GEC in conduit

[jetlag]

While we are on the grounding subject I have been wanting to post something . Copper theft is so bad in some areas that I started putting the # 4 GEC in a piece of 1/2 EMT from where it leaves the bottom of the disconnect down to the ground. IT seems to help if they dont see the new shinny copper when they walk by . Well I got flagged for that and the AHJ said I was parallelling the ground, that I had to take the emt off or use pvc. It cost me a 37 mile trip to do as he asked. I see in 250.64 B where EMT is allowed to protect the GEC from physical damage . When I get some replies I am tempted to send the city a bill for the service call.

 

[jumper]

What about 250.64 (E) and bonding the sleeve?

 

[Buck Parrish]

Nice diagram jumper.
Jetlag I 've had the same problem. Somebody cut and stole my ufer ground.
But I now use car flex.

 

[al hildenbrand]

. . . I started putting the # 4 GEC in a piece of 1/2 EMT . . . the AHJ said I was parallelling the ground, that I had to take the emt off or use pvc. . .

I work in an area that has a significant percentage of the housing that was built when the local electrical ordinances required that all wiring be installed "in metal" (1930s - 1970s). There are countless installations of small gage GECs in EMT, NEC approved, that one finds here.

That inspector is just plain wrong.

 

[jetlag]

I work in an area that has a significant percentage of the housing that was built when the local electrical ordinances required that all wiring be installed "in metal" (1930s - 1970s). There are countless installations of small gage GECs in EMT, NEC approved, that one finds here.

That inspector is just plain wrong.

This was a new service on existing dwelling so would the post by jumper apply ?

 

[jetlag]

What about 250.64 (E) and bonding the sleeve?

Good work jumper, I had a bonding lock nut at the top but didnt dream the code would require both ends bonded . Seems to me one end bonds both

 

[al hildenbrand]

Seems to me one end bonds both

That's the really interesting thing, given your inspector's reason for failing your install.

When a fault current travels in the GEC, when the GEC is in a ferrous raceway, the magnetic field created around the current induces eddy currents in the metal of the raceway. The eddy currents, in turn, have their own magnetic field that opposes the magnetic field of the GEC, increasing the impedance, choking the fault current.

When the EMT (in your case) is bonded at both ends to the GEC, as the fault current impedance increases for the GEC current, the parallel path in the EMT becomes easier for the current to flow in. The 250.64(E) required bonding creates a deliberate parallel path to improve the fault current path.

 

[don_resqcapt19]

Maybe we just need to go back to the use of 1/2" rigid conduit as the grounding electrode conductor...connected to a length of 3/4" rigid conduit used as the grounding electrode with a wedge clamp. That way there is no copper to steel. You just ran an empty 1/2" rigid with a short 90 from the meter can down into the soil and connected it to the 3/4" conduit electrode with a wedge clamp.

 

[jetlag]

That's the really interesting thing, given your inspector's reason for failing your install.

When a fault current travels in the GEC, when the GEC is in a ferrous raceway, the magnetic field created around the current induces eddy currents in the metal of the raceway. The eddy currents, in turn, have their own magnetic field that opposes the magnetic field of the GEC, increasing the impedance, choking the fault current.

When the EMT (in your case) is bonded at both ends to the GEC, as the fault current impedance increases for the GEC current, the parallel path in the EMT becomes easier for the current to flow in. The 250.64(E) required bonding creates a deliberate parallel path to improve the fault current path.

The inspector never said any thing about the bonding , he didnt dig down to see if the bottom was bonded , If all was bonded correctly he still would have flagged me for parallelling the ground, which is not a violation that I can see.

 

[al hildenbrand]

This was a new service on existing dwelling so would the post by jumper apply ?

Sorry, I missed this post of yours.

You describe work you did to the GEC now, protecting it with EMT . . . That means jumper's current NEC citation is dead on.

The bonding requirement for the GEC is very old, but is basically unchanged to today.

One must bond both ends of the raceway to the length of GEC in it. If the raceway is just a short section, then just the short section needs the bonding at both ends.

 

[jumper]

Sorry, I missed this post of yours.

You describe work you did to the GEC now, protecting it with EMT . . . That means jumper's current NEC citation is dead on.

The bonding requirement for the GEC is very old, but is basically unchanged to today.

One must bond both ends of the raceway to the length of GEC in it. If the raceway is just a short section, then just the short section needs the bonding at both ends.

Whahoo!! You mean I got one right?

 

[jetlag]

Whahoo!! You mean I got one right?

congratulations, but we are out of cigars :grin:

 

[jumper]

congratulations, but we are out of cigars :grin:

No problem, I got plenty for everyone.

 

[jwjrw]

By bonding one end only I think I read it can produce a "choke". Dennis might be the one who posted something about it. IDK

 

[Pierre C Belarge]

Nice diagram jumper.
Jetlag I 've had the same problem. Somebody cut and stole my ufer ground.
But I now use car flex.

Carflex is not permitted where subject to physical damage, see 356.12(1).

 

[Pierre C Belarge]

That's the really interesting thing, given your inspector's reason for failing your install.

When a fault current travels in the GEC, when the GEC is in a ferrous raceway, the magnetic field created around the current induces eddy currents in the metal of the raceway. The eddy currents, in turn, have their own magnetic field that opposes the magnetic field of the GEC, increasing the impedance, choking the fault current.

When the EMT (in your case) is bonded at both ends to the GEC, as the fault current impedance increases for the GEC current, the parallel path in the EMT becomes easier for the current to flow in. The 250.64(E) required bonding creates a deliberate parallel path to improve the fault current path.

The GEC is not installed for fault current protection, it is for grounding to EARTH, See 250.4(A)(1) & (A)(2)

 

[jwjrw]

Carflex is not permitted where subject to physical damage, see 356.12(1).

In NC we are required to run #4. Not to many cases where it would be subject to damage. He is sleeving it to hide it only I think.

 

[Pierre C Belarge]

While we are on the grounding subject I have been wanting to post something . Copper theft is so bad in some areas that I started putting the # 4 GEC in a piece of 1/2 EMT from where it leaves the bottom of the disconnect down to the ground. IT seems to help if they dont see the new shinny copper when they walk by . Well I got flagged for that and the AHJ said I was parallelling the ground, that I had to take the emt off or use pvc. It cost me a 37 mile trip to do as he asked. I see in 250.64 B where EMT is allowed to protect the GEC from physical damage . When I get some replies I am tempted to send the city a bill for the service call.

I am thinking this is a great idea.

I am thinking of doing the same, thanks for the idea!!!! I am dead serious, it is a great way to get their attention. One just has to be correct when installing/referencing the code.

 

[al hildenbrand]

The GEC is not installed for fault current protection, it is for grounding to EARTH, See 250.4(A)(1) & (A)(2)

A GEC connected to a conductive municipal water system will, in certain conditions, be the called on to carry major fault clearing current, say when an energized service conductor comes in contact with a grounded enclosure or raceway on a service supplied by a drop or lateral with an open grounded service conductor.

Now, in this case, the #4 seems to be going to the ground rod, so for that I take your point, but the NEC still makes no exception to the bonding of both ends of the EMT.

 

[Pierre C Belarge]

A GEC connected to a conductive municipal water system will, in certain conditions, be the called on to carry major fault clearing current, say when an energized service conductor comes in contact with a grounded enclosure or raceway on a service supplied by a drop or lateral with an open grounded service conductor.

Now, in this case, the #4 seems to be going to the ground rod, so for that I take your point, but the NEC still makes no exception to the bonding of both ends of the EMT.

I am not denying this in my post.


I have never seen this happen, and it is not the purpose of the GEC of premises wiring systems.

It may happen, I could only see that as a very rare coincidence.