Getting Shocked From a Panel

Status
Not open for further replies.
Little Bill

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
I had a "long distance" land lord call me and ask me to check a problem at her rental property. She said the tenants claimed they were being shocked when touching the panel box. She also said there was some kind of problem with a breaker but that "supposedly" it had been fixed. But now they claim the receptacles are shocking them.

If the panel is/was shocking them wouldn't that more than likely be because the panel wasn't bonded?
Also probably the same reason the receptacles are shocking them. Of course there would have to be some kind of fault for a shock to occur. If there was no (or loose) bond the breaker wouldn't trip.

I hate dealing with 3rd party descriptions because very relevant information could be missing. I'm also leery when renters report problems to "long distance" land lords. You never know if they really have a problem or are just trying to get their rent lowered!:happyyes:

Any thoughts?
 
Little Bill said:
I had a "long distance" land lord call me and ask me to check a problem at her rental property. She said the tenants claimed they were being shocked when touching the panel box. She also said there was some kind of problem with a breaker but that "supposedly" it had been fixed. But now they claim the receptacles are shocking them.

If the panel is/was shocking them wouldn't that more than likely be because the panel wasn't bonded?
Also probably the same reason the receptacles are shocking them. Of course there would have to be some kind of fault for a shock to occur. If there was no (or loose) bond the breaker wouldn't trip.

I hate dealing with 3rd party descriptions because very relevant information could be missing. I'm also leery when renters report problems to "long distance" land lords. You never know if they really have a problem or are just trying to get their rent lowered!:happyyes:

Any thoughts?
Click to expand...

Sounds like they've got a static electricity issue, walking around in bare feet with heavy carpeting.
 
There is voltage above local ground on the neutral, may be on premises, may be on POCO's primary neutral, but primary and secondary grounded conductors are bonded together and this voltage is present everywhere on the POCO system. Not likely to be a neutral problem on the 120 volt neutral between the transformer and house though or you would have voltage fluctuation issues, so I am leaning more toward POCO having either a bad neutral on primary distribution or fairly unbalanced neutral and a high voltage drop (high meaning as little as maybe 10-20 volts, on the line because of it.

Using an isolated earth probe in an area away from the grounding electrodes of the premises measure voltage from service neutral to this probe. Measure with and without load (preferably with main open to ensure no load). If voltage exists, there may be some, but should be below 5 or even below 2 or 3 volts no load, disconnect the service neutral and check again. If the voltage is only present on incoming neutral - the problem is on POCO side of things. If voltage is present on premises side - be careful it is likely trying to return to the disconnected neutral and could even be at an increased level since you opened it, in fact be very careful when initially disconnecting the service neutral, because if there is current flowing on it you could put yourself in the path when you open that path. If voltage is on the premises side of this connection, you are going to have to find out where it is coming from, which may be a topic for another thread if that is the case.
 
So what is the safeguard inbuilt in NEC against shock such as mentioned in the OP for a lost service neutral?
 
Sahib said:
So what is the safeguardon sitelt in NEC against shock such as mentioned in the OP for a lost service neutral?
Click to expand...
Proper bonding & grounding will help for the most part. To receive a shock you must be touching items with a potential difference, otherwise we are a bird on a wire. Wood frame construction helps. Concrete flooring or ongrade construction opens up another can of worms.

The facts will need to be determined with an onsite visit.
 
My guess is a main supply GFCI would provide the safeguard, because when the POCO neutral is intact, the ground leakage current is usually low enough not to give a shock and not to trip the GFCI. But during a broken service neutral, the ground leakage current increasing high enough to give a shock should necessarily trip the GFCI.

Code Proposal please.

:)
 
Sahib said:
My guess is a main supply GFCI would provide the safeguard, because when the POCO neutral is intact, the ground leakage current is usually low enough not to give a shock and not to trip the GFCI. But during a broken service neutral, the ground leakage current increasing high enough to give a shock should necessarily trip the GFCI.

Code Proposal please.

:)
Click to expand...
That would be real handy. 40 plus circuits in my house and we loose power in all because one of them somewhere has an intermittent problem.
 
ptonsparky said:
That would be real handy. 40 plus circuits in my house and we loose power in all because one of them somewhere has an intermittent problem.
Click to expand...

With all load current passing through ground on lost service neutral, real nasty shock might be expected but for the provision of mains GFCI, but do have some ready emergency lights.:)
 
The problem with GFCI is we use the grounded service conductor for both a circuit conductor and equipment grounding purposes up until the service equipment. Outside current can be flowing via grounding electrodes and onto the grounded service conductor, and this is not considered objectionable current yet is going to cause a GFCI on the service conductors to trip.

In order to use a GFCI on the service and have better reliability we would need to run separate grounded and equipment grounding conductors to the service equipment and have no bonding between them beyond the source. Any incidental bonding between them would cause tripping.

This still would not do anything for a rise in voltage to earth that is imposed on the EGC as a result of voltate drop on POCO MGN and other similar sources of rise in volts on the grounded conductor(s) of the system, and the GFCI would not respond to currents associated with this on the equipment grounding system either.
 
kwired said:
Using an isolated earth probe in an area away from the grounding electrodes of the premises measure voltage from service neutral to this probe. Measure with and without load (preferably with main open to ensure no load). If voltage exists, there may be some, but should be below 5 or even below 2 or 3 volts no load, disconnect the service neutral and check again. If the voltage is only present on incoming neutral - the problem is on POCO side of things. If voltage is present on premises side - be careful it is likely trying to return to the disconnected neutral and could even be at an increased level since you opened it, in fact be very careful when initially disconnecting the service neutral, because if there is current flowing on it you could put yourself in the path when you open that path. If voltage is on the premises side of this connection, you are going to have to find out where it is coming from, which may be a topic for another thread if that is the case.
Click to expand...

I would have to do all this from the panel as we are not allowed to touch POCO lines or pull the meter. Or I could wait for the POCO and have them stay until I finish the testing.

How deep would I need to drive a probe for testing?
 
Little Bill said:
I would have to do all this from the panel as we are not allowed to touch POCO lines or pull the meter. Or I could wait for the POCO and have them stay until I finish the testing.

How deep would I need to drive a probe for testing?
Click to expand...

Not very deep. Screw driver length. Long Skinny. #2 Phillips. Hopefully your not in sand or gravel. At one time I had a ground rod set up with a weight I could use to drive it down a couple feet, then use the weight again to bring it out. You don't need to pass more current than what the meter takes for a voltage check.
 
Little Bill said:
I would have to do all this from the panel as we are not allowed to touch POCO lines or pull the meter. Or I could wait for the POCO and have them stay until I finish the testing.

How deep would I need to drive a probe for testing?
Click to expand...
Like Tom said, just a screwdriver would work in most cases. If you have soil with little to no moisture at surface then you need something longer, but really only need to penetrate to the point where there is fair amount of moisture.

Checking at the panel instead of meter is probably the place to start anyway, you can then decide from those readings whether or not the problem is upstream - which if it is you then need to get the POCO involved in most instances anyway.
 
I might add if you are seeing a full 120 volts from what is supposed to be grounded objects to remote earth - you probably have a situation of a "hot" and neutral conductor reversed for some reason, but that probably would have also presented itself with other problems long ago unless someone recently tampered with something. Having wrong conductor grounded at source is a possibility, but this is probably more likely if separately derived on premises then if utility supplied system.
 
Sahib said:
My guess is a main supply GFCI would provide the safeguard, because when the POCO neutral is intact, the ground leakage current is usually low enough not to give a shock and not to trip the GFCI. But during a broken service neutral, the ground leakage current increasing high enough to give a shock should necessarily trip the GFCI.

Code Proposal please.

:)
Click to expand...

You have plenty of time to write one up...public inputs (proposals) for the 2020 code will be due at 5 pm on the first Friday of November 2017.

As far as the main GFCI, maybe if it was GFP, not GFCI. I would expect that the normal leakage current on all of the circuits in the panel would exceed the 5mA trip of a GFCI.
 
Status
Not open for further replies.
Top