Is it permissible to elimate EGC between two OP Devices by neutral grounding

[LISHAJI]

If I have two panelboards at two opposite walls of a building 25ft apart. And the Electrical Sercive enters at Panelboard#1 with MCB where the neutral is grounded. A sub feed goes from this panelboard#1 to another Panelboard#2 also with a MCB where the neutral is grounded. There is no EGC connection between these two panel. The conduit is PVC.

Is it okay? If not okay what are the reasons.

The usual way of doing it is that at Panelboard#2 the neutral has to be seperated from Ground and running a EGC conductor between the two panelboards.

 

[walkerj]

Not OK in the same structure. If it were feeding an outbuilding, in PVC, with no other conductive paths between the two buildings, and before 2008, it would be ok. So no

 

[raider1]

If I have two panelboards at two opposite walls of a building 25ft apart. And the Electrical Sercive enters at Panelboard#1 with MCB where the neutral is grounded. A sub feed goes from this panelboard#1 to another Panelboard#2 also with a MCB where the neutral is grounded. There is no EGC connection between these two panel. The conduit is PVC.

Is it okay? If not okay what are the reasons.

The usual way of doing it is that at Panelboard#2 the neutral has to be seperated from Ground and running a EGC conductor between the two panelboards.

You are not permitted to make a grounding connection to a grounded conductor on the load side of the service disconnecting means. (See 250.24(A)(5))

Chris

 

[celtic]

Is it okay? If not okay what are the reasons.

It's not okay because it may create a parallel path and/or objectionable current:

(from Mike's Free Stuff.. G vs B)

More info here:
Grounding Presentation

 

[LISHAJI]

It's not okay because it may create a parallel path and/or objectionable current

If I am using PVC conduit then there would exists parallel paths through building steel or floor rebar/concrete. I quess the current could reach dangerous levels if the neutral get accidentally disconnected load side.

 

[Buck Parrish]

That diagram is showing metal conduit. Since yours is Pvc, that wouldn't be an issue. However, This is elementary, One of the first things you learn is
YOU ALWAYS HAVE TO ISOLATE YOUR GROUND AFTER IT LEAVES THE FIRST DISCONNECT. Now if you we're useing metal conduit you could put a grounding bushing on one side or the other and use the conduit as you eqipment grounding conductor. Your sub panel does not need a main breaker.

Exception would be to an out building. You are allowed to use a ground rod as your ground for your egc.

 

[bphgravity]

buckofdurham,

1. Even with a nonmetallic raceway between the two panels, any and all effectively bonded or grounded parts or equipment will provide a path back to the source, thus the problem isn't eliminated simply running non-metallic conducits.

2. Grounding electrode systems can NEVER servce as an EGC or effective fualt path. Even to separate structures, the effective fault path must be an intentional conductor. Earth is prohibited to be used as an effective fualt path.

 

[LISHAJI]

What is the intend on NEC 250.32(b)(1)?

What is the intend on NEC 250.32(b)(1)?

2. Grounding electrode systems can NEVER servce as an EGC or effective fualt path. Even to separate structures, the effective fault path must be an intentional conductor. Earth is prohibited to be used as an effective fualt path.

I agree that the grounding electrode system should never serve as a intentional fault path. In my case the grounded neutral would be the intentional fault path, but given the fact that there exists a parallel path through the grounding system which is running inside the building, there is a potential of stray current effecting the inhabitants of the structure. And this stray current is not limited to fault condition but would also exist continuously carrying the unbalanced neutral current. Maybe the intent of the NEC CODE is to prevent this. While outside the structure it is allowed because the hazard of stray current may not be much obvious or affecting anybody. The utility have all their transformers primary & secondary bonded at the star point to their neutral bus and grounded and a continous stray current exists from your service point to transformer, but its okay because it is outside the structure.