CT Conductor Ampacity

[big john]

So I'm replacing the normal feed for an ATS. It's current fed with 4/0 type CT cable, protected by a 150A breaker. This seems like a bit of an overkill to me.

Per 392.11(B)(2) it seems like I can run individual conductors of 2/0 tray-rated THHN in a ladder type tray and have it rated at 152.75A.

Is this correct? Thanks.

-John

 

[Smart $]

Need more details...

What else is in the cable tray? ...cable tray size? ...cable/conductor spacing? ...how far from source? ...anything else that might be pertinent?

 

[big john]

What else is in the cable tray?

A mixture of individual TC conductors and cables. The largest being 4/0 4-conductor.

...cable tray size?

2 feet wide.

...cable/conductor spacing?

Comply with 392.10(4)

...how far from source?

Only 62 feet; VD not a problem.

...anything else that might be pertinent?

Not sure, that's why I asked.

Thanks so far.

-John

 

[Smart $]

A mixture of individual TC conductors and cables. The largest being 4/0 4-conductor.
2 feet wide.
Comply with 392.10(4)
Only 62 feet; VD not a problem.
Not sure, that's why I asked.

Thanks so far.

-John

Complying with 392.10 is only regarding the number of conductors and to some degree how they are installed. For ampacity, please reder to 392.11(C), then 392.11(B)(2) in particular. This requirement limits your 2/0 Cu single conductor ampacity to 65% (or 60% if solid unventilated covered) of values listed in Tables 310.17 or 18. That would put your ampacity through the tray around 190A for 90?C-rated TC single conductor.

You are green across the board. Houston we are go for launch.