Connecting the GEC to the bonding conductor

[A/A Fuel GTX]

I have two 200 amp panels coming from a 400 amp meter socket. A PVC nipple comes out the back of the meter socket, into a metallic auxiliary gutter and the panels are nippled off of the gutter for the service entrance conductors to be run through. If I am interpreting 250.70 correctly, I could run my GEC from the ground rods into the metallic auxiliary gutter, install a listed lug with three ports and from there run my bonding jumpers to each of the two panels to be connected at the neutral bar in each panel. Are my thoughts correct?

[ December 08, 2005, 04:03 PM: Message edited by: m73214 ]

 

[augie47]

Re: Connecting the GEC to the bonding conductor

I would have no problem with bonding jumpers from the panels to bond your metallic wireway.
My preference on the GEC would be that it be brought from the meter socket, 2nd preference would be that it be run, unbroken, from 1 panel with a tap to the 2nd panel.

 

[suemarkp]

Re: Connecting the GEC to the bonding conductor

Terminating the GEC in the gutter is about as good as terminating it in the meter. You don't need to do anything further at this point if the neutral to each panel is sized per 250.66 (probably #2 or 1/0 copper).

Were you planning to run additional wires from this lug to each panel (paralleling the neutral), or will the lug just have the GEC, an incoming neutral, and an outgoing neutral? Wires paralleling the neutral are not a good idea.

If you're running two 1/0 copper neutrals from the meter, one to each panel through the gutter, I believe you could either split bolt your GEC to one of the neutrals, or put in a 3 hole 200A lug bar for a neutral from the meter, neutral to panel, and GEC.

Alternatively, you could run a 350 MCM neutral from the meter into the gutter and separately split bolt three wires to this -- neutral for panel 1, neutral for panel 2, and a GEC. Each will need to be 1/0 copper, and perhaps more for the neutrals. The GEC could be less than 1/0 if you only have rods or other electrodes that have a maximum required GEC size.

[ December 09, 2005, 12:26 AM: Message edited by: suemarkp ]

 

[A/A Fuel GTX]

Re: Connecting the GEC to the bonding conductor

I have two 3/0 neutrals coming from the meter socket, into the gutter and one going to each panel from there. There is no metallic water piping in this building so my only grounding electrode is two 5/8 ground rods, six feet apart and I used a #3 copper as a GEC. I realize #4 would have been adequate but I had some extra #3. In the gutter, I used one of those Blackburn three port taps with one port for the GEC coming in from the rods and then the other two ports had a #3 going into each panel through the nipples along with the ungrounded and grounded conductors.

 

[BruceH]

Re: Connecting the GEC to the bonding conductor

That sounds fine to me. Around here the poco does not allow the gec to terminate in the meter socket, no exceptions.

 

[A/A Fuel GTX]

Re: Connecting the GEC to the bonding conductor

Wires paralleling the neutral are not a good idea

Suemarkp.....Please explain why " Parallel Paths " are not desirable. I have often heard this and am not clear on the theory here. Thanks

 

[suemarkp]

Re: Connecting the GEC to the bonding conductor

The code doesn't want them if this current is considered objectionable (250.6). Just what is considered objectional can probably be easily debated, and I don't see it defined in the code, but it's related to parallel grounded paths.

Here's about the only reason I can think of which makes me consider this a bad practice. Lets say your current needs are such that you really require a 3/0 neutral. A parallel neutral sized #3 will most likely be insufficient to carry the full neutral load. If for some reason the 3/0 becomes loose or otherwise degrades, that parallel wire will make up the difference. This will mask the symptoms of a loose neutral. As the 3/0 further degrades or totally fails, that #3 in parallel has to do too much work and will probably overheat too. Eventually, this connection will also fail and you'll begin to get the symptoms of a loose neutral as this happens. End result, two failed wires, and probably two sets of overheated lugs.

I don't see how a parallel path helps anything and just takes twice as much work replacing things when you fix it. NEC 250.142 allows the neutral to ground service equipment, so why add another wire to "help" it?

Services done in metallic conduit have the same issues, but I don't know the ampacity of 2" RMC. To me, the ideal service would use PVC conduits between all of the service equipment and have only one neutral bonded in each piece of the service equipment. As a counter point though, services done in all metal conduit have been done forever, without much ill effect.

Finally, I'm not sure if your ground tap is correct. You need to have an unspliced GEC. Isn't that Blackburn tap a splice, or is there an unbroken wire running through it? Running a #3 from a rod to one panel, unbroken, would be fine. If you wish to tap off of this unbroken GEC to run another GEC to the second you are permitted to do this. But why bother. Did you bond/ground the gutter to the neutral (I hope so)? You could run the GEC from that bonding point if you have the a lug there to do it. It is OK to use busbars to splice GEC's, but is your Blackburn tap a busbar?

 

[A/A Fuel GTX]

Re: Connecting the GEC to the bonding conductor

I used a bond bushing on one of the nipples going from the gutter to one of the panels. The gutter had no knockouts so the hole punched for the nipple is solid. I also used a lug to bond the actual gutter. In reading 250.70, I assumed that the GEC which in this case is continuous from the ground rods to the gutter could then be spliced on to the bonding conductors which then terminate on the neutral bar.

 

[augie47]

Re: Connecting the GEC to the bonding conductor

Finally, I'm not sure if your ground tap is correct. You need to have an unspliced GEC.

thats what I was refering to in my post. I don't feel making up GEC's on a mechanical lug will satisfy the NEC.