Bonding at 2nd means of Disconnect.

[David Emery]

My question is this:

We isolated neutrals and grounds at the second means of disconnect on a cell tower site. The tower engineer specs call for them to also be bonded together at the second means of disconnect. What are your thoughts on this? What is potential problems by doing this.

 

[haskindm]

What do you mean by second means of disconnect? If you are referring to a service disconnect that consists of two (or more) switches, then the grounds and neutrals would be "tied together" in both disconnects and of course the disconnects will need to be grouped together. See 230.71 and 230.72. If you are referring to a sub-panel then ground and neutral must be kept seperate.

 

[infinity]

The potential problem is that the EGC is now in parallel with the grounded conductor and will carry current which is a violation.

 

[tom baker]

My question is this:

What are your thoughts on this?

If you created a neutral to case conection downstream of the service, then you've violated 250.24 and 250.142. You now will have neutral current on all metal parts. This can cause fires and improper operation of electronic equipment.

 

[M. D.]

What is meant by second means of disconnect.? do you mean sub panel on feeders?