The 18th Edition IET Wiring Regulations – BS7671:2018 Requirements for Electrical Installations was published on 1st July 2018 and will come into effect on 1st January 2019. Installations designed after 31st December 2018 must comply with BS7671:2018. It is important that all electrical designers, installers and contractors understand the changes made and the implications of not complying. It should be noted that installations installed to a previous version of the wiring regulations are not required to be upgraded providing they are in a safe condition. Any alterations or modifications to existing electrical installations must comply with the 18th Edition. I want to go through some of the main changes that will affect you and your installations.
Part 1 – Scope requires installers to declare that any intended departures made from the regulations or where non certified electrical equipment is installed is declared in the Electrical Installation Certificate under sections “FOR DESIGN” AND “FOR INSPECTION AND TESTING”. An example of this would be the use of SY & YY cables which do not conform to any British or European Standards. Hence the designer and installer must satisfy themselves that the cable meets the safety requirements of an equivalent standard.
Part 2 - Some definitions such as Bonding conductor have been expanded for clarity. There are several new definitions introduced such as Departures, Combined short circuit protection and selectivity (which replaces co-ordination). I would urge you to familiarise yourselves with the new terms used.
Part 3 – Assessment of general characteristics. No changes made to the types and configuration of electrical supplies e.g. single-phase, three-phase, TNS, TNC-S, TT etc.
Part 4 – Protection for safety.
Shock Protection – no changes to basic and fault protection terminologies.
It is now recognised that non-conducting service pipes (plastic gas, water etc) need not be bonded to the main earthing terminal. Also if there is a plastic insert in the metal service pipe as it enters the building then the service pipe does not need to be bonded.
Maximum disconnection time for distribution circuits up to 63A is 0.4 seconds (previously this time was for circuits up to 32A).
Maximum disconnection time for supplying current using equipment up to 32A is 0.4 seconds.
All socket outlets with a rating not exceeding 32A (previously 20A) must be protected by a 30mA RCD unless there is a documented risk assessment carried out by the designer in conjunction with the site duty holder and must be kept throughout the life of the installation. The risk assessment is not applicable for domestic installations. The practice of labelling a socket for a particular use e.g. freezer or IT server for omission of an RCD is no longer acceptable.
All mobile equipment with a rating not exceeding 32A must be protected by a 30mA RCD.
All lighting circuits within domestic type premises must be protected with a 30mA RCD.
Precautions against fire
It has been known for some time that series and parallel faults are not always picked up by a protective device and an RCD resulting in fires. A new device called an Arc Fault Detection Device (AFDD) has been introduced for providing additional protection against fires caused by arc faults in AC final circuits. AFDDs should be installed in high risk areas such as:
- • Locations with sleeping accommodations ie hotels, student accommodation, residential and nursing homes etc.
- • Locations with high risk of fire due to process and stored materials such as textiles and flour.
- • Wooden buildings
- • Locations with endangering or irreplaceable goods.
Protection against voltage disturbances
Voltage disturbances are caused by :-
- • Lightning
- • Transient overvoltage
- • Electromagnetic fields
- • Switching operations
- • Faults on high or low voltage systems
- • Protection against overvoltage is achieved by installing a Surge Protection Device (SPD). The correct type of SPD should be installed for the application. SPDs are required to be installed where the consequences of an overvoltage could:
- • Result in serious injury or loss of life
- • Interruption to public services or damage to heritage sites
- • Interruption of commercial or industrial operations
- • Affect a large number of co-located individuals i.e blocks of flats, student accommodation, hotels, etc.
Risk assessment can be carried out to justify omission of SPD.
Part 5 Selection and Erection of Equipment
- • Structural metalwork or other metalwork embedded in the foundations of a building or structure can be used as an earth electrode.
- • RCDs should be tested using the manual trip button every 6 months.
- • RCD installed for additional protection and where disconnection times cannot be achieved.
- • Maximum allowable leakage current for a single RCD is 30% of rated RCD current.
- • Cables throughout an installation must be supported/fixed using non-flammable fixings or metal trunking/conduit. Gone is the requirement that non-flammable fixing are required on escape routes only, the requirement now is throughout the installation.
- • Part 6 Inspection and Testing has been restructured to align with international standards. This now details all the inspections and tests required to be carried out prior to energising an installation and during periodic inspection and testing. Slight modifications to the model forms have been made. Minor works certificate requires the installer to ensure the whole installation has been inspected for safety and not just the work that has been carried out.
Part 7 Special locations
- • Construction and Demolition sites - All surface run and overhead cables to be mechanically protected. Greater use of RCDs for individual equipment e.g.hand tool, transformers and lights.
- • Caravan and Camping Park installations – Protective Multiple Earthing (PME) supplies are prohibited. The supply to a mobile or residential home shall be protected by a 30mA RCD. The supply cable must not be greater than 20m in length. Individual socket outlets shall be protected by a 30mA RCD.
- • Medical locations have additional inspection and testing requirements to the general requirements.
- • Electric vehicle charging installations – PME supply to the charging unit is prohibited except under certain conditions. An earth electrode must be installed in addition to the supply earth facility. Automatic disconnection of supply must be triggered if the open circuit voltage between earth conductor and earth electrode rises above 70V. Every unit shall be protected by a 30mA RCD, an appropriate over current protective device and have means of isolation. One socket outlet per unit is allowed and must be of the commando type socket and interlocked.
- • Energy Efficiency of installations and equipment is in Appendix 17, and is only informative at this stage. This details the requirements for selecting, installing, operating and monitoring electrical installations for maximum energy efficiency. More work on this is required and will no doubt be introduced and expanded in future editions of the regulations.
SUMMARY
The 18th edition has introduced additional measures for the protection against electric shock, fires and over voltages to users of installations, livestock and property. If used correctly it will provide greater protection and should reduce injury to persons and fires.
