"Shocking Ground"

Status
Not open for further replies.

JDB3

Senior Member
I have not been to the site yet (just wanted to clear that up). An air conditioner friend of mine told me that when he went to this ( metal exterior wall church building) and touched the outside unit while his feet were on the ground, he got shocked. :happysad: With all of the wires disconnected from the unit, he still got shocked. :jawdrop:
Apparently, the service (meter & panel/disconnect) runs underground to the structure. I do not know how he checked the voltage, but said that it ranged up to 120 volts.
Any suggestions on how to measure/check the possible voltage from the ground to the building? Any suggestions as to the possible cause of this (building is not new) :?

Sorry, but till I can get out there, this is all the information I have.
 

iwire

Moderator
Staff member
Location
Massachusetts
Where the refrigerant lines still connected to the unit?

If so I would suspect a bad service neutral that is causing the potential relative to the earth of all grounded objects at that building to rise.
 

kwired

Electron manager
Location
NE Nebraska
If he had up to 120 volts there should be more serious voltage issues around the place if the service neutral is what is lost.

Could be bootleg ground off the neutral to the indoor blower/furnace, and that is what is open, or something of that nature if there isn't voltage issues all over the place.
 

hurk27

Senior Member
If he had up to 120 volts there should be more serious voltage issues around the place if the service neutral is what is lost.

Could be bootleg ground off the neutral to the indoor blower/furnace, and that is what is open, or something of that nature if there isn't voltage issues all over the place.

Or the other way around some one use the ground for a neutral but the ground opened and you now have 120 volts from that loads hot through that load to this ground, I have seen control transformers done like this, but not very likely since the building has a metal skin which is most likely grounded to the service because it is all mounted on it, including the disconnect for the AC unit, I'm suspecting a lost primary neutral to the transformer.

Best to start with a long wire to a short rod stuck into the earth, then using a DVM check for voltage between this wire and the service case, the buildings metal skin, if the service shows hot, then you could have a bad primary neutral, if it is a pad mounted transformer check the transformer case to this wire, if it is also hot then call the utility ASAP as it will only go higher in time as the grounding electrodes dissolve away, in this case the concentric neutral may have gone bad, some are not insulated and can dissolve over time if the connection at the pole to the MGN is lost, very common problem with exposed concentric neutrals on underground primaries, what happens is when the connection to the MGN at the pole goes bad the primary neutral starts dissolving and once it is almost gone the voltage on all the grounding starts to rise this is because the primary current tries to return through the earth via the services grounding electrodes back to the pole grounding, but this slowly dissolves them away also and eventually you can end up having close to the primary voltage on all the grounding of the building., unlike a lost secondary neutral, you will not see the lights getting brighter and dimmer as loosing 120 volts out of 7200 volts (or what ever your primary voltage is) is a small percentage, so the electric will seem fine, but the voltage to remote earth will gradually rise until someone gets shocked or worse, get something done before some child gets hurt!!! this is a church and will have children around it!!!

Another sign of this is copper water pipes getting holes in them, which many times the plumber puts a plastic section in to fix it then the voltage jumps up higher, but they may have plastic water lines so don't only go by that do the above checks.

Even if it is a pole mounted transformer you could have a lost primary neutral to this transformer.
 
Last edited:
Status
Not open for further replies.
Top