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  1. #1
    Join Date
    Oct 2004
    Location
    Lyons, CO
    Posts
    3,030

    Default AWG for sub panel

    Talking with a buddy (yes, who's an electrician), but I'm confused about wire gauge. There's a 50A double-pole breaker on the main that I no longer use since switching to a gas stove. I want to replace it with a 60A breaker to run to a subpanel. It'll be about 50' of cable from the main panel to the sub-panel which will have 4 breakers. Currently he's recommended using the existing 50A to run to a 50A subpanel master using 10/3 (same 50' run), but I think I want more capacity to expand for the future. Table saw, hot tub, outdoor lighting, man the amps add up fast ).

    Questions assuming I go for the 60A: do I need to use 6/3, or would 8/3 work (for ease of bending and price)?

    If I can find a 60A GFCI breaker as the sub's master, will that cover all the circuits from the sub or are individual GFCI breakers preferable? I'd rather do them as breakers than individual outlets, unless I'm missing some reason that's not a good idea.

    If I do the 50A, is 10/3 adequate?
    Bees, brews and fun
    in Lyons, CO

  2. #2
    Join Date
    Feb 2009
    Location
    Pigeon Falls, WI
    Posts
    2,527

    Default Re: AWG for sub panel

    Is your electrician friend licensed? 10 ga copper is only good for 30 amps max. I'm not an electrician but I did take a course for certified home inspections. Here is what is stated in my "Home Reference Book" per National Electric Code

    Copper Wire:
    temp rating....60 C......75 C...........90 C..............wire size
    __________________________________________________ ____
    AMP rating.......30........30..............30......... .......10
    .....................40........50..............55. ................8
    .....................55........65..............75. ................6

    I would use 6/3(as required minimum) copper from the main panel to the sub panel with a 60amp double pole main breaker. If using aluminum you would need to go 1 size larger and you need special connectors but I highly recommend not using it because there is a higher risk of trouble(hot spots at connections). You also should have a 60 amp double pole breaker main in the sub panel if the service wire into it is more than 5' in length. You can use GFCI breakers in your sub panel for each circuit run from the sub panel if you want protection for a direct wired device(table saw, planner, etc). For outlet circuits I would use a regular breaker and then a GFCI outlet for the first in the circuit then wire additional outlets in that circuit on the output(protected outfeed) from that first GFCI. You could also just use a GFCI breaker for each circuit in the sub panel but I wouldn't use a GFCI in the master panel to run everything in the sub panel. You could end up with false tripping of the master GFCI breaker when running multiple items at the same time. When the electricity coming back though the neutral(white) is more than .005 amps less than the power going through the black(line[hot]) the GFCI will trip. Like I said I am not an electrician but I did study what to look for that no good electricians do sometimes.
    Last edited by Beeslave; 03-11-2010 at 12:21 AM.
    Leer Family Honey Farm-Shannon Leer

  3. #3
    Join Date
    Oct 2009
    Location
    Plant City, Florida
    Posts
    175

    Default Re: AWG for sub panel

    main panel 60a breaker, use 4/4 se cable ( three insulated conductors, one bare ground) it will be aluminum use nolox on the connections, sub panel can be a main lug, use GFI receptacles. If using pipe and wire, 1" emt with copper #6, 2 hot wires, one white and, one ground. Connect the ground to the ground bar in the main panel and make sure you install a ground bar in sub-panel and connect the ground there. do not re-ground the white wire (neutral) in the sub panel
    Bob

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