05: 54 Earthing Arrangements and Protective Conductors (193)

Question 1

Metallic supply pipework can be used for an earth electrode if (542.2.6 p.195)

a) It is water utility pipework
b) It is other than water utility pipework
c) It is an unused gas pipe that is less than 10 years old
d) It is other than utility pipework providing precautions have been made against its removal

Answer 1

d) It is other than utility pipework providing precautions have been made against its removal.

542.2.6 p.195
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.

Question 2

Where equipment has a protective conductor current in excess of 10 mA it may be connected via a (543.7.1.202 p.201)

a) BS EN 60309-2 32 A plug and a flexible cable with a 2.5 mm2
b) BS EN 60309-2 16 A plug and a flexible cable with a 2.5 mm2
c) BS 1363 plug and socket
d) 2 pin cable coupler

Answer 2

b) BS EN 60309-2 16 A plug and a flexible cable with a 2.5 mm2

543.7.1.202 p.201
Equipment having a protective conductor current exceeding 10 mA shall be connected to the supply
by one of the following methods:

(i) Permanently connected to the wiring of the installation, with the protective conductor selected in accordance with Regulation 543.7.1.203. The permanent connection to the wiring may be by means of a flexible cable
(ii) A flexible cable with a plug and socket-outlet complying with BS EN 60309-2, provided that either:

(a) the protective conductor of the associated flexible cable is of a cross-sectional area not less than 2.5mm2
for plugs rated at 16 A and not less than 4 mm2 for plugs rated above 16 A, or

(b) the protective conductor of the associated flexible cable is of a cross-sectional area not less than that of
the line conductor

(iii) A protective conductor complying with Section 543 with an earth monitoring system to BS 4444 installed
which, in the event of a continuity fault occurring in the protective conductor, automatically disconnects the
supply to the equipment.