Grounding electrode conductor connections

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mhanson

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Redwood City, CA
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General Journeyman Electrician
Good day all,
I am installing a new 1phase residential service 240v 100amps
QUESTION: can I use existing #6 bare copper ran from the water main where it enters the house, and land it on the newly installed ground rod. Then install a second#6 copper conductor from ground rod to new Meter/Main panel?

Thank you
 
IMO, yes, but you would likely need two clamps at the rod as the ones in use here only allow one wire.
(Locally, due to the poor soil, you would also need a 2nd ground rod if the rods and water are your only grounding electrodes)
 
mhanson said:
Good day all,
I am installing a new 1phase residential service 240v 100amps
QUESTION: can I use existing #6 bare copper ran from the water main where it enters the house, and land it on the newly installed ground rod. Then install a second#6 copper conductor from ground rod to new Meter/Main panel?

To me that defeats the purpose of a supplemental ground. If your ground from the meter main to the rod comes off you have nothing. We always run from the water meter to first means of disconnect (your meter main) and a separate run from the rods to first means of disconnect. The only time I saw what you are describing the ground wire was continuous through the acorn clamp and on to the water meter, or vice versa.
Click to expand...
 
GerryB said:
mhanson said:
Good day all,
I am installing a new 1phase residential service 240v 100amps
QUESTION: can I use existing #6 bare copper ran from the water main where it enters the house, and land it on the newly installed ground rod. Then install a second#6 copper conductor from ground rod to new Meter/Main panel?

To me that defeats the purpose of a supplemental ground. If your ground from the meter main to the rod comes off you have nothing. We always run from the water meter to first means of disconnect (your meter main) and a separate run from the rods to first means of disconnect. The only time I saw what you are describing the ground wire was continuous through the acorn clamp and on to the water meter, or vice versa.
Click to expand...

It has been long standing that you can build a grounding electrode system by bonding grounding electrodes together

It has also been long standing that many prefer a single point grounding electrode system

IMO there is nothing weak about what the OP wants to do
Click to expand...
 
GerryB said:
mhanson said:
Good day all,
I am installing a new 1phase residential service 240v 100amps
QUESTION: can I use existing #6 bare copper ran from the water main where it enters the house, and land it on the newly installed ground rod. Then install a second#6 copper conductor from ground rod to new Meter/Main panel?

To me that defeats the purpose of a supplemental ground. If your ground from the meter main to the rod comes off you have nothing. We always run from the water meter to first means of disconnect (your meter main) and a separate run from the rods to first means of disconnect. The only time I saw what you are describing the ground wire was continuous through the acorn clamp and on to the water meter, or vice versa.
Click to expand...

AFAIK the reason the water pipe needs supplemented is the possibility of the water pipe being repaired or replaced with non metallic components. Otherwise as long as it remains intact the water pipe is normally going to be a lower resistance electrode than the rod.
Click to expand...
 
The GEC goes to the first electrode, water pipe, structural metal, ground rod, etc. The conductor to the other electrodes are bonding jumpers. The GEC does not have to be continuous, IE for 2 ground rods, it does not have to be one wire and two clamps.
The installer picks which electrode to hit first, often its the largest conductor required in 250.66, and then use 250.66(A)(B) or (C) which are always smaller electrodes.
A water pipe, if 10 ft or more in contact with the earth is always supplemented with another electrode, which is often a ground rod or two.
the water pipe connection must be within 5 ft of the entrance to the building.
If the water pipe does not have 10 ft in contact with earth, then a bonding connection is required somewhere, per 250.104
 
tom baker said:
The GEC goes to the first electrode, water pipe, structural metal, ground rod, etc. The conductor to the other electrodes are bonding jumpers. The GEC does not have to be continuous, IE for 2 ground rods, it does not have to be one wire and two clamps.
The installer picks which electrode to hit first, often its the largest conductor required in 250.66, and then use 250.66(A)(B) or (C) which are always smaller electrodes.
A water pipe, if 10 ft or more in contact with the earth is always supplemented with another electrode, which is often a ground rod or two.
the water pipe connection must be within 5 ft of the entrance to the building.
If the water pipe does not have 10 ft in contact with earth, then a bonding connection is required somewhere, per 250.104
Click to expand...

Your post clarifies something for me, I think, when you said the installer picks which electrode to hit first. I have seen many services dating back probably to the 60's that have no ground rods but always have the water main grounded. There is a comment in the code/handbook (so not the code) after 250.53(D)(2). (I'm looking at 2005, I don't have my 2014 and 2017 with me) It says in part "Section 250.53(D)(2) requires that rod, pipe, or plate electrodes used to supplement metal water piping be installed in accordance with 250.56. This requirement clarifies that the supplemental electrode system must be installed as if it were the sole grounding electrode for the system....One of the permitted methods...is to connect it to the service enclosure."
As I said this is a comment so it is not part of the code book, but it seems like they are saying the intent of the code is if one system fails you have the other one. That is why I said the in the OP's scenario if the ground clamp
from the disconnect to the rod came off or the wire pulled out another ground clamp and conductor going to the water main is useless.
 
The GEC does have to be continuous, from the service to the first electrode. Technically once you get past the first electrode it's no longer the GEC but a bonding jumper. However, YMMV depending on the AHJ. Mine does.
 
GerryB said:
As I said this is a comment so it is not part of the code book, but it seems like they are saying the intent of the code is if one system fails you have the other one. That is why I said the in the OP's scenario if the ground clamp
from the disconnect to the rod came off or the wire pulled out another ground clamp and conductor going to the water main is useless.
Click to expand...

The water pipe was also the electrode of choice. Then in the late 50's non metallic water service lines were starting to be used, leaving no grounding electrode. NEC then required in early 1970s to require an additional electrode(s) and came up with the concept of the grounding electrode system.
For a large service >200 amps the water pipe or structural metal will be the largest GEC, as a ground rod is never required to be larger than 6 AWG. Hit the water pipe with the big wire, then a bonding jumper to the ground rod. I have a nice drawing that shows this maybe I can post it this week
 
Don't forget that a Ufer (CEE) will often be as good as or better than a water pipe ground, and the current NEC and many jurisdictions require that one be used if there is qualifying rebar or wire in concrete as part of the building.
 
Most resi-sparks carried #4 , good for 100&200A services , predicated on #6's physical protection....where #4 would skate.....however i see there's been a '17 change to >>>>>250.64 Grounding Electrode Conductor Installation.B(2) Exposed to Physical Damage.

~RJ~
 
jaggedben said:
The GEC does have to be continuous, from the service to the first electrode. Technically once you get past the first electrode it's no longer the GEC but a bonding jumper. However, YMMV depending on the AHJ. Mine does.
Click to expand...
So somewhat related I'm trying to understand the irreversible crimp you solar guys use, NEC 690.47(3) in the 2014. Seems like they use it everywhere, maybe to not have an issue with the inspector. Is it not required on an AC system?, panels with microinverters.
 
GerryB said:
So somewhat related I'm trying to understand the irreversible crimp you solar guys use, NEC 690.47(3) in the 2014. Seems like they use it everywhere, maybe to not have an issue with the inspector. Is it not required on an AC system?, panels with microinverters.
Click to expand...

It is a holdover from earlier technology and thankfully it essentially goes away in the 2017 NEC.

Until about 6 years ago PV inverters had a grounded DC conductor and galvanic isolation between DC and AC. This requires a GEC for that grounded DC conductor, per UL or also if you look at it as an SDS. So the NEC basically threw the whole shebang at that, 250.64 etc.

Then PV inverters started going to an ungrounded topology (i.e. no grounded DC conductor and no transformer). That took away justification for needing a GEC. Also I think after several years of widespread PV installations it became obvious that an EGC connection to existing GES was plenty sufficient for safety. Also there was recognition that most of those 'grounded' DC conductors weren't really grounded, since the connection was done through a fuse that opened in a ground fault. Anyway, it took two code cycles for the code to catch up, and some inspectors take a whole code cycle to catch up themselves. :roll: So in the 2014 you still have this GEC language even though for example it says you can size to 250.122 for ungrounded systems.

There's no strict correlation to microinverters.
 
Oh, also, there's this really dumb requirement called 690.47(D). I'm not even going to go into it, but Mike Holt has a 26min video about why it's dumb. It's also gone from the 2017 NEC.
 
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