Spare capacity in Industrial Control Panels

The Doubt: In an Industrial Control Panel, is it required to leave a certain Spare capacity for “future” development?

Considerations: The reference standard for Electrical Equipment of machinery is IEC 60204-1 (In Europe that becomes EN 60204-1). That standard does not require any spare capacity inside control panels

Another standard sometimes used is IEC 61439-1 and IEC 61439-2. Also inside those 2 standards there is no request for spare capacity to be present inside the panel.

So, where is this requirement coming from? The requirement comes from some National Electrical Codes like the Italian CEI 64/8 that requires, for Electrical Panels installed in houses, “To allow subsequent expansions, the panels must be sized for 30% more than the modules installed, with a minimum of two modules, or a larger space if required by constraints linked to the maximum power dissipated by the panel [CEI 64/8 §37.4.1]”.

We can also have a look at the North American Standards, only to realise that there is not any mentioning of spare capacity language in any of them: nothing in UL 508A; nothing in NFPA 79 nor C22.2 N° 286, nor C22.2 N° 301.