How To Tap Off Common GEC

[Jerramundi]

That should be fine just keep in mind that your water pipe electrode must be supplemented by another electrode. See 250.53

Am I right to think 250.64(C)(1) applies only to a single GEC and say, for example, splice onto it in order to extend it?

... and that I SHOULD be looking at 250.64(D), in which 250.64(D)(1)(1) allows for taps to a common GEC to be simply "connectors listed as grounding and bonding equipment?"

 

[Jerramundi]

Most people refer to them as C taps. You can get a crimper for a few hundred that would work. Cost and needing a specific die are why a lot of people on residential or even some commercial use split bolts. No special tools required.

You are not splicing the grounding electrode conductor, the larger conductor is considered the GEC. The smaller wires are taps/jumpers and are not required to have irreversible crimps. Yes the connection in a Junction Box is perfectly fine with split bolts. Look up the definitions for all of these items in article 100. It will really help you figure out how to read/understand the NEC better. Just make sure you use 3 separate split bolts as most split bolts are only listed for 2 or 3 wires only. Also make sure the range on the split bolt is correct and they are listed for bonding and grounding.

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Thank you brother. You've been very helpful.

I just have one last question... is there any way to size the junction box appropriately for containing the split bolt and bonding bushings?
I'm thinking of going with a 2-1/8"deep 4" x 4" just to have room to work, but if there's a NEC method for these items I would like to do it the right way.

I'm thinking just standard volume calculation of length x width x height for the cubic inches of the split bolt.

 

[infinity]

How does this look to everyone? Thoughts? Suggestions?

Note #1: The "Common GEC" will be sized according to 250.66 according to the AWG of the Overhead Service Conductors (outside)
Note #2: The "GEC Taps" will be sized according to 250.66 according to the AWG of the Ungrounded Service Entrance Conductors in each
respective panel (100A)

View attachment 2552773

Why the junction boxes?

 

[Jerramundi]

Why the junction boxes?

If my math is correct, I need a #2 Common GEC, which is larger than #4 and would require protection from physical damage according to 250.64(B)

Also, an aesthetic choice I suppose?

 

[Eddie702]

Run the gec to the farthest panel#3 full size. Then run a 100amp gec #8 between panels #1 & #2 in the same raceway. Connect both GEC's with 1 split bolt. Done

 

[Jerramundi]

Run the gec to the farthest panel#3 full size. Then run a 100amp gec #8 between panels #1 & #2 in the same raceway. Connect both GEC's with 1 split bolt. Done

It sounds like your advocating for using a GEC tap with the #8, but you say a single #8. I don't think panels #1 and #2 could share the same tap.

Common GECs are new to me. I'm used to a single one to the main panel and that's it. So, I could be wrong. But if I'm reading my handbook correctly, it boils down to either (1) all individual GECs or (2) all GEC taps to one common GEC... depending on your circumstances of course.

 

[Another C10]

I'm thinking of running a common GEC from the water main to j-boxes below each panel and using a c-clamp in each j-box to tap off it for each respective panel.

using the water system as a ground is not a good idea, bonding a water system is to protect the water system from becoming energized, not to be used as a path to earth ground for the purpose of diverting a fault current from an electrical system, I would attach the earth ground of each 100 A panel from the grounding electrodes and make the #4 continuous, uncut, I know its a hassle but uncut is the best practice if possible.

 

[electrofelon]

I think think you are making this far more complicated then it needs to be. A supply house should have a grounding bus bar for far less than $100. If you don't like that idea, just run your GEC to one panel, then split bolt a tap off it to the other two. Suggest nixing all those jboxes and conduits for the GEC.

 

[Jerramundi]

using the water system as a ground is not a good idea, bonding a water system is to protect the water system from becoming energized, not to be used as a path to earth ground for the purpose of diverting a fault current from an electrical system....

Well, underground water piping is a code approved electrode... and in my 10 years + in the field as a residential electrician, we've always done one GEC to the street side of the water main and another at the meter to two ground rods. Are there other code approved methods? Absolutely. But this is common practice in my experience. To your point, I actually just stumbled upon a comment by Mike Holt that the water utility doesn't like this practice, which is news to me, but it's NEC approved nonetheless.

It's true that the grounding electrodes aren't meant to sustain fault currents and that if done correctly, faults should be carried to the system's grounded conductor. I am ensuring this with the installation of the proper system jumpers. This Common GEC is just one aspect of the grounding and bonding system that I needed input on because it's relatively new to me as I don't typically work outside of a residential setting in which I have, at most, one main breaker panel and one sub panel that can be handled with a single GEC.

 

[Jerramundi]

...I would attach the earth ground of each 100 A panel from the grounding electrodes and make the #4 continuous, uncut, I know its a hassle but uncut is the best practice if possible.

Uncut is not just best practice, it's required for the GEC unless you use exothermic welding or irreversible connections.

I've never done exothermic welding and I don't have the means to purchase the tools required for irreversible connections, so I am running a continuous Common GEC. I am able to bypass the "irreversible connection" requirement because, as pointed out to me by another forum user, the "splice points" are allowed to be done with mechanical connectors (e.g. split bolts) listed for grounded and bonding because they are jumpers/taps.

 

[Jerramundi]

...A supply house should have a grounding bus bar for far less than $100...

I mean a grounding bus bar would essentially be the same set up - a common GEC and taps to each panel, but it would cost more than a couple split bolts.

I think think you are making this far more complicated then it needs to be.... If you don't like that idea, just run your GEC to one panel, then split bolt a tap off it to the other two. Suggest nixing all those jboxes and conduits for the GEC.

I hear you and appreciate the feedback. Your point is not invalid, but I wouldn't call a couple junctions boxes making this "FAR more complicated than it needs to be." Something about a split bolt resting in the main panel just seems sloppy to me, hell the split-bolt in a j-box still seems sloppy to me, I would prefer a nice C-tap but don't have the tools required.

I will grant you that with your suggestion I could save on the cost of some conduit, a few junction boxes, and the number of bonding bushings required, but as I said, something about a split-bolt resting in the main panel just seems sloppy to me. That's just my own personal opinion.

 

[wwhitney]

If my math is correct, I need a #2 Common GEC, which is larger than #4 and would require protection from physical damage according to 250.64(B)

Huh? #4 and larger only require protection when "exposed to physical damage".

Cheers, Wayne

 

[electrofelon]

I mean a grounding bus bar would essentially be the same set up - a common GEC and taps to each panel, but it would cost more than a couple split bolts.


I hear you and appreciate the feedback. Your point is not invalid, but I wouldn't call a couple junctions boxes making this "FAR more complicated than it needs to be." Something about a split bolt resting in the main panel just seems sloppy to me, hell the split-bolt in a j-box still seems sloppy to me, I would prefer a nice C-tap but don't have the tools required.

I will grant you that with your suggestion I could save on the cost of some conduit, a few junction boxes, and the number of bonding bushings required, but as I said, something about a split-bolt resting in the main panel just seems sloppy to me. That's just my own personal opinion.

I wouldn't put the split bolts in the panels, do it outside the panels.

 

[Chamuit]

I would attach the earth ground of each 100 A panel from the grounding electrodes and make the #4 continuous, uncut, I know its a hassle but uncut is the best practice if possible.

I'm with this method. Drop two ground rods, run continuously to the furthest panel from the rods, then, tap off to the two panels in between. #4 solid so no need for any protection unless the environment or conditions require. Least amount of wire. 2 pink c-taps for the jumpers. Legal.

 

[Another C10]

we've always done one GEC to the street side of the water main and another at the meter to two ground rods.

The way I've learned and the way I understand the 2 methods mentioned is that yes we bond the water system typically within the 1st 10' of were the water main enters the structure , I usually put it on the load side of the water meter for inspection purposes, again that bond is specifically for stray or fault current to find its way back to the grounding rods which is the true fault current bleed off.

As a scenario lets say Mr Electrician decides to bond an outlet or even a panel on a nice big copper or galvanized water pipe oh ya, that's a strong negative reference to mother earth, years later Mr Plumber comes in and re plumbs the entire house in plastic or simply uses a plastic fitting somewhere on that pipe the bond was relying on, Will it work on a water line .. yes is it a good practice, my science says no. Everyone has their way of doing things based on what is accepted within their region, in California it would fail inspection.

 

[Another C10]

faults should be carried to the system's grounded conductor.

Grounding electrodes have 2 functions that I am aware of

1 .. Diverting fault current to a sound ground path allowing the breakers to heat up quickly allowing that thermal overload to trip quick.
2).. To divert a power surge from a lighting strike blocks away that will surge every home connected, now this is where the idea of not using a water line as ones relied ground return, I've heard stories from instructors were sinks or shower heads have blown off their mounds from a severe lightning strike, I'd rather the electrodes driven into the earth get that surge back to its home quick as possible.

 

[electrofelon]

Grounding electrodes have 2 functions that I am aware of

1 .. Diverting fault current to a sound ground path allowing the breakers to heat up quickly allowing that thermal overload to trip quick.

false. https://forums.mikeholt.com/threads/heating-up-two-ground-rods.2554242/

2).. To divert a power surge from a lighting strike blocks away that will surge every home connected, now this is where the idea of not using a water line as ones relied ground return, I've heard stories from instructors were sinks or shower heads have blown off their mounds from a severe lightning strike, I'd rather the electrodes driven into the earth get that surge back to its home quick as possible.

Maybe but probably not.

I think a MV line falling on a LV line is the most likely scenario where a rod will do anything significant.

 

[Another C10]

false. https://forums.mikeholt.com/threads/heating-up-two-ground-rods.2554242/

Not sure what this argument was ..

Maybe but probably not.

That does sound pretty scientific, but probably not.

The point being whatever the nature of a power surge blasting toward a dwelling, the grounding rod is the best path of least resistance at that point of entry. If people want to attach their surge suppression to a water line then have at it, just be careful showering or sitting on the bowl during lightning storms.

 

[LarryFine]

. . . that bond is specifically for stray or fault current to find its way back to the grounding rods which is the true fault current bleed off.

Diverting fault current to a sound ground path allowing the breakers to heat up quickly allowing that thermal overload to trip quick.

Sorry, but that's incorrect. The supply neutral is the fault-current pathway that assures protection activation.

 

[Another C10]

The supply neutral is the fault-current pathway that assures protection activation.

what if the surge coming in to ones service drop is rushing toward the home, it seems at that point the utility return is alittle late
or what if the utility loses its neutral, then what.