Duplex and connecting to GEC

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flick

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Just wondered what everyone else is required to do for connecting to the GEC in a duplex. Depending on the AHJ, there are 2 configurations here.

1) Ground rod connected to neutral at duplex meter base.
GEC run to one panelboard neutral bus bar from water main, and the other panelboard has a short lenght of copper wire brought out from neutral bus bar and split bolted to the GEC going to water main.

2) Same as above, but compression connector used for connection instead of split bolt

3) Separate GEC's run from each panelboard to water mains

In all scenarios, the GEC hits both water mains.

Anyone else use the same methods? The main reason I'm asking is that one AHJ requires the compression connectors instead of split bolt connectors for tapping the second panelboard to the GEC. Is this required or is the splitbolt acceptable?

I understand where the irreversible connection requirement comes from, which as I read it is, in the 2002 NEC, 250.64(C) and 250.64(D). Am I missing something that would allow a split bolt type of connection?

I assume this is to prevent tampering. However, in a dwelling at least, what is to prevent the homeowner or a plumber from disconnectiing the GEC at the water main and not hooking it back up? Or the GEC to the supplemental ground rod which uses a clamp type connector?

Any opinions on this? Thanks.

John
 
How far apart are the two panels? I have used a single, unbroken length of #6 cu to connect both panels to both rods. Once, from rod to disco to disco to rod. The inspector initially poo-poo'ed it on his way in, but changed his mind by the time he was done.
 
1) Ground rod connected to neutral at duplex meter base.
GEC run to one panelboard neutral bus bar from water main, and the other panelboard has a short lenght of copper wire brought out from neutral bus bar and split bolted to the GEC going to water main.
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This sounds fine with the split bolt. The requirement is for the GEC to the first panel to be unbroken. Split bolt taps are permitted. Look at 250.64(D).
 
250.64D is what I tried to use for the AHJ requiring irreversible connection. He will not accept a split bolt.

Larry, how are you keeping the GEC unbroken? How are you connecting your GEC taps from the panels? If I run the GEC unbroken from panel A to the water main, I will have to tap onto it from panel B somehow.

The AHJ requiring crimped connections said "What if the homeowner disconnects the splitbolt?"

Of course, the homeowner is much more likely to disconnect the ground clamp at the water main.

All I know is that on this last duplex, I'm going to have a dickens of a time getting my MD 6 crimpers on a C crimp! not much room up there to get the handles open!

John
 
What the HO might do is not part of the NEC. If he's enforcing the NEC than he can't make you use something that isn't required.
 
1-unless you have 10 feet of metallic water line in contact with the earth it is not considered to be be a grounding eletrode.
2- I believe the one post who said he loops his GEC had the services mounted close to each other, was refering to the ground rod connection, and probably ran a seperate conductor to the water line.
3- tapping the water bond would be aceptable in the conductor is sized properly,continues to one disconnect, the tap could be split bolted and made accesible 250.64 and 250.68
 
Bea said:
I believe the one post who said he loops his GEC had the services mounted close to each other, was refering to the ground rod connection, and probably ran a seperate conductor to the water line.
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That would be I, I did, I was, and I didn't (because it was all PEX).
 
bonding neutral more than once ??

bonding neutral more than once ??

yo flick, I think I read that you attach a GEC to the Main Meter Neutral then you attach it to the other two panel Neuts ... isn't that wrong or am I reading something wrong ... M
 
This is a question that I have never completely resolved to the satisfaction of my little brain.

I think there is a difference between a service with more than one disconnecting means, and multiple services.

In the case of a duplex, isn't it correct to view this arrangement as two services? (as opposed to one service with two disconnecting means)

If we are looking at two services, 250.24(1) says we can make the connection at any point between the service drop or lateral and the service disconnecting means. That is, the GEC never has to enter the panels if we choose to make the connection at the metering equipment.
 
Ok, let me try to clarify the situation.

The home is an actual duplex, not a converted single family home.

4/0 Al service entrance conductor to dual meter base.

Each meter then feeds one 100A panelboard inside a duplex half.

Supplemental ground rod installed outside at meter can, and neutral is connected to ground rod outside of the structure using the meter base connection available. Only one ground rod, and one #4 copper wire connecting to ground rod.

Inside dwelling, both water mains enter at same point in basement of one side of duplex. The panelboards are about 4 feet apart on basement wall.

One panelboard has #4 copper wire running from neutral bus bar inside the panelboard to water main at meter (about 40' run) and it jumps to the other water main next to it, about 1' away.

The second panelboard has a #4 copper wire approx. 4' long, connected from it's own neutral bus bar and then connected by a split bolt to the #4 which came out of the first panelboard. The 4' wire does not enter the first panelboard. It is connected to the GEC outside of the first panelboard.

I hope the above clears up the situation.

John
 
Is this picture essentially accurate?

Earsduplex.jpg
 
LarryFine said:
How far apart are the two panels? I have used a single, unbroken length of #6 cu to connect both panels to both rods. Once, from rod to disco to disco to rod. The inspector initially poo-poo'ed it on his way in, but changed his mind by the time he was done.
Click to expand...

Larry, what about instead one piece from disco to rod to rod to disco?
 
monkey said:
Larry, what about instead one piece from disco to rod to rod to disco?
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I would consider that perfectly acceptable; each panel is electrically connected to both rods.

In fact, it need not be a single piece. Only the run from each panel to the first rod must be continuous; the rods can be joined via a separate conductor with a second clamp on each rod.

In my example, I bent the #6 into a tight U, routed the U through a KO, and inserted it into a lug on the disco's neutral bus.

Disco.jpg
 
Isn't inserting the "U" under one lug the same as installing two conductors under one lug?
 
infinity said:
Isn't inserting the "U" under one lug the same as installing two conductors under one lug?
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I agree, it certainly is not tested and listed for that use.

I doubt it would ever cause a problem but it is IMO none the less a violation.
 
George, that's exactly how it's hooked up. Nice drawing! Either my explanation wasn't as bad as I thought it was or you are a mind reader!

Anyway, what's the final concensus? Is a split bolt ok? I feel that it is.

Thanks for the replies everyone!


John
 
BTW George, what drawing program is it that you're using? That's pretty nifty to be able to do that!
 
flick said:
George, that's exactly how it's hooked up. Nice drawing! Either my explanation wasn't as bad as I thought it was or you are a mind reader!
Click to expand...

Actually, I've been following you to work for the past few days, hope that doesn't freak you out too much. :D

Anyway, what's the final concensus? Is a split bolt ok? I feel that it is.
Click to expand...

This is a hard question, for many reasons. First, the big question is, is this one service or two?

I'd say it has to be two. Based on this conclusion, I originally would have said this grounding configuration is not legal.

The reason I'd call it two services is simply because the handles are not grouped. Therefore, two services have been employed, perhaps falling under 230.2(B)(1). As a result, it affects how we can use the rest of the code. 250.64(D) could not be used, because it is in reference to one service with several handles. 250.24(A) requires a GEC run to each service.

I look at it this way. Each service disconnect looks at itself and upstream to find it's GE connection. Unit #1 looks at itself and sees a water main connection, and then looks upstream and sees a ground rod supplementing the water main as it should be.

However, Unit #2 looks at itself and sees a connection to a conductor, which does not fit in with 250.64(C). It looks upstream and finds a ground rod, which is fine, but there is a water main in the building that has not been connected to. So, Unit #2's service is in violation of 250.50.

However, after further review, I would say this installation is legal, based on 250.58. Since the ground rod is connected (via the GEC and service neutral) to each service, and then one service is connected to the water main, then the second paragraph of 250.58 kicks in and says that all the electrodes are connected together, good enough so for the purposes of a common grounding electrode to both services.

I would say you could omit the conductor between Unit #2's panel and the GEC, as it is not required. The bonding jumper between water mains could be considered a bonding jumper to connect two 250.52(A)(1) electrodes per 250.50, or as a bonding jumper required by 250.104. Either way, it's kosher and required.

As for me and my house, we shall continue to install disconnects outside and avoid all this headache. :D
 
flick said:
BTW George, what drawing program is it that you're using? That's pretty nifty to be able to do that!
Click to expand...
Appleworks 6 on my iMac. I like it. I haven't looked into drawing pictures on my PC yet, 'cause the Mac is just nice and comfy. :D

Two things I would like to note, if the picture is correct:

I'd say your service conductors are in violation of 310.15 - I would say that you cannot use Table 310.15(B)(6) for the sizing of the service conductors (on the line side of the meters) because they do not serve an individual dwelling unit, they serve more than one dwelling unit. The conductors on the load side could use the Table, but the line side ones should technically be sized greater than the calculated service load, using Table 310.16.

I'd call it a minor violation, because if left to their own devices, the utility would likely have installed conductors smaller than that anyway. :D

I am also curious about your routing for the service entrance conductors between the meters and the panels. Are they through the slab?

(Not trying to pick on you, I've learned I had some bad habits before folks here pointed them out to me. ;) )
 
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