IEC Symbols

Others here will have access to the appropriate standards so will be able to give you the definitive answer.


At first glance, the detail looks a little blurry to me but it looks like a switch contact symbol with switched signal at the bottom and + and -  at the top - I can't tell whether they're inputs or outputs though. Any clue as to the context? I might guess at some kind of pressure switch or even relay - but that really is just a wild guess not knowing what it is the system is trying to achieve.


   - Andy.

They look like relay coils to me. The associated contacts should be elsewhere on the drawing. If it's IEC I would guess that I:2/91 is an off delay coil with a separate control and power input, the other two are something else, though from the nomneclature and geometry I'd be unsurprised if it wasn't a to a different (or in-house) standard. I would be looking for a BOM or some notes on the drawing to confirm what the components are.

2/91 looks to be an off delay timer relay. 2/92 I would consider it is likely to be an on delay timer relay, but these normally have an X across the left hand segment. Some on delay relays don't need the third trigger wire, some do.

Thanks for all your inputs! They are tied to PLC inputs. Some are labeled as a reference switches, overtravel switches and position switches. I'm not sure why they would be time delayed, but maybe.