Voltage Imbalance

Bugsy717

Member
Location
Raleigh, North Carolina
Occupation
Electrician
I was called to a home last night that had multiple issues across multiple circuits. They had a tile installer working that day and had a lot of equipment plugged into one circuit. It's a 400 amp service that feeds multiple panels. Voltage coming in from the utility is balanced, but something in the main 200 amp panel is causing a voltage imbalance. I get around 90 volts on one leg and around 150 on the other. I ran a separate wire for the neutral for that panel, but did not affect. What could cause this imbalance?
 
It is not buried. I actually ran a neutral through the window but no affect.
What points on the system are you getting all of your various voltage readings? Can you post some photos of the panel in question?
 
The very first thing I tell customers to do is call the utility. They don't waste any time coming to check for open neutrals. 99.8873% of the time, it is on their end.
 
I have tested at the 200 amp main on the outside by the service. Still reading the same with a fluctuating around 90 to 100 volts on one leg and 140 to 150 on the other leg. It tests the same to neutral and ground in both locations. Voltage from the utility seems to be fine.
 
I have noticed on the outside service that there is a #4 bare copper that I can only assume is run to rebar on the basement walls for ground. I see no other ground rods only one of the 200 amp panels has the ground running to it and looks to be depending on the chase nipples to continue the ground from panel to panel. Could an insufficient earth ground cause this problem?
 
I have noticed on the outside service that there is a #4 bare copper that I can only assume is run to rebar on the basement walls for ground. I see no other ground rods only one of the 200 amp panels has the ground running to it and looks to be depending on the chase nipples to continue the ground from panel to panel. Could an insufficient earth ground cause this problem?
No...in general the connection to earth has nothing to do with any type of voltage issue, other than the case of a separately derived system with no system bonding jumper.
 
I have tested at the 200 amp main on the outside by the service. Still reading the same with a fluctuating around 90 to 100 volts on one leg and 140 to 150 on the other leg. It tests the same to neutral and ground in both locations. Voltage from the utility seems to be fine.
What is in between the panel and the point where you find the utility voltage to be fine? If the utility voltage is correct, there is a problem with the neutral between the panel and the point where you tested the utility voltage.
The high voltage can damage equipment, so everything should be off or disconnected until you resolve the problem.
 
I have tested at the 200 amp main on the outside by the service. Still reading the same with a fluctuating around 90 to 100 volts on one leg and 140 to 150 on the other leg. It tests the same to neutral and ground in both locations. Voltage from the utility seems to be fine.
If you tested at the main and still saw the fluctuating voltage, where did you test to see that the utility voltage was fine?
 
I have tested at the 200 amp main on the outside by the service. Still reading the same with a fluctuating around 90 to 100 volts on one leg and 140 to 150 on the other leg. It tests the same to neutral and ground in both locations. Voltage from the utility seems to be fine.
Then the problem is on the utility's side.
 
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