lost one phase of 200 amp service panel, power company says they are providing fully

Discussion in 'Electrical Forum discussion & Blog' started by dweller, Jan 6, 2012.

  1. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC
    This problem came up last week and I found it coming home when noticed the motion detected light in drive was dim. Porch light also dim. Came in and found fridge lights dim. Started looking about and finding receptacles not working, or barely working, and then working fine again. Appears the lights/receptacles were cycling back and forth dim to bright.
    No hot water, dryer not operating. Trying to work the dryer makes lights dim.

    So, spent a few days checking appliances (working or not) and made my way back to service panel. I find i have 125v and 135v on both sides of breaker for water heater and dryer, but not 220v across either sides. Same at thermostats of water heater and poles of dryer receptacle. But when the cycling (dimming) occurs one side drops to 80v. at both breaker and appliance (thermostat or poles of dryer receptacle). Also,several 20amp breakers drop to the same 80v during dimming cycle.

    In checking breakers I found one for the lights that were dimming sparking and moved the wire to another free 20amp and that solved the problem with the dimming. But i still don't have 220 for water heater and dryer. Called the power company and they came and checked the voltage at meter and said it was fine, problem was in the buried cable to my home. Not their problem.

    I had found that when the dimming cycle was occurring one phase of my service panel was dropped to 80v, then back to 125v, so thought it was a power company problem. But switching the wire for the lights to another free breaker cleared that up and I get 125v steady on that phase _unless_ I turn off the breaker to the water heater, then it drops to 26v on that phase. I get 135v on one side of breaker, 26v on the other. Same on the dryer breaker, 135v on one side and 26v on the other. Two of the lights/receptacle 120v breakers also drop to 26v. When I turn the breaker for the water heater back on I get 135v on all breakers (120v and both sides of water heater and dryer). But can't get 220v across either water heater or dryer breakers. So, apparently I've lost one phase.

    My first question: why am i seeing 125v everywhere when the water heater breaker is turned on, but lose 125v at the main phase wire coming in when i turn the water heater is off.

    Both elements of water heater have checked for continuity (13 ohms) have 125v/135v on the thermostat posts, and at the wires coming into it, but not 220 across the wires/thermostat. I can't eliminate the water heater as bad since i'm not getting full voltage on both phases according to my testing, and the power company's test of their service.

    I realize i will have to call an electrician to come in, but don't want to start digging up the yard to replace the service wires coming in if the problem is actually inside with the water heater, or the service panel. I want to eliminate as much as i can to save on chasing something not causing the problem.

    More details: 200amp service panel in an older mobile home, setup 3 years ago. Power meter is approx. 30 feet from home with line coming in underground. Service to home connected in weatherproof box and run additional 20 feet to back of home where service panel is installed. For that 20 feet new 4/0 200amp service wire run in conduit to service panel, so i don't think that is where a fault could be due to weather/nicks, etc. Either underground original service wires, or inside house somewhere is my outlook on this.

    Any clues appreciated and will observe absolute safety procedures checking any procedures suggested. Will be glad to answer any questions to the best of my knowledge concerning voltage checks, tests etc.
    But honestly, i'm starting to get stumped with this problem.

    thanks in advance,
    dp
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,080
    Location:
    NW Ontario, Canada
    Your 240V loads are backfeeding the dead leg from the live leg and that is what is confusing you. If you turn off all breakers feeding 240 volt loads it removes them all as supects. If you then still don't have 240 before the main breaker, the problem must be between the main breaker and the meter base if the PoCo confirmed power at the meter base.
  3. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC
    Okay, thanks, that i can do. Will check in the morning and report back.
    Appreciate the info.
    dp
  4. leejosepho

    leejosepho DIY scratch-pad engineer

    I once had your kind of problem when the bars under the breakers had corroded and the main breaker was not always getting full power on one side.
  5. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,250
    Location:
    Land of Cheese
    What I don't understand is why you wasted all the time testing individual circuits and appliances when you could have taken a single measurement in the service panel to verify that the buss maintains 220 when loaded.
  6. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC
    okay, turned off the breakers to wh and dryer and have 130v on one phase, 12-14v on the other.
    turned off all breakers and have 130v on one phase, 39.5v dropping to <33v on the other - 177v before main breaker
    turned back on the dryer breaker - 130v on one, 18v on the other
    turned off dryer, wh breaker on - 130v and 130v - makes sense that the wh is backfeeding, not dryer
    turned back on wh breaker - 130v and 130v

    i checked with breakers on/off, one on,one off, etc just out of curiosity.

    so this confirms one phase is dead, or almost dead? since i still have some 12-14 volts with 220 breakers off, or 33-39v with all breakers off?

    I will be in touch w/ electrician hopefully this afternoon, see if he has fault finder equip for finding problem in yard.

    thanks for your help
    dp
  7. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC

    i'll have electrician check it
    thanks for your help
    dp
  8. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC
    I guess i wasn't thinking worst case scenario? Initially lights were dimmed/brightened fairly cyclic, every 7-8 minutes or so. So was trying to determine what was pulling power, flipping off breakers to see what made the dimming quit. Found a bad 20amp breaker on the lights that were dimming and corrected that. But then no 220v for wh/dryer so started checking phase feeds. I'll admit i have been confused and stumped on this until now.
    live and learn i guess
    dp
  9. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    All you need do is test the incoming main wires to the house and see if you get 240 volt across them. Then test the other end of the wires at the poco area. if you got 240 there, you got big fried gophers. Or a bad main breaker, most likely. Trip your main a few times.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,874
    Location:
    Cave Creek, Arizona
    quote; Or a bad main breaker, most likely. Trip your main a few times.

    Why NOT test power to AND FROM the breaker to see if it is supplying power to the line. You lost a leg of the 240 line, because you have single phase power. I assume you have a direct burial power line, rather than one in conduit, with the meter at the property line, rather than at the house.
  11. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC
    poco checked at the meter and below at the main, found full power, i watched him and discussed possibilities of where the loss could be, he thinks underground.
    I've tested at the main breaker of inside service panel, and have 130v and 40v on both main wire connections at my main shutoff of service panel.

    dp
  12. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC
    yes, meter at property line, ~25' underground to the underside of my home. There it is joined with new 4/0 wire traveling ~25' to the back of my home where the service panel is. That 2nd 25' is enclosed in conduit, and the junction btwn underground and conduit is enclosed in a waterproof box, wires joined together w/ large clamps, wrapped securely, etc.
    The last 25' of conduit enclosed wire to service panel is ~3yr old, installed when i moved in. The underground is possibly 30yrs old.
    I'm thinking either the underground has a problem, or the junction is a problem, and will have to check all of it eventually.

    dp
  13. kevink1955

    kevink1955 Member

    Messages:
    33
    Location:
    L.I. New York
    The only other thing you can do to narrow it down further is open up the splices where the new wire meets the old underground. Just because it is made up with clamps (bugnuts) and tape does not mean it is a good splice.

    I once had a similar problem and the utility went right to the service entrance where my copper cable joins their alum cable. Tech saw it was bugnutted and taped and went right for it, he cut the wires on both sides of the bug and tossed them to the ground. I picked them yp and found that the tape on 1 of them was dry and hard as a rock. I could not unwind it from the splice, the other one had tape like brand new.

    The one with the hard tape must have had high restance for years and cooked the tape, I finaly got the tape off and the thing was still tight but had developed a film on the alum that was causing it not to contact the copper properly. The tech says he sees about 5 a week like this, replaced with hydralicly crimped splices and all is well.
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,183
    Location:
    New England
    Aluminum is VERY reactive...most people think it is fairly inert, but it almost always has a (thin) coating of AlO2 on the outside of it. Depending on how it is attached to something, it is very easy for it to develop enough of an insulating coating on it so it does not conduct electricity well. There are some very strict rules about how to connect aluminum wires to anything and if they aren't followed, you'll have problems. Take powdered aluminum and iron oxide (rust), mix them together and add heat, the aluminum will strip the oxygen off the iron, leaving liquid iron - the aluminum wants that oxygen that much more than the iron does. Commonly called a thermite reaction. While Al is cheaper than copper and can work well, it can have its problems when not installed properly.
  15. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC
    Okay, you are thinking along my same lines, narrowing down the possibilities. I'll check the junction. I don't think the new wire is failed, the underground is more likely a culprit in this scenario, altho nothing has disturbed it in the time i've been here, no digging, etc.

    thanks for your input.
    dp
  16. dweller

    dweller New Member

    Messages:
    10
    Location:
    blue heaven, NC
    Thanks for that, not sure what i can do with it, but thanks for offering your advice. As far as i know, the wire i bought (4/0) was the correct one to connect to the wire underground, and the clamps were sold to me to hook them together.
    i'll take a close look at it.

    dp
  17. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,351
    Location:
    Houston, TX
    If it was me, I would kill all the circuits in the breaker box until the problem was solved.
    Just to avoid Burning appliances up.

    You can use 2 120 V Circuits (1 on each leg) for testing that only have resistive loads. Or Maybe the water heater, If that is not the cause of your problem(Shorted Element). Just to provide a load.

    I would suspect the MAIN breaker, If the splices were properly connected. A little resistance in a bad Main Breaker or its connections can cause a BIG problems, and is not safe for you or your Electrical devices.
  18. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,080
    Location:
    NW Ontario, Canada
    Diagnosing the main breaker with a volt meter would be trivial. Just need to see if 240V is available before the breaker but not after the breaker.
  19. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,351
    Location:
    Houston, TX
    You can measure the Voltage Drop Across the Breaker and that will tell you if the breaker is bad. Or You can even feel heat coming from it.

    Or measure the voltage from the out of the breaker to the Buss and that will tell you if it is a connection problem.

    But it does need to have a load on it.

    Measuring the input for 240 will tell that the input is bad, But not if it is good. Needs a load to test properly.


    It could very well be on the input side. In that case Jim explained it very well.
  20. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,351
    Location:
    Houston, TX
    What I said is "I would suspect the MAIN breaker, If the splices were properly connected"

    If you are going to Quote me then please Include my complete sentence, Or go back to working on pumps...


    DonL
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