The user shall provide an unobstructed space for operating and maintenance staff at the back and front of all switchboards, and the space at the back shall be kept closed and locked except for the purpose of inspection, alteration or repair: Provided that the requirements of this regulation with respect to the unobstructed space at the back of the switchboard shall not apply in the case of-
a. switchboards which have no uninsulated conductors accessible from the back;
b. switchboards, the switchgear of which is of a totally enclosed construction;
c. switchboards, the backs of which are only accessible through an opening in the wall or partition against which they are placed, such openings being kept closed and locked; and
d. switchboards which can be safely and effectively maintained from the front and which have all parts accessible from the front.