I've run across a few different kinds of numbering systems in my career. Just looking for some opinions and perspective on the different systems out there. What do you prefer and why?
I've used/seen the three below, they all seem to have their pros and cons.
Point to Point: both 'ends' or terminations of the wire share the same wire number. So lets say the wire comes from a PLC input and is called I:02/11, the point that that wire terminates at (push button, level switch etc) would also be numbered I:02/11 even if the wire passes through a terminal block. I've seen these systems also have a generic wire number for any power wires, neutrals or commons no matter where they go; a 120vac control power wire would be labelled something like 'X1' no matter how many 120vac control power wires are on the machine or in the building.
PROS: schematics/ladder diagrams are very simple. Easy to follow for novices. OK for small equipment with only a few wires (<100) Easy to readdress IO or use spares.
CONS: fault tracing is difficult in the field because multiple wire numbers might be the same wire or they might not be. You need to have the schematics to find where a wire ends up. If you loose a wire number and don't have a schematic, you're screwed unless you feel like ringing out a hundred different wires.
To and From/Source-destination: Each wire connection has a unique number for the entire run, the number at the termination says where that wire is coming from (or going to). Let’s say I:02/11 passes through a terminal block called TB2- and then to a level switch called LSH203. The wires would be numbered like this: The wire on the Level switch(LSH203) would be called TB2-2, the wire on that side of the terminal block would be called LSH203, the wire on the other side of the terminal block would be called I:02/11 and the wire at the PLC input would be called TB2-2. All control power has a unique number as well, usually something like X1-1, X2-1, X3-3 etc. A lot of these systems will also have a modifier on the end of the wire number that tells you what page and line number in the schematic to find the wire on. Super helpful in schematics that are 100 pages long.
PROS: Easy to trace and troubleshoot in the field, all you have to do is look at the number on whatever you’re troubleshooting and you automatically know where the other end of that wire ends up, even without a schematic. This is especially helpful on more complicated equipment with 100s or 1000s of IO points, devices, instruments etc.
CONS: complicated schematics, complicated numbering system. Can be confusing for novices or people unfamiliar with the site. Makes readdressing or moving wires to spares a more complicated process. It can get confusing trying to keep track of multiple wire numbers for the same wire.
Combination: Each wire has a common number at both ends along with the to and from numbers.
I’ve only seen this used once in the field which is unfortunate because it’s the best system out there IMO.
I've used/seen the three below, they all seem to have their pros and cons.
Point to Point: both 'ends' or terminations of the wire share the same wire number. So lets say the wire comes from a PLC input and is called I:02/11, the point that that wire terminates at (push button, level switch etc) would also be numbered I:02/11 even if the wire passes through a terminal block. I've seen these systems also have a generic wire number for any power wires, neutrals or commons no matter where they go; a 120vac control power wire would be labelled something like 'X1' no matter how many 120vac control power wires are on the machine or in the building.
PROS: schematics/ladder diagrams are very simple. Easy to follow for novices. OK for small equipment with only a few wires (<100) Easy to readdress IO or use spares.
CONS: fault tracing is difficult in the field because multiple wire numbers might be the same wire or they might not be. You need to have the schematics to find where a wire ends up. If you loose a wire number and don't have a schematic, you're screwed unless you feel like ringing out a hundred different wires.
To and From/Source-destination: Each wire connection has a unique number for the entire run, the number at the termination says where that wire is coming from (or going to). Let’s say I:02/11 passes through a terminal block called TB2- and then to a level switch called LSH203. The wires would be numbered like this: The wire on the Level switch(LSH203) would be called TB2-2, the wire on that side of the terminal block would be called LSH203, the wire on the other side of the terminal block would be called I:02/11 and the wire at the PLC input would be called TB2-2. All control power has a unique number as well, usually something like X1-1, X2-1, X3-3 etc. A lot of these systems will also have a modifier on the end of the wire number that tells you what page and line number in the schematic to find the wire on. Super helpful in schematics that are 100 pages long.
PROS: Easy to trace and troubleshoot in the field, all you have to do is look at the number on whatever you’re troubleshooting and you automatically know where the other end of that wire ends up, even without a schematic. This is especially helpful on more complicated equipment with 100s or 1000s of IO points, devices, instruments etc.
CONS: complicated schematics, complicated numbering system. Can be confusing for novices or people unfamiliar with the site. Makes readdressing or moving wires to spares a more complicated process. It can get confusing trying to keep track of multiple wire numbers for the same wire.
Combination: Each wire has a common number at both ends along with the to and from numbers.
I’ve only seen this used once in the field which is unfortunate because it’s the best system out there IMO.
