Voltage at the ground rod.

[Mark Ash Fork Electric]

Doggone it! After writing that post I got involved with the job and I cannot find that voltage on the ground wire to Earth at all anymore. I'm kinda disappointed. I separated the ground wire from the rod and cannot reproduce the voltage anymore, no matter what I turn on or off.
And when I had mentioned breaking rotor, I know when a motor first starts up it can take up to 300% of its average running power. And like I said then it's settled down to 240 something.
I am not walking away from this. I feel that I must try to duplicate the scenario and figure out what was going on. Thank you

 

[hillbilly1]

The plot thickens! You say this is a manufactured home? I can put money on it is fed by three wires instead of four. Fault to ground on one of the circuits, if this is in a park possibly another manufactured home with the same problem, but on a different leg, that would explain 240 volts to ground. Breaker probably finally tripped in the other trailer.

 

[LarryFine]

"I'm sticking with my bad (intermittent) primary neutral theory, Bob!"

The A/C starting would momentarily increase the primary current.

And that's the only way I can see the voltage rising beyond 120v.

 

[kwired]

"I'm sticking with my bad (intermittent) primary neutral theory, Bob!"

The A/C starting would momentarily increase the primary current.

And that's the only way I can see the voltage rising beyond 120v.

Malfunctioning regulation equipment may make it rise but not to 500 some volts.

 

[winnie]

...The original problems started with voltage in the ground and was frying out a cable TV contactor. They put in their own separate ground rod and fix that problem. Meanwhile I separate the number fouqr ground wire from the ground rod and would find voltage there. Between the number four wire and ground rod. When the heat pump started voltage jump to 583 volts and then settle down to 240 something after a minute. Not paying attention, I went to reconnect the ground wire to the rod just as the heat pump started. Didn't turn that breaker off. And I got the full Voltage from thumb to small finger.

Ok, so your voltage measurement was between the 'GEC' (the wire that is supposed to connect the building electrical system to the ground electrode) and the actual ground rod when the two were not connected.

IMHO you should for a moment ignore everything happening in the building and just focus on the ground rod, the GEC, and other parts of the 'grounded' circuit. The other end of the #4 GEC is presumably connected in the main panel to the ground/neutral bar. This is connected to the utility neutral back on the pole, and all of the other ground rods connected to that, as well as all of the other 'things' connected to the utility neutral conductor. The utility gives you a neutral conductor that is shared with all the houses nearby, and also both the 120/240V secondary and heaven knows what primary voltage.

When you had the #4 disconnected, you were measuring the voltage between your local patch of shared neutral and that isolated ground rod. You could get voltage if the shared neutral back to the substation is compromised (@LarryFine suggested this). You could also get voltage if there is current flowing through the soil and you have two separated grounding electrodes (say on the shared utility neutral vs the local disconnected ground rod). You might also get this if the 120/240V neutral was not grounded at all and there was some other fault 'energizing' the system.

Doggone it! After writing that post I got involved with the job and I cannot find that voltage on the ground wire to Earth at all anymore. I'm kinda disappointed. I separated the ground wire from the rod and cannot reproduce the voltage anymore, no matter what I turn on or off.
And when I had mentioned breaking rotor, I know when a motor first starts up it can take up to 300% of its average running power. And like I said then it's settled down to 240 something.

Do you mean that during normal operation you have 240V to the ground rod and you are trying to figure out the 583V? Because the measurement you described (from the #4 GEC to the rod when the wire is disconnected) you should be concerned if you have more than a few volts. 240V means something is wrong.

-Jonathan

 

[ptonsparky]

Malfunctioning regulation equipment may make it rise but not to 500 some volts.

This goes back to what kind of test equipment he was using.

side note:

480 corner grounded delta. The Beha tester i had looped around my neck was passing a spark about 1/2” as I would disconnect. My Fluke 87 showed in excess of 700 volts. Pretty sure ghost voltage was not involved. Never looped another tester around my neck either. I met the POCO truck with new pole top transformer(s) on the way back to town.

 

[gjgish]

are you drawing any current on that on that #4 ground wire ?

 

[Dsg319]

This goes back to what kind of test equipment he was using.

side note:

480 corner grounded delta. The Beha tester i had looped around my neck was passing a spark about 1/2” as I would disconnect. My Fluke 87 showed in excess of 700 volts. Pretty sure ghost voltage was not involved. Never looped another tester around my neck either. I met the POCO truck with new pole top transformer(s) on the way back to town.

I think I’ve had that happen trying to test a ballast on a fluorescent lamp with my meter on low impedance

 

[Mark Ash Fork Electric]

I am going to go back there tomorrow morning, Friday to examine the situation with a customer present. That's if I that's if I can get my truck to start! Having a little fuel flow difficulties I believe. Meanwhile, the manufactured home is on its own separate service. Out in the wilderness by itself on very dry Northern Arizona soil. One ground rod. Using a simple Greenlee multimeter from Home Depot with the amp probe attached. The panel is 200 amp single phase, 240 volts. When I was getting the voltage on the ground wire it was when I had the number four Bare wire disconnected from the ground rod and had the meter in between. When the heat pump would start it would peek at 583 volts and then creep down to 240. Everything is checking out good for me now. No voltage at all detected on the ground system. Something intermittent must be going on. Going to try to duplicate it tomorrow.

 

[ptonsparky]

Why is the rod disconnected?

 

[LarryFine]

Try to take several pics of the transformer on the pole, including the wires to it.

If it's a ground mount, the POCO must get involved, if I'm right.

 

[winnie]

As the system is described, I think @LarryFine is likely correct, the transformer primary current was dumping current into the local ground electrode.

This current needs to return to the substation, and can follow a bunch of unintentional paths such as through the soil or through the CATV grounded shield.

At this point I wouldn't disconnect anything, but would probe for current using a sensitive amp clamp.

Jonathan

 

[kwired]

As the system is described, I think @LarryFine is likely correct, the transformer primary current was dumping current into the local ground electrode.

This current needs to return to the substation, and can follow a bunch of unintentional paths such as through the soil or through the CATV grounded shield.

At this point I wouldn't disconnect anything, but would probe for current using a sensitive amp clamp.

Jonathan

If out in wilderness in very dry Arizona soil, it could easily be a bad connection in the primary neutral somewhere. Very well may not be enough other electrodes in the area to help stabilize the neutral to earth voltage