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Thread: Possible loose neutral issue

  1. #1
    Join Date
    Nov 2007
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    Louisville, KY
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    438

    Possible loose neutral issue

    Long story, so pass if you're not in for a long read.

    Probably a ton of posts on this but anyways...

    My neighbor has a 1950s house with a 60 amp service. Someone replaced the panel with a 100 amp main breaker panel.

    Neighbor told me the lights were blinking when the central air came on. They wanted the top half of the service upgraded anyway and I assumed that would fix it. I never actually saw any blinking.

    After I upgraded top half of service to 100 amps they said lights still blinked. I did find a loose wirenut on the hot side in one box that caused a living room lamp to blink when I moved the wirenut. Didn't fix the issue.

    At the main breaker I measure right at 240 volts and 120 to both neutrals. At the living room lamp I measured 117 volts. When we turned on microwave oven the voltage went up to 119 volts. Didn't check to see if they were on opposite phases or not.

    The garage is on it's own 2 pole 30 amp circuit with a sub panel. They tell me lights blink there too but I didn't see it.

    I'm thinking since blinking is on different circuits and all connections at panel and meter are tight, it must be a power company issue. Will be calling them tomorrow.

    Anything different I should have done? Any magic blinking light troubleshooting techniques I need to be aware of?

    Thanks for reading.





    Sent from my SM-G930V using Tapatalk
    Dale

  2. #2
    Join Date
    Apr 2005
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    Atlanta,GA
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    Quote Originally Posted by dhalleron View Post

    Neighbor told me the lights were blinking when the central air came on.

    I'm thinking since blinking is on different circuits and all connections at panel and meter are tight, it must be a power company issue. Will be calling them tomorrow.
    The power company is the right way to go. Let them put a load on the service with the "beast".

    It doesn't have to be a neutral to cause the lights to blink. One of the hot cables could have a bad splice that heats up because of the AC load.
    The 95% of people that you can't trust give the other 5% a bad name.

  3. #3
    Join Date
    Jul 2007
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    Call the POCO and have them check their connections.

  4. #4
    Join Date
    Feb 2012
    Location
    Athol, ID
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    824
    How long is the service drop? If it's a long ways and the wires are minimum for the service, you could just be dealing with voltage drop. Starting surges from motor loads starting are a common source of problems. POCO should be able to tell if that's the problem, or the transformer may have too much load if it's shared between several customers. They should measure voltage at the transformer and at the meter under heavy load to see if there's a voltage loss. That's what a beast is for. Fairly common but often hard to convince the POCO to upgrade the service. We have added transformers and split the customers many times, especially in older areas where the original service was inadequate for the increased load of all the "new-fangled electrical gadgets". Transformer overloading is usually seen as blinking lights when you are not starting anything yourself that would cause it but the neighbor might be.
    Last edited by meternerd; 06-12-18 at 10:10 PM.

  5. #5
    Join Date
    Jul 2007
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    Other possibilities lie in the compressor itself. Aging/malfunctioning start capacitor. Debris-laden vent fins. Clogged refrigerant line. Over-pressurized refrigerant line.

  6. #6
    Join Date
    May 2018
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    Boyertown, PA, USA
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    You said it's central AC, so assuming it's 240v, a neutral problem wouldn't cause a load variance between the phases, so voltage shouldn't seesaw between them with 240v loads.

    Did the the blinking lights problem exist before the panel was changed? If so then I agree with previous suggestions that the relatively large central air startup load on a system with relatively small service wire is causing the voltage fluctuation.

    House dates to the 50's....is any of it aluminum wire?
    Last edited by Craigv; 06-13-18 at 08:57 AM.

  7. #7
    Join Date
    Nov 2007
    Location
    Louisville, KY
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    438
    It may be fixed but time will tell.

    I found the main lugs on the existing panel had some corrosion. I cleaned it up and put on some deox.

    Customer said no blinking last night or this morning.

    There is no aluminum wire that I have seen in this house.

    The poco transformer appears to feed about 10 houses and this house is near the end of the run but not last. A neighbor at the same connection point reported no blinking.

    Will give it a few days and if it happens again I will call poco.

    Thanks for the input. Been doing this a lot of years but only part time the last 25 years or so. Always helps to get other opinions.

    Sent from my SM-G930V using Tapatalk
    Dale

  8. #8
    Join Date
    Nov 2007
    Location
    Louisville, KY
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    Forgot to mention the lights did blink before the upgrade, I just never saw it.

    The AC unit is fairly new on a 25 amp breaker but could still be a problem.

    Waiting for now.

    Sent from my SM-G930V using Tapatalk
    Dale

  9. #9
    Join Date
    May 2005
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    Richmond, Virginia
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    I always tell customers that some amount of flicker upon start-up of A/C or electric heat is normal, as long as there is no other issue from it.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  10. #10
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    NE Nebraska
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    Quote Originally Posted by dhalleron View Post
    It may be fixed but time will tell.

    I found the main lugs on the existing panel had some corrosion. I cleaned it up and put on some deox.

    Customer said no blinking last night or this morning.

    There is no aluminum wire that I have seen in this house.

    The poco transformer appears to feed about 10 houses and this house is near the end of the run but not last. A neighbor at the same connection point reported no blinking.

    Will give it a few days and if it happens again I will call poco.

    Thanks for the input. Been doing this a lot of years but only part time the last 25 years or so. Always helps to get other opinions.

    Sent from my SM-G930V using Tapatalk
    I'm guessing it is mostly a problem with lights dimming when compressor is starting, and that you are experiencing voltage drop during this starting period because of the length of the run and size of conductor's.

    Problem is POCO may come out and check running voltage and say it is within range of what they are required to deliver and won't do anything about it.
    I live for today, I'm just a day behind.

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