voltage drop

Discussion in 'Electrical Forum discussion & Blog' started by Mike Pastorelli, Jan 22, 2014.

  1. Mike Pastorelli

    Mike Pastorelli New Member

    Messages:
    34
    Location:
    Florida
    My meter point is right at the ( hot ) conductor before the main breaker. The two hots that come off the meter can and into the house before hitting the main panel.. One meter lead is on the neutral and the other on the hot.. Both show 120 volts.. Then, when I turn the microwave on or any large load from any plug everything dims down and on the one conductor the voltage drops to 95 V and the other conductor swings up to 155 Volts.. Cant figure out what is going on? Please advise? Recently purchased forclosure house with what appears to be new service panel.. Thanks :confused:
  2. Reach4

    Reach4 Well-Known Member

    Messages:
    2,805
    Location:
    IL
    Both hots show 120 volts to neutral and you will measure 240 hot-to-hot.

    Are you saying that only two wires come from the "meter can" into the house? That's a big problem that needs fixing.

    Or are you saying that a third wire comes in. Is that third wire at the same potential as your neutral bar? If so, you probably will need to involve the power company. One of the problem may be in the power company wiring. At least one of the problems is in your local wiring. I think you probably want to call your electrician first, but maybe calling the power company first is better. I don't know.


    You have an additional problem in that your local ground connection is not good enough.

    So probably two problems that need fixing. It may be good that you have two problems because one problem alone might have never been noticed.
  3. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,281
    Location:
    Land of Cheese
    The connection to neutral is failing. Make sure yours is tight in the main panel, and if so call the power company. Here, the line from the pole to the meter belongs to the p.c.
  4. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,511
    Location:
    Houston, TX
    You may have a grounding problem at the Pole Pig, HV transformer.

    The neutral can float if the ground is missing.

    That can be a Big problem.


    Good Luck.
  5. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    1,001
    Location:
    NY State, USA
    This is NOT a grounding problem. It is a neutral problem on the secondary side of the utility transformer.
  6. ActionDave

    ActionDave Electrician

    Messages:
    363
    Location:
    Colorado
    Agree with others, bad neutral. Shut off the main and call the power company.
  7. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,511
    Location:
    Houston, TX

    OK.

    This old dog loves to learn new tricks.

    Is the Neutral and Ground NORMALLY not the same at the Transformer ?

    They are around here.

    And the Ground at the Meter Service is a safety, just encase there is a neutral fault. It can keep HV from going into the House. Like when a HV transformer shorts out Primary to secondary.

    I understand that it depends on the system used. Some systems carry neutral, some rely on Earth Ground.

    I do like to be corrected if I am wrong.


    Thank You, I want to learn more.
    Last edited: Jan 23, 2014
  8. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Just to repeat what you have been told:

    This is a bad neutral from the power company. And it ain't no joke.

    Your whole house could get fried. Have the electric company come out yesterday.
  9. Reach4

    Reach4 Well-Known Member

    Messages:
    2,805
    Location:
    IL
    You are presuming that the neutral wire was wired into the breaker panel from the meter box.

    We all agree that quick action is required, but the OP seems to be gone.
  10. Mike Pastorelli

    Mike Pastorelli New Member

    Messages:
    34
    Location:
    Florida
    3 conductors come off the meter can and into the service panel. 2 hots and a neutral. As I said, my DMM reads 118V off each leg with light loads. But, when I plug in larger loads ( microwave or fridge ) the voltage jumps all over the place. I am still looking over this previous owners work ( panel appears to be new - maybe few years old GE goldmark copper conductor bus bars ) Couple observations I can add. I noticed on some romex 12/2 in a crawl space area the wire is chisel damaged a bit, maybe a nick in the neutral. Would a nick in 1 wire cause all this dimming? Also, the meter can and the service panel have separate ground rods that are not connected in a closed loop, but are in contact via the metal conduit pipe that runs from the meter can to the main panel ( through the wall of the house ) I removed the bulb and cleaned and tightened all contacts in the meter can using acetone on a long wood handled small service brush. Please advise? EDIT - Also, forgot to add - I observed a split bolt connector on the neutral leg. I guess the wire was to short and they added 20" of #2 conductor to it. The split bolt connector is very clean and tight and I'm wondering if that could be my issue whereas I vaguely remember people saying this is a no / no. But, if its clean and tight that shouldn't be an issue, correct??? Also, neighbor and I share the same transformer and he says he has no issues with lights flickering or dimming. Problem seems to be mine alone. Thanks Again
    Last edited: Jan 24, 2014
  11. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,511
    Location:
    Houston, TX

    Where are you measuring the voltage ?

    If you are measuring the voltage at the main breaker, then that would indicate a problem on the service feed.

    You should have the electric company check at the pole or HV transformer.

    They should not charge you for that service.


    Good Luck.
  12. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,565
    Location:
    North Carolina
    No. There is a big difference between the neutral and ground every where on an electrical system
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,565
    Location:
    North Carolina
    As many has already told you call the power company right now.
  14. Reach4

    Reach4 Well-Known Member

    Messages:
    2,805
    Location:
    IL
    Now you are just trolling. You know that is not true.
  15. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,565
    Location:
    North Carolina
    The neutral is the center tap of a transformer but grounding is the connection to earth in an ungrounded system there will be no neutral from the utility but there will always be an earth connection or grounding if one pleases.

    It is very true that the utility connects their earth ground to the neutral just as we do at the service equipment but the neutral is a current carrying conductor and the grounding is not current carrying a very huge difference.
  16. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,511
    Location:
    Houston, TX

    That may be true if JW calls 1 Volt a big difference. But that is about normal, at a outlet on a long wire run drawing 10 amps.

    The difference in ground and neutral, is the Voltage drop on the neutral wire feeding the outlet.

    There should not be a big voltage difference at the breaker panel, If so the feeder wire is to small, or the panel is not bonded properly.


    I doubled with you JW, You did not say "Over" , my mistake, but what you say is true.

    Over
    Last edited: Jan 24, 2014
  17. Reach4

    Reach4 Well-Known Member

    Messages:
    2,805
    Location:
    IL
    Edit: paragraph withdrawn.

    At each house there is normally a ground rod or two that is electrically connected to the incoming neutral conductor. 2. True? 3. Are those ground or neutral rods? In side the first breaker box, the neutral terminal and "ground" terminal strips are connected electrically together inside the breaker box. 4. True? . We understand that is not the case in a sub-panel.

    I know none of those things come as a surprise to you.

    Edit: I just figured out that when you said "big difference" (even on a thread with Voltage in the subject) you meant "big distinction". Green vs white is a difference too, but in the voltage world, I see 2 volts as a difference.
    And jadnashua, care two answer the first 3 questions?

    The Kirchhoff's current law review -- you do have only power 1 wire coming to your neighborhood, right?

    And here is an extra question if you want to respond jadnashua: 5. If there had been a proper grounding/neutralling/wtf system in place at the house, but the neutral wire on the drop was broken, would that symptom the OP saw have been observed? At least 2 flaws here IMO. Power company first. Then maybe more.
    Last edited: Jan 24, 2014
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,319
    Location:
    New England
    The only time the ground wire/rod should ever carry current is if there is an induced voltage as from a lightning strike or a fault in the system...IOW, the ground lead should NEVER have current running through it except in exceptional circumstances. Power needs a complete circuit and that's from the hot lead to either the other side of the transformer directly (in a typical 240vac residential system), or via the neutral lead, which still gets to the other side of the transformer, but not passing through ground.
  19. bluebinky

    bluebinky Member

    Messages:
    408
    Location:
    Santa Clara, CA
    I agree with JW on this one. Also, agree about shutting off the main breaker until the problem is fixed.

    I have a silly question. Are there any main breaker panels that can be configured as a sub-panel -- by removing a bonding screw?
  20. Reach4

    Reach4 Well-Known Member

    Messages:
    2,805
    Location:
    IL
    It looks like I was wrong about the distribution transformer grounds; it seems they have separate ground rods and wires for the high and low voltage sides. I wonder if it has been like that forever or if that practice started after sharing grounds for years. Anyway, here is the schematic using separate grounding rods: [​IMG] I still think the OP's system has at least two problems.
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