Electrical Drawings

mad4x4

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Mar 2009
Location
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Posts
352
Is there a standard list of Letters (prefixes) for components on an electrical drawing

Eg.

CB = Circuit Breaker
U = Power supply
F = Fuse
 
IEC 81346-2 is the favourite in my experience. If you aren't able to purchase or need to stay awake - try downloading the Eaton wiring manual which summarises it. In practice I see plenty of minor variations.

NFPA79 has a completely different list if I remember rightly but it is not mandatory so firms I've worked that export to the US have still followed 81346-2.
 
There are several different standards that different companies / countries follow, the same as the symbols and the way the cable numbers are done. If you are working for a customer who has a specific requirement follow that if not choose which set you want to work with and stick to it. I try on all my drawings to number the same components the same and also the same cable numbers for similar parts. Eg all supplies for plc inputs has same cb number and cable number same with the outputs, safety cct etc. across all projects as much as possible to make it simpler to go from project to project and for fault finding.
 
NFPA 79 Annex E (Selections from ANSI Y32.2/IEEE 315) for US designations.

Note it does not include some designations for things like PLCs, VFDs, and HMIs.
 
IEC, NFPA-79, ISA, UL508A......That’s the beauty of standards, there are so many to choose from.

Then many customers have their own version of each standard.
 
IEC, NFPA-79, ISA, UL508A......That’s the beauty of standards, there are so many to choose from.

Then many customers have their own version of each standard.

Not to mention people that don’t know that there are standards and make up their own as they go along...

Best practice is to remove all doubt and have a sheet explaining all symbols and abbreviations used. That way everyone will know the standard that YOU used for THIS project. When I still did drafting, I had my own sheet for that, it was always Sheet 2 of any project, right behind the Title sheet. No guessing allowed.
 
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Not to mention people that don’t know that there are standards and make up their own as they go along...

Best practice is to remove all doubt and have a sheet explaining all symbols and abbreviations used. That way everyone will know the standard that YOU used for THIS project. When I still did drafting, I had my own sheet for that, it was always Sheet 2 of any project, right behind the Title sheet. No guessing allowed.


Hah, I should get one of these sheets, because I totally make my own up as I go.
 

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