Correcting outlet wiring errors (120V)?

Discussion in 'Community Discussion' started by Cubytus, Nov 21, 2015.

  1. Cubytus macrumors 65816

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    Mar 2, 2007
    #1
    Hi there,

    in order to prevent early failure of my electronics and for peace of mind, I'd like to identify and correct miswirings in my appartment's outlets. No law requires anyone to do anything about it.

    First things first: my budget is exactly 0$ for this repairs, and no, my landlord won't correct anything unless an unfortunate event forces him to do so, so don't ask.

    I do have: a digital multimeter, common 3-prong 120V outlets.

    I still don't know: even with 3-prong, the "earth" may be unconnected. The building is from the 50s and its electrical system was not upgraded, and ungrounded outlets were common back then.

    I measured: 112V between neutral and line (normal), but about 47V between neutral and ground, and around 66V line-to-ground.

    It would normally mean than ground and neutral are reversed, but from looking at the wiring from one plug, there's no wire connected to the green screw, meaning it's ungrounded.

    What else would cause the "ground" to be almost half the potential of the line? How would I find the exact faulty outlets?
     
  2. DeltaMac macrumors 604

    DeltaMac

    Joined:
    Jul 30, 2003
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    Delaware
    #2
    By far the easiest is to get a simple outlet tester, something like this...

    If you don't have US standard outlets, then whatever is available for your country.
     
  3. MacNut macrumors Core

    MacNut

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    #3
    Is there conduit connecting the box? That would give it a ground. The chances are most of the building is not grounded if it's original 1950's wiring. If there is no ground to the box you can't add a ground.
     
  4. mrkramer macrumors 603

    mrkramer

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    #4
    If you aren't an electrician, which based on the fact that you are asking about it on a tech forum you probably aren't, the safest thing is to leave it alone. You are far more likely to create problems than fix them if you try to redo the wiring in your apartment based off of what you can find on Internet forums.
     
  5. MacNut macrumors Core

    MacNut

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    #5
    Plus the fact that it is just one apartment, it could do damage to the entire building. It's one thing to do work on your own house. This is wiring that he doesn't own that could cause more damage to neighbors. I would bet that there isn't much he could do anyways without doing some major rewiring.
     
  6. DeltaMac macrumors 604

    DeltaMac

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    #6
    The simple test with outlet tester will at least give you some facts about your outlets. You may just be guessing about grounding issues, and that you don't actually have those at all.
    Or, it will give you information that you can pass on to your manager/landlord, etc. Or give you assurance that you don't have a serious issue.
     
  7. hallux macrumors 68020

    hallux

    Joined:
    Apr 25, 2012
    #7
    Do you have a lease? If so, review it, there may be language in there prohibiting you from making changes to wiring in the building. Mine does but I'm in a large complex. As was noted by @mrkramer if you need to ask about HOW to make these changes, it's likely over your head and you shouldn't be doing it in a building you don't own.
     
  8. Cubytus thread starter macrumors 65816

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    Mar 2, 2007
    #8
    Internet forums are not necessarily full of ignorant people, quite the contrary :) The lease doesn't mention anything regarding electrical wiring, and even if it did, I wouldn't let crappy wiring reduce the life expectancy of my electronics.

    I opened two readily accessible outlets, and the earthing lug on the outlets block is left unconnected.
    Would an unconnected earth give an arbitrary VAC reading when testing against line and neutral?

    I couldn't see behind the boxes, but they seem unconnected. Just a cable coming into each one, black insulation material, wires wrapped in paper. However, there's probably a grounding point somewhere for the dryer.

    Example of issues: UPS has "faulty wiring" light on constantly. When fridge runs, radio sensitivity appears much lower as I have difficulty staying tuned on the station.
     
  9. mrkramer macrumors 603

    mrkramer

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    #9
    There probably are some electricians on here who would know what they are doing, but you have no way of knowing who they are and who the random person is that is giving you advice that will lead to you burning down your apartment complex by messing with the wiring. If you really think something needs to be changed about your wiring hire an electrician to do it.
     
  10. Cubytus thread starter macrumors 65816

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    Mar 2, 2007
    #10
    Interestingly enough, the fuse box seems to be grounded: 111VAC line-to-ground, 110VAC line-to-neutral…

    BTW, my budget doesn't cover a licensed, 50$-an-hour electrician. I know the law requires hiring one even for changing a switch, but who really does? Otherwise the parts wouldn't be available in dollar stores.

    How would I find out if the outdated wiring is causing problems in my electronics?
     
  11. mrkramer macrumors 603

    mrkramer

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    #11
    Does your budget cover replacing your electronics if you mess them up through your changes to the wiring, or replacing your apartment if you burn it down due to faulty wiring?
     
  12. DeltaMac macrumors 604

    DeltaMac

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    #12
    Where do you find electricians that only charge $50 per hour? :D
     
  13. Cubytus thread starter macrumors 65816

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    #13
    Huh, everywhere? Cheaper one are just amateurs, just like me. That doesn't mean they won't do a good job, just that I trust my skills as much as theirs. My budget doesn't cover premature failure of electronics due to non-standard wiring.

    So how would I find out what the risk for these device is? Running an oscilloscope 24-hrs a day with data logging just isn't practical.
     
  14. Huntn macrumors G5

    Huntn

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    #14
    Disclaimer: Don't mess with your electric wiring unless you have a basic understanding of what you are doing.

    What prompted/triggered you to decide your wiring was messed up and start testing it?

    As @MacNut said, metal conduit if it's there can act as a ground. And if this is the case, with individual wires, a ground wire may not have been pulled into the box, but IMO, it should have been. This is different than Romex (plastic wrapped wire) which usually includes a bare ground wire.

    If you look at house wiring, both the neutral (usually white wire*) and the ground (usually green or bare wire go back to the same bus in your circuit breaker panel. If you are reading voltage off a wire intended to carry electricity to an electrical device, it should read the same voltage via the multimeter if you are using a neutral or a ground terminal in the receptacle to take the reading. If you take off the receptacle cover and unscrew the receptacle to get a look inside the box, you may have temporarily broken the ground via the metal box and conduit.

    Regarding 47v between neutral and ground, I don't beieve this is unusual as neutral wires do carry voltage back to the ground bus. You can get a shock from a neutral wire. :)

    *white wires can be hot (carry electricity) in a variety of circumstances functioning as a black wire. It's common to see this in light fixtures and switches.
     
  15. Cubytus thread starter macrumors 65816

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    #15
    What prompted me to check it was an old email from a friend I read , where she determined, with the help of her electrical engineer father, that faulty wiring in a building as old as mine triggered repeated failure of her external hard drives.

    Most residential buildings don't include metal conduit between boxes. The wire just goes through the beams to the boxes, and indeed, looking at the outside of electrical boxes housing the outlets, there was no sign of a conduit. There's no unconnected bare wire inside. There's no breaker box either, just a 2-fuses box painted so thick I can't figure out what shape the screws really are.

    From my basic understanding, ground-to-neutral can be non-zero, but never as high as 47VAC (tested on a fully-assembled receptacle).
     
  16. DeltaMac macrumors 604

    DeltaMac

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    #16
    So far, you are just guessing, and perhaps getting an incorrect assessment of your own wiring, when you may be missing something simple.
    The problem, as you said, was in your friend's building. Electrical issues are not contagious, so your friend's issues only make you curious.
    At least try an outlet tester. That will provide a quick read of every outlet in your apartment. You may find out that you have potential grounding issues. Or, you may find out that you don't have any significant issues, other than older wiring - which, on its own, does not mean that you have a problem.
    "Old wiring" really only becomes a problem for you if you need to bring your residence up to code, and you get a quote for redoing all the wiring in an old building.

    Maybe ask your friend if the electrical engineer/father can do you a favor and come check out your place, to help ease your mind, and there's no problems - or give you some (knowledgeable) backup when you ask the owner to fix up their potentially dangerous building.

    What's the old saying? "a little knowledge is a dangerous thing!"
     
  17. maflynn Moderator

    maflynn

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    Boston
    #17
    Get a battery backup UPS, that will give you clean power and protect your equipment from electrical irregularities. I agree with the others, if you don't have the training, don't mess with it. Electricity can kill you, plus if you damage the apartment, you'll be liable, plus you may injure someone else. Most electricians won't even work on an apartment since you don't own anything, and they don't want to be liable to changing anything that the owner didn't wished changed.
     
  18. Cubytus thread starter macrumors 65816

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    #18
    UPS rely on correct wiring to operate safely and are just that, a UPS, not a power conditionner, unless they're part of the most expensive line-interactive ones that fully insulate mains from outlets. And the one UPS I have keeps this light on at all times "faulty wiring". Most of today's apparatus is designed to operate properly with a ground. I fear it may not behave well under adverse conditions, and would like to know it before such conditions arise.

    The owner doesn't want to change anything as it is not required by his insurance company nor the fire department. Outlet tester is a quick way that can be done with a DMM just as well.

    Our buildings are of similar age, with decades of neglect, in the same city were "bringing up to code" was never mandatory. You're right, educated guess is at work here, just like you are just guessing that a seatbelt may well save your life in a car accident without actually having to crash to verify the hypothesis.

    Why I have reasons to think wiring may be problematic:
    - radio loses sensitivity when fridge is running (doesn't imply grounding problem by itself)
    - large potential difference neutral-to-ground (suspected faulty ground)
    - unconnected earthing lug on the receptacles (not at today's standards)
    - apparently grounded fuse box (meaning there's a grounding point)
    - no loose wire coming out of the cable inside one box.
    - "wiring fault" light lit on UPS and another power bar

    I never thought I would have to justify my intent to Americans, widely seen as people who readily follow the DIY mantra.
     
  19. chown33 macrumors 604

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    Aug 9, 2009
    #19
    If there isn't a grounding wire in the power cable running into the outlet box, and there isn't a grounded metal conduit, how do you propose to run an electrically suitable grounding wire to the affected outlets?

    In other words, supposing that grounding is the problem, what remedies do you have?

    If your proposed remedy is sound (e.g. it doesn't violate building codes, rental agreements, etc.), then why don't you just do it?

    As a simple effectiveness test, you could do it on one outlet, then see if it solves the problem. You have at least two zero-expenditure test mechanisms available:
    1. the "faulty wiring" light on the UPS,
    2. the DMM.

    I would suggest testing with both.
     
  20. maflynn Moderator

    maflynn

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    #20
    The issue is, that you're looking to do your DIY project on someone else's property and that can be problematic.
     
  21. MacNut macrumors Core

    MacNut

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  22. chown33 macrumors 604

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    #22
    Those would either be ineffective or unnecessary.

    If the outlet box isn't grounded, then the screw going through that grounding lug won't connect to an electrical ground. It'll just connect to the ungrounded outlet box. This would be ineffective.

    If the box is grounded, then this adapter is unnecessary. All that would be needed is to take a bare copper wire of suitable gauge and connect the ground terminal of the 3-wire outlet to the grounding screw in the box. However, if the box is ungrounded, this would still be ineffective.
     
  23. MacNut macrumors Core

    MacNut

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    #23
    Stop ruining my punchline! :p
     
  24. Huntn macrumors G5

    Huntn

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    #24
    But the sound of it, you have Romex, wires wrapped in plastic. But I don't like the sound of a fuse box with two fuses in it. Where is that powered from? Modern romex usually has a bare ground wire, but this is old wire. I'm not clear on what you consider to be the ground. If you open a receptacle and look inside, you might be able to see if there is a bare ground wire roll up, which could be connected to the receptacle's ground screw. However, depending on the condition of the wire insulation, if it is brittle, you might be better to leave it alone and instead ask an electrician to make a house call and tell you if you have a electronic cal/fire hazard on your hands.
     
  25. satcomer macrumors 603

    satcomer

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    #25
    Sounds like the scene from the movie Patriot Games when the electrical in he book store said the wiring is from the War, the First One, in my business is what we call rare! :p
     

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