Why you should use 81346 for your reference designations
Many engineers are tempted to design their own tagging systems. I’ll make it intuitive, they think. I won’t make the same mistakes that I’ve seen on all the other tagging systems. I’ll make it flexible, yet consistent across everything across this system.
They will most likely assign M for motors, PU for pump, FN for fans, R for relay, CB for circuit breaker, CP for compressor etc. Numbers are then assigned: 100 for cooling, 200 for heating, etc. Devices associated with these get letters, such as PT for a thermistor or SN for solenoid.
Solenoid 1 on the first pump in the cooling circuit becomes PU100SN1. The circuit breaker for the pump is CB100. Then they add the compressor CP100. They can’t assign CB100 to the compressor, so the neat alignment where the number would correspond to the CB is broken.
In desperation they might assign the compressor to be CP101, so that they can make CB100 go to PU100, and then CB101 go to CP101. But this means that the pumps start at 100, while the compressors start at 101. Then they want to assign a letter to a control panel. ”How about CP?” No, that’s already assigned as a compressor. Add in a few last minute design changes, and the system is no longer intuitive.
The tag system is broken, and it will only get messier over time. You eventually need an extra document that tells you what the exceptions are.
Everyday usage
You probably use a great reference designation system every
day without thinking about it. If you are telling someone
where to find you, you probably are using the postal address
system. If they are in the same city, you'll give them the
suburb, street, number, and maybe a unit number. If they are
in the same suburb, you'll just give the street and house
number. If they are in another country, you'll give the
country, state, and postcode, along with the other
information. You can make more designations. If you are both
in the same house, you can tell someone where to find a roll
of cling wrap. In the kitchen, third drawer down, on the right
hand side.
You could use latitude and longitude, Melways reference, or
What Three words, but under most circumstances, the system
described above is convenient and accurate.
IEC/ISO 81346 uses the same principles. Tags or Reference Designations have the same tree like structure, with the implied part of the branch omitted. For example, a relay might be physically labelled K1. There will be many relays marked as K1, the same as there are many houses marked as No 10. However, since the panel that they are located within have different tags, the same as streets have different names, an unambiguous reference designation is achieved. Yes, there are may be duplicate streets, but these will be in different suburbs. The same is true for control panels. You can have more than one U1 control panel, as long as the reference designation above it is different
Where IEC/ISO 81346 differs from the postal address system is that it allows different aspects. Addresses only use locations and sub locations to designate a place. IEC/ISO 81346 uses three aspects."
The Three Aspects
IEC/ISO 81346 uses three prefixes to keep the logic consistent without ever needing to "break" the numbering alignment:
- = Function: What the object does.
- + Location: Where the object is physically located.
- - Product: What the object is (the specific component).