Solid bottom tray with solid cover number of conductors

[Coco_HueHueHue]

Hello,

Quick question that keeps me a bit confused since i almost never worked with enclosed trays.
Canadian Electrical Code asks me to interpret enclosed cable trays (solid bottom with solid cover) a bit as a single big raceway.

So, i need to add the number of conductors to apply the appropriate de-rating in ampacity to the cables.

I was thinking to install a divider to separate controls cables from power cables. But, having the control cables in the same tray as the power cables (remember, i need to interpret both in the same tray as enclosed tray even if i have a spacing since the code interprets an enclosed tray as one big raceway) brings the total number of conductors very high while i only have 6 power conductors.

In a ventilated tray, with a diameter spacing between control cables and power cables, i would have a de-rating factor of 0,8 only for 6 conductors.
But, adding up those control cables, the number of conductors indicate a de-rating factor of 0,5 (43+ conductors).

However, those control cables do not generate heat (or very little... neglectable...).
I would like your opinion on that... can i not consider the control cables in the total number of conductors and only consider power cables?

Thank you for your input.

 

[waross]

I have the 2015 code.
Is this new in the 2018 code?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Coco_HueHueHue]

Hi Waross,

If you talk about the fact of counting the total number of conductors when a tray is enclosed. I do not think this is new.
See article 12-2210 (3) - There is no revision tag next to this article.

Personally, i do not think it is logic to count control cables' conductors in the total... as they will never produce heat... but i am just trying to do it right
What do you think?

Thanks for your help.

 

[Coco_HueHueHue]

Hi Waross,

I just noticed another article though.
12-2210 (4). It refers to 4-004 (7) which basically says to only consider power and lighting conductors.

I believe this answers my question haha.
You had to make me re-read the article to finally notice the other one below it and now my question is answered!

Thank you!

 

[davidbeach]

Back when I was doing that type of design work, the local AHJ would accept a solid divider as creating an additional raceway. The count rules applied on both sides of the divider. Your AHJ might or might not accept that.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Coco_HueHueHue]

Hi David,

I would tend to totally agree with you if the tray is ventilated.
The divider can then act as a spacer/heat sink between both sections and free air will clear the heat no problem.

But, in my case, everything is enclosed. So, i tend to believe the heat from one side of the divider will impact the cables on the other side of it as the heat has just nowhere to dissipate. I would not consider both independent in a totally enclosed installation.

 

[waross]

At one time in the far distant past, there was a rule that limited the maximum heat disipation in Watts per foot of the cables in a raceway. (There was a table for various sizes of raceway.)
That rule may have helped you here.
Calculating that for a large project would be a lot of fun.
Enforcement would be difficult.
Another old rule:
The pulling force when conductors are drawn into a raceway shall not exceed 40 times the weight of the conductors.
Again, tough to enforce.

Bill
--------------------
"Why not the best?"
Jimmy Carter