17TH 18TH EDITION BS7671 HOW THIS AFFECTS …

1 A bitesize LOOKat RCDs and parts of the 18th EDITION EDITIONBS767118TH EDITIONBS7671 HOW this AFFECTS CHOOSE ANYTHING LESS? CHOOSE ANYTHING LESS? INTRODUCTION. 17TH EDITION CHAPTER 31. WHAT IT SAYS ABOUT DIVISION OF THE INSTALLATION. INTRODUCTION TO 18th EDITION DRAFT FOR PUBLIC COMMENT. 18th EDITION . ADDITIONAL PROTECTION; SOCKET OUTLETS. 18th EDITION . ADDITIONAL PROTECTION; CIRCUITS WITH LUMINAIRES. 18th EDITION . CIRCUIT PROTECTOR (PE) CURRENTS NOT DUE TO A FAULT. 18th EDITION . TYPES OF RCD. 18th EDITION . SELECTIVITY BETWEEN RCDS. 18th EDITION . RCDS DISCONNECTING ALL LIVE CONDUCTORS. 18th EDITION . SPECIAL LOCATIONS document looks at some of the proposals, within the draft 18th EDITION , relating to EDITION Requires: Provision of additional protection (30mA RCD) Maintain power continuity Avoid unwanted tripping of RCDs Make provision for safe inspection, testing and maintenance?

2 HOW this AFFECTS trend over the past 20 years has been towards more use of RCDs on a higher number of circuits and a wider number of locations. this is likely to continue. this document looks at some of the the requirements change when the 18th EDITION is published?WHY CHOOSE ANYTHING LESS?INTRODUCTION. 17 THEDITION17 THEDITIONHow do you achieve power continuity and avoid unwantedtripping of RCDs and makeprovision for safe inspection, testing and maintenance?Regulation (i)Every installation shall be dividedinto circuits as necessary to:Avoid danger and minimize inconvenience in the eventof a this AFFECTS required number of individual circuits should be provided so that all healthy circuits provide power continuity and that only the individual circuit with fault is powered CHOOSE ANYTHING LESS?

3 17TH EDITION CHAPTER IT SAYS ABOUT DIVISION OF THE do you achieve additional protection, power continuity andavoid unwanted tripping ofRCDs, and make provision forsafe inspection, testing and maintenance?Regulation (iv)Every installation shall be divided into circuits as necessary to:Reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents (not due to a fault).HOW this AFFECTS currents within the protective conductor can be such that they add up to more than 50% of the rated residual operating current. this will cause the RCD to trip. Dividing equipment with PE currents over a larger number of circuits will help to avoid this EDITION CHAPTER IT SAYS ABOUT DIVISION OF THE CHOOSE ANYTHING LESS?17 THEDITION17 THEDITIONHow do you achieve additional protection, power continuity andavoid unwanted tripping ofRCDs, and make provision forsafe inspection, testing and maintenance?

4 Regulation (iii)Every installation shall be dividedinto circuits as necessary to:Take account of hazards that may arise from the failure of a single circuit this AFFECTS circuits should be individually protected by their own protective device and not share devices such as RCDs that serve groups of circuits. Grouping circuits on one 30mA RCD should be EDITION CHAPTER IT SAYS ABOUT DIVISION OF THE CHOOSE ANYTHING LESS?17 THEDITION17 THEDITIONF ootnote: disconnection of all live conductors (L&N) may also be required for purposes of isolation and mechanical do you achieve additional protection, power continuity andavoid unwanted tripping ofRCDs, and make provision forsafe inspection, testing and maintenance?Regulation (ii)Every installation shall be dividedinto circuits as necessary to:Facilitate safe inspection, testing and this AFFECTS required number of individual circuits should be provided so that only the individual circuit in test or maintenance is safely powered EDITION CHAPTER IT SAYS ABOUT DIVISION OF THE CHOOSE ANYTHING LESS?

5 17 THEDITION17 THEDITIONThe 17th EDITION is due to bereplaced by the 18th draft for public comment was released in 2017, comments willbe considered prior to publishingthe final 18th EDITION is due to be published in July 2018 and all installations designed after December 31st 2018 are to comply with BS7671 :2018. However, earlier adoption of thenew regulations is not 314 (Division of Installation) is this AFFECTS DPC of 18th EDITION contained a large number of changes, and additions that considerably expanded the content of the regulations. It willbe necessary for designers and installers to undertake training on these changes and CHOOSE ANYTHING LESS?INTRODUCTION TO 18th EDITION DRAFT FOR PUBLIC 41 Additional protection by means of a 30mA RCD is required for:Socket outlets rated to 20A.

6 Mobile equipment rated to 32 Aand for use 41 Additional protection by means of a 30mA RCD is required for:Socket outlets rated to equipment rated to 32 Aand for use this AFFECTS change brings extra sockets and circuits into scope for additional protection by 30mA devices, and requires designers and installers to make provision for additional devices within consumer units and distribution PROTECTION; SOCKET CHOOSE ANYTHING LESS?17 THEDITION18 THEDITIONC hapter 41No specific mention of RCDs on luminaire circuits in domestic (household) 41 Additional requirements forcircuits with luminaires indomestic household premises, requiring additional protectionby an RCD rated not morethan 30mA for circuitssupplying this AFFECTS new requirement probably brings into scope circuits that were not covered by regulations group (buried cables etc) and extends scope of 30mA protection to include luminaire circuits.

7 this may require A Class RCD devicesin some PROTECTION; CIRCUITS WITH CHOOSE ANYTHING LESS?17 THEDITION18 THEDITION18TH (PE) CURRENTS NOT DUE TOA FAU 314 Division of the installation (Chapter31) requires designers to reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor (PE) currents, not dueto a fault. But gives no values forPE 531 Section 531 cross references with 314 and includes specific values for PE currents, and division of the installation still requires designers to reduce the possibility of unwanted tripping of RCDs due to excessive protectiveconductor this AFFECTS the good practice of dividing the installation into a larger number of sub circuits as required to fully meet all 6 criteria listed in 314 may cater for these new requirements that are explained further on the next CHOOSE ANYTHING LESS?

8 17 THEDITION18 THEDITIONR egulation 531No specific value given for the maximum permitted (PE) circuit protector currents/earth leakage currents that are present duringnormal operating 531 The accumulation of circuit protector currents/earth leakage currents that are present during normal operating conditions shall not be more than 30% of the rated residual operating current of the RCD a PE of no more than 30% of this AFFECTS of the installation into circuits with individual RCD/RCBOs may be an adopted method. Unless designers and installers are familiar with values for leakage currents (of equipment) under normal operating conditions and know that unwanted tripping will not CHOOSE ANYTHING LESS? 18th (PE) CURRENTS NOT DUE TOA FAU 531No detailed explanation of the types of RCD available or how the presence of DC components can be taken into 531 Different types of RCD are described type AC, type Aetc.

9 Certain criteria are also provided on device behaviour when in the presence of DC components. Designers are required to select the appropriate this AFFECTS section is expanded considerably but the additional information on types of RCD and the references to behaviours and operating characteristics should make RCD selection CHOOSE ANYTHING LESS? 18th OF BETWEEN 536 Where selectivity is necessary to prevent danger and required for proper functioning of the installation, manufacturers instructions shall be taken into account and the device characteristics shall be such that intended discrimination is 536 Where selectivity is required verificationshall be made either: By desk study By software tools By tests to the applicable product standard By manufacturer s declarationHOW this AFFECTS section is expanded considerably but the additional information on types of RCD and the references to behaviours and operating characteristics should make RCD selection CHOOSE ANYTHING LESS?

10 17 THEDITION18 THEDITIONHOW this AFFECTS do not appear to be addressing the same point. The Draft of the18th EDITION appearsto require RCDs to switch theneutral conductor as well as the live phase. Some RCD products do not switch all live poles. Designers needto be aware of which DISCONNECTING ALL LIVE - disconnection of all live conductors may also be required for other purposes isolation or mechanical maintenance. See also notes for TN, TT systems & special 531In a TN system where, for certain equipment in a certain part of the installation, the requirement of cannot be satisfied, that part may be protected by an 531An RCD shall disconnect all live conductors of the circuit includes such devices as RCCB, RCBO, CBR and : disconnection of all live conductors may also be required for other purposes, isolation or mechanical maintenance.