Can I use 10/2 cable on a regular 12 or 20amp circuit?

Discussion in 'Electrical Forum discussion & Blog' started by PabNYC, Mar 4, 2009.

  1. PabNYC

    PabNYC New Member

    Messages:
    18
    Location:
    NYC
    I think the answer is yes but i just want to make sure.

    I already have a 10 gague home run that goes to my garage. Currently it is disconnected at the panel and in the garage it just runs to a box where the wires are capped. Can I just connect this to a 20 amp breaker in the panel and put a regular receptical at the garage end? GFCI of course : )


    Thanks
  2. Billy_Bob

    Billy_Bob In the Trades

    Messages:
    422
    10/2 with ground I presume?

    Safety wise, it is fine to use a larger than required wire.

    Mechanical wise, a #10 should fit in the breaker OK (look at specs on breaker), but might not in the GFCI. The new GFCI's I've seen have a hole in the back for the wire and you tighten the connection with the screw on the side - can't wrap the wire around the side and I don't think you would want to try that with a #10 anyway. But the hole on one I have here looks like #12 is the largest it will accept, but mine is a 15 amp. Maybe a 20 amp GFCI would accept a #10? I don't know?

    I don't see wire sizes when looking at the GFCI specs on the internet.

    Then cramming everything into the electrical box wise... I would use a deep double gang box with a single gang plaster ring.
  3. PabNYC

    PabNYC New Member

    Messages:
    18
    Location:
    NYC
    Thank you Billy Bob
  4. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    You could always pigtail #12 wire on the end for connections
  5. iminaquagmire

    iminaquagmire DIY Senior Member

    Messages:
    207
    NO PIGTAILING. What happens when somebody comes in and sees that 10-2 and decides to up the breaker? A responsible person would check first, but a lot would see the 10-2 and add a new breaker, overloading any pigtailed 12ga.

    Cooper GFCI's can handle 10ga solid or stranded in the backwire holes and I believe 8ga in the screw terminals.
    Last edited: Mar 4, 2009
  6. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    Duh, the same thing that happens when somebody ups the breaker without checking in the 1st place with 20a devices in place
    #10 wire is commonly used for long 20a runs
    When have you last seen a 30a residential outlet 120v :confused: :rolleyes:
  7. 99k

    99k Radon Contractor and Water Treatment

    Messages:
    460
    Location:
    Fairfield Co.,Connecticut

    I'm no electrician but I have to agree ... pigtail is fine. My electrician does this.
  8. rgsgww

    rgsgww New Member

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    53
    Location:
    Ia
    Attached or detached garage?
  9. iminaquagmire

    iminaquagmire DIY Senior Member

    Messages:
    207
    I've never seen a 30A residential receptacle. That doesn't mean somebody down the line can't change the line to something else or add a junction elsewhere. Like I said, a responsible person would check before changing a breaker, but I'll never pretend everybody is responsible or smart.

    You can put aside the average person's intelligence anyway, as there is no need to pigtail in this instance. 10ga wire will connect just fine to either Leviton or Cooper GFCI receptacles.
  10. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    And you can't possibly plan for everything somebody else might do
    Telling someone they can't do it is wrong
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,516
    Location:
    Cave Creek, Arizona
    back wiring

    A few years back restrictions were placed on back wired devices. The holes could not accept a larger wire than the device was rated for. #14 ONLY for 15 amp items, #14 or smaller for 20 amp ones. Therefore the #10 wire will not fit into a back wired receptacle, but would work with screw terminals or devices with wired connectors.
  12. gogden56

    gogden56 New Member

    Messages:
    1
    The number 10 wire is good for 30 amps. That is max. Yes you can use it for a smaller breaker.
  13. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT

    Your a goof ball. :D Who cares what the next idiot does?
  14. rgsgww

    rgsgww New Member

    Messages:
    53
    Location:
    Ia
    The next idiot may tap off the service conductors, how am I suppose to prevent that? :D
  15. GabeS

    GabeS Remodel Contractor

    Messages:
    294
    Location:
    Brooklyn NY
    20 amp breaker means 20 amp circuit. The breaker determines the amps of the circuit, not the wire size. If someone switches to a higher breaker, then they don't know what they are doing and shouldn't be doing it. How can you prevent them from sticking a live wire in their mouth?
  16. iminaquagmire

    iminaquagmire DIY Senior Member

    Messages:
    207
    Okay, maybe you shouldn't care what the next idiot does. After all it doesn't affect you in the least. When I have to go pull the idiot's body out after his house catches fire, it makes me care.

    Make your smaller pigtails and branches all you want, just don't do it in my town.

    Anyways, the next idiot that comes along aside, there is no need to pigtail here. Look up the Cooper GFCI pdf. It can be installed with 10ga just fine.
    Last edited: Mar 11, 2009
  17. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    The next idiot shouldn't be touching the panel box unless he knows what he is doing in the first place (e.g.: licenced electrician), and the electricians that I know will always double check a circuit 20 amps or higher to see where it leads, escpecially when there is no ryhm or reason for a 20 amp breaker to be there.
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