On the 220v circuit one leg reads 120v and the other reads ov at the subpanel. Both legs read 120v v at the main panel. The panel has a separate ground wire connected to a ground at the subpanel. I used the green wire (4 gauge) as a test lead and connect it to the main and subpanel and now have 120v on both lines and all circuits are working. The line that is disconnected and capped at both ends reads 80v. How can this be?
Loss one leg of a 300' AL 2,2,2,4, 220v line, buried in electrical conduit.
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kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Probably capacitive coupling. Did you read that with a standard DMM or a low impedance meter? If you don't have a low impedance meter connect a load to it that then check voltage again, if it is zero it is capacitive coupling. If there is still voltage your swapped line maybe also damaged and some leakage is occurring between conductors at the damaged area. Not uncommon at all to see this with damaged underground aluminum in my experiences. A small hole in conductor insulation is all it takes to start this, it may take time for it to fail, soil moisture does factor in how long this may take. Once the conductor has oxidized enough cross section away, the smaller remaining cross section has to carry all the load and heats up. That does help accelerate further oxidation. Insulation on an adjacent conductor may be damaged by the heat and now you start having deterioration of the adjacent conductor.
winnie
Senior Member
- Location
- Springfield, MA, USA
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- Electric motor research
Did you connect the green wire in place of the burnt hot wire as a test?
You will need to replace the feeder, the sub panel cannot be left without its EGC.
You will need to replace the feeder, the sub panel cannot be left without its EGC.
Yes i connected the green wire in place of the burnt wire as a test. And yes i wil replace the green with a 4 gauge black wire. I realize that I need return the green wire to the main panel as a ground return even though I have a case ground and the sub panel is not bonded. Do you have any idea what might have caused this issue?
readydave8
re member
- Location
- Clarkesville, Georgia
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- electrician
In conduit all the way? Can you pull old wire out and new in?
petersonra
Senior Member
- Location
- Northern illinois
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- Semi-retired engineer
Look into directional boring.
Should i be concerned about the condition of the conduit. It might be full of water too
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