Earthing & Bonding Flashcards
6 cards from real PART P practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Earthing & Bonding flashcards as text
What test is performed to verify the continuity of a circuit protective conductor?
Answer: R1 + R2 test: measuring the combined resistance of phase and CPC conductors from the consumer unit to the furthest point of the circuit
The R1 + R2 test connects the phase and CPC at the far end of the circuit and measures their combined resistance from the CU; this confirms the CPC is continuous and correctly sized throughout the circuit.
What is the purpose of bonding a TV aerial (coaxial) cable screen to earth?
Answer: To discharge static and induced voltages on the aerial cable screen, preventing dangerous voltages being introduced into the installation or equipment
The outer screen of a coaxial aerial cable should be earthed at the point of entry to the building to provide a safe discharge path for lightning-induced surges and static charges, preventing them from reaching equipment.
What is the minimum cross-sectional area of a supplementary bonding conductor between two exposed conductive parts?
Answer: 2.5 mm² if mechanically protected, 4 mm² if not mechanically protected
BS 7671 Regulation 544.2 specifies minimum sizes for supplementary bonding conductors: 2.5 mm² when mechanically protected (e.g., in conduit) and 4 mm² when not protected against mechanical damage.
What is a PME (Protective Multiple Earthing) warning label and where is it required?
Answer: A warning label fixed at the origin of a PME installation advising that additional bonding may be required, as required by the electricity supplier's distribution code
Where a PME supply is used, the electricity supplier's conditions include a requirement to label the installation at the origin with a PME warning, noting that the neutral is used as the earthing conductor and that disconnection of the PEN conductor would energise metalwork.
What risk is associated with using PME earth terminals for caravan or boat hook-up?
Answer: If the PEN conductor breaks in the supply, the caravan or boat metalwork could rise to near line voltage — PME earth must not be used for caravans, boats or temporarily connected equipment
A broken PEN conductor (common in ageing networks) would cause any PME-earthed metalwork to rise to dangerous voltages. For this reason, BS 7671 prohibits using a PME terminal as the earth for caravans, boats or temporary structures.
What is the purpose of testing continuity of main protective bonding conductors during an installation inspection?
Answer: To confirm the bonding conductors are connected and have a low resistance, ensuring they can carry fault current and limit potential differences
Continuity testing of bonding conductors confirms they are correctly connected at both ends and have a resistance low enough to carry fault current and maintain equipotential conditions between all bonded metalwork.