What Size Ground Rod For 100 Amp Service

I but dug an 18" deep trench from the house to my detached garage and I'one thousand well-nigh to run 3-guess service cable for my new 100-amp sub panel. The garage is simply x feet away from the house. The cablevision will exist encased in PVC conduit. The main 200-amp service console at the house is well-grounded, and a couple of electricians here in LA take told me that I don't demand any additional grounding rods for the sub-console, merely a dark-green grounding wire that will become run back to the main service console.

Anybody know what size wire I need for the green ground wire? I recollect I read 8 someplace, only I want to exist sure.

Cheers!

- Jason

100 amp feeder (al) is 2-two-four-half-dozen

Jason, I would suggest y'all get to know your local inspector and ask him what he wants to meet. Municipalities don't HAVE to follow the NEC, or even the latest NEC, but every bit far every bit I know, the NEC a basis rod (sometimes 2 ground rods) is required for discrete structures.

Quote Originally Posted past John Coloccia View Post

Jason, I would propose you get to know your local inspector and ask him what he wants to see. Municipalities don't Have to follow the NEC, or fifty-fifty the latest NEC, but every bit far equally I know, the NEC a footing rod (sometimes 2 ground rods) is required for detached structures.

The State of California mandates which code & when it is adopted, currently the 2011 is being enforced. 250.56 states if you lot cannot show 25 Ohms of resistance or less then a second one is required at least half-dozen feet apart from the 1st one & that is all that is needed, considering the testing equipment is expensive it's cheaper & simpler to simply drive the 2nd rod.

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

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

Jason, A separate edifice always requires a grounding electrode arrangement in addition to the equipment grounding conductor that you mention. The only exception is if the dissever building is fed with just a single branch circuit (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 simply way that you tin can go by with a single ane, is if you can bear witness by 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. Information technology is almost always easier and more cost constructive to satisfy the NEC requirement past supplementing i ground rod with an boosted 1 (250.53(a)(two). Although the minimum size grounding electrode usher is typically #viii copper for a 100 amp service (it'southward actually determined past feeder size, not amperage), the NEC requires that conductors smaller than #half-dozen be physically protected (usually conduit). If you lot run a #6 bare copper GEC, you tin can run it exposed on the surface unless it is field of study to severe physical damage (250.64(B).

Thanks for the advice, guys! Only to exist safe, I went ahead and installed 2 copper ground rods and continued with #6 bare copper (sleeved in PVC conduit until is disappears below ground). I besides used a #6 THWN green ground wire to connect back to the master service console. Grounds and neutrals in the sub panel are separated.

Quote Originally Posted past Matt Marsh View Post

Jason, A carve up building always requires a grounding electrode system in addition to the equipment grounding conductor that you mention. The just exception is if the separate building is fed with but a single branch circuit (2014 NEC 250.32a). If yous are using rod type electrodes, yous really need to drive two of them, at a minimum of 6' autonomously. The only manner that y'all tin become by with a single 1, is if you can prove 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 about always easier and more than cost effective to satisfy the NEC requirement by supplementing i ground 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 (it's actually adamant by feeder size, not amperage), the NEC requires that conductors smaller than #6 be physically protected (usually conduit). If y'all run a #6 bare copper GEC, you can run it exposed on the surface unless information technology is subject to severe physical damage (250.64(B).

Quote Originally Posted past Mark Bolton View Post

100 amp feeder (al) is ii-2-four-6

Delight note that the OP's situation does not fit the criteria in the NEC allowing one 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 apply ii AWG AL or iv AWG CU for 100 amperes. The applicable section is Table 310.15(B) in 2011 and earlier NEC editions, it has been deleted in the 2014 NEC.

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

Quote Originally Posted past Rollie Meyers View Post

Please notation that the OP'south state of affairs does not fit the criteria in the NEC allowing one to undersize the conductors, which is where they handle the unabridged load of a residence, a feeder to a outbuilding or a feed to a subpanel are not immune to use two AWG AL or 4 AWG CU for 100 amperes. The applicative section is Table 310.xv(B) in 2011 and before NEC editions, information technology has been deleted in the 2014 NEC.

Here you could not become a pass on installing electrical wire eighteen" deep unless the circuit handles 20 amps or less. Hither they mandate the NEC 30" only as if it'southward a commercial burial. Information technology wouldn't affair if it 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. In that location will also be a directive on the minimal length of the grounding wire. NEC is 8' minimal depth if retentiveness serves correctly. Not certain of California code, but they typically meet or exceed the codes of the NEC.

Quote Originally Posted by Rich Riddle View Post

Here yous could non get a pass on installing electrical wire 18" deep unless the circuit handles 20 amps or less. Here they mandate the NEC 30" but as if it's a commercial burying. Information technology wouldn't matter if it was encased in conduit or not. Regarding the size of the grounding wire, I prefer to become one size larger than mandated for the grounding wire. There will also be a directive on the minimal length of the grounding wire. NEC is viii' minimal depth if memory serves correctly. Non certain of California code, but they typically meet or exceed the codes of the NEC.

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

I actually dug the trench closer to 20 inches so that I accept at to the lowest degree eighteen inches of make full on top of the conduit ane-1/two" conduit.

Quote Originally Posted by Rollie Meyers View Post

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