BS7671:2008 Amendment 3 Update
Throughout the electrical industry, the requirements contained within BS 7671 - commonly referred to as the 17th Edition Wiring Regulations - are used to achieve compliance with the relevant parts of the statutory Electricity at Work Regulations. It sets the standard for electrical installation in the UK, as well as many other countries.
Wiring requirements must keep pace as technology and our environments develop and change, resulting in necessary amendments to the regulations. Over a period of time, the IET (Institution of Engineering and Technology) combines all of
the changes that affect the design, installation and verification of electrical installations into one single revised issue of the regulations.
A new regulation numbering system
Currently .100 attached numbers are UK specific. The proposed Amendment 3 document introduces a new regulation numbering system. Any regulations with the number .100 attached represent CENELEC Harmonized Document requirements and numbers .200 represent requirements that are specific to the UK.
Protection against electric shock
Currently the installation of general purpose 13A sockets for use by ordinary people requires additional protection in the form of an RCD to be provided. Currently, there is an exemption whereby if the installation is under the supervision of a skilled or instructed person, the installation of the RCD is not required.
A reduction in Earth Loop
Impedance Values Currently the earth fault loop impedance tables within Chapter 41 provide the maximum earth fault loop impedance values for protective devices and are based upon the value of the incoming supply voltage being 230V. However, this may not be the case as values lower than 230V may be present at the supply intake. Amendment 3 realises that voltages below 230V will have an adverse effect upon the values within the tables and as a direct result the disconnection times of the protected circuits may not be achieved. Therefore, a minimum voltage factor designated Cmin given a value of 0.95 appears for the first time in Part 4 Chapter 41. For example, where U0 is 230V, the minimum voltage at a consumers terminals must not be less than 230V x 0.95 = 218.5V All of the earth fault loop impedances values for the protective devices listed in Amendment 3, part 4 Chapter 41 will be effectively reduced by this Cmin factor.
Protective devices
The characteristic curves for both 2A and 4A ratings have now been included for BS 88-2 system E and G devices and a new graph for BS 88-2 system E devices for ratings from 250A to 1250A also appears.
Model inspection, testing certificates and reports
Appendix 6 contains three model forms for the inspection and testing of electrical installations. At first glance the changes appear to be mainly editorial, but in the ‘Electrical Installation and the Minor Electrical Installation Works Certificates’ in the section titled ‘Details of Permitted Exceptions’, a risk assessment identifying the reasons for the identified exceptions is now required to be produced and attached to the related certificate. The Schedule of Inspections for the Electrical Installation Certificate has been deleted from the requirements and replaced by a comprehensive list of examples in the format as those currently required in the condition report. This will result in a complete change to electrical installation certificates. It is to be assumed that the person carrying out the inspection will have to produce his own Schedule of inspections from the examples provided. With regards to the Limitation section contained within the Condition Report, the statement regarding the inspection in roof spaces being a limitation has been deleted, and the requirement now states that an inspection should be made within an accessible roof space where electrical equipment is present.

Until Amendment 3 is published in January 2015, the contents of this document are correct but may be incorrect once BS 7671 Amendment 3 becomes available. The draft copy of the amendment may be subject to change as it is dependent upon the comments received regarding its content.
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