TBB bonding condutor costs...

[BrianMuir]

Hello,
Today an electrical contractor asked my opinion on his project, which includes bonding distributed telecom equipment in a school.
(My work does not tend to include distributed telecom, so I am learning as I go here.)

He showed me a guideline from Leviton indicating that the TBB conductor (TBB is the bonding conductor between telecom rooms) should be 3/0 copper for distances greater than 66 feet). I chased this back to the TIA 607-B standard and there it lists conductor sizes even larger as the distances increase, up to a whopping 750 kcmil at 300 feet!

(I am not sure anyone even makes bonding cable in 750, does it mean parallel runs in practice?)

I haven't priced out copper bond wire these sorts of sizes but I imagine it is incredibly expensive.

My question to you is, is this standard for TBB bonding actually implemented on your projects as written, and at what cost?

thanks

 

[iwire]

There is nothing special about a bonding conductor, getting 750 copper would be easy as long as you have deep pockets.

Personally I think that it would be ridiculous to follow those guide lines.

 

[tom baker]

That sounds like a spec from Bell Telephone for central offices.