Power mystery

Discussion in 'Electrical Forum discussion & Blog' started by tnt2492, May 24, 2010.

  1. tnt2492

    tnt2492 New Member

    Messages:
    4
    Location:
    mn
    I have been remodeling my house for about a year now and updating my electrical and so on. The box that is in that was too small and i have to put a sub panel in. I got a 8 space box with a 50 amp breaker from the main to the sub running on a 8-3 gauge wire. Now we have been having trouble with one of the 110 volts that come into the house. At times the light and outlets will go out on that current and won't come back on for a while, but it does trip any breakers and comes back on by itself. When it goes out got my test and check both lines coming in one is good with full power and the other one will either have some power or none at all. I don't if this is from the meter or something inside the house triggering it, because sometimes if you use something on that side that's having trouble it will shut off. I have replaced the main breaker and checked for any opens that would cause an arc. I don't know where too go from here.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    If the power to the main breaker is intermittent, you may need to call the power company. Depends on where you live how far they own, but it could be a bad connection at the transformer, or from the meter to the panel. If you measure from hot to hot, what do you read on the meter? It could be a bad neutral. A bad neutral can mess up all sorts of things.
  3. tnt2492

    tnt2492 New Member

    Messages:
    4
    Location:
    mn
    I live by Rochester,Mn. I was thinking about giving them a call and having them check out everything on there side. But sometimes if i turn on the light it will shut off. Will that still do it if its on there side?
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    If the power at the main breaker is intermittent, anything after that would be the same and may be the power company's problem - depends on where they draw the line. If it is solid at the main breaker, then you have something wrong internal to the house, and they can't help. Check not only the hots to neutral and hots to ground, but the hot to hot (110/220).
  5. tnt2492

    tnt2492 New Member

    Messages:
    4
    Location:
    mn
    Ok and checking the hot to hot will tell me if its in or out. When could of be if it was interal?
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    To get 110/120, you need the neutral to be solid. From one hot to the other, you should get a solid 220/240. If this is not on the input to the breaker, it's somewhere from the street to the panel. Depending on where it is would dictate whose problem it is. It could be anywhere in between. If it is stable coming into the panel, it's in the panel. Could be a busbar, breaker, or if it is isolated to a specific branch, that breaker or the wiring from it.
  7. drick

    drick In the Trades

    Messages:
    392
    If you are losing one of the legs of your service before the main breaker in the original panel you have a serious problem that has nothing to do with anything you have done. This is a service side problem you cannot fix. You should discontinue use of any 240V appliances until this has been addressed because when one leg drops out an active 240V appliance can act like a bridge for the dead 120V leg and attempt to route power needed for the dead leg through the 240V appliance. This creates a low voltage condition on the dead leg which can damage equipment and is a potential fire hazard. You should notify your power company ASAP.


    -rick
    Last edited: May 24, 2010
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,837
    Location:
    Cave Creek, Arizona
    IF your neutral were the problem, you would burn out almost everything which was turned on at the time because all circuits would revert to 220/240v, and thus any unbalanced loads, which would normally be all of them, would burn out.
  9. tnt2492

    tnt2492 New Member

    Messages:
    4
    Location:
    mn
    alright thank you i'm going to get them out here asap.
  10. andrew79

    andrew79 Licensed Electrician

    Messages:
    18
    Location:
    Ontario Canada
    hit the nail right on the head.....get it fixed fast. Thats why your getting a power reading on the bad leg but it's turning off when you switch something on. The 120V is comming around through the 240V appliances but there's not enough juice there the actually supply any current. A bad leg from the POCO can cost a ton of money....not to mention a ton of danger.
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