Stray or induced voltage?

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Hammocktestpilot

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Prescott,Arizona,USA
Went on a service call for a friend, humming from the service panel, been going on for a few years I'm told. 20 year old 200 amp GE meter/load center, overhead service with a newer "smart" meter. Obvious hum from what seems to be isolated to the meter section, amplifies or diminishes with pressure on the enclosure. loads on or loads off makes no difference. Thinking about an induced hum from the utility, tho we also noted a small arcing between the meter section exterior and the hinges at load section when replacing the cover. Subtle signs that this has arcing has been happening for awhile. Multi-meter shows 3 volts between the meter section enclosure and ground. They have also had some fluorescent flickering in the past. All bonding/grounding appears right. No shared neutrals. Comments? Thanks.
 
Hammocktestpilot said:
Went on a service call for a friend, humming from the service panel, been going on for a few years I'm told. 20 year old 200 amp GE meter/load center, overhead service with a newer "smart" meter. Obvious hum from what seems to be isolated to the meter section, amplifies or diminishes with pressure on the enclosure. loads on or loads off makes no difference. Thinking about an induced hum from the utility, tho we also noted a small arcing between the meter section exterior and the hinges at load section when replacing the cover. Subtle signs that this has arcing has been happening for awhile. Multi-meter shows 3 volts between the meter section enclosure and ground. They have also had some fluorescent flickering in the past. All bonding/grounding appears right. No shared neutrals. Comments? Thanks.
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Any significant current flowing on the grounding electrode conductor?
 
Can't explain the hum, but I'd bet the neutral is double bonded and there's current flowing through the cabinets as a result, which would explain the small arcs.

Seen that many times with services: Neutral bonded to meter can and in service disconnect, RMC run between the two completing a parallel circuit.
 
big john said:
Can't explain the hum, but I'd bet the neutral is double bonded and there's current flowing through the cabinets as a result, which would explain the small arcs.

Seen that many times with services: Neutral bonded to meter can and in service disconnect, RMC run between the two completing a parallel circuit.
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The part where he mentions it does it with loads on or off sort of rules that out to some extent - that is why I asked if there is any significant current on the grounding electrode conductor. Could be current flowing from neighbors or something through water pipe and then through his service.

Voltage measured from meter section enclosure to ground (need to know exactly what those two points of measurement were) could be voltage drop on the supply side neutral, and it there shouldn't be any current to cause a drop when the loads are off.

Again some more details will help with this analysis, but is a possible direction this could go.
 
kwired said:
The part where he mentions it does it with loads on or off sort of rules that out to some extent....
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I assumed he was only talking about investigating the hum. While those may be related, I'm guessing the hum is independent of the sparking. But I agree, it also could be neutral current from a neighbor.
 
Hammocktestpilot said:
Went on a service call for a friend, humming from the service panel, been going on for a few years I'm told. 20 year old 200 amp GE meter/load center, overhead service with a newer "smart" meter. Obvious hum from what seems to be isolated to the meter section, amplifies or diminishes with pressure on the enclosure. loads on or loads off makes no difference. Thinking about an induced hum from the utility, tho we also noted a small arcing between the meter section exterior and the hinges at load section when replacing the cover. Subtle signs that this has arcing has been happening for awhile. Multi-meter shows 3 volts between the meter section enclosure and ground. They have also had some fluorescent flickering in the past. All bonding/grounding appears right. No shared neutrals. Comments? Thanks.
Click to expand...
I think hum (from any mechanical vibrations) and arcing due to loose connections. Check tightness of connections.
 
Sahib said:
I think hum (from any mechanical vibrations) and arcing due to loose connections. Check tightness of connections.
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I would expect some heat at those loose connections, and if it has been going on for a few years probably discoloration of lugs, melting of insulation, or even complete connection failure by now.
 
kwired said:
I would expect some heat at those loose connections, and if it has been going on for a few years probably discoloration of lugs, melting of insulation, or even complete connection failure by now.
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That would not happen as thermal equilibrium might have been already reached in OP case.
 
growler said:
I would check the connections and also would get the power company to check out that "newer smart meter". I have not had any problems with them but I have herd that others have.
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Don't know a lot about what is in the smart meters, but is likely a control transformer within it, maybe it is the source of the hum?
 
Thanks all for the input. As this service is out of town for me , my followup may take some time. I know all the customer side connections are tight. There was no indication of heat, arcing or discoloration at any wire or buss connection. The 3 volts was metered from unpainted hinge point on meter section cover to earth ground ( bare copper to ground rod) No voltage from rest of can to ground.. I suspect the utility and a lack of an isolated neutral ?, and as soon as I can follow up I'll check on some of your suggestions as well.
stay safe.
 
Hammocktestpilot said:
Thanks all for the input. As this service is out of town for me , my followup may take some time. I know all the customer side connections are tight. There was no indication of heat, arcing or discoloration at any wire or buss connection. The 3 volts was metered from unpainted hinge point on meter section cover to earth ground ( bare copper to ground rod) No voltage from rest of can to ground.. I suspect the utility and a lack of an isolated neutral ?, and as soon as I can follow up I'll check on some of your suggestions as well.
stay safe.
Click to expand...
What types of grounding electrodes are present and used? Water pipe has the best chance of bringing in current from a neighbor when there is bad neutral conditions involved. If you don't have a water pipe electrode then it is more likely either voltage drop on your service neutral, but if it is still there when there is no load on your service, then it is most likely coming from voltage drop on POCO's MGN (primary neutral) which is bonded to the secondary neutral making them one and the same to an extent.
 
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