10.7 Suspended ceilings
The conductive parts of a suspended ceiling will not introduce a potential that does not already exist in the space in which the ceiling is installed. In normal circumstances therefore, there is no need to arrange for the conductive parts of the ceiling to be equipotentially bonded, which would be unnecessary as well as difficult and costly to achieve.
The exposed-conductive-parts of Class I equipment are required to be connected to the MET of the installation by a protective conductor designed to conduct any earth fault current. Class II equipment is designed such that any basic insulation fault in the equipment cannot result in a fault current flowing into any conductive parts with which it may be in contact. The conductive parts of a suspended ceiling incorporating Class I and/or Class II equipment are not therefore intended to conduct an earth fault current, and so such parts need not be intentionally earthed. Some conductive parts of a suspended ceiling may be earthed, however, by virtue of fortuitous contact with the exposed-conductive-parts of Class I equipment.
The installation of all electrical equipment, including wiring systems above and incorporated in a suspended ceiling, should fully comply with the requirements of BS 7671 if the risk of electric shock from the ceiling is to be avoided. In particular, cables for fixed wiring should be supported continuously or at appropriate intervals, independently of the ceiling. The method of support is required to be such that no damage or undue strain occurs to the conductors, their insulation or terminations. Figure 10.8 shows a typical arrangement of supporting cables above a suspended ceiling
