Ladder Tray and Free Air Rating

[gbd]

I am installing single conductors for feeders in a ladder tray per section per 392.80 (A) (2) (D) and I am wanting to use table 310-15-B-17. Once I meet the requirements of 392.80 which for example will allow me use a parallel 4/0 instead of (3) sets of 500MCM's. I will need to terminate these conductors on a breaker in the switchboard and field disconnect. Per section 110-14-C, will I have to change this transition over to the 3 sets of 500MCM before terminating the breaker and disconnects per section 310-B-16. I do not want to splice all free air conductors prior to terminating the breakers if possible. I'm trying to determine the reason for 110-14-C?

 

[ron]

This has been a problem for me on several projects. We have either transitioned to the 310.15(B)(16) ampacities or had to forget the free air rating business all together.

Since 110.14(C)(1) specifically calls out 310.15(B)(16), it messes us up.

I do not why they tie our hands like that.

 

[Smart $]

This has been a problem for me on several projects. We have either transitioned to the 310.15(B)(16) ampacities or had to forget the free air rating business all together.

Since 110.14(C)(1) specifically calls out 310.15(B)(16), it messes us up.

I do not why they tie our hands like that.

Yeah... I was wanting to propose a change to that requirement but missed the deadline.

 

[Smart $]

On the plus side, splices are permitted in cable tray without an enclosure.