To answer that question we need take into consideration the differences between the XB4 and XB5 ranges:

XB4: Class I, material: metal
XB5: Class II, material: plastic

Therefor, the XB4 pushbuttons must be connected to earth while on the XB5 this is forbidden.

Please be aware that, the Class of the enclosure must match the Class of the pushbutton.

Released for:Schneider Electric UK