Lights Getting Brighter - Possible Loose Neutral?

Discussion in 'General Electronics Chat' started by mostlydrummer, Feb 8, 2016.

  1. mostlydrummer

    Thread Starter New Member

    Feb 8, 2016
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    I have a strange electrical situation in a house that I bought last summer and would appreciate any insight I can get here. The house is about twelve years old and has a completely finished basement. There is a small refrigerator in the basement, and when the compressor motor cycles on, the fifteen overhead can lights in the main room of the basement, which are on the same branch circuit as the refrigerator, flash brighter for a second or so and then go back to their previous level of brightness. I had a backup sump pump installed not long after I bought the house, and this required rewiring an outlet box (on a different branch) so the two sump pumps could be on separate breakers. At the time I had the rewiring done, I had the electrician (who was from a large and well-regarded electrical contracting company where I live) investigate, and he concluded there was nothing to be concerned about.

    As I continued to observe the same behavior with the lights over the next few months, I took to Google and saw a lot of discussion about this, and the responses were consistent: lights getting brighter with a motor turning on = loose neutral = dangerous. I had the same electricians out again to fix a fancy and over-complicated Lutron dimmer that was misbehaving and pointed them to the basement lights again. The guy tightened all of the connections on the relevant service panel (there are two, both of which are located in a separate room in the basement) and said neither he nor his boss, the lead electrician, had encountered lights brightening as I described but that they would be happy to install a separate circuit with a "new" neutral for the basement refrigerator. I passed for the time being. Since I had found descriptions of this issue (and dire warnings about its potential consequences) myself all over the internet, this did not inspire much confidence, so I'm taking to this forum for insight.

    My questions and additional observations:

    1. Much of the discussion that I've seen about this counsels people to call the power company immediately, and suggests they are likely to show up quickly to check the main connection to the utility electrical supply. In my case, the only part of the house that behaves this way is the overhead lights in the basement (which, as noted, are on the same branch circuit as the refrigerator). Assuming this is being caused by a loose neutral, could a loose connection on the main utility supply cause only one circuit in the house to behave this way, or does this behavior suggest a loose neutral only on the branch circuit (assuming such a thing is even possible...I'm a layman). If the latter, can the loose connection causing the problem be either at the service panel or the receptacle?

    2. I've never observed the basement lights getting brighter when anything else happens in the house, and I've never observed any other lights in the housing getting brighter. Tonight, however, I might have observed the basement lights getting slightly brighter when the garbage disposal was turned on once upstairs on the main floor. I was in the middle of the Super Bowl and didn't go back and test this before everyone else went to bed, but assuming that actually happened, would this change your perspective on my questions above?

    3. Since this appears to be "contained" to the one part of the basement, assuming it is a loose neutral, are the concerns as significant? I also have a lot of electronic equipment plugged into the same or an adjacent circuit.

    4. Is it really possible that a large and well-regarded electrical contractor would be unfamiliar with a situation like this?

    Thank you for any and all insight you can provide!
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
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    Did the service guy attach a meter to your power panel and make measurements when the appliances were on?? If he did not make measurements then he is in the dark. Call the power company.
     
  3. mostlydrummer

    Thread Starter New Member

    Feb 8, 2016
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    He took no measurements. But before I call the power company, given the apparent "containment" of the issue, is there a possibility that this is isolated to the interior circuits of the house vs. the power company connection? In other words, should I be starting with a more informed electrician? It troubles me greatly to think that I seemed to have learned more about this via the internet than a large electrical contractor seems to know (and I'm presuming a bit here, but since they didn't even have a theory and claimed not to have ever encountered the symptoms...). Thanks.
     
  4. #12

    Expert

    Nov 30, 2010
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    At my house, I found an illegal splice in the wire from the meter to the neutral bus in the breaker box. It was completely concealed from the inspector and me by the proper wires going to each circuit breaker. The moral of this story is that you have to see every inch of wire from the transformer on the pole to the neutral bus in the breaker box. Every connection must be solid from the transformer on the pole to the neutral bus in the breaker box.

    Adding a new branch circuit will not fix this.
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Can you temporarily run the fridge from another branch and see if the problem persists? That might help track down whether the fault is with the basement branch only or the whole house.
     
  6. Lestraveled

    Well-Known Member

    May 19, 2014
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    @mostlydrummer
    The symptoms you describe strongly suggests a loose neutral connection. The question is, where is it? It has to be in two areas, in your power panel (your responsibility) or, from your power panel out (power company's responsibility). Call your power company and talk with them about it. They might be willing to check your panel out for free.

    It is highly unlikely that the problem is between the power panel and the appliance. Not unless someone did some very bad things with they built your house.

    It does not sound like you have the knowledge of how to work around high voltage safely. So, we are not going to suggest that you grab a meter and go probing around in your power panel. If the power company won't check out your power panel connections, then you need to find a smarter electrician. You know how ask the right questions. Don't hire someone unless he gives you the right answers.
     
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    The time I had lights getting brighter the issue was out at the power pole to my house. The local utility company was called, they checked my exterior connections and re spliced all the ends to make sure, though only one connection was found to be faulty. I suspect the fault was a tree branch that used the line for support during Sandy.

    It took over a year for the problem to develope. The power company check out and fix was free, so start with them.
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Very common for lights to "dim" when high draw devices are turned on (vacuum cleaner,etc..) but getting "brighter" could be seen as a loose connection and should be investigated..
     
  9. mostlydrummer

    Thread Starter New Member

    Feb 8, 2016
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    Thanks to all. I have called the utility and they are going to come out and check the external connections. I am still puzzled that only the basement overhead lights are impacted, but I will start with here. I did test the upstairs disposal this morning and it did not cause the basement lights to brighten as I thought I might have observed last night, so as far as I know the issue is limited to the one basement circuit with the overhead lights and refrigerator. I'm not sure whether this is good or bad, but seemingly I will know more once the utility has checked the main supply connection.

    Thanks again, and any additional insight is welcome!
     
  10. BillB3857

    Senior Member

    Feb 28, 2009
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    If the refrigerator and the lights are on the same branch, I hope someone can explain how a poor neutral would cause this. Any time I've seen a poor neutral, the lights on the same side of the 120/240 volt line would experience reduced power, not increased power.
     
  11. Lestraveled

    Well-Known Member

    May 19, 2014
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    @BillB3857
    OK, In order for the refrigerator to cause the lights to brighten, they would have to be on different branches. The neutral is common to both and if it had a high resistance connection to the mains the following would happen: The lights and the refrig form a voltage divider between the two branches. If both lights and refrig were drawing about the same current they would see the same voltage, and the neutral would see little current. When the compressor kicks on and draws more current, the voltage divider is changed, the refrig will see less voltage and the lights see more voltage. This can only happen if the neutral is high resistance.
     
  12. #12

    Expert

    Nov 30, 2010
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    A poor neutral can't cause that scenario, so just use your common sense and assume the OP is wrong. The lights and the motor are on opposite sides of the 240 VAC line.
     
  13. BillB3857

    Senior Member

    Feb 28, 2009
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    Thanks for the confirmation that I hadn't suddenly lost my mind, Lestraveled and #12. Sometimes I am wrong, but never too old to learn something.
     
  14. mostlydrummer

    Thread Starter New Member

    Feb 8, 2016
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    New developments. The utility was out this morning and confirmed that the connections at the pole and on the "line" side of the meter were good and reading as they should. The readings on the "load" side of the meter were unclear, so he pulled the meter, cleaned the terminals, and reconnected the meter and then got perfect readings on the load side of the meter. I'm not home to check, but will check tomorrow to see if this eliminated the problem. The guy from the utility was thoughtful and very knowledgeable and indicated that while this might fix the problem, it could be unrelated and there could still be a loose neutral inside the house.

    Re: the points above, I'm not 100% certain the refrigerator is on the same circuit as the overhead lights as I indicated above but will confirm tomorrow. I thought I remembered that they were, but there are two large panels and it's entirely possible that they're not. From above, it seems if a loose neutral is the problem that they can't be on the same circuit. Now that I've eliminated external issues, I'm hopeful that it will turn out that they're not on the same circuit and the problem is a loose neutral wire in the outlet where the refrigerator is plugged in and that tightening it will fix the problem. More to come.

    Thanks!
     
  15. #12

    Expert

    Nov 30, 2010
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    1) He's right. You still might have a second error.
    2) Trust us. We're nerds. Half of us could wire your house without looking at the book.
    3) A loose neutral at the outlet won't cause this problem. If anything else is wrong, it's between the meter lugs and the Bond terminal in the breaker box.
     
  16. mostlydrummer

    Thread Starter New Member

    Feb 8, 2016
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    Thanks, AAC.

    Nerds or not, I searched the internet about my symptoms because I wasn't satisfied with my electrician's answers and found the discussions here about similar issues to be, by far, the most thoughtful and detailed. So I joined to get some help!

    Regarding your third point, to make sure I understand, are you saying that even though the problem appears to be isolated to one circuit (or perhaps to be caused by one and appearing on another nearby one, if in fact the refrigerator and lights are on separate circuits), that the problem would still have to be a "global" one? And more specifically, that it would be between the meter lugs (I assume that's where the main service line from the meter to the house is connected to the meter?) and where the main service line from the meter connects to the breaker box (is that what you mean by "bond terminal in the breaker box")? If so, and since I have two breaker boxes, could there also be a problem with the way the second breaker box is wired? Note that all basement circuits are in one box, although that box does have circuits for the rest of the house as well.
     
  17. #12

    Expert

    Nov 30, 2010
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    My moniker is pronounced, "Number Twelve".
    That is the whole list.
    That is what went wrong at my house. There was an illegal splice in the neutral wire from the meter to the breaker box. Your electric company doesn't work on anything after the meter. The part from the meter to the breaker box is your responsibility.
    Now, instead of speculating, go see if it's fixed.
    One actual result is worth a dozen theories.
     
  18. BillB3857

    Senior Member

    Feb 28, 2009
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    You say you have two breaker boxes. Which box is the refrigerator powered from? Which is the one powering the lights? Which is directly fed from the meter?
     
  19. mostlydrummer

    Thread Starter New Member

    Feb 8, 2016
    18
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    Updates:

    1. I'm home, and the issue persists despite the minor cleaning work performed outside on the meter terminals by the power company, which as noted did result in a proper reading on the load side of the meter vs. the previous unsteady reading.
    2. The overhead lights and the outlet where the refrigerator is plugged in are on separate circuits with adjacent breakers. Not sure if it matters, but the overhead lights have a 15A breaker and the outlets have a 20A breaker.
    3. BillB, both breakers in question are in a "sub-panel" (my term) that is connected to a "main panel" (also my term) that is connected directly to the main service line/meter. For what it's worth, a pair of breakers in the main panel have handles that are connected so they move together when switched; these are labeled as controlling the feed to the sub-panel (although I haven't tested whether turning them off turns off the entire sub-panel as you would conclude from the labeling).
     
  20. Lestraveled

    Well-Known Member

    May 19, 2014
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    The plot thickens. I suspect the neutral connection between the two panels.
     
    ErnieM, cmartinez and #12 like this.
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