I've noticed that when I turn on a microwave on one of my circuits, there is a 10-13VAC drop on that circuit and unrelated circuits on the other leg experience a rise of 10-13VAC.
I was trying to diagnose this further to see if it is an issue that I could fix/diagnose on my side, or if this is an issue that can only be fixed by my utility company.
Voltage between both legs is 246.3 VAC
When I apply a load to the right leg (running circular saw), I observe this change - from no load to circular saw load:
- On the left leg 119.2 VAC goes to 123.1 VAC, and 8.7A goes to 9A
- On the right leg, 127.4 VAC goes to 123.5 VAC, and 1.9A goes to 7.7A
Does it mean that I have a bad service neutral coming in?
Does it mean something else?
Can one confidently say that the issue is "on my side" or "on the service side"? Is there anything I can do to help diagnose or fix this issue?
(All measurements were taken using Fluke 323).
With all breakers ON, grounding wire shows 5.5A.
- When I applied load on right leg, GEC went down to 2.3A.
- Applying load on the left leg GEC went from 6.1A to 2.8A. (not sure what caused it to go from 5.5 to 6.1 between my measurements)
Are Certain multiple Circuits leaking current into GEC?
I have 24 breakers right now in my panel. When I turned off breakers 2, 4, 6, 8, 10, 11, 12, which I figured out by trial and error, the grounding wire went to 0A!
Once I identified all the "problem breakers", I turned them off (leaving non-problem breakers on) and tested problematic breakers one at a time.
- Breakers 2, 6, 8, 10 one at a time GEC was showing between
0.3A for each.
- Breaker 4 put
0.9A into GEC
- Breaker 12 put
- Breaker 11 put
Earth ground to Panel ground
With all breakers in the ON position, the voltage measured from Earth-ground to panel-ground using a method mentioned by @Edwin was 4.7 Volts. Method - wrap a conductor around a screwdriver, stick it into the ground 15 feet away from the panel, then measure voltage between panel ground and earth ground.
I shut off all other breakers, installed a new 20A breaker with a short wire, rigged it up into a circuit connected to right leg hot and neutral bus, and tested it with a circular saw load. No ground (saw plug had no ground either).
Measured load running circular saw: 6A
When the saw is on that sole breaker, it also threw 3.9A current onto the grounding conductor.
during no load right leg: 123.7 VAC
during no load left leg: 123.6 VAC
with circular saw load on right leg: 127.3 VAC
with circular saw load on left leg: 120.0 VAC