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Thread: Generator feeder questions

  1. #1
    Join Date
    May 2005
    Location
    Richmond, Virginia
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    Generator feeder questions

    I'll be installing a Generac 16kw genny that has a 70a output breaker. How do I know whether I can use the 90-degree columns in Table 315/316?Presuming I must use the 75-degree column, can I use #6cu or #4al and the next-breaker size allowance?

    Also, can the control wires be run in the same conduit if properly voltage-insulated and jacketed, or must they be run separately?
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  2. #2
    Join Date
    Jul 2005
    Location
    Tennessee
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    Other than for derating purposes (ambient, fill, etc) you can not use the 90° rating.
    Likely your terminations are rated at 75° so you can use that rating (110.14) unless you are using Romex (and in some cases SE) then you are limited to 60°.
    IMO, you can not use the "next size up" rule as the conductor must be sized to carry the load and it is possible, although not likely, that the conductors may be fully loaded.

    As far as wire mix, check your install manual. At one time Generac called for separate raceways.
    If not, I believe, it is permissible if you follow the rules in Art 725.
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  3. #3
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    Thank you, so full-size conductors, and yes, the control wires may now occupy the same raceway, as long as they're suitably insulated.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  4. #4
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    If you are under the '17 Code you might check Art 336. Tray Cable is a possibility now also (with limitations).
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  5. #5
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    We're not, but what would be the advantage? I'll be using 1" PVC with three #4 cu for power, one #8 cu EGC, and up to five #18 cu control.

    The distance from the generator to the ATS will only be 12-15 feet, all outdoors, with the ATS nippled directly beside the existing main disco.

    The 4-0 al line and load conductors will share the 2" nipple, so I should only need to use the #4 neutral between the ATS and the main disco.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  6. #6
    Join Date
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    Location
    Massachusetts
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    Quote Originally Posted by LarryFine View Post
    We're not, but what would be the advantage? I'll be using 1" PVC with three #4 cu for power, one #8 cu EGC, and up to five #18 cu control.

    The distance from the generator to the ATS will only be 12-15 feet, all outdoors, with the ATS nippled directly beside the existing main disco.

    The 4-0 al line and load conductors will share the 2" nipple, so I should only need to use the #4 neutral between the ATS and the main disco.
    I think Generac calls for six control wires. Three line voltage and three 12 volt. I run #14 thhn for all six. I can’t picture what #18 line voltage wire looks like. I have seen people use thermostat wire but obviously this is no good.

  7. #7
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    I might need all six, but if I do, I need smaller than 14 to avoid having to use 1-1/4" PVC. #18 is good for up to 115 ft.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  8. #8
    Join Date
    Dec 2006
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    Quote Originally Posted by LarryFine View Post
    I might need all six, but if I do, I need smaller than 14 to avoid having to use 1-1/4" PVC. #18 is good for up to 115 ft.
    There's a problem with 1.25" pvc? We don't pull #4 in anything smaller than it.

  9. #9
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    The problem is that I need to bore a hole through these steps and my largest solid SDS-max bit is 1.5". I will get an SDS-max extension. The plan is to come out of the generator toward the steps, use an elbow to turn alongside the steps, use an LB to go through them, and an elbow up into the bottom of the ATS, which will be nippled into the disconnect under the meter.

    Side view, Gen location, Step front, ATS location

    Click image for larger version. 

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    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  10. #10
    Join Date
    Apr 2009
    Location
    Williamsburg, VA
    Posts
    5,438
    personally, if I had to go through that step, I would use a concrete saw to cut a notch through the step, Roto chisel out a U-shaped trough, lay in the conduit, then backfill and form-in with new concrete. Either that or core drill as far as possible, knock out the slug, repeat until through.

    You know if you get that Roto Hammer bit jammed in 3 foot of concrete, you're going to have a very bad day... also, if I remember correctly, you may need up to 10 control wires two more each for a battery tender and engine block heater.

    Is there no way to go through the brick to the left of the steps, behind the steps and back out? Or under the steps?
    Last edited by JFletcher; 03-12-18 at 01:50 AM.
    Electricians do it until it Hertz!

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