Panel wire numbers versus destination wiring

[eeprom]

Fellow engineers,
I grew up with control wiring having wire numbers. Each wire would maintain a single wire number until that wire passed through a device which could result in a voltage change during normal operation, such as a fuse, a switch, a lamp, etc. A wire passing through a terminal block does not require a change in wire number.

In the past few years I have seen a trend towards using destination wiring, where each end of the wire has a different number, the number refers to the destination of the other end of the wire. Example, if a wire were connected on one end to CR1, pin 5, and then on the other end to TB-2, pin 11, one end of the wire would be labeled CR1-5, and the other end would be labeled TB2-11, or something similar.

I find this destination wiring horrible to work with for everyone except the panel builder. Yet it seems to have become the new standard. It makes troubleshooting nearly impossible. You may as well leave the labels off.

Can anyone please explain the merits of this wire labeling system?

thanks
EE

 

[davidbeach]

The only useful, in my opinion, wiring tagging scheme combines both. The "wire", which can be multiple wires, has an alpha-numeric designation, which changes as you describe for your number, but it also has some meaning. The tag that goes on each end has that designation AND the location of the other end of the wire. What it is and where it goes. You can't effectively trouble shoot if all you know is what it is, nor can you if all you know is where it goes. You need both.

 

[stevenal]

I like destination wiring. Combined with schematics and point diagrams, concepts are clear. The older drawings with tables of "From", "To", and "Wire" are a pain to work with, and nearly always incomplete. A single wire # may have numerous sections as it jumps from place to place, so knowing the # only narrows things a bit.

 

[ScottyUK]

While I can see the benefit of destination end wiring for panel builders, personally I hate it from a maintenance perspective. The only worse system is that adopted by a Swiss outfit whose abbreviated name might mean Another Big Bill - in the early nineties they used unmarked black wiring for everything.

When fault-finding I usually want to know what the signal does, e.g. K1 is a positive tripping supply, K2 is negative tripping supply, etc. Having many different names for the same signal is crazy. A decent schematic is essential, unless you spend so much time in panels that you memorise the IEC terminal numbering system. At that point you need a shrink.

 

[eeprom]

ScottyUK, I agree completely. I have spent many hours troubleshooting panels, and destination wiring is so confusing I try to ignore it. The wire number represents a voltage node, which is how people troubleshoot, by checking nodes. A node cannot have multiple voltages, so it shouldn't have multiple names. I think people believe that destination wire labeling is a substitute for a schematic. This is remarkably wrong.

 

[xnuke]

I'm a fan of the scheme described by davidbeach where both terminations, not just the destination, appear on the wire label. I find this convenient for construction purposes, reconnecting loose wires, and for reverse engineering systems whose documentation has been lost. I also agree with others who are saying wire labels are no substitute for schematics or wiring diagrams for troubleshooting.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[jraef]

I personally think this is something that stemmed from people mixing concepts a little. Source-destination wire numbering is excellent for large marshalling cabinets with hundreds or thousands of wires entering and leaving it in large bundles or control cables that have long runs to other pieces of equipment, often through junction boxes. troubleshooting a bad connection in a circuit like that can be made much shorter by knowing which wires to look for/at just be looking for the numbers.

But inside of a control cabinet, the wire numbers can get ridiculously long; I've had to put 12 digit wire numbers on some panels I've built where the source-destination numbering scheme was a requirement Boeing is famous for that). In many cases, we actually had trouble bending the wires because of the wire numbers, and finding a terminal block numbering strip that large is almost impossible. I prefer that INSIDE of a control panel, the wire numbering scheme should be as brief and clear as possible.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[itsmoked]

Geeez I never see any more than a number! And I NEVER get to use a schematic. I'm always grateful for having at least numbers. About 50% of the time I don't even get those.

I see little merit in that scheme eeprom, sounds horrid.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[flexoprinting]

Hello all

I work on German equipment and now that I know how to navigate the schematics I find this numbering system very convenient. The switches have addresses which are located in operating station boxes with addresses. The terminal blocks have addresses which are located in boxes with addresses. Those addresses are indexed in the diagram book, most books have block diagrams of box locations it's just takes a little time to wrap your head around their system.

Chuck

 

[controlsdude]

Using EEprom system you could not locate where the wire number is on prints. I find it unusuable.

Wire number should give you a line reference on prints. End of story.

Line number 1111
Wire number passing thru 1st device on line number = 1111A

IEC and JIC use this method.

This other method does not work with field tagging the wires since wire number portable machines that electrician use are only approx 10 chars long. So now your describing two wire labels needed to tag a wire. The wire label should show next to its termination and not go into the wireway where the rest of the tag is ending.

 

[flexoprinting]

We buy used machines from Europe and just recently from Singapore, The control wires are numbered and tagged per EEprom's example. I think the biggest benefit is the tags are easier to
see when terminating all the connections. Otherwise you would need to continuously check the schematics and compare numbers to terminal location while making connections.

Chuck

 

[FreddyNurk]

When I first started out I loved the system controlsdude mentioned, in terms of troubleshooting panels and equipment, it was awesome. Drafting it, however, and making sure things matched for the schematics that were used, not so much. This was largely due to the way the schematics were laid out, and they weren't laid out in a ladder style format where numbers were easy to ascertain.

I got used to other IEC numbering schemes (not the destination scheme mentioned, however), where similar performance was attempted by referencing drawings against specific panels. It was workable, certainly not unusable, but it was certainly set up in such a manner that drawings ended up with a lot of duplication, panels were larger and more expensive than they needed to be, and the drafting effort was still substantial, even without having to double check wire numbers against drawing lines.

If I had the option to start from scratch, I'd look at some sort of automated line numbering scheme within the drawings. Fault finding for my applications was often more important and needed to be done faster than drafting effort, thus the additional effort in drafting was worthwhile, although it was certainly intensive at making sure the drafters and checkers found all the incorrect or altered wire numbers.

I can't see the destination scheme being workable outside of large marshalling panels or similar, I had the experience of attempting to diagnose a gas turbine protection scheme that had it once, there were some serious issues with that installation.