My main panel doesn't have neutral/ground bars big enough to accept #4. So, rather that adding a lug nut to the bars, or only attaching a few strands of the #4 to the bars, I'm thinking of snaking another #10 awg (neutral) and #8 awg (ground) into this greenfield. Is it possible and ok to do this? I'll leave the extra 2 #4 wires in case I'd like more amperage to the subpanel one day. Any ideas?
2007-12-17 03:04:03 · 4 answers · asked by tonymonton 2 in Home & Garden ➔ Do It Yourself (DIY)
based on national electrical code table 27 for rewiring you are allowed 40% conduit fill. and table 29 the 1.25" conduit 40% fill, the total combination area of conductors is 0.60 sq.in (table 29 column 7)
now go to table 30 see how many combination of different size of conductors (column 1 and column 5) add up to be equal to 0.60 sq.in. example each #4 conductor has 0.1087 sq.in for 4-#4 the total area is 4*0.1087=0.4348 sq.in. it is less than 0.60 sq.in so you can pull 4-#4 in 1.25" conduit.
this selections is good only for rewiring not for new wiring.
2007-12-17 04:12:50 · answer #1 · answered by Anonymous · 0⤊ 2⤋
You didn't specify what type of wire you have and that makes a big difference in the answers. I will take a wild guess and pick THHN or THWN copper wire. If this is not correct, this answer will not be correct. Using the 2005 National Electric Code.
Table C.3 states a 1 1/4 flex conduit will allow 6 #4 conductors of the type I picked above. THHN or THWN.
Your #4 wires are rated for 85 amps at 75C in Table 310.16. However Table 310.15B6 allows #4 copper to be used on a 100 amp service.
Using the 100 amp figure, Table 250.122 specifies a minimum of a #8 copper wire for the equipment grounding conductor. Your ground wire in other words.
Now for the neutral conductor. You mentioned a number 10. That is not allowed. 250.24C1 states the grounded (neutral) conductor shall not be smaller than the grounding electrode conductor specified in 250.66. Table 250.66 specifies a #8 copper wire. So your neutral cannot be smaller than #8. And you still need to do the proper calculations that show that a #8 will be large enough to handle the current imposed on it. Any more than 50 amps will require a larger wire. Most inspectors will not allow you to go more than 1 size smaller on a neutral. That would be a #6 copper wire. Burned off neutrals can be very dangerous both to people and equipment.
So you are allowed to pull another #6 neutral and a #8 ground into your 1 1/4 flex conduit.
Don't take electrical advise from the untrained and unqualified people on yahoo. Especially those posing as electricians. They are guessing. If you need more help just email me.
PS: most service panels will take a #4 wire in the neutral and ground busses. Just a little struggle to get them in there. But they are rated for #4.
2007-12-18 06:51:09 · answer #2 · answered by John himself 6 · 1⤊ 0⤋
Without looking at the Code Book, I think your'e maxed out. Do it right and get the proper lugs to attatch your #4's to the neutral bus in the main panel. Sounds as though you're wiring to a sub-panel, be sure and seperate neutrals and grounds and make sure the neutral bus in your sub is isolated. Don't cut corners on this, do it right!
2007-12-17 04:12:16 · answer #3 · answered by gr8alarmguy 4 · 1⤊ 1⤋
take the advise of gr8alarmguy!
it will cost more and be more work to pull more wire. do it right! get the proper lugs and be sure your neutral is isolated.
2007-12-17 05:20:21 · answer #4 · answered by doug c 2 · 1⤊ 1⤋