KEY ISSUE FIRST STRUCTURE
The structure of BS 7671:2008 (2011) remains similar to the previous edition in that there are still seven parts with the titles of the seven unchanged. There were 15 Appendices and now there are 16.
The numbering in BS 7671:2008 (2011) is similar to that in the previous standard with the exception that a change has been introduced for UK only regulations. The change involves a ‘100 numbering system’ which enables future regulations from the International Electrotechnical Commission (IEC) to be included without altering the overall numbering system, e.g, Regulation 522.6.5 has become 522.6.100.
Part 1, Scope, Object and Fundamental Principles There are a few minor editorial changes within Part 1. For example, Regulation 120.4 ‘New materials and inventions’ has become 133.5 and Regulation 131.8. ‘Additions and alterations to an installation’ has become 132.16.
Part 2, Definitions
The first alteration in Definitions that you would notice is the inclusion of a number in brackets. This is to indicate that the definition applies within that Section only, e.g ‘Medical location (710)’.
Several definitions have been modified and some new definitions have been introduced: Discrimination, Medical locations, Operating and maintenance gangway and Triplen harmonics.
Diagrams for the various electrical supply systems have been removed to Part 3. The symbols table in Part 2 has been updated.
Part 3, Assessment of General Characteristics An important change to Part 3 is the introduction of the diagrams for conductor arrangements and types of system earthing – and a more thorough explanation of the TN-S, TN-C-S (PME), and TT supply systems together with definitions. Diagrams have also been included for single phase, two phase, three phase AC systems and two and three wire DC systems. Part 3 also includes the requirement that all electrical equipment must meet the appropriate electromagnetic compatibility (EMC) standards.
Part 4, Protection for Safety Due to changes to certain fuse standards, some values of maximum earth fault loop impedance in Table 41.2 and Table 41.4 have been amended. Table 41.5 which gives maximum earth fault loop impedance (Zs) values for circuits protected by RCDs now applies to all final circuits, including those exceeding 32A. Consequently, where there were previously four columns with a range of line to earth voltage, U0, now there are only two columns under the heading of U0 of 230V, one for RCD Ratings and the other for the maximum earth loop value.
FRANK BERTIE OF NAPIT HIGHLIGHTS SOME OF THE KEY CHANGES TO TAKE NOTE OF IN THE FIRST AMENDMENT TO THE 17TH EDITION WIRING REGULATIONS.
Section 444, Measures Against Electromagnetic Disturbances
This is a new section which deals with electromagnetic interference, the requirements for avoidance and reduction of electromagnetic disturbances on electrical equipment. There are diagrams detailing how to comply with the requirements, including an annex with diagrams for protective conductors and dimensions for segregation of circuits.
Part 5, Selection and Erection of Equipment Chapter 51 contains numerous alterations to existing regulations. The requirement for a voltage warning label in regulation 514.10.1 to be present between separate but simultaneously accessible items of equipment or enclosures has been removed. The sole requirement now is that the voltage warning label must be clearly visible before gaining access to live parts for equipment with voltages exceeding 230V to earth.
Chapter 52, Selection and Erection of Wiring Systems Chapter 52 contains alterations to existing Regulations. Two groups of Regulations in particular contain substantial changes - Regulation Group 521.5, A.C. circuits: electromagnetic effects and Regulation Group 521.9, Use of flexible cables. (All references to flexible cords have been removed.) SELV and PELV circuits have been exempted from
the requirement for concealed cables to be given RCD protection.
Regulation 526.3, which lists a number of exceptions
to the requirement for access to connections has been modified. Item (v) is now worded to the effect that equipment connections made by the manufacturer and not intended to be inspected or maintained do not need to be inspected or maintained. An extra item - Item (vi) - has been added. It adds equipment complying with BS 5733 for a maintenance free accessory and marked with the symbol MF (in a circle) and installed in accordance to the manufacturer’s instructions.
Chapter 53, Protection, Isolation, Switching, Control and Monitoring Chapter 53 has relatively minor changes, with the introduction of a new Section 534, Devices for Protection Against Overvoltage. Section 534 addresses the important and hitherto somewhat underemphasised topic of surge or overvoltage protection. It describes in detail the use of surge protection devices (SPDs) complete with diagrams and an annex.
Part 6, Inspection and Testing The changes to the text of Part 6 are few and editorial. Chapter 63, Certification and Reporting, introduces an Electrical Installation Condition Report (EICR) which replaces the Periodic Inspection Report (PIR).
Part 7, Special Installations or Locations Section 702, Swimming Pools and Other Basins,
has added information in Regulation 702.410.3.4.3 regarding bonding and RCDs. Sections 708 and 709 regarding caravan parks and marinas respectively, now have the restriction on TN-C-S systems as prescribed in the Electricity Safety, Quality and Continuity Regulations, stated as a regulation now rather than in a note.
Section 710, Medical Locations, is now included with diagrams and details on this specialised area. A new Section 729, Operating and Maintenance Gangways, contains requirements regarding accessibility.
Appendix 6, Model Forms for Certification and Reporting
The Electrical Installation Condition Report The PIR form has been replaced with an, ‘Electrical Installation Condition Report’ (‘EICR’). The EICR includes guidance which is set out more clearly than in the previous versions.
The EICR contains a significant number of changes to the method of detailing the findings of the inspection. The observations now have the following classification codes: • Code C1 – Danger present, risk of injury, immediate action required.
• Code C2 – Potentially dangerous, urgent remedial action required.
• Code C3 – Improvement recommended. The new codes will promote consistency in compiling
reports and in determining any remedial actions which need to be taken by giving clear priorities. The EICR is to be used only for reporting on the condition of existing electrical installations and must be accompanied by two schedules – the Schedule of Test Results and the Inspection Schedule. These differ from the previous schedules. The Schedule of Test Results is similar to the previous one but it now includes five extra columns to enable the results of ring circuit testing to be recorded and for recording the operation of the RCD test button. The Inspection Schedule is now entitled, Inspection Schedule for Domestic and Similar Premises with up to 100A Supply. However, a note just below this title states that this Inspection Schedule is not exclusively for domestic use as it is suitable for many types of smaller installations.
Appendix 16, Devices for Protection Against Overcurrent
Appendix 16 is a new Appendix which complements Section 534, with diagrams showing how SPDs are to be connected in different situations.
This article has been intended as an overview of the changes in BS 7671:2008 (2011). More could be said about certain aspects of these changes but NAPIT felt this would give you enough to think about for now and give you some useful insight into the changes.
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