What Size Ground For 100 Amp Service

1. What size footing wire for 100-amp sub-panel?

   I simply dug an 18" deep trench from the house to my detached garage and I'k about to run 3-estimate service cable for my new 100-amp sub panel. The garage is only 10 anxiety away from the firm. The cablevision will be encased in PVC conduit. The primary 200-amp service panel at the house is well-grounded, and a couple of electricians here in LA have told me that I don't need any additional grounding rods for the sub-console, just a green grounding wire that volition get run back to the main service console.

   Anybody know what size wire I need for the greenish basis wire? I think I read 8 someplace, but I want to be sure.

   Thanks!

   - Jason

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3. 100 amp feeder (al) is 2-2-iv-6

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4. Jason, I would suggest you get to know your local inspector and ask him what he wants to see. Municipalities don't HAVE to follow the NEC, or even the latest NEC, simply as far every bit I know, the NEC a ground rod (sometimes two ground rods) is required for detached structures.

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5. Originally Posted past John Coloccia

   Jason, I would suggest y'all get to know your local inspector and enquire him what he wants to see. Municipalities don't Take to follow the NEC, or even the latest NEC, but as far as I know, the NEC a ground rod (sometimes 2 ground rods) is required for detached structures.

   The Country of California mandates which code & when information technology is adopted, currently the 2011 is being enforced. 250.56 states if you cannot prove 25 Ohms of resistance or less and then a 2nd one is required at least 6 anxiety apart from the 1st one & that is all that is needed, because the testing equipment is expensive it's cheaper & simpler to only drive the 2nd rod.

   A jurisdiction may have stricter regs, just may not have lesser requirements, so the above quote does non apply in the State of California.

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6. For a excursion protected by a 100 A breaker, the minimum ground wire size is #8 copper or #half-dozen aluminum.

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7. Jason, A dissever building e'er requires a grounding electrode arrangement in add-on to the equipment grounding usher that yous mention. The only exception is if the separate building is fed with just a single co-operative circuit (2014 NEC 250.32a). If you are using rod type electrodes, you lot actually need to bulldoze two of them, at a minimum of 6' apart. The simply way that you can get by with a single ane, is if you lot can show past measurement that the ground resistance is 25 ohms or less. The measurement must be performed with a dedicated ground resistance meter, something that very few contractors have. It is almost always easier and more price effective to satisfy the NEC requirement by supplementing one basis rod with an additional one (250.53(a)(2). Although the minimum size grounding electrode conductor is typically #8 copper for a 100 amp service (information technology's really adamant past feeder size, non amperage), the NEC requires that conductors smaller than #6 exist physically protected (usually conduit). If you lot run a #6 bare copper GEC, you can run information technology exposed on the surface unless information technology is subject to severe physical damage (250.64(B).

   Last edited by Matt Marsh; 10-02-2014 at 2:37 PM.

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8. Cheers for the advice, guys! Just to exist condom, I went alee and installed 2 copper footing rods and continued with #vi bare copper (sleeved in PVC conduit until is disappears below footing). I also used a #6 THWN dark-green basis wire to connect back to the principal service panel. Grounds and neutrals in the sub panel are separated.

   Originally Posted by Matt Marsh

   Jason, A separate building always requires a grounding electrode system in addition to the equipment grounding usher that you mention. The simply exception is if the separate building is fed with simply a single co-operative excursion (2014 NEC 250.32a). If you are using rod type electrodes, you actually need to drive two of them, at a minimum of 6' apart. The just way that you tin become past with a single i, is if you can show by measurement that the ground resistance is 25 ohms or less. The measurement must be performed with a defended ground resistance meter, something that very few contractors have. It is almost always easier and more than cost constructive to satisfy the NEC requirement by supplementing one ground rod with an additional one (250.53(a)(ii). Although the minimum size grounding electrode usher is typically #viii copper for a 100 amp service (it's really determined past feeder size, not amperage), the NEC requires that conductors smaller than #6 be physically protected (usually conduit). If you lot run a #6 bare copper GEC, you tin can run information technology exposed on the surface unless it is subject to severe physical impairment (250.64(B).

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9. Originally Posted by Mark Bolton

   100 amp feeder (al) is 2-2-four-six

   Please notation that the OP's situation does not fit the criteria in the NEC allowing i to undersize the conductors, which is where they handle the entire load of a residence, a feeder to a outbuilding or a feed to a subpanel are not allowed to utilise 2 AWG AL or 4 AWG CU for 100 amperes. The applicable section is Table 310.fifteen(B) in 2011 and earlier NEC editions, information technology has been deleted in the 2014 NEC.

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10. I used #2 copper for both hots and neutral and #6 copper for the grounds.

    Originally Posted by Rollie Meyers

    Please note that the OP's situation does not fit the criteria in the NEC allowing 1 to undersize the conductors, which is where they handle the entire load of a residence, a feeder to a outbuilding or a feed to a subpanel are not immune to use 2 AWG AL or 4 AWG CU for 100 amperes. The applicable department is Table 310.15(B) in 2011 and earlier NEC editions, it has been deleted in the 2014 NEC.

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11. Hither you could not become a pass on installing electric wire 18" deep unless the excursion handles 20 amps or less. Here they mandate the NEC 30" simply as if it'southward a commercial burial. It wouldn't matter if it was encased in conduit or not. Regarding the size of the grounding wire, I prefer to go ane size larger than mandated for the grounding wire. There will as well be a directive on the minimal length of the grounding wire. NEC is 8' minimal depth if retention serves correctly. Non sure of California code, but they typically meet or exceed the codes of the NEC.

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12. Originally Posted past Rich Riddle

    Here you could not get a pass on installing electrical wire xviii" deep unless the excursion handles 20 amps or less. Here they mandate the NEC xxx" merely equally if it'due south a commercial burial. It wouldn't matter if information technology was encased in conduit or not. Regarding the size of the grounding wire, I prefer to go one size larger than mandated for the grounding wire. There will also exist a directive on the minimal length of the grounding wire. NEC is 8' minimal depth if memory serves correctly. Not sure of California code, but they typically run into or exceed the codes of the NEC.

    In that location is no requirement for 30" burial in the NEC for 600V & less, (depression voltage), medium & loftier voltage are not relevant hither.

    Concluding edited past Rollie Meyers; 10-13-2014 at 9:31 PM.

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13. I actually dug the trench closer to 20 inches then that I have at to the lowest degree xviii inches of fill on top of the conduit 1-1/2" conduit.

    Originally Posted by Rollie Meyers

    There is no requirement for 30" burial in the NEC for 600V & less, (depression voltage), medium & high voltage are not relevant here.

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What Size Ground For 100 Amp Service,

Source: https://sawmillcreek.org/showthread.php?222258-What-size-ground-wire-for-100-amp-sub-panel

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