Current on Service Raceway

[JoeStillman]

What is the source of that comment? The code clearly permits the use of the neutral for all required bonding and grounding within and on the line side of the service equipment enclosure and that will always result in a parallel path for neutral current where the service conductors are in a metal raceway.

Somehow, I had it in my head that conduits aren't supposed to carry any current, that's all.

 

[ptonsparky]

Just revisited article 250 and I have to admit you are right, according to the letter of the law. But I also can't shake all the other things I've read, like this passage from the handbook, in 250.30 on separately derived systems;

What damage is it doing?

 

[jap]

Somehow, I had it in my head that conduits aren't supposed to carry any current, that's all.

As soon as the bonding jumper is installed to clear a fault, everything metal becomes a current carrier.

JAP>

 

[JoeStillman]

What damage is it doing?

This is my only experience where the conduit was used as a neutral. Not quite the resi application under discussion...

 

[ptonsparky]

This is my only experience where the conduit was used as a neutral. Not quite the resi application under discussion...
View attachment 2558081

Yes, not quite indeed.

 

[don_resqcapt19]

This is my only experience where the conduit was used as a neutral. Not quite the resi application under discussion...
View attachment 2558081

That was not caused just by the conduit being in parallel. It was a result of a neutral conductor failure and the conduit was in parallel with the neutral. When the neutral failed the conduit tried to carry the neutral current. This does not happen unless there is an impairment of the neutral.

 

[jap]

That was not caused just by the conduit being in parallel. It was a result of a neutral conductor failure and the conduit was in parallel with the neutral. When the neutral failed the conduit tried to carry the neutral current. This does not happen unless there is an impairment of the neutral.

That's sure speculating a lot by that picture.

That could have been caused by a lightning strike for all we know.

Partial pictures always leave opinions open to speculation.

JAP>

 

[don_resqcapt19]

That's sure speculating a lot by that picture.

That could have been caused by a lightning strike for all we know.

Partial pictures always leave opinions open to speculation.

JAP>

Just commenting on what the poster of the picture said. Sure there could be lots of other causes.

 

[ptonsparky]

I can't tell anything by that picture, other than a connection, I think, failed.

 

[JoeStillman]

That was not caused just by the conduit being in parallel. It was a result of a neutral conductor failure and the conduit was in parallel with the neutral. When the neutral failed the conduit tried to carry the neutral current. This does not happen unless there is an impairment of the neutral.

Actually, there was no neutral. They used the conduit as a neutral for a pair of 4WD panel feeders. That fault occurred on the line side of that fused switch, so the fuse never blew. Unoccupied building with a bitcoin mine running flat out. The line-side fault heated up the service drop cables enough that they ignited. When the neighbors saw that on fire, the fire co and poco came and put a stop to all the nonsense with a pair of loppers.

 

[ptonsparky]

Not following the description.
I strongly suspect there was a connection failure that may have eventually led to ground fault.
A feeder would not necessarily require a neutral and an EMT, GRC or IMC is entirely acceptable as an EG when properly installed.
A SE would require a grounded conductor brought to it.

 

[electrofelon]

No.
1st It is not objectionable current.

So what is objectionable current?

 

[don_resqcapt19]

So what is objectionable current?

It is a subjective and undefined term. Only your AHJ knows what it means.

 

[JoeStillman]

Not following the description.
I strongly suspect there was a connection failure that may have eventually led to ground fault.
A feeder would not necessarily require a neutral and an EMT, GRC or IMC is entirely acceptable as an EG when properly installed.
A SE would require a grounded conductor brought to it.

An amateur electrician connected a bunch of branch circuit neutrals to the ground busses in two panels that had no neutral conductors in their feeders, just the conduit as a ground.

 

[jap]

An amateur electrician connected a bunch of branch circuit neutrals to the ground busses in two panels that had no neutral conductors in their feeders, just the conduit as a ground.

Ooooops,,,,,

JAP>