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Thread: ohm's law sucks.

  1. #41
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    Quote Originally Posted by kwired View Post
    Well I thought that is what I was explaining
    I think in this case of only a 20 amp circuit you are correct. My mind went to a larger circuit where the math would be different.

  2. #42
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    Quote Originally Posted by texie View Post
    I think in this case of only a 20 amp circuit you are correct. My mind went to a larger circuit where the math would be different.
    And if OP runs a 6 AWG feeder instead of a 6 AWG branch circuit protected at 20 amps table 250.122 says minimum size equipment grounding conductor is 10 AWG. A loop hole to get around using a #6 EGC is to make the majority of the run a feeder and it is code compliant to use 10 AWG instead of 6 AWG, yet your conductors are effectively supplying the same thing.

  3. #43
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    Quote Originally Posted by kwired View Post
    If this is a 20 amp circuit and conductor size is increased to #6 for voltage drop purposes then the equipment grounding conductor also needs to be increased to #6.

    If this is a 60 amp circuit using 6 AWG conductors - the equipment grounding conductor can be 10 AWG.

    Just doesn't quite sound right does it? But that is what code says.

    A code compliant way to use the 10 AWG EGC is to run a feeder to near the outlet with 10AWG EGC. Then run shorter 20 amp branch circuit to the outlet with smaller conductors.
    well, unmarred by facts, my first thought was that the EGC needed to be sized to match the overcurrent
    device, at 20 amps. the fact that i can use the emt as a ground and not even use a ground wire......

    my electrical engineer, who gets to bless the drawing i do with his signature, when i spoke with him, whining
    about having to pull #6, i asked him what size ground do i pull... and he said.... #8.....

    and that is where that is at. i'm open to any opinions to the contrary....
    thanks for taking the time to reply.
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  4. #44
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    Quote Originally Posted by kwired View Post
    And if OP runs a 6 AWG feeder instead of a 6 AWG branch circuit protected at 20 amps table 250.122 says minimum size equipment grounding conductor is 10 AWG. A loop hole to get around using a #6 EGC is to make the majority of the run a feeder and it is code compliant to use 10 AWG instead of 6 AWG, yet your conductors are effectively supplying the same thing.
    now, how might i make a pair of #6 wires, serving a quad outlet 500' away, be a feeder? by setting a panel with
    a single circuit breaker in it 3' from the quad?

    interestingly, there is not a single branch circuit in this facility that has larger than #10. the dock light plugs,
    which run 300' from the panels, are #12.

    building is 6 years or so old.
    Last edited by Fulthrotl; 05-31-12 at 12:58 AM.
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  5. #45
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    Quote Originally Posted by Fulthrotl View Post
    now, how might i make a pair of #6 wires, serving a quad outlet 500' away, be a feeder? by setting a panel with
    a single circuit breaker in it?
    That meets definition of a feeder pretty well. The branch circuit is the portion after that breaker.

  6. #46
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    Quote Originally Posted by Fulthrotl View Post
    well, unmarred by facts, my first thought was that the EGC needed to be sized to match the overcurrent
    device, at 20 amps. the fact that i can use the emt as a ground and not even use a ground wire......

    my electrical engineer, who gets to bless the drawing i do with his signature, when i spoke with him, whining
    about having to pull #6, i asked him what size ground do i pull... and he said.... #8.....

    and that is where that is at. i'm open to any opinions to the contrary....
    thanks for taking the time to reply.
    Texie disagrees and so do I. Read 250.122(B). If it is a 20 amp circuit and you use 6AWG circuit conductors the conductors are "increased in size" and the equipment grounding conductor must be proportionally increased in size.

  7. #47
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    Quote Originally Posted by kwired View Post
    Texie disagrees and so do I. Read 250.122(B). If it is a 20 amp circuit and you use 6AWG circuit conductors the conductors are "increased in size" and the equipment grounding conductor must be proportionally increased in size.
    (B) Increased in Size. Where ungrounded conductors are increased in size,
    equipment grounding conductors, where installed, shall be increased in size
    proportionately according to the circular mil area of the ungrounded conductors."

    so, on this 110 volt single circuit, is there any reason i have to pull a ground wire?
    or is the EMT a sufficient ground path? it's a 3/4" emt conduit, with, at this point,
    two wires in it.
    Last edited by Fulthrotl; 05-31-12 at 01:22 AM.
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  8. #48
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    Quote Originally Posted by Fulthrotl View Post
    so, on this 110 volt single circuit, is there any reason i have to pull a ground wire?
    or is the EMT a sufficient ground path? it's a 3/4" emt conduit, with, at this point,
    two wires in it.
    Good to go, sans green.

    You know this though. What's up?
    Last edited by ActionDave; 05-31-12 at 01:35 AM. Reason: added
    If Billy Idol or John Denver is on your Ipod go and re-evaluate your life.

  9. #49
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    Quote Originally Posted by Fulthrotl View Post
    (B) Increased in Size. Where ungrounded conductors are increased in size,
    equipment grounding conductors, where installed, shall be increased in size
    proportionately according to the circular mil area of the ungrounded conductors."

    so, on this 110 volt single circuit, is there any reason i have to pull a ground wire?
    or is the EMT a sufficient ground path? it's a 3/4" emt conduit, with, at this point,
    two wires in it.
    If using raceway as a EGC then you have no conductor to increase. We are allowed to use metallic raceways as EGC but there is no minimum size raceway for any particular overcurrent device T250.122 applies only wire type conductors. 250.122(A) tells us this.

  10. #50
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    Quote Originally Posted by ActionDave View Post
    Good to go, sans green.

    You know this though. What's up?
    simple fatigue, mostly. i decided to sleep in till 4:30 am today.
    i was cranky yesterday....

    lessee... #6 is $250 or so a spool... three spools is $750.
    and all the conduit and box is caddy clipped or screwed to building
    steel.

    yeah, i think it'll be grounded. delete ground wire.....
    “Give a person a fish and you feed them for a day;
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