Grounding separate structure steel

[Anderman123]

Group,

I have a single 20A (3#12) branch circuit feeding a separate structure. There is a disconnect where it enters the building. I believe I need to ground the building steel. Should it be grounded to the disconnect with #8, or brought back to the branch panel with #8? Or other...

 

[infinity]

I'm inclined to say other, meaning do nothing. The steel will be bonded to whatever can potentially energize it.

 

[Hv&Lv]

Group,

I have a single 20A (3#12) branch circuit feeding a separate structure. There is a disconnect where it enters the building. I believe I need to ground the building steel. Should it be grounded to the disconnect with #8, or brought back to the branch panel with #8? Or other...

250.32.

 

[Rock86]

250.32.

...(A) Exception

 

[tom baker]

What type of disconnect, does it have over current protection?

 

[petersonra]

Group,

I have a single 20A (3#12) branch circuit feeding a separate structure. There is a disconnect where it enters the building. I believe I need to ground the building steel. Should it be grounded to the disconnect with #8, or brought back to the branch panel with #8? Or other...

If you want to you can bond it to the incoming EGC but it probably won't do any actual good. As a practical matter it might already be bonded by nature of the disconnect or handy box being effectively bonded to the steel.

Why would you want to use a #8? Just curious.

 

[petersonra]

What type of disconnect, does it have over current protection?

does this make any difference?

 

[augie47]

250.102(C) would require a bond if "the structure is likely to become energized" so it's somewhat a judgement call.

 

[petersonra]

250.102(C) would require a bond if "the structure is likely to become energized" so it's somewhat a judgement call.

but probably whatever would be likely to energize the structure would also inherently bond it.

 

[infinity]

250.102(C) would require a bond if "the structure is likely to become energized" so it's somewhat a judgement call.

Isn't that usually accomplished by the EGC of the circuit likely to energized it?

 

[augie47]

Isn't that usually accomplished by the EGC of the circuit likely to energized it?

In reality, yes and if the circuit is GFCI I see less reason to worry BUT, that said, I don't see where the NEC is in agreement. Pethaps I'm missing something.

 

[tom baker]

does this make any difference?

Yes. If there is over current protection then it’s a feeder and requires a GES

 

[petersonra]

Yes. If there is over current protection then it’s a feeder and requires a GES

but it does not change whether the building steel has to be bonded.

 

[Hv&Lv]

...(A) Exception

A ground rod was never discussed or brought up.
I was looking at B.

am I missing something? I see it as steel structure needs to be bonded

 

[tom baker]

but it does not change whether the building steel has to be bonded.

Perhaps the building steel qualifies as a GES, and if a GEC is installed it could hit steel and ground rods

 

[infinity]

but it does not change whether the building steel has to be bonded.

The bonding requirement would be when it is considered likely to become energized.

250.104(C) Structural Metal. Exposed structural metal that is inter‐connected to form a metal building frame and is not intentionally grounded or bonded and is likely to become energized shall be bonded to any of the following:
(1)Service equipment enclosure
(2)Grounded conductor at the service
(3)Disconnecting means for buildings or structures supplied by a feeder or branch circuit
(4)Grounding electrode conductor, if of sufficient size
(5)One or more grounding electrodes used, if the grounding electrode conductor or bonding jumper to the grounding electrode is of sufficient size

 

[Hv&Lv]

The bonding requirement would be when it is considered likely to become energized.

Well…
I guess that negates the one I mentioned…

 

[Anderman123]

Thanks for the discussion. If anyone is still interested:

Proposed #8 because that is the min size for Table 250.102(C)(1).

The owner seems to think the building could be energized by the lighting circuit. Could we bond to the circuit grounding conductor or would it need to go back to the Panel feeding it?

It is a single branch circuit with no overload protection at the building.

 

[Hv&Lv]

Thanks for the discussion. If anyone is still interested:

Proposed #8 because that is the min size for Table 250.102(C)(1).

The owner seems to think the building could be energized by the lighting circuit. Could we bond to the circuit grounding conductor or would it need to go back to the Panel feeding it?

It is a single branch circuit with no overload protection at the building.

Just because you don’t have to doesn’t mean you can’t IMO.
^{What are we talking about here.. 2’ of wire?}

 

[JoeStillman]

If you want to you can bond it to the incoming EGC but it probably won't do any actual good. As a practical matter it might already be bonded by nature of the disconnect or handy box being effectively bonded to the steel.

Why would you want to use a #8? Just curious.

Bonding building steel to the EGC is a good idea because then there is a path back to the main bonding jumper and ground fault current can find it's way home. Earth is not a good conductor.