HOW WRONG IS THIS GROUND ROD AND CONDUCTOR LAYOUT?

Z

ZBOLTMAN

Member
Location
Cerritos, CA
Occupation
Retired Industrial Journeyman Electrician & Automation Technician
Retired Industrial Journeyman electrician here. Great on Industrial code, but still need guidance on residential code.
I'll be doing this about the end of April. Doing LOTS of planning and getting all my ducks in a row.
Swapping out a 100 for a 200a panel. Underground feed.
Want to install a modern ground rod connection. Currently it is grounded to the conduit coming from the ground for the infeed.
OK, is #8 bare copper conductor large enough for this length and will the 3/8" flex conduit be enough to protect it?
Is it OK, or do I need to bond it to the copper water pipe that is near the ground rod?
(Oh, I have a 1/2" 8 feet copper ground rod. Please don't tell me I have to upgrade to 3/4")
28523658-ac21-4def-9255-b1b7178af0cf.jpg
 
IF you were only connecting the ground rods a #6 GEC would be sufficient but with the metallic water pipe in the equation a #4 would be required (assuming 3/0Cu or 4/.0AL Service). See 250.66
There are many advantages to using PVC to enclose your GEC . Metal conduits need bonding at both ends (see 250.64)
 
GEC size is based on service conductor size. A 100A service typically uses a #8 copper and a #4 copper is used for a 200A service. Rods have a max requirement of #6, so you don't have to go bigger to those. But to a UFER or water pipe, you need the full #4. Length doesn't matter.
 
suemarkp said:
GEC size is based on service conductor size. A 100A service typically uses a #8 copper and a #4 copper is used for a 200A service. Rods have a max requirement of #6, so you don't have to go bigger to those. But to a UFER or water pipe, you need the full #4. Length doesn't matter.
Click to expand...
OK, here's the mystery to me. I'm going to ground my panel to the rod. Why should I ground it to the water pipe? Is it required? What are the advantages to it?
 
ZBOLTMAN said:
Retired Industrial Journeyman electrician here. Great on Industrial code, but still need guidance on residential code.
I'll be doing this about the end of April. Doing LOTS of planning and getting all my ducks in a row.
Swapping out a 100 for a 200a panel. Underground feed.
Want to install a modern ground rod connection. Currently it is grounded to the conduit coming from the ground for the infeed.
OK, is #8 bare copper conductor large enough for this length and will the 3/8" flex conduit be enough to protect it?
Is it OK, or do I need to bond it to the copper water pipe that is near the ground rod?
(Oh, I have a 1/2" 8 feet copper ground rod. Please don't tell me I have to upgrade to 3/4")
28523658-ac21-4def-9255-b1b7178af0cf.jpg
Click to expand...
OK, I need to make something clear about the water pipe. It is a hose bib. It does enter the house about 30 feet away.
 
ZBOLTMAN said:
Retired Industrial Journeyman electrician here. Great on Industrial code, but still need guidance on residential code.
I'll be doing this about the end of April. Doing LOTS of planning and getting all my ducks in a row.
Swapping out a 100 for a 200a panel. Underground feed.
Want to install a modern ground rod connection. Currently it is grounded to the conduit coming from the ground for the infeed.
OK, is #8 bare copper conductor large enough for this length and will the 3/8" flex conduit be enough to protect it?
Is it OK, or do I need to bond it to the copper water pipe that is near the ground rod?
(Oh, I have a 1/2" 8 feet copper ground rod. Please don't tell me I have to upgrade to 3/4")
28523658-ac21-4def-9255-b1b7178af0cf.jpg
Click to expand...
Well, I learned something. Wrong about the #8 GEC. I will change it to #4. Thank You. This is why I ask.
 
ZBOLTMAN said:
OK, here's the mystery to me. I'm going to ground my panel to the rod. Why should I ground it to the water pipe? Is it required? What are the advantages to it?
Click to expand...
If the metal water pipe is in contact with the earth for more than 10 feet, it is required to be used as a grounding electrode. And then the code requires that to be supplemented with a rod or plate, etc.
 
Here are the pertinent article sections. 250.50, 250.52, 250.53, 250.66, basically all of part III of 250.

250.104, might come into play too.
 
Bonding for GEC on the water pipe will usually be done within 5 ft of entry into the structure. Might want to look at wording and exception in 250.68(C)(1).

Personally I wouldn't trust that someone later on decides to alter the continuous metal pipa for PVC or PEX and loose the connection extension allowed in the exception. Consider 250.68(B). Also not sure I would do as illustrated in 250.66(C) Enhanced Content using the water pipe as the point of bonding for all other GEC jumpers. No maximum length is noted for this Pipe Bonding jumper, note the pipe is not a GE until it leaves the structure to an underground location.
So while "compliant" and I couldn't enforce otherwise on someone, I would do it.

So now let's get into the argument as to use of a ground rod to supplement the water pipe electrode and do you need 1 or 2 rods.
 
As roger suggests, you really need to spend some time in Art 250. If there is a metallic water pipe involved then you would likely be required to either treat it as a rounding electrode or bond it depending on the details.
 
Found a website that has info on section 250: Article 250 |
Been reading alot of it. Need tylenol now...

250.52.A 1.1 States it is OK to bond to a water pipe in ground for 10 feet or more.

250.52 (3) (A) 1.4.2 Basically a water pipe used as a grounding conductor must be accompanied by another. a ground rod. Where two are within 6ft; they shall be considered a single electrode system. Properly bonded together, if these two will measure 25 ohms or less, then I will not need a 2nd ground rod. If more than 25 ohms, well a 2nd ground rod gets installed.

Does all this sound about right?

Now, I can get a Ground resistance checker on EBAY for about $170. If you folks know of a better way to check for 25ohms, please inform me.
 
ZBOLTMAN said:
Now, I can get a Ground resistance checker on EBAY for about $170. If you folks know of a better way to check for 25ohms, please inform me.
Click to expand...
You also would need to have it certified for calibration for the AHJ to accept the 25ohm to be valid.
Also know that the resistance value would be highly dependent on soil conditions such as moisture levels. So you tested and it had been raining and you test out under 25ohms, now the AHJ comes out and it has been baking out for several days and the ground has dried right out and now you have 45ohm while the inspector is there, and now he says you need more GECs. Or you can just drive 2 rods and be done with it and never have to prove the 25ohms.
So is it better to test and hope for 25ohm or just drive 2 and go.
 
ZBOLTMAN said:
Found a website that has info on section 250: Article 250 |
Been reading alot of it. Need tylenol now...

250.52.A 1.1 States it is OK to bond to a water pipe in ground for 10 feet or more.

250.52 (3) (A) 1.4.2 Basically a water pipe used as a grounding conductor must be accompanied by another. a ground rod. Where two are within 6ft; they shall be considered a single electrode system. Properly bonded together, if these two will measure 25 ohms or less, then I will not need a 2nd ground rod. If more than 25 ohms, well a 2nd ground rod gets installed.

Does all this sound about right?

Now, I can get a Ground resistance checker on EBAY for about $170. If you folks know of a better way to check for 25ohms, please inform me.
Click to expand...
The more you study Art 250 you will likely need something stronger than Tylenol :)
A point on 250.52(A)(1):: If you have 10 ft or more of metallic water line in contact with the earth it's not just' O.K. to "bond" to it' (your words), i9t is required that you use it as a grounding electrode and you must connect to it within the 1st 5 ft of the pipe entry to the building.
 
OK, two ground rods it is. So NEC 250.53(B) states minimum distance is 6 feet?
Now I'm going to have to run about 30 feet of #4 to the back yard.
 
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