Key things you need to know about Amendment 2 in the IET Wiring Regulations
*This piece was written during the draft for public comment. Now Amendment 2 has been published, you can find the 5 key things you need to know here.*
Each new edition of the wiring regulations brings about improvements in safety standards for our electrical installations, and the recent draft for public comment on BS7671 IET Wiring Regulations (Sept 2020) is no exception. Here we look at some of the proposals from the draft document;
Protection Against Electric Shock
There will no longer be an option to use a risk assessment to justify omitting 30mA RCD protection on certain socket outlets (not exceeding 32A) in premises other than dwellings. All installations will be treated the same as dwellings and all sockets (up to and including 32A ratings) will require protection by 30mA RCD.
Unwanted Tripping of RCDs
Grouping several circuits together on one or two RCDs in a consumer unit may not meet the requirements of Amendment 2. The use of RCBOs for each individual final circuit in domestic installations will be proposed as a specific means of avoiding unwanted tripping and ensuring power continuity to healthy circuits. This is in addition to existing requirements for subdividing final circuits and considerations for each circuit having its own RCDs.
There are several existing regulations to consider, 314.1 - division of the installation into individual circuits to avoid danger from unwanted tripping. 531.3.2 - requires the designer to ensure that PE currents from connected equipment are no more than 9mA on any 30mA RCD.
Grouping several circuits together on one or two 30mA RCDs will not meet this regulation.
Types of RCD & Appropriate Selection
The appropriate RCD should be selected from the four types listed in 531.3.1 but it is likely that Type AC RCDs will only be allowed for use on fixed equipment where the load characteristic does not contain any DC components e.g. basic electric heating, filament lighting, it is expected that Type A RCDs will be recommended for general purpose use instead of Type AC.
Protection Against Overvoltage
The requirements for overvoltage protection are expected to remain broadly unchanged. Overvoltage must be provided in certain circumstances (serious injury, loss of life, serious financial or data loss) for other circumstances risk assessments must be carried out to decide if protection is required.
Single Unit Dwellings
In single unit dwellings overvoltage protection will be required where the value of the loss of equipment & damage to the installation justifies the cost of the SPD.
Switching Overvoltages
Also, designers must consider protection against overvoltages where equipment is likely to produce switching overvoltages exceeding the rated impulse voltage of equipment in the installation.
Recommendations for AFDDs
AFDDs are recommended in the 18th Edition as a means of providing additional protection against fire caused by arc faults in 230v AC final circuits, it is proposed in the 2020 draft for public comment that AFDDs will be specified as a requirement for certain circuits. AFDDs would be used in addition to the other measures that are required in BS7671.
Earthing arrangements
This is a significant addition to the regulations. For new premises / buildings constructed upon foundations the proposal is to have some type of foundation earth electrode. This applies where the installation uses automatic disconnection as the protective measure. The proposals gives 3 options for the foundation earth method and a maximum resistance value.
Part 8
Part 8 is brand new section relating to “Prosumers Electrical Installations”. A prosumer is a producer & consumer of electricity. Chapter 8 contains requirements for safe operation, sustainability, and efficient use of electricity when integrated into smart grids. Part 8 is a significant addition to BS7671.
The Draft for Public comment was issued in September 2020 and closed in December 2020 the next stage is for the technical committees to review the comments so there may be changes between the close of the DPC & publication following review by the IET & BSI technical committees.
