MCB tripped signal

[Lucky_Bugger]

Thanks

Thanks for all your replies.

I've decided to go with normally open auxiliaries and label the PLC signals as "Healthy". This is what I would normally have done but I came across a set of drawings where they had been wired the other way and it got me thinking....

 

[parky]

An example of the use of N/C (N/O on) contacts is due to cost. Some motor isolators used for local isolation use the Aux N/O contact (often the only N/O one supplied as standard) as the interlock directly to remove the supply from the contactor thus removing the supply from the incoming side of the isolator. This is where the N/C contact is used for the PLC indication. Just to re-iterate the use of N/O & N/C in this post these are in the de-energised or non operational state. (I hate AB & XIC XIO.).