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After a recent power outage i have serious power issues in my garage. With no load, i get solid 123vac from both channels in the box and a solid 240vac across both legs. As soon as i apply a load one channel drops to approx 100vac and the other shoots up to near 180vac. I have tried isolating individual circuit breakers, but so far only helps minimally and still have no usable power in the garage. It looks to me like multiple breakers were damaged. Is this plausible?

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    Sounds more like a damaged neutral connection. Is this garage directly utility fed with its own meter, or fed from another building where power is still good?
    – Ecnerwal
    Oct 23 at 23:16
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    Zero potential between ground and neutral is only relevant if you have a 4-wire feeder, and the neutral-ground bond in the sub panel has been removed (as it should on a 4-wire feeder). On a 3-wire feeder, your garage will have a local neutral-ground bond that will affix ground to neutral (which gets quite dangerous if you don't have local ground rods!) Oct 24 at 0:59
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    Crap. I screwed up. I missed that the power problem was only in the garage. But since isolated to the garage, the POCO is probably not to blame. I agree with @Harper-ReinstateMonica that you've got a bad neutral between the main panel and the sub-panel. Sorry for missing that point. I'll delete that comment after a bit. Oct 24 at 1:06
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    Why are you risking so much asking a bunch of internet strangres, rather than paying a qualified expert? Oct 24 at 20:42
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    @manassehkatz-Moving2Codidact That does sound reasonable, and what I foolishly forgot to mention was, in this or any other technical situation the solution is to ask as many qualified experts as it takes to find one who is happy to first re-summarize the situation, then explain the answer in terms that suit whoever's asking… Oct 25 at 18:21
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Based on my diy.se reading, you may have a damaged neutral wire to your garage or whole house, which is dangerous. See Loose Neutral or Poor Ground?

You may need to get an electrician to investigate.

The neutral wire balances the two opposite legs of the 240/120 split-phase power system, keeping both legs at approximately 120V despite different loads on each leg. If the neutral connection is weak or breaks, then the power from one leg goes through the loads on it, then through the loads on the other leg, and the different loads can have substantially more or less voltage than they are designed for, with the potential to destroy the devices and start a fire.

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This sounds like a lost neutral. Assuming it affects everything on the same power company feed, CALL THE ELECTRIC UTILITY. NOW!!!. This is a serious problem that can affect safety and damage equipment.

The key is "everything". You mentioned "garage". If your power comes into your home (main panel) and from there feeds your garage (subpanel) and the circuits in the house are fine but the garage has problems, then you need to call an electrician as the problem is in the main panel (breaker to subpanel), subpanel or (more likely) the wiring in between.

However, if it is "everything" - i.e., house and garage, or the garage has its own meter, then call the power company first, because they will come for free and an electrician won't, and typically after outages (especially weather-related), the problem is more likely on utility-owned wires/equipment.

See Circuit Breakers on and outlets not working for more information.

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    thanks for the feedback, truly appreciated. Based ob the info you and others have provided, I think the issue may be lost or very weak neutral. Not sure how to test for that but i will chase that down. I will post updates as I progress.
    – wsnbh
    Oct 24 at 0:36
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    @wsnbh First thing you do (before trying to test and investigate), disconnect all the loads in the garage or turn off all breakers there. Things like the 180V you see on a 120V circuit can easily fry your stuff.
    – TooTea
    Oct 24 at 19:37
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    @wsnbh If this is the "everything" case - STOP. Don't chase anything down, turn everything electrical in your house OFF and call the power company first.
    – J...
    Oct 25 at 13:57
  • When you call the power company, use the words "lost neutral". This may cause them to prioritise your call more highly than if you just talk vaguely about the voltages being wrong in your garage. Oct 26 at 1:56
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    @TooTea don't disconnect the loads as there's some chance it will cause the voltage to shift more and break something that's not broken yet. Rather just turn the power off.
    – user253751
    Oct 26 at 16:45
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First, make sure the house is OK. The "Lost Neutral" symptoms are slippery as can be, and are often mild enough to not be noticed. My cottage complex had an epidemic of appliance failures until my sweetie noticed a Crock Pot not heating well and the toaster being "slow".

But if the house has no trouble, this is a failure of the neutral wire on the feeder between house and garage. 90% of the time, wire failures are at the terminations (ends/lugs).

So, the right answer is to de-energize the feeder, then remove the neutral wire from its lug in the main panel, inspect the lug, inspect the wire end, clean it, refresh the anti-oxidation goop, put it back in and torque it to the panel specification.

And then, go out to the sub panel and do the exact same thing.

Chances are that'll nick it. If not, look for an intermediate splice that failed. If no splices have failed, then you have the less likely but more expensive case of a wire failure inline or underground, e.g. from a rock penetration (which is what you get when you do direct burial in rocky soil without lining the trench with sand above and below).

If you need to replace the feeder, remember that aluminum is a perfectly fine and safe choice for large feeder. The lugs are aluminum anyway.

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    I'm not even American, and thought "lost neutral" while reading the question. It is scary how unrestricted the US power legislations are.
    – Criggie
    Oct 25 at 0:44
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    @Criggie they are not "unrestricted", they have their honest share of rules and restrictions. And, losing neutral in an european 3-phase system (230/400V) is just as bad. Actually worse, because in US your expensive stuff is likely to have 100-240v universal psu and survive. Good luck with any electronics at 300V
    – fraxinus
    Oct 25 at 6:40
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    Have you considered renaming your user account to The Lost Neutral Guy?
    – user253751
    Oct 25 at 9:17
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    @fraxinus I have had exactly this a few weeks ago in EU. The neutral wire was installed too deep in its clamp and had a bit of insulation wedged in. It ran on a weak connection at first, then a spark gap for almost a year, before the metal was finally eaten away. When I measured 400V on a power socket after multiple applicances died, I called the power company. Luckily, the emergency electrician diagnosed the botched installation of the neutral wire, so the original electricians' insurance paid the bill.
    – orithena
    Oct 25 at 16:35
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    @Criggie and it can happen with European single-phase also, it just happens out at the transformer. People keep misestimating how US power works. Oct 27 at 19:20

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