2365 203 #18 - Earthing and Bonding

What is the main purpose of earthing in an electrical system?

• To reduce voltage

• To allow higher current flow

• To provide a path for fault current to safely return to earth

• To balance load across phases

What does bonding do?

• Increases cable flexibility

• Ensures all exposed metal parts are at the same potential

• Replaces circuit breakers

• Boosts voltage levels

What is the CPC?

• Consumer Phase Connector

• Circuit Protection Clamp

• Circuit Protective Conductor

• Copper Parallel Core

What does the Main Earthing Terminal (MET) connect?

• Lighting only

• Bonding clamps

• All CPCs, main protective bonding, and incoming earth

• The RCD to the fuseboard

What is the minimum size of main protective bonding conductor for a TN-C-S system with 16mm² line conductors?

• 2.5mm²

• 6mm²

• 10mm²

• 16mm²

What is supplementary bonding used for?

• Enhancing lighting control

• Connecting metallic parts within the same location (e.g. bathroom)

• Supporting CCTV

• Isolating earthing systems

Where is supplementary bonding commonly required?

• Kitchens

• Outside sheds

• Bathrooms and similar special locations

• Meter cupboards

What regulation in BS7671 covers bonding requirements?

• Regulation 411.3.1.2

• Regulation 522.8.1

• Regulation 433.1.1

• Appendix 4

What test is used to confirm bonding is correctly connected?

• Insulation resistance test

• Earth fault loop impedance test

• Continuity of protective conductors test

• Voltage drop test

What must be bonded to the main earthing terminal in a TN system?

• All light fittings

• Any extraneous conductive parts like gas and water pipes

• Door handles

• Cable trays only