Wiring Best Practrices

Hello all I have been working for an integration company for about 5 months now and starting to do some small field jobs on my own.

This week I have a project where I will need to take an analog output of 4-20ma from a power flex 70 drive in one machine and connect it to a 1769-IF4 card on the compact logix in another machine.

These are 2 different machine made by 2 different companies so how would be the best practice to number this wiring and add it to the drawings of each machine.

Would I use the numbering from the source machine where the drives is? I have not went through all the drawings because each machine has a set of drawings 50 pages and above on each so I don't know if using the numbering in the source system will conflict with numbering in the destination system.

Could a unique numbering system be used and would that be the best way to handle it and if so what is a common scheme that is used?

I am using Belden 8761 for the connection which has a paper foil shield and a drain wire so should it be connected on both ends in the application or only at the source component which would be the drive in this case?

I will also post the shielding as a separate topic.

Welcome to the forum David.

I would connect the shield at one end only. It doesn't matter which end.

For wiring I suggest you use a unique numbering system. Choose numbers that are beyond the range of numbers for both machines, for example if the machines have three digit wire numbers, then use a four of five digit number, or use text ID instead of numbers.

You also need to label the cable clearly that the signal comes from another panel. In these situation, I usually label not only the cable, but I also place labels next the conduit entry point on the inside of the panels.

I have seen it done where the cable is numbered according to the schematic and goes from the PLC into terminals within each panel. The interconnecting cable is numbered to a high (spare) number.

I think there are dozens of ways but the main thing is to LABEL and LABEL again plus mark the schematics like you already mentioned

There are many ways to do this and almost everyone does it a little differently and that's OK as long as it's documented.

Dashed lines around things that are in another cabinet is pretty much a standard but many people used dashed lines for other things so I don't really like that but I do dashed lines for equipment that is in another cabinet.

I do cloud lines to show controls that are existing / customer supplied.

I do a surrounding box made of asterisk to show controls that are interlocked with another system.

Show this on your legend but also put a notation where the box, cloud or whatever you use is so that a person knows what it is even if the legend is lost or Bubba tore it off to write a serial number on some years back.

As far as numbering on this site I have a numbering scheme that uses the 4 digits of the building address with the asset number for the line and then 4 more digits for the wire number.

I almost always draw a separate set of prints 2-5 pages for the interlocks on the line between each system.

Voltage that remains live when the panels main disconnect is in the off position should be orange (used to be yellow) wires and orange terminal blocks on their own strip if you can.

to avoid this many times though I make a small interlock panel that has a relay so that system 1 power is used to open and close the relay and system 2 is the contacts and the wiring in each panel does not have to be orange because the power in that panel will be off with the disconnect in the off position but when you work on the interlock panel you will have to isolate the voltage using both systems but because it's an interlock panel you very seldom go in it because you can do all your troubleshooting from system 1 and system 2 control panels.

The only time you go into the interlock panel is to replace the relay every few years if needed but mark the interlock panel so that it shows that voltage has to be isolated from 2 different sources so it does not have a local disconnect.

For analogs I would just label them. I normally use white labels with black text so for the analogs like this I would use a white table with orange text and maybe some orange shrink tubing on the plc end as it remains on when the local disconnect is on even though it is low potential.

Labeling them near the conduit entrance as other suggested is a good idea also.

On Field Device wire numbering I have also seen Source/Destination wiring methodology.
Municipal Water plants seem to be fond of this and it makes sense considering the scale of the area and amount of devices controlled.

Cabinet.Terminal BLock.Wire Number / Field Device.Terminal Block.

or something similar.

For Example: CP100.TB4.1254/VFD201.14

My suggestion is that however you do it, grab one of the maintenance guys, if there are any, and ask them, "Does this make sense to you?" In the end, long after you are gone, they will be the ones supporting the machine.


Will.