CODE OF PRACTICE FOR THE ELECTRICITY (WIRING) REGULATIONS Electrical and Mechanical Services Department 2009 Contents Page Acknowledgements 9 Part I 1. Introduction 10 2. Interpretation 11 3. Application 15 3A General Application of the CoP 16 3B Application to Category 2 Circuit 16 3C Exempted Fixed Electrical Installations 16 4. General Safety Requirements 17 4A General 18 4B Workmanship and Materials 19 4C Design, Construction, Installation and Protection 19 4D Identification, Maintenance, Inspection and Testing 20 4E Working Space 22 4F Switchroom/Substation 22 4G Safety Precautions for Work on Low Voltage Installation 24 4H Safety Precautions for Work on High Voltage Installation 25 4I General Safety Practices 27 5. Segregation of Circuit Categories 29 5A Circuit Category 30 5B Segregation of Category 1, 2 and 3 Circuits 30 5C Segregation of Category 4 Circuits and Circuits of Other Categories 31 5D Segregation of Circuits from Overhead Telecommunication Lines and Telephone Lines 32 6. Circuit Arrangement 34 6A Division of Installation into Circuits 35 6B Basic Requirements of Circuits 35 6C Ring Final Circuit Arrangement 36 6D Final Circuits Using 5A or 15A Socket Outlets to Requirements Prescribed in Appendix 1 37 6E Final Circuits Using 13A Socket Outlets to Requirements Prescribed in Appendix 2 37 6F Final Circuits Using 5A, 15A or 30A Industrial Socket Outlets to Requirements Prescribed in Appendix 3 38 3 Page 6G Final Circuits Using 16A Industrial Socket Outlets to Requirements Prescribed in Appendix 4 39 6H Final Circuits Using 32A, 63A or 125A Industrial Socket Outlets to Requirements Prescribed in Appendix 4 39 7. Current Demand 46 7A Current Demand of a Circuit 47 7B Determination of Current Demand 47 8. Isolation and Switching 50 8A Provision of Isolation and Switching 51 8B Requirements of Isolation and Switching Devices 53 9. Overcurrent Protective Devices 57 9A General Requirements 58 9B Relation Between Circuit Conductors and Overcurrent Protective Devices 58 9C Breaking Capacity of Overcurrent Protective Devices 59 9D Position of Overcurrent Protective Devices 60 9E Other Requirements of Overcurrent Protective Devices 61 10. Neutral Conductor Protective Devices, Isolators and Switches 65 10A Linked Circuit Breakers, Linked Isolators and Linked Switches 66 10B Protection of Neutral Conductor 66 10C Single-pole Switch in Earthing Conductor 66 11. Earth Leakage and Earth Fault Currents 67 11A General 68 11B Basic Requirements 68 11C Protective Conductors 69 11D Earthing of Exposed Conductive Parts 70 11E Equipotential Bonding 71 11F Supplementary Bonding 72 11G Main Earthing Terminal 73 11H Earthing Conductor 74 11I Earth Fault Loop Impedance (Zs) 74 11J Residual Current Device (RCD) 75 11K Earth Electrodes 76 4 Page 12. Earthing Arrangement 84 12A General 85 12B Bonding Connections to the Point of Supply 85 12C Earth Electrode 86 13. Conductors, Joints and Connections 88 13A Selection and Sizing of Cable Conductors 89 13B Basic Protection 91 13C Joints and Connections 91 13D Other Requirements of Cables 92 14. Wiring Installation Enclosure 95 14A General Requirements 96 14B Steel Conduit System 96 14C Steel Trunking System 97 14D Plastic or PVC Conduit or Trunking 98 14E Cable Capacity of Enclosures 99 14F Enclosures of Busbar Trunking System and Powertrack System 100 14G Workmanship 100 15. Adverse Conditions Installation 104 15A Presence of Water (AD) or High Humidity (AB) 105 15B Ambient Temperature (AA) 106 15C Presence of Corrosive or Polluting Substance (AF) 107 15D Installation Exposed to Fire or Explosion 108 15E Impact (AG) 109 15F Vibration (AH) 110 15G Other Mechanical Stresses 110 16. Overhead Line Installations 116 16A General 117 16B Installation of Overhead Lines 117 16C Joints of Overhead Lines 117 16D Service to Building 117 16E Conductor to Ground Clearance 117 16F Pole 118 16G Stay Wire 118 16H Carrier Wire 118 16I Earthing of Metallic Parts and Earth Leakage Protection 119 5 Page 17. Display of Labels and Notices 120 17A Warning Notice for Substations and Switchrooms 121 17B Warning Notice for Connection of Earthing and Bonding Conductors 121 17C Warning Notice for Repair 121 17D Notice of Periodic Testing of Electrical Installations 122 17E Notice of Testing for Residual Current Devices 122 17F Warning Notice for Installation Having Both New and Old Cable Colours 122 18. Alterations and Additions 123 18A Requirements for Alterations or Additions to a Fixed Installation 124 18B Approval from the Electricity Supplier 124 19. First Inspection, Testing and Certification 125 19A Certification on Completion of an Installation 126 19B Work Completion Certificate 126 20. Periodic Inspection, Testing and Certification 128 20A Fixed Electrical Installations Specified in Regulation 20(1) 129 20B Fixed Electrical Installations Specified in Regulations 20(2), 20(3) and 20(4) 130 20C Periodic Test Certificate 131 21. Procedures for Inspection, Testing and Certification 132 21A Inspection of Low Voltage Installations 133 21B Testing of Low Voltage Installations 134 21C Inspection of High Voltage (H.V.) Installations 138 21D Testing of High Voltage Installations 139 21E Points to be Noted by Registered Electrical Workers 139 22. Making and Keeping of Records 148 22A Keeping of Records by the Owner of an Electrical Installation that Requires Periodic Inspection, Testing and Certification 149 22B Making and Keeping of Records by a Registered Electrical Contractor 149 22C Types of Records 149 22D Checklists 149 23. ⎫ ⎬ (Reserved for Future Uses) 152 24. ⎭ 6 Part II Page 25. General Workmanship 153 25A Wiring Installation Using Conduits 154 25B Wiring Installation Using Trunkings 156 25C Installation of Cables 156 25D Cable Joint and Cable Termination 159 25E Installation of Socket Outlets 163 26. Requirements for Specific Installations and Equipment 168 26A Domestic Installation and Appliance 170 26B Busbar Trunking Distribution System 175 26C Electric Motor 177 26D Supply Connection to Transformers 178 26E Supply Connection to Welding Sets 179 26F Installation of Fluorescent and Gaseous Discharge Lamps 179 26G Installation of Category 3 Circuits 179 26H High Voltage Discharge Lighting Installation (Neon Signs) 179 26I Lightning Protection Installation 183 26J Rising Mains Installation 183 26K Temporary Supply Installation for Construction and Demolition Sites or Repair and Testing Purposes 183 26L Hot Air Saunas Installation 186 26M Swimming Pools and Fountains Installation 188 26N Installation in Restrictive Conductive Locations 193 26O Installation of Equipment Having High Earth Leakage Currents 195 26P Renewable Energy Power System 197 26Q Temporary Electrical Installation for Exhibitions, Shows, Stands and Festive Lighting 198 7 Page Appendices 208 1. Prescribed Requirements for 3-pin (non-reversible) 5 ampere and 15 ampere Socket Outlets 209 2. Prescribed Requirements for 3-pin (non-reversible) 13 ampere Socket Outlets 217 3. Prescribed Requirements for Protected Type Non-reversible 5 ampere, 15 ampere and 30 ampere Socket Outlets 226 4. Prescribed Requirements for Industrial Type 16 ampere, 32 ampere, 63 ampere and 125 ampere Socket Outlets with Retaining Devices 236 5. Correction Factors for Sizing of Cable Conductors 252 6. Current Carrying Capacities and Voltage Drop Tables for PVC Insulated and XLPE Insulated Cables 256 7. Typical Methods of Installation of Cables 274 8. Graphical Symbols for Electrical Diagrams 279 9. Performance Monitoring Points System for Registered Electrical Workers / Contractors 287 10. Degree of Protection Provided by Enclosures (IP Code) 288 11. Forms of Internal Separations for Switchgear Assemblies 290 12. Worked Examples for Application of the CoP 292 13. Sample of Schedule of Test Results for Electrical Wiring and Checklists 296 14. References 313 15. Safety for Live Work 319 16. Sample of Permit-To-Work 321 17. Sample of H.V. Enclosure Log Book 324 18. New Cable Colour Code for Fixed Electrical Installations- Installation Guidelines 325 Index 331 8 ACKNOWLEDGEMENT The Electrical and Mechanical Services Department of the Government of the Hong Kong Special Administrative Region would like to express gratitude to the organizations listed below for their kind permission to reproduce materials from their copyright publications: — British Standards Institution (BSI) —The Institution of Engineering & Technology (IET) (as the joint copyright holder with BSI for BS 7671—IEE Wiring Regulations) — International Electrotechnical Commission (IEC) The organizations listed above retain the copyright on the reproduced materials which may not be reproduced without the prior written permission the organizations. Copies of the complete standards listed above are available for sale from the respective organizations. The addresses of the organizations are: — British Standards Institution: 389 Chiswick High Road, London W4 4AL, UK — The Institution of Engineering & Technology: Michael Faraday House, Six Hills Way, Stevenage, UK — International Electrotechnical Commission: IEC Central Office, 3 rue de Varembé, P.O. Box 131, CH-1211 Geneva 20, Switzerland Copies of the complete standards can also be bought through the Product Standards Information Bureau, Innovation and Technology Commission at 36/F, Immigration Tower, 7 Gloucester Road, Wanchai, Hong Kong (tel. no.: 2829 4820). 9 PART I Code 1 INTRODUCTION This Code of Practice should be titled ‘Code of Practice for the Electricity (Wiring) Regulations’ hereinafter referred as the ‘CoP’. The CoP is published to give general technical