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-   -   Main to sub (main lug) panel wiring (http://www.houserepairtalk.com/f9/main-sub-main-lug-panel-wiring-2073/)

newdiyer 03-21-2007 11:04 AM

Main to sub (main lug) panel wiring
 
I have a full 100 AMP main, installed a main lug fed by a 60AMP breaker on the main. Between the main and main lug I have NM 6-3 WG copper. I did not use conduit or an offset conduit, but rather 1" DIA. clamps and less than 6" length of NM 6-3 between the main and main lug. The gound wire on the 6-3 is not 6 gauge wiring of course, and I was wondering if there are NEC guidelines on appropriate gauging for the ground. There of course might be local specific codes, but I was first going to see what guidance people on this board might suggest.

I can either use the ground in the 6-3 to ground the main lug to the main panel, or optionally add a larger gauge ground dedicated between the main lug and the main. Any suggestions? Also, if I use a larger gauge ground between the two panels, should I bust a new pair of holes claimp too? I doubt it makes sense to go through the 1" dia clamps where the 6-3 NM is.

Finally, my neutral of the 6-3 doesn't fit in any of the open screw terminals on the main panel bus, and was wondering if there is a way to appropriately get it to fit. Ideas, in no particular order, include:
a. reduce the strands of the 6 gauge neutral (from the 6-3) until it fits into the terminal
b. find and buy some sort of adapter (if they exist) to accomodate the larger size
c. branch the 6 gauge neutral into two strands and fit each strand into adjacent open terminals on the neutral bus of the main panel.

I am guessing that option B is the best, if not most appropriate solution.

Your thoughts and suggestions are appreciated.

newdiyer 03-22-2007 10:16 AM

Quote:

Originally Posted by newdiyer (Post 8780)
I have a full 100 AMP main, installed a main lug fed by a 60AMP breaker on the main. Between the main and main lug I have NM 6-3 WG copper. I did not use conduit or an offset conduit, but rather 1" DIA. clamps and less than 6" length of NM 6-3 between the main and main lug. The gound wire on the 6-3 is not 6 gauge wiring of course, and I was wondering if there are NEC guidelines on appropriate gauging for the ground. There of course might be local specific codes, but I was first going to see what guidance people on this board might suggest.

I can either use the ground in the 6-3 to ground the main lug to the main panel, or optionally add a larger gauge ground dedicated between the main lug and the main. Any suggestions? Also, if I use a larger gauge ground between the two panels, should I bust a new pair of holes claimp too? I doubt it makes sense to go through the 1" dia clamps where the 6-3 NM is.

Finally, my neutral of the 6-3 doesn't fit in any of the open screw terminals on the main panel bus, and was wondering if there is a way to appropriately get it to fit. Ideas, in no particular order, include:
a. reduce the strands of the 6 gauge neutral (from the 6-3) until it fits into the terminal
b. find and buy some sort of adapter (if they exist) to accomodate the larger size
c. branch the 6 gauge neutral into two strands and fit each strand into adjacent open terminals on the neutral bus of the main panel.

I am guessing that option B is the best, if not most appropriate solution.

Your thoughts and suggestions are appreciated.

I figured out the answer to the second question (answer = B), but I still have some questions about the first question in terms of ground wire gauge.

Thanks in advance.

petey_racer 03-22-2007 04:14 PM

DEFINITELY asnwer B.

As to the ground size. The cable is a factory made assembly. They would not use a ground smaller than would be code required.
A #10 ground is adequate for anything you would use #6 circuit conductors for.
If you want to look it up see NEC Table 250.122

AndyD5 03-29-2007 08:22 PM

I agree to Answer B and for the size of ground must be equal or greater to that which you are grounding. if you use a 2/10AUG romex it should have a 10 guage ground wire in the middle my A/C unit has a heavy guage wire all wires to it are in the same romex covering one black one red one white and one green

Square Eye 03-29-2007 08:43 PM

Andy, buy an NEC code book.
The table that Petey Racer is talking about clearly shows that a smaller gorund wire is sufficient.

AndyD5 03-29-2007 09:03 PM

Quote:

Originally Posted by Square Eye (Post 8898)
Andy, buy an NEC code book.
The table that Petey Racer is talking about clearly shows that a smaller gorund wire is sufficient.

I just go with what I was taught and what makes sence too much protection is better than not enough. It may not be required but it surely doesn't hurt anything either. So I'm over cautious!

petey_racer 03-30-2007 07:03 PM

Quote:

Originally Posted by AndyD5 (Post 8902)
I just go with what I was taught and what makes sence too much protection is better than not enough. It may not be required but it surely doesn't hurt anything either. So I'm over cautious!

That is absolutely the wrong attitude to have when it comes to electrical work.
What makes "sense" and what may seem over cautious sometimes can be counterproductive.

Square is correct. GET A CODE BOOK. Know it. Then come back and give advice.

It is not a wise man who gives advice on such things merely according to "what he was taught" or "what I've always learned".

This is how misconceptions and incorrect practices get perpetuated.


You are correct. A circuit run with #10 should have a #10 ground. Same with #12 & #14. Larger than that is DIFFERENT.
See NEC Table 250.122 and get back to us.


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