... only the park host was able to see 50 volts from the earth to the RV pedestal
Click to expand...
50 volts from nearby earth to pedestal means that either the pedestal is not grounded (not connected to neutral or EGC or local ground electrode) OR there is current flowing into the dirt creating a voltage gradient. If the pedestal has metal parts going into the dirt, it could be a combination of both.
If the pedestal is not grounded the voltage might (long shot) be phantom voltage on the metal from capacitive coupling.
Definitely a good idea to clear out the grass though.

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uwireme said:
There is no equipment ground but the neutral and GEC are bonded to the pedestal and is in the earth about two feet
Click to expand...
The simplest way to tell whether the pedestal or the earth is at an odd voltage is to run a wire to a distant screwdriver in the ground, far from any electrical equipment. Commonly known as "remote earth" and assumed to be at the same potential as the rest of the earth.
If there is a problem with the neutral (corroded, high resistance connection, etc.) then the GEC connection will just serve to drive current into the earth and raise the voltage near the pedestal. Could easily be 50V from that, and it would only show up when there was an unbalanced line to neutral load on the two lines. A hot plate, portable heater, or hair dryer would be good test loads.
The nice thing about a hair dryer is that you don't usually have to let it cool down before you pack it up again. But it may be a much lower power load.

When current that should be going through the neutral is forced to travel through the earth you will see constantly decreasing absolute voltage (constantly increasing pedestal to dirt voltage) as you move your test probe (screwdriver with insulated handle) away from the pedestal.
Near zero almost touching the pedestal, up to near line voltage as you get farther away.

You may not have been able to duplicate the problem because there were no unbalanced loads during your test. Or you might have bumped the neutral back into temporary good contact while clearing the grass away.

If it is a bad neutral you will also clearly see a difference between the L1-N and the L2-N voltages under load.
 
uwireme said:
I have done a voltage and amp test to to see if its drawing amps when there is no load connected and nothing, but that was after I removed the grass

I was never able to simulate the 50 volts.... only the park host was able to see 50 volts from the earth to the RV pedestal
Click to expand...
An RV was plugged in at the time they saw 50 volts - there was a ground fault in the RV - but you have no EGC in the pedestal so instead of allowing a low impedance path back to the source and operating overcurrent protection it just energizes everything connected to the EGC - including the pedestal housing.

Just a possible explanation of what might have happened.

As mentioned this pedestal should have separate neutral and EGC run to it. If there is no EGC or even a bond to the neutral (though not right) there is no return path for faults to the EGC except for the high resistance connection via earth. A ground rod won't help much either.
 
uwireme said:
Thanks for all your replies...I will try the remote earth test and let you know
Click to expand...
I think you should first look for any sort of bonding jumper from neutral to the case. Something tells me you won't find one - meaning the case is not bonded to the source grounded conductor in any way other then through earth.

If an RV was plugged in that had a ground fault within it and it is no longer there the thing that triggered the problem is gone and you won't re-create it unless you make your own ground fault.
 
kwired said:
I think you should first look for any sort of bonding jumper from neutral to the case. Something tells me you won't find one - meaning the case is not bonded to the source grounded conductor in any way other then through earth.

If an RV was plugged in that had a ground fault within it and it is no longer there the thing that triggered the problem is gone and you won't re-create it unless you make your own ground fault.
Click to expand...

The neutral is factory bonded to the case and ground rod connected to the neutral also.....no equipment ground, was installed in the 70s

Did the remote ground test today, the ground was very wet I went out with some #12 about 200' away from any power and established a ground went back to the pedestal and tested the earth and pedestal for voltage and nothing. Plugged in my 1000w heat gun on both phases to check if the imbalance was also leaking to ground and nothing. Checked for voltage drop with the heat gun and went down about half a volt.
Not sure what else to do
 
uwireme said:
The neutral is factory bonded to the case and ground rod connected to the neutral also.....no equipment ground, was installed in the 70s

Did the remote ground test today, the ground was very wet I went out with some #12 about 200' away from any power and established a ground went back to the pedestal and tested the earth and pedestal for voltage and nothing. Plugged in my 1000w heat gun on both phases to check if the imbalance was also leaking to ground and nothing. Checked for voltage drop with the heat gun and went down about half a volt.
Not sure what else to do
Click to expand...

A highly likely explanation at this point is that something (RV?) plugged into the pedestal at the time of the problems had a major ground fault somewhere that was not quite bad enough to trip any OCPD.

Or you can blame it on the grass. :)
 
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