this grounding and bonding can create confusion sometimes. im doing a residential custom home, that requires a 400 amp panel i have two sub panels coming out one 200 amp and one 100amp for the pool area. my question is about grounding the 400 amp panel. i told the home owner too put in two half in. 20ft long, rods (rebars). as to code 250.52(a)3. he says he rather heve me put in 20ft of #2 stranded copper into the footing. i dont see why that would make it better. and another qeustion im running 3, 1/0co and one #4co for ground to the 200amp service from the main, and my qeustion is if i need another ground for that sub panel or would that make it enough? thanks for all the help and support
grounding
- Thread starter wiredup
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ty
Senior Member
- Location
- 3rd Rock from the Sun
Re: grounding
jwelectric
Senior Member
- Location
- North Carolina
Re: grounding
Originally posted by wiredup
this grounding and bonding can create confusion sometimes. im doing a residential custom home, that requires a 400 amp panel i have two sub panels coming out one 200 amp and one 100amp for the pool area. my question is about grounding the 400 amp panel. i told the home owner too put in two half in. 20ft long, rods (rebars). as to code 250.52(a)3. he says he rather heve me put in 20ft of #2 stranded copper into the footing. i dont see why that would make it better. and another qeustion im running 3, 1/0co and one #4co for ground to the 200amp service from the main, and my qeustion is if i need another ground for that sub panel or would that make it enough? thanks for all the help and support [/QUOTE
There is no reason to have two 20 foot pieces of rebar in the footer one would be all that would be needed.
As to the #2 stranded in the footer I think that a solid #4 would be better and all that is required by 250.52
As to the sub panels that you are setting you are looking at the wrong table to size the feeders. You will need to go to 310.16 to size the ungrounded conductors and 250.122 to size the equipment grounding conductor.
For the 200 amp panel use 3/0 copper phase and #6 copper equipment ground and for the 100 amp panel use #3 copper phase and #8 copper equipment grounding.
Should you decide to use SER (four wire SE cable) to feed these sub panels you will need to take a long and hard look at Article 680.25(A)&(B).
- Location
- Massachusetts
Re: grounding
FWIW 2 stranded is what the engineers in this area often specify for CCEs.
Just curious why it would be better?
FWIW 2 stranded is what the engineers in this area often specify for CCEs.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: grounding
Mike, what about 680.21(A)(4)?
jwelectric
Senior Member
- Location
- North Carolina
Re: grounding
Maybe I should have stated that solid would have been better, but please note that I pointed out that a #4 is all that is required. I made this statement partly based on how badly he had missed the size of the other conductors and the fact that he was installing two pieces of rebar.
If he was wiring from panel to motor as outlined in 680.23(A)(4) then that part of the branch circuit that was inside the house could be any wiring method outlined in Chapter 3. (680.21 Motors.(A) Wiring Methods. (1) General. The branch circuits for pool-associated motors )
For the installation on a dwelling unit it has been my experience that using a stranded conductor the conductor gets damaged before the panel gets set. The one and only time that I used a stranded conductor the strands were untwisted and frayed badly when I returned.
Maybe I should have stated that solid would have been better, but please note that I pointed out that a #4 is all that is required. I made this statement partly based on how badly he had missed the size of the other conductors and the fact that he was installing two pieces of rebar.
George I was addressing the feeders that will be supplying the 100 amp sub panel that was outlined in the original post. The feeders are required to be in conduit from panel to panel as outlined in 680.25.
If he was wiring from panel to motor as outlined in 680.23(A)(4) then that part of the branch circuit that was inside the house could be any wiring method outlined in Chapter 3. (680.21 Motors.(A) Wiring Methods. (1) General. The branch circuits for pool-associated motors )
- Location
- Massachusetts
Re: grounding
I am more nervous about solid running out of a concrete pour.
It would be very easy to have it break right at the surface of the cement.
By the way I do agree that 4 AWG is all thats required.
Does that matter?
I am more nervous about solid running out of a concrete pour.
It would be very easy to have it break right at the surface of the cement.
By the way I do agree that 4 AWG is all thats required.
Re: grounding
i saw that in the nec it required only one number 4. but it wasnt saying for what size of panel its for or that dosent matter? i spoke with the inspector and he said if there is no rebar coming from the footing you will need two 20ft number 4s coming from the footing? is there a reason for that?
i saw that in the nec it required only one number 4. but it wasnt saying for what size of panel its for or that dosent matter? i spoke with the inspector and he said if there is no rebar coming from the footing you will need two 20ft number 4s coming from the footing? is there a reason for that?
jwelectric
Senior Member
- Location
- North Carolina
Re: grounding
Only one piece of rebar that is 20 feet long and ? inch in size that has a #4 ground electrode conductor is required for any size service.
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