I have 100 amp sub panel in garage about 150 ft away from main. Everything worked fine for about month than one leg gets 120 volts, other leg gets 29 volts. I have dug up wire no damage. I switched the wires in sub panel still the one side only gets 29 volts. Please give me something to look for.

  • 3
    You checked the wires in the subpanel. What about at the main panel? Pictures of subpanel and main panel? What kind of cable/wires/conduit? Feb 14, 2023 at 20:43
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    Did you switch at both ends? Would guess bad wire insulation or a bad connection.
    – crip659
    Feb 14, 2023 at 20:45
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    Check the main lugs for voltage and then check the load terminals on the breaker that feeds the sub panel.
    – JACK
    Feb 14, 2023 at 20:50
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    When you switched the wire, does the same side get only 29V (problem is at or downstream from the subpanel), or did the problem move to the other buss (problem is in the feed to the subpanel)?
    – keshlam
    Feb 14, 2023 at 21:15

1 Answer 1


Did the problem switch sides when you switched the wires?

If not and the subpanel has a main breaker then my prime suspect would be a bad main breaker. Or possiblly a bad bus connection somewhere in the panel. If not then it suggests a wiring problem or a problem with the breaker in your main panel.

Either way I would suggest methodically working through the installation, testing for voltages at each stage. Start at the output lugs of the breaker in your main panel. Then if it tests out ok there test at the input lugs of your subpanel. Then the busbars of your subpanel. You should be able to narrow down where the problem is this way.

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