Cable Trays Installed Vertical In A Different Manner 2

[ThePunisher]

This may sound dumb, but it happens when somebody non-electrical plays electrical.

We have been routing our cable trays horizontally along the conveyors as per code and standard requirements. The cable trays are ran along the side of the conveyor platforms.

However, the general manager is presently commenting on them and insisting to run the trays along the sides of the conveyor platforms in a vertical position instead of horizontal. I informed the person that running the trays vertically sideways is not logical on our application and it will require special fastening requirements on both cable trays and cables. I also added that it will be difficult to structurally support them.

Is there anybody here who can give me a hand on educating this "hot-shot" fellow technically in case I missed some important points in my explanations.

Thanks.

 

[MikeHalloran]

Running the trays on edge requires that you secure every cable to every rung of the tray. In my limited experience, the biggest added risk is the greater opportunity for a baboon installer to overtighten a ty-rap, cutting through the cable insulation. .... or, worse, not quite cutting through it, so it fails later.



Mike Halloran
Pembroke Pines, FL, USA

 

[EEJaime]

Added to what Mike has stated, I doubt the cable tray manufacturer has had these structurally tested, and UL listed in that configuration. You are going to get added cable heating as well as you will have a much deeper stack of cables with heat rising through a lot more cables, collecting a lot more heat. The main purpose of using cable tray is to allow for future additions and changes, you just threw that out the window. Bad idea all around IMO.

EEJaime

 

[ThePunisher]

Good point on the heating effects EEJaime. Since heat dissipates on an upward direction. I am presently wrapping up responses and these comments are inclusive on my list. Thanks.

Any additional comments are highly appreciated.

 

[waross]

Ask the boss to put his instructions in writing and sign off as the engineer of record on this detail.

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

 

[PHovnanian]

There are cable rack systems intended for vertical stacking of horizontal cable runs. I don't have any part numbers off the top of my head. Most of them tend to be some sort of vertical rail with hooks attached in which the cable hangs. This keeps the cables supported should the cable ties (still required) fail. But since the cable ties are not needed to maintain cable position, they don't tend to get over tightened by gorilla installers. If you just turn a horizontal tray on its side, the ties are all that keep the cables from sliding down and piling up against each other.

 

[BigJohn1]

Get any of your plant electricians to give their professional input on such an install, and after they stop laughing, they'll categorically say it's ridiculous: Your boss is advocating spending a whole lot of time and money to totally defeat the functionality of the cable tray.

For all the effort that will be required to install cables in such a configuration, it would be easier and prettier to put in racks of conduit. I honestly don't see a hazard to his idea, but I do see a ton of wasted money in labor.

-John

 

[ThePunisher]

With all the valuable comments I am getting, it is evident that the installation is doable but with a lot of caveats:

1. More de-rating of cables should be applied due to deeper stacking of cables of different circuits.

2. Bigger size of cables for the same load and length due to lower ampacity de-rating factors.

3. More installation costs due to specific and durable cable fasteners required to keep the cables in place, specially large power cables.

4. Higher labor costs and contruction time on installing these cables in this particular cable tray orientation.

 

[rcw retired EE]

Cable side rails provide the suport for the cable tray. They are designed as I-beams, channels or extruded shapes to support the weight in the "normal" vertical direction. An I-beam laying on its side cannot support the same weight.

Your tray supports will have to be closer to accomodate the loss of strength.

However, I have seen this done on short runs inside cooling towers where normal horizontal trays were thought to block too much air flow. All of the issues you mentioned were considered. Conduit racks would have been better.