DIY Home Improvement Forum banner

1 - 20 of 29 Posts

·
Registered
Joined
·
109 Posts
Discussion Starter #1
My panel has a arrmor protected ground wire run to the water lines. There is a similar jumper around the water meter. The existing line to the street is steel, but needs to be upgraded due to much corrosion.

The person who put in the breaker panel for the previous owner made a "fake" ground connection. It consisted of about 8 inches of ground rod, appropriately smashed and dented up on the top as if it had actually be driven into the ground. This he dropped into a whole in the floor which isn't even drilled all the way through the floor slab. It was held in the hole with some sort of putty or caulking type stuff. I guess it tricked the inspector, who gave the whole job an "Accepted" ticket.

I realize that I need a ground rod to supplement the water-pipe ground -- especially once the water main is changed. How and where should I install the new ground rod? Should I just try to drill all the way through the slab (and also part of the footer below it) where the "fake" ground was located, or should I start with a fresh hole through the basement floor below the electric box? The meter is inside adjacent to the breaker box. Will I need a second real ground round once the water line is changed.
 

·
Licensed electrician
Joined
·
13,386 Posts
Why not try to drive the two rods outside? More room to work and no possiblity of ground water coming up thru the slab.
 
  • Like
Reactions: MTN REMODEL LLC

·
Registered
Joined
·
109 Posts
Discussion Starter #3
I was thinking this would be a lot easier. If I do this, how do I run the ground wire back into the house, and if I use 2 ground rods, do I need to run 2 wires through the walls, or can the rods be daisy chained together?

I have never seen this done, but could a ground rod (or rods) be driven horizontally through the foundation wall? I know that ground rods are sometimes laid in trenches made for this purpose.

(Sorry for not looking this up myself, but I seem to have lost my NEC books in the recent move!)
 

·
Registered
Joined
·
70 Posts
You only need 1 run of conductor from the panel to the first gnd rod. Connect the 2 outside rods together. You can use the same conductor to
connect to the 2nd rod.
 

·
Licensed electrician
Joined
·
13,386 Posts
You only need to drill a 3/8" hole thru the foundation for the ground wire.
 

·
Master Electrician
Joined
·
1,453 Posts
I'd run a #6 copper (bare or green) from the panel, outside to the first ground rod, then unbroken over to the 2nd rod. The run of wire from the panel to the first rod has to be unspliced though. You can terminate at the first rod, cut the wire, use a 2nd clamp on the first rod and a 3rd on the second rod if you wish. Only one wire needs to leave the panel. I wouldn't drill through the wall or the floor...what a pain. I could have both rods in and wired before drilling a hole in the wall and then driving a rod sideways.
 

·
Semi-Pro Electro-Geek
Joined
·
3,403 Posts
I realize that I need a ground rod to supplement the water-pipe ground -- especially once the water main is changed. How and where should I install the new ground rod?
This might be unpopular advice, but if it were my house I wouldn't do anything. Having some type of functional earth ground is important, but it's not as important as many people seem to think. Your incoming water line is much more effective as an earth connection than any ground rod could be. Unless it gets replaced with plastic, I would be perfectly satisfied with it alone.
 

·
Mad Scientist
Joined
·
951 Posts
I think that's exactly his problem; that his incoming water line is soon to be replaced, and it'll likely be plastic. True, the earth ground is largely unimportant for the normal functioning of the system. But one direct or close lightning strike will demonstrate the purpose of the earth ground quite handily.
 

·
Semi-Pro Electro-Geek
Joined
·
3,403 Posts
I think that's exactly his problem; that his incoming water line is soon to be replaced, and it'll likely be plastic. True, the earth ground is largely unimportant for the normal functioning of the system. But one direct or close lightning strike will demonstrate the purpose of the earth ground quite handily.
Well I certainly wouldn't go without an earth connection! However, supplementing the existing connections seems unnecessary.
 

·
Registered
Joined
·
109 Posts
Discussion Starter #10
I'd run a #6 copper (bare or green) from the panel, outside to the first ground rod, then unbroken over to the 2nd rod. The run of wire from the panel to the first rod has to be unspliced though. You can terminate at the first rod, cut the wire, use a 2nd clamp on the first rod and a 3rd on the second rod if you wish. Only one wire needs to leave the panel. I wouldn't drill through the wall or the floor...what a pain. I could have both rods in and wired before drilling a hole in the wall and then driving a rod sideways.
Wouldn't the size of the conductor be dictacted by the size of the service? I have plenty of #6 green left over from an industrial panel job, but thought I needed to use #4 as a ground. (Again, I must appologize for loosing my NEC book in the move!)
 

·
Registered
Joined
·
109 Posts
Discussion Starter #11 (Edited)
You only need to drill a 3/8" hole thru the foundation for the ground wire.
Should this hole be above grade, or should it be put lower? There is a flower garden immediately outside where the ground rods would be placed. On the one hand, having the ground and wiring low would be better looking (as far as the garden goes). On the other hand, I would worry about someone with a roto tiller hitting the ground rods or wires if they are not exposed! Also, how far apart should the ground rods be driven?

Best advice would again be appreciated!

PS -- I think maybe I can plant a few bushs in the garden to hide the ground rods and wiring.
 

·
Master Electrician
Joined
·
1,453 Posts
Wouldn't the size of the conductor be dictacted by the size of the service? I have plenty of #6 green left over from an industrial panel job, but thought I needed to use #4 as a ground. (Again, I must appologize for loosing my NEC book in the move!)
#6 copper is the maximum required when it's connected to a rod.
 

·
Wire Chewer
Joined
·
3,579 Posts
I think the point of two grounds is that if one is being worked on there is still one that is active. If there was a fault and the ground was carrying curent, someone changing a pipe or something would get a nasty shock.
 

·
Semi-Pro Electro-Geek
Joined
·
3,403 Posts
That is an incredibly irresponsible statement, whatever it's intended context
Please do elaborate. I stand by it. The earth ground connection serves only two purposes: it stabilizes the system voltage compared to ground (draining any current capacitively coupled from primary to secondary in the utility's transformer), and it provides some slight degree of protection from nearby lightning strikes, again by ensuring the system voltage stays relatively close to the local ground potential. Since utility transformers are grounded at the pole and are also bonded to the utility neutral which is grounded at regular intervals, your own ground rod is already redundant several times over.

Just to be clear, the grounding electrode plays no role whatsoever in clearing faults or protecting people from shocks due to ground faults.

As further evidence of the relative unimportance of the grounding electrode, consider what the NEC requires: If the first ground rod has an impedance greater than 25 ohms, you have to drive a second one - no need for any further testing, or to achieve any specific impedance. Thus, if the first rod is in dry rock and has an impedance of 10,000 ohms and the second one does too, then you have a perfectly code compliant grounding system with an utterly useless impedance of 5000 ohms. And that's OK. Because it doesn't really matter much.
 
  • Like
Reactions: brric

·
Registered
Joined
·
109 Posts
Discussion Starter #16
An update on this post.

The long anticipated wait for the city to upgrade the water lines is over. They replaced the steel line with a plastic line, and installed a new meter. They left the old steel line in place, only capping it off inside the basement wall, and left the ground clamp on it. They installed a couple of split-bolts and a short piece of solid copper ground cable across the place where the meter used to be, and said the old steel line would serve as the ground for the house. They also added a jumper from the split bolt up to a nearby copper water pipe to ground it since the ground through the existing house pipes had been disconnected from the steel pipe had been disconnected in the piping side of the thing.

They said I do not need a secondary ground to replace the water line since the old water line being left in place was a sufficient ground. (I did fix the faked ground rod some time ago.)

What was interesting was that they said was that they needed to ground the water lines to the same ground as the electrical panel (the split bolt in my case). They said if I had installed all-plastic piping, they would have had to install a short piece of metal water line between the water meter and the house plumbing, and grounded that point. This way the water inside the plastic pipes would be grounded too.
 

·
Remodel and New Build GC
Joined
·
9,461 Posts
#6 copper is the maximum required when it's connected to a rod.
I'm probably off one wire size, (I agree with electrical aspect) but if that ground wire does not closely follow house contour (ie there is a potential physical hazard to it) don't you have to drop down to #4 or cable it???
 

·
Registered
Joined
·
9,018 Posts
A metal water pipe exiting the house underground counts as a grounding electrode and must have a fat ground wire (grounding electrode conductor) running from it to the panel. A metal gas pipe exiting the house underground does not count as a grounding electrode and, under some conditions, requires a similar ground wire to the panel which wire is called a bonding jumper.

Bonding jumpers should be used to interconnect sections of metal plumbing separated by plastic sections with one bonding jumper going to the panel. Should the latter bonding jumper first reach a grounding electrode conductor of at least the same size, it may end there.
 
  • Like
Reactions: MTN REMODEL LLC

·
Remodel and New Build GC
Joined
·
9,461 Posts
That is an incredibly irresponsible statement, whatever it's intended context
Please do elaborate. I stand by it. The earth ground connection serves only two purposes: it stabilizes the system voltage compared to ground (draining any current capacitively coupled from primary to secondary in the utility's transformer), and it provides some slight degree of protection from nearby lightning strikes, again by ensuring the system voltage stays relatively close to the local ground potential. Since utility transformers are grounded at the pole and are also bonded to the utility neutral which is grounded at regular intervals, your own ground rod is already redundant several times over.

Just to be clear, the grounding electrode plays no role whatsoever in clearing faults or protecting people from shocks due to ground faults.

As further evidence of the relative unimportance of the grounding electrode, consider what the NEC requires: If the first ground rod has an impedance greater than 25 ohms, you have to drive a second one - no need for any further testing, or to achieve any specific impedance. Thus, if the first rod is in dry rock and has an impedance of 10,000 ohms and the second one does too, then you have a perfectly code compliant grounding system with an utterly useless impedance of 5000 ohms. And that's OK. Because it doesn't really matter much.

AntiWing...... MPoul is just telling us the truth:yes:

I appeciate the truth and really trying to understand an issue.... not just a code rule addressing it.... I'll bet you do too when ya consider it:)
 

·
Registered
Joined
·
164 Posts
I'm probably off one wire size, (I agree with electrical aspect) but if that ground wire does not closely follow house contour (ie there is a potential physical hazard to it) don't you have to drop down to #4 or cable it???
a ground rod is considered suplemental and only needs a #6 even if it is the only available ground.
 
1 - 20 of 29 Posts
Top