electrical subpanel questions

[danbo]

I'm having trouble reconciling various information I keep reading regarding grounding on a sub-panel. I have a detached garage that I'm installing a subpanel in. The inspector said to drive 2 ground rods, which I've done, but now I have a couple questions.

In regards to the bonding strap in the subpanel, I've read the following: 1) don't use it in the subpanel, 2) always use it and 3) only use it if it's used in the main panel. So which is it? I've separated neutral and ground in the subpanel, so I see no reason why I would need it.

And as far as bringing the #6 bare copper wire from the ground rods, how do I physically bring them into the box. I can't imagine I have to use a clamp through a knock-out. Can I just drill a hole in the side of the box to bring the wire into the grounding bar? If not, how am I supposed to do it - I can't find any specific information on that aspect of the grounding wire.

thanks,

danbo

[Doug Miller]

#1 is required (and #2 and #3 prohibited) by the National Electrical Code.

Imagine it. Then do it.

No.

With a clamp through a knockout -- which is easiest and fastest, properly secures the wire to the box, and raises no issues of Code compliance. Why would you want to do it any other way?

[RBM]

You would not use the bonding jumper in this situation, with one exception. The exception being that the driven grounding conductor is the ONLY grounding conductor at the detached building, No grounding conductor run with the feeder, and nothing conductive linking the detached building and the main building other than a neutral conductor and two ungrounded conductors

[John Grabowski]

#1 is correct.

Just use a two screw Romex connector in a 1/2" knockout. You need to have some strain relief.

[gfretwell]

You didn't answer the key question. Did you run a 3 wire or 4 wire feeder to the garage? If you ran 4 you separate the ground and neutral, using the insulated bar for neutral and the one screwed to the panel can for ground (you may need to buy this separately), that is where your ground rod #6 goes.

If you used 3 wire, bond the neutral to the ground, just like you do in a main. That provistion 250.32(b)(2) will go away in 2008

A #6 needs to be in a conduit, make your life easier and use plastic. You can use EMT but then you also need to bond it at the rod with a "city hub" (one that bolts to the rod clamp and connects to the EMT) If you use a #4 it can run without "proterction" and can go in one of the 1/4" holes in the bottopm of the panel.

[danbo]

Thanks for all the replies - yes I ran 4 thw wires to the subpanel from a 6/3 feed. So, I will now buy another clamp connector and run the ground wire in from the grounding rods - I have a fleeting thought that using a clamp it might be the way to do it, I've just never seen a grounding wire run by itself, so I wasn't sure, but now it makes sense. And I'll throw the bonding strap away.

- danbo

[gfretwell]

Either run a 4 guage to the ground rod (the easy answer) or buy some PVC conduit to sleeve your #6. That will also go into the 1/2" KO and put that question to bed. It is code that anything less than 4 needs a conduit. You can jumper between rod 1 and 2 with the #6 if it is buried. (not exposed to physical damage)

[Doug Miller]

No, it's not.

"A 6 AWG grounding electrode conductor that is free from exposure to physical damage shall be permitted to be run along the surface of the building construction without metal covering or protection where it is securely fastened to the construction; otherwise, it shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor. Grounding conductors smaller than 6 AWG shall be in [the same types of conduit]." [2005 NEC, Article 250.64(B)]

[gfretwell]

Most inspectors say that is exposed to physical damage. I was just trying to save him from doing it twice.

[Doug Miller]

Perhaps -- but that's the inspector's call. The *Code* says 6 AWG doesn't necessarily have to be in conduit.

[hallerb]

i ran a tiller into my service entrance cable, after the tiller hit a rock.

spark city and could of easily died that day

[Doug Miller]

What was your service entrance cable doing that close to the surface and not in conduit?

[hallerb]

1950s home, all of them in the neighborhood that way. cable enters high up on garage wall.......

oddly enough they replaced it the same way. but that was maybe 1980s.

[RBM]

You are correct , but personally, I've never used smaller than #4 regardless of service size. The difference in cost is minimal, and it eliminates the possibility of an anal inspector giving you problems, or at least he has to be more creative

[gfretwell]

This is the language they are working with.

(B) Securing and Protection from Physical Damage. A grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried. A 4 AWG copper or aluminum or larger conductor shall be protected if exposed to severe physical damage. A 6 AWG grounding conductor that is free from exposure to physical damage shall be permitted to be run along the surface of the building construction without metal covering or protection where it is securely fastened to the construction; otherwise, it shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor. Grounding conductors smaller than 6 AWG shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor.

The "free from exposure to (any) physical damage" is what makes it troubling for some inspectors. If a kid can touch it, it is exposed to physical damage.

[<kjpro]

[e-mail]

doesn&#39;t

That&#39;s just criminal!!!

[Steve Barker]

i&#39;d be more inclined to ask "why was your service entrance so close to your garden?"

[Thomas D. Horne, FF EMT]

Tom Horne

Well we aren&#39;t no th> On Fri, 6 Jul 2007 20:33:38 -0400, "RBM" this)@optonline.net> wrote: >

It is not your kid that most of them are concerned about it is your weed eater or other powered garden or lawn maintenance equipment. By personal experience I can tell you that schedule forty rigid nonmetallic conduit is not adequate against weed eaters, trimmers, or edgers.

-- Tom Horne