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Thread: 240 2pole30amp breaker testing

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    DIY Junior Member MartinE's Avatar
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    Default 240 2pole30amp breaker testing

    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. #2
    DIYer, not in the trades LLigetfa's Avatar
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    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.

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    DIY Junior Member MartinE's Avatar
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    It is a double wide breaker. It will not trip one breaker seperate like a ganged breaker.

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    Electrician ActionDave's Avatar
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    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?

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    DIY Junior Member MartinE's Avatar
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    Quote Originally Posted by ActionDave View Post
    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?
    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. #6
    Electrician ActionDave's Avatar
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    Just one breaker panel in the house? Did you check voltage at the other 240V outlets?

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    DIY Junior Member MartinE's Avatar
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    Quote Originally Posted by ActionDave View Post
    Just one breaker panel in the house? Did you check voltage at the other 240V outlets?
    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. #8
    Electrician ActionDave's Avatar
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    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. #9
    Engineer Furd's Avatar
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    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. #10
    DIY Junior Member MartinE's Avatar
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    Quote Originally Posted by Furd View Post
    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.
    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. #11
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by MartinE View Post
    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.
    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 by BobL43; 08-30-2011 at 08:13 AM.
    I am definitely not a pro plumber, but I am a pro crastinator

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    Retired Defense Industry Engineer jadnashua's Avatar
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    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Electrician ActionDave's Avatar
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    Quote Originally Posted by MartinE View Post
    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.
    Quote Originally Posted by MartinE View Post
    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.
    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. #14
    Consultant cwhyu2's Avatar
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    FPE-stab-lok breaker are no longer made,it could be the breaker or the way the receptical was wire.
    Check this out, www.inspectapedia.com/fpe/fpetest.htm

  15. #15
    Electrical Contractor/Instructor jwelectric's Avatar
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    here is a link from our grovenment that holds a little more salt
    http://www.cpsc.gov/CPSCPUB/PREREL/prhtml83/83008.html

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