If installing a system using only siemens equipment as part of a fixed installation is ce marking (uk/eu) , of my system not just individual components, always required?

Some people say to me yes others say only under certain circumstances such as when the machinery directive is relevant.

For example... 

If I use a controller and hmi to control relays for light switching and this system is not connected to the rest of the plant. 

Closed cause question posted twice.

The second thread with the subject ce certification / mark is published within the conference Industrial Controls.

Best regards

Jen_Moderator