Putting in a new 200 amp service, am planning on sinking two ground rods over 8′ apart – no grounds currently installed though it is bonded to the cold water pipe in the slab.
I had initially thought I could sink the ground rods within the sill of the exterior wall, but now I’m not so sure. I went down with a 3/4″ bit 14.5″ (16″ tip – sill thickness) and still am pulling up concrete dust. House built in 1960 in SoCal on a slab.
Do I just run it down an interior wall sill? How thick is the foundation near the edges, and how far in can I expect it to go?
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
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You really don't need two ground rods if you are also bonded to copper that is part of the slab and water service. An interior ground rod would be in very dry ground that would have more resistance than if it was in moist exterior ground. The best and cheapest would have been 20' or rebar in the bottom of the footing coming up 6" above the mudsill.
Run the ground rods into the earth 8' apart outside of the structure. Run some conduit to get the ground wire from the load center to the exterior. Run the ground wire to the roof drip line exterior of the building.
Someone else will tell you how to do it inside the building but it is best if the ground rods are in a location where it will be close to moist earth.
The following bad example is different but drives home the problem.
Industrial food service plants are notorious for having floating grounds. These are mainly caused by multiple grounds for the multiple services entering the building(s). Each ground rod is driven thru the concrete in what was the new section at the time. Then 10 years later they expand and build another building next to it. The buildings grow like mold grows. Eventually the original 8' ground rod is in an area where the soil is so dry that the potential varies from that ground rod to another point. There are other things that can cause this change in potential but often it is an insubstantial ground that fails to keep the attached equipment referenced.
OK, here is a way I could run the ground wire outside to the fenceline, at the base of a brick wall:
The bare 4ga. wire would come out the bottom of the panel and run 13' inside one wall, then another 15' down another. Here it would meet the cold water bond. It would then run outside about 4' to the first ground rod. There would be another 10' of wire to the next ground. This way allows me to follow walls without having to bury a cable under a concrete pad.
Is this still OK?Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Just get the two rod eight feet apart anywhere outsde, it doesnt matter. and then hook a copper wire to it to the neg/ground at the meter. also good idea to hook to frame of outside hvac. lighting loves them.Note: I got wrote up by the county for havent two rods, they was about fifteen feet apart, The inspector was sooooo stupid that he thougth you cpould only have one. so I drove the other one below the dirt and it still there. In Fact I have six rods now.
Edited 12/1/2006 7:38 pm by brownbagg
Holy Cri-Yi-Yi-A !!
Where is the weather head and incoming power source? That path sounds convoluted. Isn't there a simpler way to the outside world?Jack of all trades and master of none - you got a problem with that?
OK, let me go through the whole setup: Single story ranch on a slab, there is also a concrete sidewalk around the perimeter of the house. Service is fed overhead - I'm getting new service run to my new 200 amp box I'm installing. Old service is embedded in bedroom wall, new service is moved over to were a closet is.
Grounding right now is fed through a stranded cable down from the old box, through the walls to the tub cold water feed. There is no ground rod.
Yes it is convoluted, attached is the overhead map for a better illustration. I'm actually following the path that gets me to dirt and the cold water bond. It would be easier doing it this way so I don't have to break a concrete trench to get to wet dirt. I planned on running some things along the fence anyway, so hanging some conduit there doesn't bother me.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Move your water bond to the cold water side of your water heater for one. The rest of it I'm still not sure what you got but the simple answer is to drive a couple of ground rods outside. More is better then less.
One question. Is your water heater electric or gas?
Pardon my fat fingers.
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IIRC, the bond to the water plumbing is required to be within 5 ft. of where the water pipe enters the building. That protects plumbers from current in the pipes, like happened to 4Lorn1. It also keeps subsequent plumbing changes, like dielectric unions or plastic plumbing, from interrupting the ground path.
-- J.S.
Yea we used to do that when I did residential. Then for some reason it got changed to the cold water side of the water heater. Maybe it was a code change. I know that it is important to have the water heater grouned especially if you have an electric water heater.
Pardon my fat fingers.
http://www.hay98.com/
No, with one exception it is still 5ft.As I read if the water pipe is 10 ft or more in lenght, underground and metalic then it must be used as grounding electrode. And if inside the connection needs to be made within 5ft of where it enters the building and that path can't be interruped by a water meter. I believe that the way it is worded is that you are also allowed to make the connection on the exterior.The one exception is that if it is a commercial or industrial building with with maintance only by Qualified Personal then you don't have to have the connection within 5ft. Nor do you need a suplimental ground electrode.Now, if the external water piping does not qualify as a ground electrode, but internal metalic piping is used then it must still be bonded. I thought that I saw a requirment that also be within 5 ft, but I could not find anything where it has to be.Also I have not seen anything about water heaters and either ground electrode or bonding requirements.
In my last code update class the reason for bonding at the water heater was explained. It's in case the heating element busts. If it's grounded then it won't blow the guy out of his shower two doors down. There was a famous case in Kansas city that was used as an example. A guy had an electric water heater that wasn't bonded. The neighbor down the street kept getting the pizz shocked out of him when he took a shower. All the big muckity mucks started investigating after several days they found the un bonded water heater with a bad element.
That's the story I was told anyway. What code book are you looking at? I'm gonna have to go out in the cold and check mine out now you got me curious.
Pardon my fat fingers.
http://www.hay98.com/
I was looking at the 2005. Actually I found a download version of the 2005 HANDBOOK. But I don't know where I got it and I don't think that it was suppose to be posted.Anyway it is hard to lookup stuff like that in a PDF file. I might rather have a hard copy, but this was CHEAP.But something is "wrong" with your example.There should be a EGC run to the WH with the power anyway.
Edited 12/4/2006 8:37 pm by BillHartmann
I don't know that's the way I heard the story.
Pardon my fat fingers.
http://www.hay98.com/
BTW if you run metalic conduit it needs to be BONDED to the ground electrode wire. I believe at both ends.Otherwise it becomes a one turn transformer and and greatly increase the impedence to high frequency currents (fast spikes).
Do you still need to bond it if it is a bare wire?Rebuilding my home in Cypress, CA
Also a CRX fanatic!
I don't believe that you can guarantee a good connection without bonding it to the conduit.
Otherwise it becomes a one turn transformer and and greatly increase the impedence to high frequency currents (fast spikes).
That would be good. Stopping E-spikes, that is.
SamT
Now if I could just remember that I am a businessman with a hammer and not a craftsman with a business.....segundo <!----><!---->
"That would be good. Stopping E-spikes, that is."NOT on the ground electrode wiring.You can to shut those to ground.
Bill,
Here's what I'm thinking. . . Well sorta, My thinking isn't always on all 8, yano?
There are three factors to consider; 1) this is residential. 2) the spike source, internal or external. 3) the operating frequency of the conduit + ground wire filter.
1) the typical conduit length is under 40'. Diameters will be 3/4" or 1/2". Wire guage will be 14 to 10.
2) Internal spikes can only be caused by failure of a reactive load, computor/TV/Radio power supplies and motors. We can ignore TVs VCRs, Radios, etc as they are usually sans equipment grounds. Computors, microwaces, etc with an equipment ground must fail by shorting a reactive component to ground to be considered in this talk. the only components to worry about are the power supply transformers and filter capacitors. These transformers have their primary windings well isolated from ground. The secondary windings and capacitors, OTOH, usually have one side at ground, but operate at low voltage. Any very rare spikes that do occur on the equipment ground side will be relatively low energy, enough to bite, but not enough to kill. Unless you're wearing a pacemaker, anyway.
3) Given 1) above, the operating frequency of the ground wire/conduit reactor is in the megahertz range which means that millisecond and longer spikes/surges will be shunted to earth anyway. Only the first few microseconds of the spike and only the extremely small energies that are in the megahertz range will be present on the equipment case.
Except the microwave, which operates internally in the many KV range and, depending on the internal engineering, could conceivably place a lot of energy on the case. Ignoring window AC units which have plastic cases leaves Refrigerators and washer/dryer units. You may have a point in these cases. Pun not intended, but I don't see a way around it.
2) Externally generated spikes. Lighting and multi kilowatt transformer failures. It would be really good to keep those spikes out of my equipment and their cases.
I offer this for your consideration as I am sure your education is more current than mine, though possibly not as deep in electronics or hi frequency effects.SamT
Now if I could just remember that I am a businessman with a hammer and not a craftsman with a business.....segundo <!----><!---->
First, put a ground rod outside below the meter base,I'd be surprised if there's not one there already. 6 foot ground rods at any electrical supplier. #4 bare copper from rod to panel. Any copper plumbing in or thru a slab is hopefully in a vinyl sleeve- turning the water on and off, plus heat expansion and contraction will eventually wear thru copper pipe in concrete not sleeved. That sleeve also insulates it from the ground. Might be worth getting somebody with a megger to check just how good your existing ground is. Jim ps whats your telephone grounded to?
Paul, have you looked into the 'ground plate' option?
Unless there is a unique property of a ground plate with a concrete slab, ground rods are best for this area. Lots of dirt here.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
20 ft of rebar or copper wire encased in concrete is really one of the best ground electrodes that you can have. That is a Ufer ground and was developed during WWII to protect explosives storage huts.But this is bascially for new construction. Although I heard of one demented inspector that was requiring them for service upgrades.While the code does not cover distance the shortest runs for the ground electrode conductor the better.I would cut a slit in the walk right across from the meter/panel. But the wire in the grove and cover with caulk.The put the rod in right at the edge of the walk.If you want you can also continue the line from the water pipe connection to other ground rods as shown, but they aren't needed by code.