240 2pole30amp breaker testing

Discussion in 'Electrical Forum discussion & Blog' started by MartinE, Aug 29, 2011.

  1. MartinE

    MartinE New Member

    Messages:
    7
    Location:
    Missouri
    I am having some issues with a 2pole 30amp 240 breaker. It appears that I am not getting 240 volts at my outlet.
    I have a multimeter and when I check each pole I get 120 on each pole, but I don't get 240 when testing both poles.
    Any help would be appreciated.
    Thanks,
    Martin
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,826
    Location:
    NW Ontario, Canada
    My guess is that it isn't a 240V breaker but rather a ganged 120V. How much space does it occupy in the breaker panel? A 240V breaker needs to be wide enough to span both legs.
  3. MartinE

    MartinE New Member

    Messages:
    7
    Location:
    Missouri
    It is a double wide breaker. It will not trip one breaker seperate like a ganged breaker.
  4. ActionDave

    ActionDave Electrician

    Messages:
    345
    Location:
    Colorado
    Bad connection at the breaker or a lost leg to the panel or the house are are possibilities. What other 240V circuits are in the house?
  5. MartinE

    MartinE New Member

    Messages:
    7
    Location:
    Missouri
    I have checked and rechecked the connections. I have a hot water heater and a range that are each 2 Pole 30 amp breakers.
    I just added the dryer 2 Pole 30 amp breaker.
  6. ActionDave

    ActionDave Electrician

    Messages:
    345
    Location:
    Colorado
    Just one breaker panel in the house? Did you check voltage at the other 240V outlets?
  7. MartinE

    MartinE New Member

    Messages:
    7
    Location:
    Missouri
    Yes, each one tests okay with 240 when testing both poles.
    The only thing that I can come up with is that the breaker is bad, but I don't understand why I get the 120v when testing each pole seperate.
  8. ActionDave

    ActionDave Electrician

    Messages:
    345
    Location:
    Colorado
    Either you have either lost one leg on the circuit in question (bad connection, bad breaker, broke wire)and the voltage is backfeeding through the other 240V circuits or you have both hots on the same phase.
  9. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    Is this in a General Electric panel? One that takes half-slot breakers? If yes, then you need to move the circuit breaker over one slot.

    There are a couple of other panels that have this quirk but I don't remember the make.
  10. MartinE

    MartinE New Member

    Messages:
    7
    Location:
    Missouri
    I had a three wire plug and wire on this breaker and had 240v at the plug.
    I switched it to a 4 wire and plug to match the dryer.
    Now I don't have the 240v.

    It's an old Panel with Federal Pacific thin Stab-Lok breakers.
  11. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,786
    Location:
    Long Island, NY
    That depends where you are measuring. If you measure from each hot leg to ground or the Neutral. You will measure 120 Volts. You said you replaced the receptacle with a 4 prong unit to match the bew Dryer's plug? Is your cable from the panel to the dryer receptacle 10/2 plus a ground or is it 10/3 plus ground. the proper cable should have a red, a black, a white and a ground wire either bare or green to properly connect the 4 prong receptacle, and at the panel end, the red and the black should each go to one phase of that 30 amp breaker. the white should connect to the bus strip with the other white (neutrals, and the ground should be connected to the ground bus. The ground and neutral buses are seperate, but may be connected together by a bolt in the panel. In any case, you first need to measure the voltage at that 30 amp breaker at each phase to make sure you have 120 volts to ground and 240 (or whatever your actual 2xx voltage is in your area) between the 2 phases. The breaker may be bad, but if it worked before with your old dryer, I am under the opinion from what you wrote so far, you may have wired something wrong at the new receptacle. Just my opinion, and you know what opinions are worth.

    I reread your posts and just noticed you installed the new breaker (was there one there before? Is the new breaker plugged onto both metal "stabs", one phase on each of the stabs?. My advice sticks: first measure at the breaker itself, if you have not already done so.
    Everybody else that has answered you is correct in what they said too, but we need to get all the details of what you did to figure out what is wrong. It is possible, but not very likely that the "new" breaker you installed is bad.
    Last edited: Aug 30, 2011
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,809
    Location:
    New England
    As already mentioned, on some panels, you can only get a 240-vac CB to work properly if it is in certain slots...you may need to move it up or down one slot. Also, some panels I've noticed may have the tabs to mount a CB in places beyond where the bus bars go...i.e., while they look like they can hold more breakers, they are not really designed to do so.
  13. ActionDave

    ActionDave Electrician

    Messages:
    345
    Location:
    Colorado
    A little confused here. Which is it, added a breaker or used an existing breaker.
    Either way, I am going to say that you have both hots on the same phase. This is very easy to do on Federal panels.
  14. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,331
    Location:
    Cincinnati OH
  15. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
  16. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,253
    Location:
    Cave Creek, Arizona
    With the right tester, and experience, it should only take about a minute to diagnose the problem. But we would have to be there to do it. It is too hard to give ALL the possible sequences over the Internet and assume you will do them correctly.
  17. MartinE

    MartinE New Member

    Messages:
    7
    Location:
    Missouri
    ActionDave you must have been correct when you said they must be on the same phase.
    I moved the breaker over one slot and it works fine.
    The buss bar has square slots for pairs of breakers.
    240v 2 pole breakers must split between two of the squares.

    Thanks for everyones input.
  18. MartinE

    MartinE New Member

    Messages:
    7
    Location:
    Missouri
    thanks Furd.
    that was the solution.
  19. ActionDave

    ActionDave Electrician

    Messages:
    345
    Location:
    Colorado
    Glad you got it sorted.
Similar Threads: 2pole30amp breaker
Forum Title Date
Electrical Forum discussion & Blog Can I use 2 single pole 30 amp pushmatic breakers as a double pole set up May 28, 2014
Electrical Forum discussion & Blog piggyback 20A breakers May 15, 2014
Electrical Forum discussion & Blog Separate lines and breakers for one receptacle?????? Apr 4, 2014
Electrical Forum discussion & Blog 50 amp main breaker panel? No such animal Mar 26, 2014
Electrical Forum discussion & Blog Removed Electric Hot water Heater - Breaker Filler Plate? Mar 6, 2014

Share This Page