residential ground conductor
- Thread starter shelco
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Re: residential ground conductor
It depends on the grounding electrode. If there is a concrete encased electrode available then #4 would be required to be installed to the footing rebar. If it wasn't available then #6 would be the largest size grounding electrode conductor required for the two ground rods.
It depends on the grounding electrode. If there is a concrete encased electrode available then #4 would be required to be installed to the footing rebar. If it wasn't available then #6 would be the largest size grounding electrode conductor required for the two ground rods.
Re: residential ground conductor
I would like to add that the last 200 amp service I did, the inspector required #4 to both ground rods. We all know that the nec requires #6 minimum to a ground rod. When I questioned this and stated code article, his reply was "#4 is standard for a 200a service around here." So, I used #4.
I would like to add that the last 200 amp service I did, the inspector required #4 to both ground rods. We all know that the nec requires #6 minimum to a ground rod. When I questioned this and stated code article, his reply was "#4 is standard for a 200a service around here." So, I used #4.
- Location
- Bremerton, Washington
Re: residential ground conductor
nec requires #6 minimum
The maximum required for a rod electrode is 6 AWG.
But 6 has to be protected against physcial damage, 4 is considered protected against severe physcial damage.
nec requires #6 minimum
The maximum required for a rod electrode is 6 AWG.
But 6 has to be protected against physcial damage, 4 is considered protected against severe physcial damage.
charlie
Senior Member
- Location
- Indianapolis
Re: residential ground conductor
He needs to be challenged. Unless there is a local amendment (this would be in writing and part of your law), #6 is the maximum that is required, even if the service were a 4,000 ampere at 480 volts.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: residential ground conductor
In that case, is there a cost advantage of one over the other? Just curious.
Re: residential ground conductor
I used # 6 and the inspector insisted on #4 even when I point out the article stating #6 was acceptable. He wouldn't hear of it so I had to change to #4. I would like to go after him for the cost diff but I have to work in his area so it was cheap insurance.
I used # 6 and the inspector insisted on #4 even when I point out the article stating #6 was acceptable. He wouldn't hear of it so I had to change to #4. I would like to go after him for the cost diff but I have to work in his area so it was cheap insurance.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: residential ground conductor
Go over his head. So what if you have to work with the guy? If you show him that you will only correct code violations, maybe he will only write up code violations. With this in mind, you have nothing to fear if you install to the minimum code.
Go over his head. So what if you have to work with the guy? If you show him that you will only correct code violations, maybe he will only write up code violations. With this in mind, you have nothing to fear if you install to the minimum code.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Re: residential ground conductor
The #4 might be a utility requirement, it is in my area.
The #4 might be a utility requirement, it is in my area.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: residential ground conductor
Once you show them the math that at 120 volts a 25 ohm rod electrode can only pass 4.8 amps of current.
And at higher voltages the fuse on the primary side of the transformer is rarly over 15 amps, so it would most defently handle it.
As for lightning, the event is so fast that the conductor dose not have enough time to heat up, even though many thousands of amps have past through it.
So other than the physcial protection issue why would it ever be needed to be more than a #6?
Once you show them the math that at 120 volts a 25 ohm rod electrode can only pass 4.8 amps of current.
And at higher voltages the fuse on the primary side of the transformer is rarly over 15 amps, so it would most defently handle it.
As for lightning, the event is so fast that the conductor dose not have enough time to heat up, even though many thousands of amps have past through it.
So other than the physcial protection issue why would it ever be needed to be more than a #6?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Re: residential ground conductor
You got me, maybe the physical protection is their reasoning. This utiltiy also requires the GEC to come out of the panel, hit the rods, and go back into the panel. I've never come across that requirement in any of the other jurisdictions I've worked in.
You got me, maybe the physical protection is their reasoning. This utiltiy also requires the GEC to come out of the panel, hit the rods, and go back into the panel. I've never come across that requirement in any of the other jurisdictions I've worked in.
Re: residential ground conductor
electrofelon,
Do you happen to work in New York State? They require an unbroken loop of #4 solid copper wire from the service ground bus, loop unbroken through both ground rods, then run back to the ground bus. The reason why I use the term ground bus is that in some service switches you use neutral and equipment ground buses joined by a wire.
NEC specifies a maximum of #6 for A ground rod. It does not say anything about 2 or more ground rods. Also, some soils have quite a bit of permanent moisture near the surface. Slightly swampy land is a great place for a substation or transmission yard.
Also, the Empire of Akron, Ohio requires a minimum of #4 solid or #2 stranded copper for a GEC. They do not want to be making judgments about the level of mechanical damage.
electrofelon,
Do you happen to work in New York State? They require an unbroken loop of #4 solid copper wire from the service ground bus, loop unbroken through both ground rods, then run back to the ground bus. The reason why I use the term ground bus is that in some service switches you use neutral and equipment ground buses joined by a wire.
NEC specifies a maximum of #6 for A ground rod. It does not say anything about 2 or more ground rods. Also, some soils have quite a bit of permanent moisture near the surface. Slightly swampy land is a great place for a substation or transmission yard.
Also, the Empire of Akron, Ohio requires a minimum of #4 solid or #2 stranded copper for a GEC. They do not want to be making judgments about the level of mechanical damage.
john m. caloggero
Senior Member
Re: residential ground conductor
The size of the grounding electrode conductor is based on the size of the conductors that will supply the fault current, not the rating of the service disconnecting means. If you use Table 310.15(B)(6), a 200 ampere service can be supplied by 2/0 cu, therefore, the GEC is based on Table 250.66 and for metal water pipe or building steel grounding electrode, it can be No. 4 Cu. If it is a ground rod(s), regardless of the size of the supply conductors, the GEC is not required to be larger than No. 6 Cu. If the supply conductors are No. 2 or smaller, the EGC for a ground rod(s) can be as small as No. 8 cu. according to 250.66(A).
The size of the grounding electrode conductor is based on the size of the conductors that will supply the fault current, not the rating of the service disconnecting means. If you use Table 310.15(B)(6), a 200 ampere service can be supplied by 2/0 cu, therefore, the GEC is based on Table 250.66 and for metal water pipe or building steel grounding electrode, it can be No. 4 Cu. If it is a ground rod(s), regardless of the size of the supply conductors, the GEC is not required to be larger than No. 6 Cu. If the supply conductors are No. 2 or smaller, the EGC for a ground rod(s) can be as small as No. 8 cu. according to 250.66(A).
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Re: residential ground conductor
mc5w,
Yes the utility I was refering to is in NY. Thats interesting, so the unbroken loop requirement is a state mandate? Always thought it was just NYSEG's requirement. New York state is interesting: no state level licensing, no afi requirement, GEC loop-back......
mc5w,
Yes the utility I was refering to is in NY. Thats interesting, so the unbroken loop requirement is a state mandate? Always thought it was just NYSEG's requirement. New York state is interesting: no state level licensing, no afi requirement, GEC loop-back......
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