17th EDITION WIRING REGS WHATS NEW

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17th EDITION WIRING REGS WHATS NEW?
Chris Johnston - Senior Electrical Tutor City
Guilds Chief Examiner
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Introduction

• Issued on 1st January 2008
• Came into effect 1st July 2008
• The Regulations are fully aligned with the IEC
  60364 series of standards (world standards) and
  CENELEC harmonization documents (European
  standards).

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Content

• Part Title
• 1 Scope, Object and Fundamental Principles
• 2 Definitions
• 3 Assessment of General Characteristics
• 4 Protection for Safety
• 5 Selection and Erection of Equipment
• 6 Inspection and Testing
• 7 Special Installations or Locations
• Appendices 1-15

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Using the Regulations
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Numbering System
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The Appendices

• British Standards to which reference is made in
  the regulations
• Statutory regulations and associated memoranda
• Time/current characteristics of overcurrent
  protective devices
• Current-carrying capacity and voltage drop for
  cable and flexible cords
• Classification of external influences
• Model forms for certification and reporting
• Harmonized cable core colours

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The Appendices

• Current-carrying capacity and voltage drop for
  busbar trunking and powertrack systems
• Definitions-Multiple source, d.c. and other
  systems
• Protection of conductors in parallel against
  overcurrent
• Harmonic currents in three-phase systems
• Voltage drop in consumers installations
• Methods for measuring insulation resistance of
  floors and walls
• Measurement of fault loop impedance increase of
  resistance of conductors with temperature
• Radial and ring final circuit arrangements

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Part 1

• Chapter 11 Scope
• Chapter 12 Object and Effect
• Chapter 13 Fundamental Principles

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Scope

• 110.1 General
• The Regulations apply to the design and
  verification of electrical installations such as
  those of
• (ix) Marinas
• (xi) Mobile or transportable units
• (xii) Photovoltaic systems
• (xii) Low voltage generating sets

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Object and Effect

• Regulation 120.3
• Any intended departure . requires special
  consideration by the designer The resulting
  degree of safety of the installation shall be not
  less than that obtained by compliance with the
  regulations

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Fundamental Principles

• 131.7 Where danger or damage is expected to arise
  due to an interruption of supply, suitable
  provisions shall be made in the installation or
  installed equipment
• 132.13 Every electrical installation shall be
  provided with appropriate documentation

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Fundamental Principles

• 134.1.1 Good workmanship by competent persons or
  persons under their supervision and proper
  materials
• 135.1 It is recommended that every electrical
  installation is subjected to periodic inspection
  and testing

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Part 2 - Definitions

• Aligned with the International Electrotechnical
  Vocabulary
• There is an increase in the number of
  definitions from around 160 to about 230.

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Part 2 - Definitions

• Competent Person
• A person who possesses sufficient technical
  knowledge and experience for the nature of the
  electrical work undertaken and is able at all
  times to prevent danger, and where appropriate,
  injury, to him/herself and others.

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Part 2 - Definitions

• Ordinary person A person who is neither skilled
  nor an instructed person.
• Skilled person A person with technical
  knowledge or sufficient experience to enable
  him/her to avoid dangers which electricity may
  create.
• Instructed person A person adequately advised
  or supervised by skilled persons to enable
  him/her to avoid dangers which electricity may
  create.

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Part 2 - Definitions

• Basic Protection (Protection against direct
  contact)
• Protection against electric shock under
  fault-free conditions
• Fault Protection (Protection against indirect
  contact)
• Protection against electric shock under single
  fault conditions
• Additional protection (Supplementary protection)
• (Not defined in Part 2)

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Part 2 - Definitions

• Line conductor replaces Phase conductor
• The term Live conductor still includes the
  neutral conductor

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Part 3 Assessment of General Characteristics

• Purpose, Supplies and structure
• Classification of external Influences
• Compatibility
• Maintainability
• Safety Services
• Continuity of Service

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Chapter 31

• 311.1 For economic and reliable design, the
  maximum demand of an installation shall be
  assessed.
• 314.1 Every installation shall be divided into
  circuits, as necessary to
  
• (iii) Take account of the hazard that may arise
  from the failure of a single circuit such as a
  lighting circuit .

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Part 4 Protection for Safety

• Protection against electric shock
• Protection against thermal effects
• Protection against overcurrent
• Protection against voltage disturbances and
  electromagnetic disturbances

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Comparison with 16th Edition
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Protection Against Electric Shock

• 410.3.2 A protective measure shall consist of
• An appropriate combination of a provision for
  basic protection and an independent provision for
  fault protection, or
• An enhanced protective provision which provides
  both basic protection and fault protection.

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Protection Against Electric Shock

• Basic Protection (Protection against direct
  contact)
• Protection against electric shock under
  fault-free conditions
• Insulation, barriers and enclosures
• Fault Protection (Protection against indirect
  contact)
• Protection against electric shock under single
  fault conditions
• Automatic disconnection of supply

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Protection Against Electric Shock

• The following protective measures are generally
  permitted
• Automatic disconnection of supply (ADS) (most
  commonly used)
• Double or reinforced insulation
• Electrical separation for the supply to one item
  of current-using equipment
• Extra-low voltage (SELV or PELV)

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Disconnection Times
If an earth fault occurs then all final circuits
rated at 230 V to earth and having a current
rating of 32 A or less must disconnect in the
time shown below.
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TN-S
Supply
Fuse Operates (0.4 s for circuits up 32 A )
LOAD
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Disconnection Times

• In a TN system the maximum disconnection time may
  be extended to 5 s for distribution circuits and
  other circuits having a rating exceeding 32 A.
• In a TT system the maximum disconnection time may
  be extended to 1 s for distribution circuits and
  other circuits having a rating exceeding 32 A.

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Earth Loop Impedance

• In order to confirm that fuses and circuit
  breakers will meet the appropriate disconnection
  times, reference to tables 41.2, 41.3 and 41.4
  must be made. (Previously Tables 41B1, 41B2 and
  41D)
• These are now based on 230 V (Uo) and not 240 V
  (Uoc)

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Additional Protection

• 411.3.3 In a.c. systems, additional protection by
  means of an RCD (having I?n not exceeding 30 mA)
  shall be provided for
• Socket-outlets not exceeding 20 A rating for use
  by ordinary persons and intended for general use,
  and
• Mobile equipment not exceeding 32 A rating for
  use outdoors.

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Additional Protection

• 411.3.3
• An exception is permitted for
• (iii) socket-outlets for use under the
  supervision of skilled or instructed persons e.g.
  in some commercial or industrial locations, or
• (iv) A specific labelled or otherwise suitably
  identified socket-outlet provided for connection
  of a particular item of equipment.

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Installations with Restricted Access

• 410.3.5
• The protective measures specified in Section
  417, i.e. the use of obstacles and placing out of
  reach, shall be used only in installations where
  access is restricted to
• Skilled or instructed persons
• Persons under the supervision of skilled or
  instructed persons.

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Installations with Restricted Access

• 410.3.6
• The protective measures specified in Section
  418. i.e.
• non-conducting location
• Earth-free local equipotential bonding
• Electrical separation for the supply to more than
  one item of equipment
• shall be applied only where the installation is
  under the supervision of skilled or instructed
  persons so that unauthorised changes cannot be
  made.

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Protection against thermal effects

• There are few changes to this chapter.
• It does include Chapter 48 from the 16th Edition
  , Precautions where particular risks of fire
  exist.

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Protection Against Overcurrent

• There are few changes to Chapter 43
• Appendix 4 cable current rating
• Now includes data for cables buried directly in
  the ground
• Cable installation methods now are lettered
  rather than numbered
• Correction factors now referred to as Rating
  factors

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Protection against voltage disturbances and
electromagnetic disturbances

• Additional information relating to protection of
  low voltage installations against temporary
  overvoltages due to earth faults in the high
  voltage system is now included

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Part 5

• Selection and Erection of Wiring Systems
• 521.8.2
• The line and neutral conductors of each final
  circuit shall be electrically separate from those
  of every other final circuit.

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Cables in Walls

• 522.6.7
• requires cables which are buried in a wall at a
  depth not exceeding 50 mm which are part of an
  installation not under the supervision of a
  skilled or instructed person and the cable is not
  substantially mechanically protected, must be run
  in the safe zones AND
• be protected by a 30 mA RCD.

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Cables in Walls

• 522.6.8
• If the cables are in a wall that includes metal
  parts and is not under the supervision of a
  skilled or instructed person and the cable is not
  substantially mechanically protected, then
• a 30 mA RCD must be used to protect the circuit
  irrespective of the depth of the cable.

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Voltage Drop
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Protection Against Overcurrent

• 533.3
• Where a protective device specifies a rated
  service short-circuit breaking capacity and an
  ultimate short-circuit breaking capacity, the
  device may be selected on the basis of the
  ultimate short-circuit conditions.
• Operational circumstances may, however, make it
  desirable to select the protective device on the
  service short-circuit breaking capacity.

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Safety Circuits

• 560.7.9
• In addition to a general schematic diagram, full
  details of all electrical safety sources shall be
  given. The information shall be maintained and
  displayed adjacent to the relevant distribution
  board. A single-line diagram is sufficient.

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Part 6 Inspection and Testing

• Inspection and testing is now Part 6 rather than
  Part 7 and has few changes.

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Insulation Resistance
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Insulation Resistance

• Note to previous table
• Where it is not reasonably practicable to
  disconnect surge protective devices (e.g. in case
  of fixed socket-outlets incorporating an SPD),
  the test voltage for the particular circuit may
  be reduced to 250 V d.c., but the insulation
  resistance shall have a value of at least 1 M?.

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Phase Sequence and Voltage Drop

• Regulation 612.12 requires that the phase
  sequence is maintained
• Regulation 612.14 requires cable voltage drop to
  be verified. This is not normally required for
  initial verification.

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Earth Loop Impedance

• Appendix 14 provides information relating to the
  interpretation of earth loop impedance test
  results.
• It states that compliance is met when
• A more precise assessment may be necessary and
  guidance on how this may be achieved is also
  given.

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Periodic Inspection

• 621.5 Periodic inspection and testing shall be
  undertaken by a skilled person, competent in such
  work.
• 634.2 Any damage, deterioration, defects,
  dangerous conditions and non-compliance with the
  requirements of the Regulations, which may give
  rise to danger, together with any significant
  limitations of the inspection and testing,
  including their reasons, shall be recorded.

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Part 7

• Numbering System
• The number appearing after a section number
  generally refers to the corresponding Part,
  Chapter, Section or Regulation within Parts 1-6
  of the Regulations and therefore may not follow
  sequentially.
• E.g. 701.414.4.5 Requirements for SELV
  and PELV circuits

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Locations Containing a Bath or Shower

• 701.411.3.3
• Additional protection shall be provided for all
  circuits of the location, by the use of one or
  more RCDs having the characteristics specified in
  Regulation 415.1.1(30 mA)

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Locations Containing a Bath or Shower

• Supplementary equipotential bonding may be
  omitted where all of the following conditions are
  met
• All final circuits of the location meet the
  appropriate disconnection time
• All final circuits of the location have
  additional protection by means of a 30 mA RCD
• All extraneous conductive parts of the location
  are effectively connected to the protective
  equipotential bonding

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Locations Containing a Bath or Shower

• Socket-outlets may be installed within a
  bathroom providing they are at least 3 m from
  zone 1

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Construction and Demolition Site Installations

• Reduced low voltage systems are strongly
  preferred for the supply to portable hand lamps
  for general use and portable hand tools and local
  lighting up to 2 kW
• For circuits supplying one or more
  socket-outlets with a rated current exceeding 32
  A, an RCD having a rated residual operating
  current not exceeding 500 mA shall be provided

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Thank you for your attention