In every other edition, the NICEIC‘s team of expert technical engineers will address crucial questions they’ve received. Here are some of the most recent enquiries.
Q. For compliance with BS 7671, can a 230 V AC fan be installed in Zone 1 of a domestic bathroom?
a) Yes b) No
A. The answer is a) Yes
Regulation 701.55 states that: “In Zone 1, only the following fixed and permanently connected current-using equipment shall be installed, provided it is suitable for installation in Zone 1 according to the manufacturer’s instructions:” and the list includes “(viii) Ventilation equipment”.
Therefore, as the fan would fall within the definition of ventilation equipment, its installation would be compliant providing the manufacturer confirms that it is suitable for installation within Zone 1 of a bathroom and the fan has a minimum degree of protection of IPX4 against external influences.
The required external influence is specified in Regulation 701.512.2 which states that: “Installed electrical equipment shall have at least the following degrees of protection: (i) In Zone 0: IPX7 (ii) In Zones 1 and 2: IPX4”.
Q. Which of the following should NOT be used as an earth electrode?
a) structural metalwork b) lead sheath of cables c) water utility pipework d) earth tape
A. The answer is c) water utility pipe
Regulation 542.2.2 states that: “Suitable earth electrodes shall be used. The following types of earth electrode are recognised for the purposes of the Regulations: (i) Earth rods or pipes (ii) Earth tapes or wires (iii) Earth plates (iv) Underground structural metalwork embedded in foundations or other metalwork installed in the foundations (v) Welded metal reinforcement of concrete (except pre-stressed concrete) embedded in the ground (vi) Lead sheaths and other metal coverings of cables, where not precluded by Regulation 542.2.5 (vii) other suitable underground metalwork.”
And Regulation 542.6 states that: “A metallic pipe for gases or flammable liquids shall not be used as an earth electrode. The metallic pipe of a water utility supply shall not be used as an earth electrode. Other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal and it has been considered for such a use”.
Q. What is the minimum size of a supplementary bonding conductor if mechanical protection is not provided?
a) 2.5 mm2 b) 4.0 mm2 c) 6.0 mm2 d) 10.0 mm2
A. The answer is b) 4.0 mm2
Regulation 544.2.1 states that: “A supplementary bonding conductor connecting two exposed-conductive-parts shall have a conductance, if sheathed or otherwise provided with mechanical protection, not less than that of the smaller protective conductor connected to the exposed-conductive-parts. If mechanical protection is not provided, its cross-sectional area shall be not less than 4 mm”.
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