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Thread: Convert 220 circuit to 110 circuit to be run to new subpanel

  1. #1
    DIY Junior Member C Willard's Avatar
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    Question Convert 220 circuit to 110 circuit to be run to new subpanel

    I have an existing 220V circuit running to my garage using 10-3 with ground wire. I want to convert this circuit to 110V adding a subpanel to the garage and run to recepticles. There will be a freezer and refrigerator.

    Do I use a 30 amp double pole circuit breaker at the main panel and run neutral, red, black and ground to the subpanel?

    How many 20 amp circuits can I add to the subpanel. If only one, can I add a 20 and a 15 amp?

    I know an alternative is converting to 110 V single pole breaker at the main panel with only 1 110V 20 amp circuit, but is it enough for the freezer, refrigerator and more recepticles.
    Last edited by C Willard; 10-24-2009 at 09:49 AM.

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Default circuit

    Your 220/240 v wire is actually TWO 110/120 circuits. Connect it to the new sub panel, and then install your new breakers in such a way as to spread the load between the two feeds.

  3. #3
    DIY Junior Member C Willard's Avatar
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    What are the maximum number of circuits and amps per circuit that can come off at the subpanel

  4. #4

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    #10 wire = 30 amps per "leg"

    You can put as many 20 amp circuits as you like on it but if you draw over 30 amps the main breaker will trip.

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    DIY Junior Member C Willard's Avatar
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    What's the maximum breaker I can use at the main panel with the 10-3 wire. Can I go higher than 30 amp at each pole?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Any single cb must be at or below the max on the wire feeding it, so with the incoming wire you have, no individual breaker after it can be greater than 30A. That does not mean that you can't have individual breakers AFTER that feed that exceed the total. IOW, you can have the sum of the breakers in the subpanel exceed 30A as long as the wires used and the breakers selected individually don't exceed 30A. That way, no set of wires capacity would be exceeded, since the branch breaker or the subpanel feed's breaker would trip first.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #7

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    What code cycle are you under?
    What does your electrical inspector say about your plans?
    How much will the permit and inspection cost?
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default breaker

    You can only use a 30 amp, or smaller, breaker at the main panel to feed the #10 wires. WIth 110/120 at the sub panel, you will probably use 15 and 20 amp breakers. Try to balance the loads on both feed wires to even things out.

  9. #9

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    What code cycle are you under?
    What does your electrical inspector say about your plans?
    How much will the permit and inspection cost?
    Uh oh. Dad's home

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