Metal lids of floor boxes will, in most circumstances, need to be earthed.
Floor boxes are often employed in open plan offices and showrooms to permit flexibility in the utilisation of the available space.
A floor box with a metal lid may inadvertently trap the flexible cord of the equipment which is plugged in.
Occurrences have been reported where the edge of the metal lid has cut into the sheath and the insulation of the cable with a risk of electric shock.
SOLUTION
Users of the installation must take care not to trap or otherwise damage flexible cables and cords. Metal lids of floor boxes must be securely earthed with a short length of flexible protective conductor.
Regulation 413-02-06 (TN systems)
Each exposed-conductive-part of the installation shall be connected by a protective conductor to the main earthing terminal of the installation and that terminal shll be connected to the earthed point of the supply source in accordance with Regulations 542-01-02, 542-01-03 and 542-01-05, as appropriate.
Regulation 413-02-18 (TT systems)
Every exposed-conductive-part which is to be protected by a single protective device shall be connected, via the main earthing terminal, to a common earth electrode. However if several protective devices are in series, the exposed-conductive-parts may be connected to seperate earth electrodes corresponding to each protective device.
Similiar requirements apply for IT systems, see Regulation 413-02-23.
