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Thread: Amperage Flow

  1. #1
    Join Date
    Oct 2007
    Location
    Stoughton, MA
    Posts
    8

    Question Amperage Flow

    Would 12 ga wire allow a microwave to draw more amperage than 14 ga wire? I had a microwave on a shared 15 amp circuit with 14 ga wiring. Whenever something else was switched on the breaker tripped. I ran 12 ga wire to the panel to a dedicated outlet for the microwave but only used a 15 amp breaker. The microwave is drawing 14 amps and is tripping the breaker. I will put a 20 amp breaker in the panel for this but my question is why didn't the breaker trip when it was wire with 14 ga?

    Thank You,
    John

  2. #2
    Join Date
    May 2011
    Posts
    251

    Default Re: Amperage Flow

    While increasing the wire size for the whole branch circuit and going to 20A might solve the problem... all major appliances should be on a dedicated circuit. A Microwave included. The installation instruction will tell you this. I believe it calls for at least a 15A, but a 20A is better. It you're out of spaces in the panel, you can get a double breaker while allows 2 branch circuits in a single space.
    1925 Two-Story Stucco Beaux Arts Neoclassical

  3. #3
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: Amperage Flow

    I believe the 14 gauge wire added enough resistance to the circuit that the microwave was running at less than full capacity and would not trip the 15A breaker, unless another load was added.

    The heavier #12 allowed the MW to trip the 15A breaker. I wonder why you didn't use a 20A?

    If you have had a motor load (instead of the MW)you could have burned it up because of the voltage drop on #14.

    Good Luck from Columbiana, Alabama
    Maurice Turgeon, http://thesemi-retiredelectrician.com

  4. #4
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,557

    Default Re: Amperage Flow

    I agree with Semi Retired. A microwave that draws 14 amps should be on a 20 amp breaker. you don't want a continuous draw in excess of 80% of the rated amperage.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  5. #5
    Join Date
    Oct 2007
    Location
    Stoughton, MA
    Posts
    8

    Thumbs up Re: Amperage Flow

    Thank you guys for answering my questions right away. My mind will now be at ease when I change the 15 amp breaker to a 20.

    Thanks once again,

    John

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