Unbalanced single phase voltage

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Dansos

Senior Member
Location
PA
So I am playing around with a 100 A main breaker panel in a residential home. Client said they lost power sometime last night. I checked everything on the service drop, meter socket and panel, ALL GOOD. I start to turn on breakers and the voltage starts going crazy. When all breakers are on, 1 leg is reading around 185V and the other is around 45-50V. Measurements are being taken from Neutral to Line as well as ground to line, no difference. I have seen this when you lose a neutral at the meter or at the POCO point of attachment, but they are all good. I can have an entire Leg energized without a problem, but when I start to turn on breakers from the other leg, that’s when problems happen. Changed the main breaker, same issue. I am wondering if something in the house is going bad and causing issues. Could a bad Electric Hot Watet heater cause a problem? Or a bad range?
 

Dansos

Senior Member
Location
PA
Another thing I forgot to add. When turning on the other leg, I can actually see the voltage start to change on my meter, it is not an instant change. It will go from 119~120v and start going down. The more I turn on the lower it goes but it is gradual, not instantaneous.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
When all breakers are on, 1 leg is reading around 185V and the other is around 45-50V. Measurements are being taken from Neutral to Line as well as ground to line, no difference.
Textbook description of open/poor neutral. The trick is to find where between the panel and the utility transformer the readings become normal while the imbalance is occurring. The meter enclosure can be tricky to check because of POCO rules, but I don't let that stop me if other readings point there.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
All symptoms of a loose neutral at or ahead of the panel. You or POCO missed something.
 

Dansos

Senior Member
Location
PA
I 100% agree. I am still poking around. Now that I have everything torn apart I found a neutral coming BACK to the panel that is carrying 95-100v. Trying to find where that is coming from now. Possibly a bad piece of electric baseboard back feeding the neutral bar
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
I 100% agree. I am still poking around. Now that I have everything torn apart I found a neutral coming BACK to the panel that is carrying 95-100v. Trying to find where that is coming from now. Possibly a bad piece of electric baseboard back feeding the neutral bar

That is the open circuit voltage of your bad neutral. Turn the power off to that circuit and it will go away. You should not be testing with the homeowners appliances. They can be destroyed. Get a cheap hairdryer or electric heater if you must load it up.
 

Dansos

Senior Member
Location
PA
That’s what I figured. I guess I should not have believed POCO without verification. We found the break in the point of attachment lol and we bugged it back.
Problem solved.
Thanks for all the answers and letting me know I’m not going crazy!
 

kwired

Electron manager
Location
NE Nebraska
I 100% agree. I am still poking around. Now that I have everything torn apart I found a neutral coming BACK to the panel that is carrying 95-100v. Trying to find where that is coming from now. Possibly a bad piece of electric baseboard back feeding the neutral bar
If you disconnect a loaded neutral conductor you will have voltage on it even if there is no other problems
 
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