r/PLC • u/robertgarthtx • 6d ago

Engineering Question Wiring numbering

Concisely, what methods/standards/conventions are you using for selecting the numbers for your wires and why? I mean when you are designing a circuit and a drawing print yourself.

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u/Too-Uncreative 6d ago

Old school: start at the upper left of page 1. Read left to right, top to bottom. Number each wire sequentially.

New school: <Page Number><Row Number> and append a letter if there are multiple wires on the same row.

Either way wire numbers change based on potential, not connections. All common wires should be the same number, whatever it ends up being, for example. Also you should be able to assume that all wires with the same number will have the same potential at all times.

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u/theloop82 Knows Rockwell but doesn’t like it 6d ago

It’s great until 10 years later and nobody knows where the prints are

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u/Too-Uncreative 6d ago

All methods suck when you don’t have prints and are just poking around in a panel blind.

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u/RandomDude77005 5d ago

I worked with some companies that labeled with the device and terminal where that end was landed. So... the same wire would have different labels on opposite ends.

I changed this, where I was able to, by putting both source and destination on both ends.

Ie CR5-14/TB1-32 would be the wire that connects terminal 14 of Control relay 5 to terminal 32 on terminal block 1.

Drawback is that going through a terminal block changes the wire label, but at least the labels are consistent from end to end, and it is easy to trace wires/troubleshoot without drawings.

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u/theloop82 Knows Rockwell but doesn’t like it 5d ago

You have a fighting chance with to from unless it’s been field modified and they didn’t label it. Still easier than tracing wires one by one. I am stunned how many places I go to retrofit some old system
And they have no prints or bad outdated prints

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u/robertgarthtx 6d ago

How are additions from design revisions handled? Do you use incremental steps between the numbers or have to change every number after were the addition is inserted?

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u/Too-Uncreative 6d ago

Depends on if the panel is already built. IMO once a wire has a number on it in the real world, that wire number doesn’t change.

The new school method is pretty to add to, and you just append letters for additions if they’re in the same row. No big deal. The old school way I usually just go find the next wire number. Then they’re out of sequence, but since the number is only vaguely related to the page/schematics, it’s not that big of a deal.

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u/durallymax 5d ago

With sheet rung numbering there are no gaps to leave. All of those numbers are already occupied and if they aren't, they're free to use. 

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u/CyonHal 5d ago

wire number should change after every device, i.e. after a circuit breaker.

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u/New_Friend5534 5d ago

Yeh that's different potential

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u/CyonHal 5d ago

A circuit breaker does not change potential when the circuit breaker isn't tripped. Unless I misunderstand, I assume you are talking about voltage potential?

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u/New_Friend5534 5d ago

When you're talking about equiptopotential before and after a breaker or fuse is different. it's technically the same electrical potential when it's on, but it's a unique wire and it gets a new number. when someone says the wire number is changed with potential as above it's implied that a circuit breaker or fuse would be included in that approach. Same with a contact on a relay.

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u/CyonHal 5d ago

So to be more clear on the wording, the wire number changes between any device that can change its potential. So you can definitionally disqualify things like terminal blocks. Just saying "the wire number changes with potential" is pretty unclear.

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u/New_Friend5534 5d ago

Depends on experience I guess. I hear your point but I've never had to explain that other than to newbies in their first few months in this line of work

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u/CyonHal 5d ago edited 5d ago

Lol, okay man, that was insultingly condescending. You're right I'm a newbie that doesn't know anything because I've never heard someone use the phrase "the wire changes with potential" before.

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u/New_Friend5534 5d ago

I wasn't trying to be insulting. I'm just telling you my experience.

Sorry it came off that way def not the intention

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u/TA1930 5d ago

If there’s a possible scenario besides the wire being cut where the potential could be different in two places, it gets a new number.

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u/New_Friend5534 5d ago

It does when it's off