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Flexible cable for generator backfeed use?

Discussion in 'Home Power and Microgeneration' started by Richard, Aug 18, 2005.

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  1. Richard

    Richard Guest

    I've been using 10/3 romex to go from my generator to the main house panel, but
    it's a pain to coil up and roll out when I need it.

    I'm thinking about replacing it with something like welders cable, but since
    that's a fine threaded copper wire, I don't know if I need to go larger or what?

    I'm only using about 50'.

    Any suggestions are appreciated.
  2. Dale Farmer

    Dale Farmer Guest

    SO 12/3 cable is readily available at anyplace that sells decent extension
    cords. fifty feet is good for about 13 amps at 120 volts, without actually
    going and looking up the tables. Small generator. May be easier to just
    run the extension cable direct to the things you are powering at the time.

  3. Vaughn Simon

    Vaughn Simon Guest

    Use #10 SO cable possibly
    available at your local Home Depot.

    Caution! Do not use that [email protected] word here, there are flamers hiding
    in the wings ready to righteously set you straight.

  4. Richard

    Richard Guest

    Not an option.

    The generator feeds the house and that's how I'm going to use it. I'm
    certainly not going to start moving and unplugging equipment every time we
    lose power.

    It's a 240V 30A output on the generator, so that requires #10 solid copper.

    10 is a very cumbersome wire to roll up and work with, so I'd rather get
    something flexible.
  5. Richard

    Richard Guest

    Thanks. I'll check that out.
    *shrug* Let them flame/complain/correct/whatever. I know what I'm doing
    is safe and I'm going to continue to use it this way.
  6. Dale Farmer

    Dale Farmer Guest

    Wire gauge is measured by the amount of copper cross section. 10 gauge
    stranded and ten gauge solid have the same amount of copper in them, the
    stranded is just slightly larger in diameter because of the air gaps between
    the strands. 10/3 SO cable is readily available at Home Depot. I would
    recommend that you upgrade to 8 gauge though, if you are drawing the full
    thirty amps, that cable is going to get a bit toasty.
    Welding cable used for temporary power applications was disallowed
    in a recent edition of the national electrical code. ( Assuming you are in
    the US. ) I'm not sure why.
    SOrry, I misread the number 10 as 12. THat's what I get for doing email
    before the caffiene kicks in.
    The correct way to do this is to get one of those generator switch over panels,
    that have an L14-30 male connector on them. Then just get the cable, and
    a pair of the connectors to make up an extension cord for your generator. You
    can also get an external box permanently wired up to the outside with the
    L14 connector, so you don't have to run the cable in through a window or
    door left open. May have to get a locally licensed electrician to do the work,
    modulo your local electrical code. Positive disconnecting means that has
    no possibility of connecting your generator to the utility power feed are
    often required by law, due to the non-trivial number of utility workers who
    got electrocuted by home generators back feeding the street after power

  7. Mark

    Mark Guest

    That is correct that gauge is gauge. I think the OP is asking if there is
    a different AWG requirement for amperage loads based on if the wire is
    solid or stranded.

    I do recall something about people who build their own hot-rods and reloate
    their battery to the rear for better traction. They use the same AWG (4 I
    believe) welders cable to do this since it's easier and more flexible. If
    they have to crank the car too long for some reason, you risk heating the
    cable too much and weaken the sheathing.

    If NEC says gauge is gauge and solid vs. stranded doesn't matter, I guess
    there is no issue.
  8. Vaughn

    Vaughn Guest

    Don't say I didn't warn you Richard! ;-)

  9. Guest

    Likely because the insulation is designed for lower voltage. (and it
    is single conductor)
  10. Michelle P

    Michelle P Guest

    8/3 SJ
    8 gauge 3 conductor Single Jacket. Flexible good up to 50 or so amps.
    Expensive and heavy but well worth it.
  11. Dave Hinz

    Dave Hinz Guest

    Well, (a) it's a valid concern, and (b) that's hardly a flame.
  12. Richard

    Richard Guest

    Please explain to me how I can zap a utility worker with the main

    Bottom line is: What I'm doing is 100% legal and safe. End of discussion on
    this "issue".
  13. Richard

    Richard Guest

    Thanks Michelle. I'll take a look at that as well. This is the weekend to
    button it all up.
  14. Dave Hinz

    Dave Hinz Guest

    If you never screw up, they'll be fine. Their life is in your hands.
    Don't screw up.
    If you installed a UL listed transfer switch, then you'd be 100% safe.
    As it is, you're less than 100% safe. Actually, _you_ are 100% safe,
    it's the other person who pays if you blow it.

    I stand by my statement that (a) it's a valid concern, and (b) this
    isn't a flame.
  15. Vaughn Simon

    Vaughn Simon Guest

    Actually, if you dig into the NEC you will find diffirent ampacities
    listed for different cables of the same guage. This is because some types
    of insulation can take higher heat without damaege. The NEC is a safety
    code. As such, it tends to ignore effiiciency (as well as other mundane
    practical matters).

  16. Guest

    This is true in the case of high frequency AC. With DC it is TOTALLY
    irrelevent. With 60 hz AC the effect is so minimal as to be almost
    impossible to measure.
  17. Me

    Me Guest

    Only true for AC Power as AC power runs on the surface of the conductor,
    whereas DC Runs thru the total crosssection of the conductor.

  18. Me

    Me Guest

    Actually, No, your not 100% Legal, or Safe if you live in a US State
    that has adopted the NEC as part of it's State Statutes, as part of
    local building codes.........

  19. Jim Baber

    Jim Baber Guest

    I am sure this is one of those city 'legends' we have all heard about.
    I suspect the real reason is that the utilities don't want uncontrolled
    generators on the grid even when it is operational. As far as
    electrocuting utility workers, there would be such a hugh load (the
    entire grid) on your generator when it was supplying power to an
    otherwise unpowered grid, it will see that load as a dead short circuit
    and trip its own circuit breakers. It sure as he... won't be able to
    electrocute anybody, but you will burn your generator up if it's circuit
    breakers don't function very quickly.
  20. RF Dude

    RF Dude Guest

    I clipped the comments out of Richard's messages and pasted them below.
    Some appear contradictory. And when valid feedback is provided, albeit
    sometimes not with a full explaination, there are interesting responses from

    It is exactly that attitude that wins Darwin awards or gets you sued if you
    caused someone else grief. The b-a-c-k-f-e-e-d issue is real. Even
    normally intelligent people forget to open the mains disconnect in a power
    failure when trying to feed their house thru a 30A dryer plug or equivalent.
    Thats why the electrical code requires a physical interlock to ensure that
    when the your generator is supplying power, the utility feed is


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