Wire tray sizing

Rube · Feb 7, 2005

Sorry guys-- a slight bit OT. I'm about to run control wiring and motor sets for a new 50 motor conveyor system, and building the motor control panel. I'm going to be using AB Powerflex 4 drives, 2HP, 480 volts to the motors and running 24 volt controls. I plan to use wire tray for the first time and I need to know just how much room I need to have between the 480V and 24V wiring in order to eliminate PWM interference in the 24V wiring. I have no experience with wire tray but my plan is to use 6x6.

Thomas Sullens · Feb 7, 2005

ok

Rube I wouldn`t run the two together.
Just personal preference though. I know all the stuff we`ve ever run to drives. The tech support we talked to didn`t want
Any other wires in the pipes going to drives. By the way alot of the drives were
ALLEN BRADLEY 1336 PLUS

Rube · Feb 7, 2005

In CONDUIT, I always keep my wires separated, 24V in one pipe, 480V in another, but I'm going to use wire tray so I was curious how much distance I needed to keep.

Ken Moore · Feb 7, 2005

We always run two wire trays, one for AC, and one for low voltage DC.

TRACY H · Feb 7, 2005

OK

It`s been several years, but if I remember correctly if cable trays
were run parallel at least 2 ft. between low voltage control tray
and the 480 power tray. If the trays crossed at 90 degrees they could be within 6 inches. Things may have changed??

:site:

danatech · Feb 7, 2005

if you can use 24" tray, running power on one side and control on the other, you'll be okay. keep at least 12" of separation between the two.(in the middle).
danatech

randylud · Feb 7, 2005

Don't forget the NEC in the US!

The NEC governs the use of ladder tray and as others have said, do not run power and signal wiring of any kind close to each other. Separate wire trays or good controlled/controllable spacing is a must. Remember, whether you or I remember the fact, induction is a fact and will indeed take place if given the right conditions. As to it causing a problem, well you know what Murphy always says!

kamenges · Feb 7, 2005

Originally posted by Rube:

I have no experience with wire tray but my plan is to use 6x6.

Are you using wire trough (wireway) or wire tray? I think of wire tray (or ladderway) as the fully open stuff you lay wires onto. The reason I ask is that the 6X6 square reference above would seem to point toward the closed wire trough.

If you are running trough I would keep them separate. If you are running ladderway I would run them together. I believe you can get ladderway with pre-installed separators for just such an application. danatech's 12" separation will definitely eliminate any trouble. I have seen systems with 6" of separation work well, especially at the power levels you are talking about. However in these systems, we always used shielded cable for the signal level stuff and VFD cable for the motor connections. You also need to babysit your shield connections and make sure that is done correctly.

Keith

Rube · Feb 7, 2005

Re: Don't forget the NEC in the US!

randylud said:
...induction is a fact and will indeed take place if given the right conditions. As to it causing a problem, well you know what Murphy always says!

Yeah, induction is what I'm trying to build out before it gets in. I should have said trough, not tray--we don't wire anything outside a conduit. I've never used trough and thought maybe I could save some time by using it. I'm probably now going to run conduit in all situations.

Thanks, guys, for your input.

elevmike · Feb 7, 2005

On many project we place the drive or motor controls in the same cabniet. However the PLC & low voltage signal wires are all mounted in the upper portion of the enclosure, and the high voltage equipment is all kept in the lower portion of the cabnet. Just keep the two seperated by 3 or 4 inches if you can. If it's necessary to cross one over the other, make it at a right angle.

The other issue besides EMF is the possability of a meltdown. In that case you dont want to end up with 480vac on your 24vdc circuit, thereby distroying the entire controller panel. So...be sure to keep them seperated as much as possable.

David_Emmerich · Feb 7, 2005

I did an air conveyor system a few years back that had 64 10 Hp VFD controlled blowers...we ran the power and the 4-20ma control and the 24 vdc control wire all in the same 20 inch wide ladder tray...and the installation wasn't all that pretty if you know what I mean...we had no apperant problems, and as far as I know, its still moving 24,000+ 20 oz PET bottles an hour 24/7...btw, plenium psi is goverened bytemp and humidity,which set vfd speeds, and bottle speed is set by air gap openning, set by loooong air valves run by cylinders... the 'valves' were each 20 feet long and 2 inches wide...
David

Johnny Rotten · Feb 7, 2005

I've run miles of cable tray, and when using Teck 90, power and control are not an issue. If your control cable is at least 480V rated, has metallic armour as well as an inner shield/drain, you won't have any issues. Does it look nice, no. Does it work, yes. Is it legal, yes.

I have seen very long runs of #18 AWG shielded twisted pair Teck 90 cable (used for 4-20mA) run in parallel and touching (if not wrapped around), 600V motor feeds for 150 H.P. motors.

When the motors started/stopped it had absolutely no effect on the 4-20mA signals.

How many cables do you have? What kind of cables are you using? Any analog - what type of cables are you using for those? How are you terminating your analog drains?

Bob Marley

Rube · Feb 7, 2005

I appreciate the replies, guys. On two of our lines, I've currently got 24V control wiring in conduit about 4" away from another conduit carrying 480V VFD/motor wiring. I did not route this, it was installed before I hired on, but we've had no issues in three years. The last line I built here, we kept a 6" separation between the different conduits with no issues. I've spoken to people in the past that said the conduit itself acts as a shield for EMF induction. When we get the go to start construction on this line, it will go fast so I'm trying to do my homework NOW. I may go ahead and use trough for my motor sets and conduit for my 24V stuff (photoeyes, pushbuttons, etc-- no analog or comms wiring will be in either).

David-- I used to work with air conveyors and PET bottling lines--it CAN be fun.

Thanks again for the info.

Johnny Rotten · Feb 7, 2005

You may also notice the cost of 6" wide tray is about the same as 12". 12" is also more sturdy, requires less support along its length, and can hold more cables (for future).

I somewhat think you will not be the person installing this.

Ted Hunchry

Wire tray sizing

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