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Thread: How Many Circuits on One Neutral

  1. #16
    Join Date
    Feb 2003
    Lafayette, IN
    Mark, if one neutral is serving two circuits connected to opposite legs of a service, the currents are subtractive. In other words, a neutral serving just once circuit with a motor running is carrying more current than a neutral serving a motor on one leg and a battery charger on the other--the total current would be the amperage of the motor MINUS the amperage of the battery charger. The amperage on that neutral can never exceed the amperage of the breakers on either circuit, again, provided those two breakers are on different legs. Using a double breaker with the two switches tied together assures this in most panels as top-bottom adjacent spaces are on different legs in typical 240V residential service.

    "Don't get stuck on stupid." --Lt. Gen. Russel Honore

  2. #17
    Join Date
    Dec 2003
    SF Bay Area, CA
    Quote Originally Posted by Mark Bosse View Post
    If you are trying to split a 220 v circuit into two 110 v cuircuits, be sure that you talk to an electrician. Some of what I am reading here on this thread is wrong.

    As an example, it is not enough that the two 110 v legs come from separate bus bars on a single phase system in order for you to use only a single neutral. If the balance between the two 110v sides is seriously out of balance (one a motor and one a battery charger for example - a very common problem), your electrician may want to either use a heavier neutral or carry two. This can be a heat issue.
    Well, Jason just called you out as this is wrong.

    Quote Originally Posted by Mark Bosse View Post
    Before the "Home Depot - How To Experts" get on me again, remember please that the major work of the designer is load balance and heat control. You can be 100% code compliant and still produce too much heat. Your "How To" books are not enough information for you to do design work.
    I suspect you are in that category, too, Mark.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  3. #18
    Wheres the popcorn. Maybe I can learn something too.

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