Interconnect Wiring on a Machine

Looking for some input. We have a new assembly machine in the design stage right now. The machine builder our company contracted is planning to use mesh-type cable tray between the main enclosure and the junction boxes, which we are a little worried about. Then, today, they told us they plan to use SO cable for most of the interconnect runs. So, my two questions are:

1. Does anyone here have any/have seen any machinery in a manufacturing plant that uses mesh cable tray for cable/wire support on the machine? Specifically, are/were there issues with dust buildup, cable damage, etc?

2. Can anyone point me towards any go/no-go citations for using SO cable for interconnecting panels (other than standard sizing issues) on a machine?

I've got NFPA 79 2012 edition that I'm currently poring over, but unfortunately, we're on a short timetable with these guys (I didn't get pulled in on this part until late in the game.) Thanks in advance!

I've seen the cable trays a lot in places with a lot of airborne debris (cardboard and tobacco mostly). The train of thought is that a solid covered tray will hold more **** than loose cables in a mesh tray (they leave a lot of room in the tray, not a solid mass of cables).

Really, you should have distributed IO in the junction boxes and some form of industrial ethernet and 24V running out to them instead of a mass of cables. You could even ditch the boxes and do IP67 IO blocks right next to where they are needed. That's a fight I used to have with OEM after OEM about how much they really spend on cable, panels, wire routing, etc, my current employer included. I once had a customer turn down a distributed IO quote that cost only $100 more in parts, not counting the wiring; turns out 50 feet of 30 conductor cable is about $200 and takes half a day to route and terminate.

Have the company provide you with the manufacturer and part number of the mesh cable tray.

If they say they are custom making it, then you can use the
code that all electrical products must be ul listed for the intended purpose. See national electric code definitions. there is another section I cannot remember.

regards,
james

They are putting Flex I/O in the junction boxes, but they are also distributing 480V/120V to some other equipment, plus are using the tray (with a divider in the middle) to carry some of the wiring out to field devices. I would be super thrilled had they used the on-machine I/O blocks.

And, unfortunately, NFPA 79 is a go for using cable tray, so that argument is out the window. Corporate gave them the OK on the design to this point, so we're going to have a huge fight trying to get them to change design just because it's dissimilar to out other equipment.

Our big concern was holding cardboard debris and dust, but if this is commonly used in dusty environments, then we may be OK on that end of things. Also, no one here had seen any production equipment using cable tray, and it just felt hokey and cheap to us.

And, James, we already looked at that angle, but they are using off-the-shelf cable tray, so I don't know that we could ding them that. I'm also not certain that corporate put anything UL-related in the equipment specs.

open cable trays are easy for them to install and less time for them to run wires. Specify what you want. In the end you have to work on it. Where I work a open cable tray wouldn't last no time. If it is expose it can be damaged. Closed cable trays and conduit is a must but we use conduit just because of that reason. Our people can tear up a anvil with a rubber mallet. As far as SO cord it is not a good idea for interconnecting machines. If the equipment needs to be moved then a single power connection is ok but DON't run control wire are motor leads with SO Cord. If it needs to be flexable then run sealtight to junction boxes with terminal blocks and the beginning of each machine.

We're trying to push back to get enclosed Hoffman wireway, but as the penny pinchers gave them the OK on the cable tray, we're looking at a not inexpensive change order, which the penny pinchers are choking on. So, we're trying to find some precedent that we can point to as "See, this is the better way, so just pay the money." Of course, by not inexpensive, it's still less than 1% of the total machine cost, but ya know...

I understand. There is never enough money to do it right the first time but There is Always enough money to do it the second time. When the machine is down all night long because 1 wire sorted and burned up several more just because it was layed in a cable tray that they agree to buy because it was cheaper this time. Then there standing over you in the morning wonder how this could of happen and how long is it going to take to fix it. When being down cost more than the conduit or closed cable tray that they wouldn't purchase. Sorry for the rant

You may not have an argument as per your contract about the cable tray itself.

But... You may have a dog in the fight when it comes to using SO cord in a cable tray.

Flexible Cable is one thing, but it must be rated as TC or be listed in Article 392.3 as approved for use in cable tray.

I dont get into the code book like I used to but I know I have run into this before.

A quick look at 392.3(A) (NFPA70) does not list SO cord in any form as Tray Rated. (I am looking in a old book but should still be valid)
I would have the contractor supply proof that the SO cord is tray rated from the manufacturer.
It is a solid bet that he will not be able to get this.

Also I cant quote the article but I think SO type cord needs to be terminated into plugs and sockets. I know there a couple of exceptions but I dont think Hard Wiring of Industrial Equipment is one of them.
You could do some searching and I think this is correct also but would not bet the bank on that one without looking.

A quick call to your local Bulding Division can give you a green or red light on both matters as to what is allowed in your area.


BCS

Good point on the cable being tray rated, BCS. That didn't cross my mind.

They were planning to use plugs/sockets (at least on the last drawing I saw) so they could disconnect everything to ship the machine. I'll bring up tray rating to see if that gets us anywhere.

I dont have the time to dig right at this moment but the code can be a labyrinth of twist and turns.

Are these machines going to be permanently installed (screwed or glued as they say) or portable / temp installations.

When you said they are running cable tray I got the impression that these will be permanently installed.

If they are portable then the SO cord MAY be legit if they will have Plugs and Sockets.

A lot will depend on how the entire installation goes together and how you word things when you talking about them.

They say that tradesmen are less educated than professionals (which is quite obvious in my spelling) but I would bet 90% of lawyers out there would have a hard time wrapping their heads around and litigating for or against the massive amounts of electrical codes that we have to wade through.

I dont really miss days when I had to fight that fight.

BCS

And, an afternoon spent reviewing their drawings and slogging through the code book (along with input from you guys) shows we have no leg to stand on with their use. The cable they're using is OK, and it's terminated with connectors and receptacles on both ends. And so far, the bean counters are refusing to pay the additional 0.6% project cost to make us happy. Because reasons. Oh, well. On to the next battle, and hopefully to get out front on the next machine.