Some NEC questions about grounding wire

sub3marathonman

OK, I really tried to research this. I think I've found some answers, but I'd like somebody to confirm this.

For the wire runs inside the house in EMT conduit, the ground wire size needs to be calculated based on the breaker rating. So a 60 amp breaker would need a 10AWG ground wire. However, if you upsized the current carrying wiring for this circuit, you would then need to upsize the ground wire by the same percentage (or greater). So if you used a #4 AWG wire, instead of a #6 AWG wire as would be called for, you would have to increase the size of the ground wire size by 59% too, going from a 10 AWG to an 8 AWG. What is confusing is if you have a 30 amp circuit protected by a 10AWG ground wire, and upsized the current carrying wire to #4 AWG instead of #10 AWG as would be called for, you would have to upsize the ground wire to #4 AWG too. Which really doesn't make sense to me.

Also, in a John Wiles article that I've probably misinterpreted, it seemed that he was saying that EVERY ground wire must be the same size. So if you grounded a metal battery box with 4/0 wire you would have to use 4/0 wire everywhere for the ground wire. Which really doesn't make sense to me either. Because somewhere I've also read that the ground rod outside really can't dissapate the electricity any faster than a 6AWG wire can supply it.

Another question I'm having is if it is really allowed to run the ground wire outside the EMT conduit. From what I've found, the code says if the ground wire is #6 or bigger it needs to only be "free from exposure to mechanical injury" if it is run outside the conduit. I would take it to mean that in the attic it could be run outside of the conduit, but 3' off the ground would be unacceptable.

Now, I've also been told that bare copper ground wire shouldn't be used in conduit, although I can't confirm that the NEC says it. I guess though that the bare ground wire could be run outside the conduit if it wouldn't get hurt.

One other thing that I can't confirm is if DC ground wire requirements are different from AC ground wire requirements. It seems that they should be the same, but I'm not sure.

And finally is the question about "continuous ground wire." Can you use an insulated ground wire, strip off a small section of insulation, connect it in one combiner box, then continue on and route it to another combiner box? What about a bare copper ground wire where you wouldn't have to strip off any insulation? Or does each combiner box need its own ground wire? And if so, can you at some point attach one wire to the other so you don't have to run two ground wires?

The grounding aspect has been extremely difficult to figure out.

Solar Guppy

Re: Some NEC questions about grounding wire

Why I can't answer every possible routing, awg size or possibility of ground I can say that your inspector is the same one that did my system and your making a mountain out of something that's simple.

If you choose, run no DC ground wire to the panels, that's legit, what I did and the inspector approved my system and will be the same individual that inspects yours

If you want a wire, then run the same size as the power conductors, 10 AWG will pass regardless of the power conductors, again I know the inspector

On the roof, you need a continuous bare wire, 10 awg is fine ... its continuous so if a panel is removed it doesn't break the ground to the remaining panels. You can for sure have a insulated 10 AWG ground wire in the combiner/junction box, then run the continuous wire ( wire nutted ) from there off to the panels.

AC should be 10AWG as well and no additional ground rod is needed for your installation.

Regardless of what ever the code has written, its the inspector and no one else that makes the rules and will sign off on your installation so you can apply for the rebate. All you have to do ( and you have been suggested this many times on two different forums ) is simply make an appointment with the head inspector ( I already gave you his name ) and have him pre-approve your plans. There is NO point on trying to guess what he wants, just ask him at your meeting and wire it up that way

sub3marathonman

Re: Some NEC questions about grounding wire

OK, that sounds good. I am always worrying though that I'm doing something wrong that will be virtually impossible to correct, so having somebody who knows is a great help.

Solar Guppy

Re: Some NEC questions about grounding wire

sub3marathonman wrote: »

OK, that sounds good. I am always worrying though that I'm doing something wrong that will be virtually impossible to correct, so having somebody who knows is a great help.

There is no such thing in electrical work. If you get red-tagged, you fix it ... worst case might be some wire and conduit .. for your small , self installed system it might take a whole day or two put in a conduit run and pull more wire ... you've spent literally months worrying about this ...

SG

niel

Re: Some NEC questions about grounding wire

guppy is right as the approval comes from the inspector and it is he that determines if it is right. getting it from him prior to the actual installation takes that fear away and it doesn't get much simpler than that. it doesn't mean that you will totally understand it all and the inspector (don't know him so i can't say for sure) may not have the time to fully educate you on the nec and all of the whys and whatfors, but he may answer a few brief questions on it that you may have.
also in elaboration here note that guppy is against dc grounding and i know of his interpretation and i respect it. a simple analogy he may give would be like a plane in the air. it may or may not get hit by lightning in the air as its charges are not any different than the surrounding air. now place a wire (ground wire) from it to the ground and the lightning is drawn to it as a prime target pathway to the ground because the ground has a different charge potential. i agree to a point that this is the case and if grounding isn't done properly that damages to life and property can be at increased risk with a ground.
now i prefer grounding as static charges that can build to a dangerous strike can be dissipated prior and thus ward off a dangerous strike(first hand experiences seeing it build to a strike due to no ground connection on an antenna once). lightning and its emp is somewhat unpredictable and at times either methodology may apply in afterthought of a strike as each holds merit, but is redundant after the lightning has hit.
both methods have safety in mind and the only right answer is the one the inspector goes along with in the long run as lightning, or its emp, does what it wants to in spite of our best efforts to stop it.
i'll shutup now as i probably confused you.

mike95490

Re: Some NEC questions about grounding wire

I don't think, outdoors, you can run bare copper ground in a conduit. Something about water, copper, zinc and steel ....