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Thread: Circuit breakers with jumper wire

  1. #1
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    Circuit breakers with jumper wire

    Check out this wiring arrangement I came across today (I’m a home inspector). This was on a 4 year old home, so I think this is the builder’s handy work. There is a 20A circuit breaker serving a 10 AWG wire with a 12 AWG jumper wire tied into a 15A circuit breaker. The combo circuit breaker was labeled “A/C spare”. I think it is used for one of the two HVAC units. I wrote it up as requiring further evaluation…This installation/configuration just seems wrong to me! Has anyone seen anything like this before? Any input would be appreciated.

  2. #2
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    Re: Circuit breakers with jumper wire

    Violation of 240.8 Fuses or Circuit Breakers in Parallel.

    This combination of a 15 and 20 results in 30 amps of overcurrent protection.

    [ March 14, 2004, 10:20 AM: Message edited by: iwire ]

  3. #3
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    Re: Circuit breakers with jumper wire

    I could not find a 240.8 in the 2002 NEC Pocket Guide (it went from 240.6 to 240.10). I'll check the full NEC. Also, I believe the "A/C spare" requires 30A. Thanks you!

    [ March 14, 2004, 10:39 AM: Message edited by: kaptnkrnx ]

  4. #4
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    Re: Circuit breakers with jumper wire

    Bob: I agree with your call on the violation, but I don't understand the formula used to get 30 amps. Would you mind showing me the math? Thanks
    Ryan Jackson, Salt Lake City
    Inspector, Instructor

  5. #5
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    Re: Circuit breakers with jumper wire

    Forget that breakers are not perfect and that they may not trip at just above their rating.

    The resistance of each breaker will be close to equal, the current will divide close to equally between the two breakers.

    Once the load exceeds 30 amps there will be more than 15 amps on each breaker, the 15 amp breaker will open followed shortly by the 20 amp breaker.

  6. #6
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    Re: Circuit breakers with jumper wire

    Iwire.
    Are you saying that if I tie the handles on two 15A single pole breakers (on opposite phase) that I have in effect created a 30A 2 pole breaker?
    steve

  7. #7
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    Re: Circuit breakers with jumper wire

    No, not at all, I am saying if you have two single pole breakers on the same phase and electrically connect them in parallel that the available current is twice the value of the lowest rated breaker.

  8. #8
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    Re: Circuit breakers with jumper wire

    Thanks for the reply. I went back and re-read all of the post. I missed the part about the breakers being parallel. I knew that you probably weren't in error and I had visions of red flags in my head.
    steve

  9. #9
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    Re: Circuit breakers with jumper wire

    Originally posted by hillbilly:
    I knew that you probably weren't in error
    Steve you never should assume that, I mess up as much as anyone.

    The only thing different about me is I spend a lot of time here and have a big mouth.

  10. #10
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    Re: Circuit breakers with jumper wire

    Think double fused ring circuit. (which I like if it could be monitored )

    Roger
    Moderator

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