2 Family Service w/ Owners Meter - Electrician Talk - Professional Electrical Contractors Forum

Magnettica · 05-02-2009, 10:59 PM

I have a service coming up that'll have (3) 100 amp main disconnect panels. One for the owner, one for the 1st floor, and 1 for the 2nd floor. Normally, I would jump from panel to panel with the GEC but I don't like the way this looks because it could look neater, IMO.

What are some other ways to accomplish this?

william1978 · 05-02-2009, 11:32 PM

Would a common ground bar look better? Run you GEC from each service to the bar.

Magnettica · 05-03-2009, 12:15 AM

That would work, but what I was thinking of doing is using split-bolt connectors and tapping the conductor to 2 of the 3 panels and terminating the main GEC in the third and final panel. I saw it done like this in the '05 Handbook.

250.64 (D)

InPhase277 · 05-03-2009, 08:59 AM

Quote:

Originally Posted by Magnettica

I have a service coming up that'll have (3) 100 amp main disconnect panels. One for the owner, one for the 1st floor, and 1 for the 2nd floor. Normally, I would jump from panel to panel with the GEC but I don't like the way this looks because it could look neater, IMO.

What are some other ways to accomplish this?

How are they fed? Where are they located relative to each other? If they are side by side, and fed out of a trough, then you just take the GEC to the neutral in the trough and that's it. You might also ask if you are allowed to put the GEC in the meter itself.

MDShunk · 05-03-2009, 09:24 AM

I usually run it from the grounding electrode directly to the furthermost panel. Drop out of each of the first two panels with a short piece and H-tap onto the GEC. About as compact as I've ever come up with. Sometimes you can do this inside the building, and you can sleeve the GEC to each exterior disconnect in PVC until it gets inside. Puts all the ugly inside the basement.

william1978 · 05-03-2009, 10:47 AM

Quote:

Originally Posted by Magnettica

That would work, but what I was thinking of doing is using split-bolt connectors and tapping the conductor to 2 of the 3 panels and terminating the main GEC in the third and final panel. I saw it done like this in the '05 Handbook.

250.64 (D)

That would work. Make sure you can use split bolts around here you have to use irreversible crimps/connectors.

redbeard43 · 05-03-2009, 02:59 PM

Whats wrong with something like this..

Mac Hine · 05-03-2009, 03:32 PM

Quote:

Originally Posted by Magnettica

That would work, but what I was thinking of doing is using split-bolt connectors and tapping the conductor to 2 of the 3 panels and terminating the main GEC in the third and final panel. I saw it done like this in the '05 Handbook.

250.64 (D)

Here is a nice graphic from the handbook

Mac Hine · 05-03-2009, 03:35 PM

Quote:

Originally Posted by redbeard43

Whats wrong with something like this..

It is hard to tell if that is legal. The main gec must be sized based on T. 250.66 and on the sum of the equivalent of all the service conductors.

Magnettica · 05-03-2009, 03:46 PM

Quote:

Originally Posted by Mac Hine

Here is a nice graphic from the handbook

That's exactly what I had in mind. I need to read the power company guide book (PSE&G) because I think they want a 200 amp main for the owners panel.

Just for the record, on the exterior will be a PVC riser to a trough, (3) nipples down to individual meters, and PVC conduit to each main circuit breaker panel in a basement. The water meter is like right next to the service

InPhase277 · 05-03-2009, 05:18 PM

Quote:

Originally Posted by Magnettica

That's exactly what I had in mind. I need to read the power company guide book (PSE&G) because I think they want a 200 amp main for the owners panel.

Just for the record, on the exterior will be a PVC riser to a trough, (3) nipples down to individual meters, and PVC conduit to each main circuit breaker panel in a basement. The water meter is like right next to the service

I personally, in that instance, would much rather ground the neutral in the trough, because as you can see from the pic, you would have a parallel path through the GEC. Your equipment ground still originates from the MBJ in the panels, of course.

Mac Hine · 05-03-2009, 05:27 PM

Quote:

Originally Posted by InPhase277

I personally, in that instance, would much rather ground the neutral in the trough, because as you can see from the pic, you would have a parallel path through the GEC. Your equipment ground still originates from the MBJ in the panels, of course.

If you use metal conduit between the trough and the main panels you still have a parallel path. Apparently that is code compliant also.

InPhase277 · 05-03-2009, 06:47 PM

Quote:

Originally Posted by Mac Hine

If you use metal conduit between the trough and the main panels you still have a parallel path. Apparently that is code compliant also.

True, but my concern isn't so much that a parallel path exists, but is more about the nature of the path. A metal conduit between a trough and meter can isn't very likely to be disconnected, at least while the thing is energized. A wire on the other hand is easily accessible and connected with split bolts. If they were cad welded, then it would be different. Also, meter cans don't get disturbed quite as often by the consumer or electricians as a panel board, so the connections likely remain intact there longer.

JohnJ0906 · 05-03-2009, 07:06 PM

Quote:

Originally Posted by william1978

That would work. Make sure you can use split bolts around here you have to use irreversible crimps/connectors.

Local amendment?

The NEC does allow "connectors listed as grounding and bonding equipment". No mention of irreversable. 250.64(D)(1)

redbeard43 · 05-03-2009, 11:14 PM

Quote:

Originally Posted by Mac Hine

Here is a nice graphic from the handbook

looks better than what i drew but still the same, check the bottom of your pic and compare it to mine..numbers a little differ but still the same

Mac Hine · 05-04-2009, 06:53 AM

Quote:

Originally Posted by redbeard43

looks better than what i drew but still the same, check the bottom of your pic and compare it to mine..numbers a little differ but still the same

Here is the problem as I see. Let's suppose what you drew was a residential setup and we had a 200 amp and 2- 100 amp disconnects. I got this by working backwards from the GEC wire sizes but we cannot be certain so I am allowing the minimum. If you take T310.15(B)(6) we get 2/0 copper and 2 sets of #4 for the respective loads. If we add the cir mil of 2/0 (133100) and the #4 (41740) twice, then we get a cir. mil of 216,580. This is equivalent to a 250KCM wire (copper). Go back to 250.66 and the gec should be a #2. From what I see on your diagram you have a #4.

See the confusion? There may be a scenario where this does work , I don't know, but that's why I said it was hard to tell if your drawing was correct.

redbeard43 · 05-05-2009, 10:57 PM

mmmmmmm,, i wasnt trying to be correct, just giving him an idea on what to do. if you wanted accurate, someone should have said so.

Magnettica · 05-06-2009, 12:09 AM

Quote:

Originally Posted by InPhase277

I personally, in that instance, would much rather ground the neutral in the trough, because as you can see from the pic, you would have a parallel path through the GEC. Your equipment ground still originates from the MBJ in the panels, of course.

I've never done it like that but that's a good idea.

Btw, does anybody know if the regular split-bolt connectors one would use for "bugging in" be listed for grounding?

InPhase277 · 05-06-2009, 12:46 AM

Quote:

Originally Posted by Magnettica

I've never done it like that but that's a good idea.

Look at the pic on page 194 of the 2005 handbook.

Magnettica · 05-06-2009, 01:01 AM

Quote:

Originally Posted by InPhase277

Look at the pic on page 194 of the 2005 handbook.

Maybe I'm stuck in my ways but I think it might not look as sharp with (2) GEC's run along the outside of the house up to the trough.