Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 09-10-2009, 01:18 PM   #1
Member
 
Join Date: Jun 2009
Location: San Diego, CA
Posts: 195
Share |
Default

Panel ground and wire size


I am replacing my service entrance panel (meter breaker). The earth ground on the existing panel is a #6 alum wire which runs about 15ft to a copper water supply pipe. The connection is about 8ft from where the pipe first enters the home.

The NEC has page after page on grounding and it isn't easy to follow.
As far as I can tell, this wire is called the 'grounding electrode conductor'.

250.52 states, "Interior metal water piping located
more than 1.52 m (5 ft) from the point of entrance to the
building shall not be used as a part of the grounding
electrode system
..." If the 'point of entrance' refers to the electrical service, then 15ft is too far. If it means water service, then I can move the clamp a few feet and it will comply.

When would a water pipe NOT be sufficient as a ground? In other words when would I have to put in a ground rod?

Table 2.52 shows that the gauge of this wire is loosely based on gauge of the service entrance wire. My #6 would be OK as long as the service wires were #2 or smaller. I'll have to find out what they plan to install for a 200amp service.

tns1 is offline   Reply With Quote
Old 09-10-2009, 02:05 PM   #2
Licensed Pro
 
Join Date: Mar 2007
Location: SC
Posts: 1,533
Default

Panel ground and wire size


The #6 (or#4) COPPER grounding electrode conductor (that's right, it must be copper) should connect within the first 5 ft of the water line entry AND a supplemental electrode (ground rod) must be used in addition to the water line.

__________________
"Life is hard. Life is harder when you're stupid." John Wayne
HouseHelper is online now   Reply With Quote
Old 09-10-2009, 03:28 PM   #3
Member
 
Join Date: Jun 2009
Location: San Diego, CA
Posts: 195
Default

Panel ground and wire size


OK, I see that in 250.53(D)(2). So two different types of ground are required.

I sure wish I knew that when I dug my service trench. I could have laid a ground bar down in the trench. Other ground electrode options (ring, plate) would also have been easy.

Is the supplemental electrode requirement something recent? It must not have existed when my house was built 30+ years ago.

Actually, I did notice that just below my meter, at the edge of the slab, I can see the very end of a piece of horizontal rebar. This rebar is, I assume, completely encapsulated in the slab (I can only just see the end). I had assumed this was just sloppy work, but now I wonder if it was intended to be a ground electrode.
tns1 is offline   Reply With Quote
Old 09-10-2009, 06:31 PM   #4
Member
 
Join Date: Jun 2009
Location: San Diego, CA
Posts: 195
Default

Panel ground and wire size


Well, that rebar would not be a very good ground since the measured resistance to my pipe ground is way too high.

The city says use #4 copper for all ground electrode conductors, and to add a ground rod (or plate, ring). What do you use to pound an 8ft rod into very hard ground? Since I have already trenched 4ft deep there, I only worry about the last 4ft, but I sure don't want to get to the last foot and find it won't go further. How much pounding can these take without bending?
tns1 is offline   Reply With Quote
Old 09-10-2009, 07:31 PM   #5
Electrical Contractor
 
wirenut1110's Avatar
 
Join Date: Apr 2008
Location: Chester, VA.
Posts: 1,046
Send a message via AIM to wirenut1110
Default

Panel ground and wire size


It's #4 for your cold water pipe, but for your supplementary electrode is not required to be larger than #6 copper.

I use my hammer drill to drive rods, some use slide hammers and some use a sledge.
wirenut1110 is offline   Reply With Quote
Old 09-10-2009, 07:49 PM   #6
Member
 
Join Date: Jun 2009
Location: San Diego, CA
Posts: 195
Default

Panel ground and wire size


So have you ever had to pull one out and put it in at an angle because the ground was too hard?
tns1 is offline   Reply With Quote
Old 09-10-2009, 08:04 PM   #7
Electrical Contractor
 
wirenut1110's Avatar
 
Join Date: Apr 2008
Location: Chester, VA.
Posts: 1,046
Send a message via AIM to wirenut1110
Default

Panel ground and wire size


No but, our area isn't that rocky. Have had quite a few difficult ones but, none that didn't eventually give in. If it's hard in a spot, I just pull it up and try another area a foot away or so.

Just whatever you do, don't cut it off and take a hammer and flare the top so you can't tell you cut it off. Put your clamps on first too, cause once the rod flares out, it won't go on.
wirenut1110 is offline   Reply With Quote
Old 09-10-2009, 08:31 PM   #8
Member
 
Join Date: Jun 2009
Location: San Diego, CA
Posts: 195
Default

Panel ground and wire size


Quote:
Originally Posted by wirenut1110 View Post
Just whatever you do, don't cut it off and take a hammer and flare the top so you can't tell you cut it off.
Very tempting I am sure. If it ohmed out less than 25ohms would the inspector know or care? He'd have to use a reflectometer to know if it was short.
tns1 is offline   Reply With Quote
Old 09-10-2009, 08:48 PM   #9
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Default

Panel ground and wire size


Also make sure you put that (acorn) nut on before you use a sledge hammer to drive it in
I had one that was tough to drive in, kept the hose running on a trickle for a while
Helped a lot
Scuba_Dave is offline   Reply With Quote
Old 09-10-2009, 09:43 PM   #10
Member
 
Join Date: Jun 2009
Location: San Diego, CA
Posts: 195
Default

Panel ground and wire size


I see in 250.64(B), the ground electrode conductor must be protected "where exposed to physical damage". If its inside the wall or underground, it isn't exposed to damage, but I'll have a very short 6" section running down the side of the slab which is exposed. I am guessing that needs to go in a short length of pvc, although I looked at a recent job that simply ran the insulated ground wire down the exterior siding into the ground.

If I read this section right, a smaller (thinner, weaker) conductor is somehow deemed to be less subject to damage than a larger one?
tns1 is offline   Reply With Quote
Old 09-10-2009, 09:47 PM   #11
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Default

Panel ground and wire size


I put my #4 in conduit about 10-16" into the ground
Not sure how much now
That stick of conduit is a lot less $$ then replacing the wire
Scuba_Dave is offline   Reply With Quote
Old 09-10-2009, 09:59 PM   #12
Member
 
Join Date: Dec 2008
Location: Dayton Ohio Area
Posts: 670
Default

Panel ground and wire size


I just put 4 rods in.

2 for the house, and I used a hammer drill.

The other two were for my barn. I only used a hammer for the last 2'. I put the rod in about 6", pull it out, put water in, and repeat.

Yes, remember to put the clamp on BEFORE you start hammering it, otherwise the top is likely to get mangled and you wont get the clamp on.
__________________
-Andrew
DIY hobbiest
AndrewF is offline   Reply With Quote
Old 09-10-2009, 10:02 PM   #13
Member
 
Join Date: Jun 2009
Location: San Diego, CA
Posts: 195
Default

Panel ground and wire size


I did not see anything about how deep the top of the rod (or conductor) needed to be to be considered 'protected'.
tns1 is offline   Reply With Quote
Old 09-10-2009, 10:08 PM   #14
Member
 
Join Date: Jun 2009
Location: San Diego, CA
Posts: 195
Default

Panel ground and wire size


Quote:
Originally Posted by Scuba_Dave View Post
I had one that was tough to drive in, kept the hose running on a trickle for a while
A great idea.
tns1 is offline   Reply With Quote
Old 09-11-2009, 07:01 AM   #15
Electrician
 
SD515's Avatar
 
Join Date: Aug 2008
Location: Near Jackson Michigan Area
Posts: 1,450
Default

Panel ground and wire size


Quote:
Originally Posted by tns1 View Post
I did not see anything about how deep the top of the rod (or conductor) needed to be to be considered 'protected'.
The way the inspectors in my area interpret the code is that the code says that 8 feet (of a 5/8" copper rod [most common here], 10 ft of galv rod) has to be in contact with the earth. Since the rod is 8 feet long (or 10), the top of the rod has to be at ground level, or slightly below. I put 'em about 1 or 2 inches below ground level, but leave it dug out some for the inspector to see the 'acorn' connection, bury it afterwards. I bury the wire from the rod to the building, and usually don't need to use conduit at the bldg if the exposed wire is a short run...usually 6" or less.

__________________
Kyle

Just because you can, doesn't always mean you should
SD515 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Panel Ground Wire Douger_F Electrical 6 03-14-2009 12:34 PM
hooking up dryer....bronx ny code SURFBUG Appliances 6 10-14-2008 09:41 PM
Ground rod or not? brotherman Electrical 30 07-15-2008 04:58 PM
Hot Tub Install--Grounding Rod Question statgeek_rob Electrical 16 09-15-2007 02:59 AM
Subpanel feeder questions Silhanek Electrical 4 03-22-2007 06:30 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.