#4 CU Required to Ground Rod

[donselec]

I know that 250.53(E) says basically the part of the bonding jumper which is the sole connection to the supplemental (in this case ground rod) doesn't have to be larger than #6 copper or #4 aluminum. But in this case the inspector says it requires a #4 copper.
On an older house I'm installing a new 200-amp service on the detached garage. It then goes through the garage, underground, and then to the house. There's no water piping at the garage and no rebar to attach to since it's an older building. Therefore the 2 ground rods (we're required in Denver) are the only ground at the garage. He agreed that normally #6 is the maximum size required, but since the rods are the only ground, the conductor has to be sized for the 200-amp service, which is #4. I can't find that in the Code, but he seemed so convinced it just might be true. Any thoughts?

 

[GoldDigger]

Is this a separate service just to the garage, so that there is no EGC?

In that case at least one of the rods is not a supplemental, it is the primary ground electrode.

 

[electrofelon]

I know that 250.53(E) says basically the part of the bonding jumper which is the sole connection to the supplemental (in this case ground rod) doesn't have to be larger than #6 copper or #4 aluminum. But in this case the inspector says it requires a #4 copper.
On an older house I'm installing a new 200-amp service on the detached garage. It then goes through the garage, underground, and then to the house. There's no water piping at the garage and no rebar to attach to since it's an older building. Therefore the 2 ground rods (we're required in Denver) are the only ground at the garage. He agreed that normally #6 is the maximum size required, but since the rods are the only ground, the conductor has to be sized for the 200-amp service, which is #4. I can't find that in the Code, but he seemed so convinced it just might be true. Any thoughts?

He is full of it (unless a local code). If you really want to be sassy, you could ask him how those two rods will ever pass enough current to warrant #4 GEC

 

[donselec]

Is this a separate service just to the garage, so that there is no EGC?

In that case at least one of the rods is not a supplemental, it is the primary ground electrode.

It's a separate service on the garage, but then I'm running a 4-wire (3 4/0 AL and 1 #4 CU ground) from there to the house, and putting a panel in the house.

 

[donselec]

He is full of it (unless a local code). If you really want to be sassy, you could ask him how those two rods will ever pass enough current to warrant #4 GEC

He was pretty nice and I'm sure I'll do it, but he didn't indicate a local code, just that since the ground rods were the only ground (at the garage) then you had to use a full-size grounding conductor, #4 for the 200-amp.

 

[curt swartz]

I agree there no need for larger than #6 unless its exposed to physical damage.

Remember you will also need 2 additional rods at the house plus the water bond.

 

[donselec]

I agree there no need for larger than #6 unless its exposed to physical damage.

Remember you will also need 2 additional rods at the house plus the water bond.

Yes, I did put 2 rods at the house and there will be the water bond; but he said I only needed one rod at the house since the main service is on the garage. Now I know that's wrong. The house is a separate building and requires all the grounding it would as if it had the main service on the house. Also as a footnote the neutral is bonded in the main service on the garage and floats thereafter.

 

[texie]

I know that 250.53(E) says basically the part of the bonding jumper which is the sole connection to the supplemental (in this case ground rod) doesn't have to be larger than #6 copper or #4 aluminum. But in this case the inspector says it requires a #4 copper.
On an older house I'm installing a new 200-amp service on the detached garage. It then goes through the garage, underground, and then to the house. There's no water piping at the garage and no rebar to attach to since it's an older building. Therefore the 2 ground rods (we're required in Denver) are the only ground at the garage. He agreed that normally #6 is the maximum size required, but since the rods are the only ground, the conductor has to be sized for the 200-amp service, which is #4. I can't find that in the Code, but he seemed so convinced it just might be true. Any thoughts?

The inspector is wrong. By this logic if you had a service with phase conductors large enough to max out per 250.66 would he then require a 3/0 to the ground rod? I think he should get some additional training.

 

[GoldDigger]

And you are running a properly sized EGC from garage to house?

Tapatalk!

 

[donselec]

The inspector is wrong. By this logic if you had a service with phase conductors large enough to max out per 250.66 would he then require a 3/0 to the ground rod? I think he should get some additional training.

That's a very good thought!

 

[donselec]

And you are running a properly sized EGC from garage to house?

Tapatalk!

Yes, that has to be #4 CU

 

[curt swartz]

Yes, that has to be #4 CU

Actually #6cu would work for that too.

 

[texie]

Actually #6cu would work for that too.

Yes, but it seems the inspector is not a fan of #6.

 

[infinity]

He agreed that normally #6 is the maximum size required, but since the rods are the only ground, the conductor has to be sized for the 200-amp service, which is #4. I can't find that in the Code, but he seemed so convinced it just might be true. Any thoughts?

Seems like his logic is flawed, first he says that the largest required is #6 then he says that is has to a #4 for some other reason. Since he didn't mention physical damage as Curt suggested he's just confused.

 

[Dennis Alwon]

The inspector is definitely confused. Why does he think because the ground rods are the only electrodes it must be #4? The only thing I can think of is that he is confused by 250.66(A). Now if you went from the rods to the water pipe or other electrode that required to be sized by T250.66 then it would not be the sole connection and a #4 would be required in this example.

 

[augie47]

Some of the POCOs in this area require a #4 minimum. For that reason I find myself saying "4 minimum" even when it's not a POCO related job. Perhaps...........

 

[Dennis Alwon]

Some of the POCOs in this area require a #4 minimum. For that reason I find myself saying "4 minimum" even when it's not a POCO related job. Perhaps...........

I don't think so based on this statement

but since the rods are the only ground, the conductor has to be sized for the 200-amp service, which is #4

but who knows.........

 

[kwired]

but since the rods are the only ground, the conductor has to be sized for the 200-amp service, which is #4

I just want to point out that a GEC is sized on the service entrance conductor size not on the overcurrent protection.

Sole connection to a ground rod is still never required to be larger then 6AWG copper and sole connection to a CEE is never required to be larger then 4 AWG copper. Those electrodes have been determined to not be able to carry any more energy then can be delivered by those conductor sizes.

 

[Canton]

I agree there no need for larger than #6 unless its exposed to physical damage.

Remember you will also need 2 additional rods at the house plus the water bond.

Even if exposed to physical damage, a larger size will do nothing. It then must be protected by an approved raceway or other means.

 

[curt swartz]

Even if exposed to physical damage, a larger size will do nothing. It then must be protected by an approved raceway or other means.

There is a difference between #6 and #4 conductors as far a protection. Look at 250.64(B)