17th Edition Parts 53 To 56


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  • Chapter 53 includes the requirements to provide compliance with the measures of protection for safety, the requirements for proper functioning for the intended use of the installation, and the requirements appropriate to the external influences foreseen.
  • Except as provided in Regulation 537.2.2.5, in multi-phase circuits an independently operated single-pole switching device or protective device should not be inserted in the neutral conductor. In single-phase circuits, an independently operated single-pole switching or protective device must not be inserted in the neutral conductor alone .
  • Although section 531is entitled Fault protection by automatic disconnection of supply (Section 531) nearly all of the requirements relate to RCDs Exercise (1) When an RCD is used for fault protection, with, but separate from, an overcurrent device, RCDs are to be capable of withstanding without damage the fault currents to which they are likely to be subjected on the load side at their point of installation (2) In a TN system, RCDs may be required where the requirements of Regulation 411.4.5 for automatic disconnection cannot be fulfilled by an overcurrent protective device, such as where the value of earth fault loop impedance (Zs) of a circuit is too high. The exposed-conductive-parts of that part of the installation must be connected to the TN earthing protective conductor or to a separate earth electrode which affords an impedance low enough to operate the RCD. In the latter case the circuit should be treated as a TT system and Regulations 411.5.1 to 411.5.3 apply.
  • Discrimination between circuit protective devices is achieved when, under fault conditions, the device electrically nearest to the fault operates, leaving other upstream protective devices still providing supplies to the remaining healthy circuits. Where two or more RCDs are in series, and where discrimination in their operation is necessary to prevent danger, the characteristics of the devices should be such that the intended discrimination is achieved.
  • RCDs in a TT system Where an installation forming part of a TT system is protected by a RCD, then either: the RCD should be located at the origin of the installation, or the part of the installation between the origin and the RCD complies with the requirements for protection by the use of Class II equipment or equivalent insulation. Where there is more than one origin, the above requirement applies to each origin.
  • Section 534 is unused Section 535 refers to Section 445
  • Section 537 provides the requirements for selection and suitability for the four different operating functions required within the term ‘Isolation and switching’
  • Switching or isolating devices are prohibited in combined protective and neutral (PEN) conductors and protective conductors except as permitted by Regulations 543.3.4 and as required by Regulation 537.1.5
  • (1) be inserted, where practicable, in the supply main circuit (2) manual operation (3) Be capable of cutting off the full load current (4) Be designed and/or installed so as to prevent inadvertent or unintentional switching on (5) Be placed and marked so as to be readily identifiable and convenient for their intended use (6) Require the open position of the contacts to be clearly visible or be clearly and reliably indicated
  • (1) Be capable of breaking the full load current of the relevant part of the installation. (2) Be Hand-held devices for direct interruption of the main circuit to be selected where applicable. (3) The means of operating devices (handles, push-buttons etc) for emergency switching to be clearly identifiable, preferably by colour. (4) Readily accessible at places of danger and, where appropriate, at any additional remote position from which that danger can be removed. (5) So placed and marked as to be readily identifiable and convenient for their intended use. (6) Such that its operation does not introduce a further danger or interfere with the complete operation necessary to remove the danger.
  • (1) Coloured red and have fixed to it (or adjacent to it) a permanent durable nameplate marked with the words ‘ FIREFIGHTER’S SWITCH’ (min. dimensions req’d). (2) The ON and OFF positions to be clearly indicated by lettering which can be easily read by someone standing on the ground. (3)The switch must have its OFF position at the top and be fitted with a lock or catch to prevent it being inadvertently returned to the ON position. (4) Most importantly, the switch must be installed so as to be accessible for operation by a firefighter. (5) Where more than one such switch is used, each switch must be clearly labeled to indicate the installation it controls.
  • IMDs are not covered in this presentation, the following slide relates to RCMs
  • The term protective conductor covered in this section relates to all the conductors used for protective earthing and protective bonding
  • Explain that protective earthing is provided for reasons of electrical safety and is divided into two parts. The first of these is source earthing, associated with the source of supply to an electrical installation . The second is electrical equipment earthing, associated with the electrical installation itself. Source earthing, sometimes called supply system earthing, is the provision of a connection between the source of energy - normally the distribution transformer secondary winding or generator winding - and the general mass of earth (Earth), via a source earth electrode. The provision and maintenance of source earthing is normally the responsibility of the owner of the source of energy, and should be carried out to an appropriate standard, such as BS 7430, Code of practice for Earthing. The purposes of source earthing are: •   To preserve the security of the supply network by limiting the potential of the live conductors (with respect to that of Earth) to a value consistent with their insulation. •   In the case of a TT system, to provide a path for earth fault current and protective conductor current to return to the source of energy via Earth. Without this path, devices for protection against electric shock and fault current to earth will not operate. Electrical equipment earthing , sometimes called electrical installation earthing, is the connection of the exposed-conductive-parts of an electrical installation to an appropriate means of earthing. Electrical equipment earthing is applicable in installations where the measure for protection against indirect contact is Earthed Equipotential Bonding and Automatic Disconnection of supply (EEBAD), as used in the majority of installations in the United Kingdom. The purpose of electrical equipment earthing is to allow operation of the devices for protection against electric shock and fault current to earth, permitting automatic disconnection of the supply to the faulty circuit in the event of an earth fault.
  • TN-S TN-C-S TT
  • Earth rods or pipes, or tapes or wires Earth plates Underground structural metalwork Welded metal reinforcement of concrete (except pre-stressed concrete) embedded in the earth Lead sheaths and other metal coverings of cables (where not precluded by 542.2.5) Other suitable underground metalwork
  • A separate MET with link is preferable and this would certainly be expected on medium/large installation. On domestic premises where there is a single consumer unit it is normal for the MET to be the consumer unit earthing bar.
  • The term protective conductor is a generic term relating to earthing conductors, circuit protective conductors, main protective bonding conductors and supplementary protective bonding conductors.
  • The c.s.a. of the conductor is to be: Not less than 2.5 mm 2 copper equivalent, if protected against mechanical damage (e.g. by a sheath or other form of mechanical protection, as the situation demands) is provided, and Not less than 4 mm 2 copper equivalent, if protection against mechanical damage is not provided.
  • 6 mm 2 16 mm 2 25 mm 2 Discuss the relevance of k by referring to Table 54.2, 54.3, 54.4, 54.5 and 54.6. An understanding of these tables will be required for the next slide when the adiabatic calculation is discussed.
  • (1) a conductor in a cable an insulated or bare conductor in a common enclosure with insulated live conductors a fixed bare or insulated conductor a metal covering, for example, the sheath, screen or armouring of a cable a metal conduit or other enclosure or electrically continuous support system for conductors an extraneous-conductive-part complying with Regulation 543.2.6. (2) 10 mm 2 (3) Gas pipes, oil pipes, flexible or pliable conduit, support wires or other flexible metallic parts, or constructional parts subject to mechanical stress in normal service, must not be used as protective conductors. (4) Regulation 543.2.6
  • 543.2.9 Where the circuit protective conductors of a final ring circuit are not formed by the metal covering or enclosure of a cable, they must be installed in the form of a ring with both ends connected to the earth terminal at the origin of the circuit. This will normally be at the distribution board or consumer unit. 543.3.1 Protective conductors must be suitably protected against mechanical and chemical deterioration and electrodynamic effects. 543.3.2 Apart from where protective conductors form part of a multicore cable or a cable trunking or conduit, protective conductors up to and including 6 mm 2 cross-sectional area must be insulated. Where the sheath of a cable incorporates an uninsulated protective conductor up to and including 6 mm 2 cross-sectional area, the protective conductor must be protected by insulating sleeving.
  • When energized and in normal use, some electrical equipment can cause current to flow in the circuit protective conductors. This process is referred to as functional earthing as the equipment concerned requires the current to flow in the protective conductor to function or operate normally. The requirements of BS 7671 relate to individual equipment and circuit protective conductor currents. The requirements depend on the value of these currents. Regulation Group 543.7 Earthing requirements for the installation of equipment having high protective conductor currents was originally considered to be a special installation (Section 607 High protective conductor currents of the 16 th edition). These requirements are detailed and it may be difficult for students to remember all the different requirements relating to different leakage current values. The most common requirement to be met probably relates to ring final circuits.
  • (1) Equipment which in normal service, will have a protective conductor current exceeding 3.5 mA, but less than 10 mA must be either: permanently connected to the fixed wiring of the installation without the use of a plug and socket, or connected by means of a connector complying with BS EN 60309-2 (that is, an industrial-type connector) (2) Five options are provided in Regulation 543.7.1.3. (i) A single protective conductor having a c.s.a. of not less than 10 mm 2 . (ii) A single copper protective conductor having a c.s.a. of not less than 4 mm 2 , the protective conductor being enclosed to provide additional mechanical protection. (iii) An earth monitoring system to BS 4444 (iv) A double-wound transformer or equivalent in which the input and output circuits are electrically separate (v) Two individual protective conductors, each one complying with the requirements of Section 543. It is permitted for the two protective conductors to be of different types (for further information see 543.7.1.3 (iii)).
  • The label should be so positioned as to be visible to a person modifying or extending the circuit.
  • Main protective bonding conductors are required to establish the requirements for protective equipotential bonding (an indispensable part of the most commonly used protective measure, Automatic Disconnection of Supply (ADS)).
  • Exercise (1) 10 mm 2 (2) 25 mm 2 (3) The main bonding connection to any gas, water or other service must be made as near as practicable to the point of entry of that service into the premises. Where there is an insulating section or insert at that point, or there is a meter, the connection should be made to the consumer’s hard metal pipework (not to a lead pipe or a flexible pipe for example) and before any branch pipework. Where practicable, the connection is required to be made within 600 mm of the meter outlet union or at the point of entry of the service to the building if the meter is external.
  • The requirement for supplementary bonding where disconnection times could not be met is covered by Regulation 411.3.2.6. However this would be an unusual situation.
  • Chapter 55 covers is in some ways different from the other chapters of BS 7671 in that it relates to electrical equipment. The Learning Guide has two sections, one covering Sections 551, 552, 553, 554 and 555, the other covering 559. The requirements of 559 now include requirements that were originally considered to be a special installation or location in the 16 th edition (Section 611 Installation of highway power supplies, street furniture and street located equipment) although this is only part of 559.
  • Requirements are included for: supply to an installation which is not connected to a system for distribution of electricity to the public, supply to an installation as an alternative to a system for distribution of electricity to the public, supply to an installation in parallel with a system for distribution of electricity to the public, appropriate combination of the above. When designing or installing generators special consideration needs to be given to the prospective short-circuit current and prospective earth fault current for each source as well as: Capacity and operating characteristics Overcurrent protection Fault protection Synchronising (if operating in parallel) Locking-off/interlock devices
  • A system of locks with a single transferable key A three-position break-before-make changeover switch An automatic changeover switching device with a suitable interlock Other means providing equivalent security
  • (1) Socket-outlets mounted on a wall or similar structure should be mounted at a height above the floor or any working surface to minimize the risk of mechanical damage, including damage that may occur to the flexible cord caused during insertion or withdrawal of the plug. Note: there are also requirements for the mounting height of accessories in Part ‘M’ of the Building Regulations (2) Where portable equipment is likely to be used, provision should be made so that the equipment can be fed from an adjacent and conveniently accessible socket outlet, taking into account the length of flexible cord normally fitted to appliances and luminaires.
  • (1) They are used for: Underfloor electric heating in dwellings and other premises (the requirements of Section 753 must also be met in this case) Heating of the playing area at open-air sports stadiums Heating roads and pavements to prevent icing Soil warming in agricultural and horticultural premises Industrial heating applications Trace heating of pipes and vessels. (2) Section 753 When installing heating conductors and cables care must be taken to prevent mechanical damage, damage from corrosion, thermal effects to adjacent material and to ensure the system temperature is not exceeded
  • Where a step-up transformer is used, a linked switch must be provided for disconnecting the transformer from all live conductors of the supply.
  • • Equipment of the owner or operator of a system for distribution of electricity to the public (distributors) • high voltage signs supplied at low voltage (such as neon tubes) • signs and luminous discharge tube installations operating from a no-load rated output voltage exceeding 1 kV but not exceeding 10 kV ( BS EN 50107 ) • temporary festoon lighting
  • Luminaire suitable for direct mounting on non-combustible surfaces only Luminaire suitable for direct mounting on normally flammable surfaces Luminaire with limited surface temperature Electronic convertor for an extra-low voltage lighting installation Transformer –short-circuit proof (both inherently and non-inherently)
  • (1) the maximum power dissipated by the lamp (2) the fire resistance of adjacent material (3) the minimum distance to the combustible materials, including those in the path of spotlight beams
  • A ceiling rose to BS 67 A batten lampholder A luminaire to BS EN 60598 A suitable socket-outlet to 1363-2, BS 546 or BS EN 60309-2 A plug-in lighting distribution unit to BS 5733 A connection unit to BS 1363-4 Appropriate terminals enclosed in a box A device for connecting a luminaire (DCL)
  • Where the fixing is intended to support a pendant luminaire it must be able to carry a mass of not less than 5 kg. If the mass of the luminaire is greater than 5kg, then the installer must ensure the fixing means can support the weight of the pendant luminaire. Remember the TV programme Only fools and horses (this was down to them releasing the wrong winch but it’s still a good story!)
  • 16 A (2) Bayonet lampholders B15 and B22 should comply with BS EN 61184 and have the temperature rating T2 (lamp cap temperatures up to and including 210 0 C) (3) Except for E14 and E27 lampholders to BS 60238 , circuits connected to TN or TT systems must have the outer contact of every ES or centre bayonet cap type lampholder connected to the neutral conductor. This requirement also applies to track mounted systems.
  • Through wiring is only permitted if the luminaire is designed for that purpose. For luminaires complying with BS EN 60598 , but with no temperature markings, heat resistant cables are not required. Luminaires to this standard with temperature marking will require suitable heat resisting cables. Where no information is provided, heat resisting cable (or conductors insulated in accordance with Regulation 559.6.2.2) must be used.
  • (1) 6 mm 2 (and not less than the supply neutral) (2) 5 seconds (3) 2.50 m
  • It is normally the case that safety service systems will be required to operate at times of “mains failure” and also continue their effective operation through the harsh environment of a fire condition. It is imperative that these potential life saving installations have adequate consideration given for their design, installation and continued verification (via regular inspection and testing) to ensure that they have and maintain, the appropriate level of operational integrity.
  • The integrity of the electrical source is of paramount importance, and as such must be of appropriate capacity capable of supplying the total load and installed as fixed equipment, located in an area that is only accessible to appropriate personnel. The majority of safety sources take the form of either a dedicated, constantly charged battery, or a combination of battery and generator set. However, the less common system of separate independent feeder supplies is also recognized, providing appropriate assurance is obtained from the supplying network or networks that these supplies are unlikely to fail concurrently. Exercise. (1) storage batteries primary cells generator sets independent of the normal supply a separate feeder of the supply network effectively independent of the normal feeder.
  • Short break. An automatic supply available between 0.15 s and 0.5 s Medium break. An automatic supply available between 5 s and 15 s
  • The required minimum operational design life of batteries should be in accordance with BS EN 50171 , with a minimum declared life of (1) 10 years for central power supply sources and (2) 5 years for low power supply sources.
  • 17th Edition Parts 53 To 56

    1. 1. Requirements for Electrical Installations IEE Wiring Regulations 17 th Edition Part 5 Chapters 53 -> 56 (Courtesy of NICEIC)
    2. 3. 53 – Protection, Isolation, Switching, Control and Monitoring <ul><li>Dispersed content from 16 th (Chapter 46 and Chapter 53 etc.) has now been brought under one long heading </li></ul><ul><li>The term ‘isolation and switching’, as used in BS 7671 , refers to four distinct functions: </li></ul><ul><li>Also study Table 53.2 (new) </li></ul>
    3. 4. 530.3 – General and common requirements <ul><li>In multi-phase circuits, the moving contacts of all poles of a multi-pole device should be so coupled mechanically that they make and break substantially together except: </li></ul><ul><ul><li>that contacts solely intended for the neutral may close before and open after the other contacts </li></ul></ul><ul><ul><li>where in accordance with Regulation 543.3.4 (protective conductors). </li></ul></ul><ul><li>Exercise: What are the requirements relating to single-pole switching or protective devices inserted in the neutral conductor? </li></ul>
    4. 5. 530 – General and common requirements <ul><li>For installations with a 230 V single-phase supply rated up to 100 A that are under the control of ordinary persons, switchgear and controlgear should either: </li></ul><ul><ul><li>comply with BS EN 60439-3 and Regulation 432.1 of BS 7671 , or </li></ul></ul><ul><ul><li>be a consumer unit incorporating components complying with BS EN 60439-3 . </li></ul></ul>
    5. 6. 531 – Fault protection by automatic disconnection of supply <ul><li>Summary of RCD requirements: </li></ul><ul><ul><li>An RCD should be capable of disconnecting all line conductors at substantially the same time. </li></ul></ul><ul><ul><li>An RCD cannot be used for fault protection on its own, for example where a circuit does not contain a protective conductor . </li></ul></ul><ul><li>Exercise: What are the requirements relating to RCDs when: </li></ul><ul><li>used for fault protection, with, but separate from an overcurrent device </li></ul><ul><li>In a TN system where Regulation 411.4.5 for automatic disconnection cannot be fulfilled by an overcurrent protective device </li></ul>
    6. 7. 531 – Fault protection by automatic disconnection of supply <ul><li>Discrimination between devices is achieved the device electrically nearest to the fault operates, leaving other upstream protective device(s) still supplying other circuits. </li></ul>Discrimination using time-delay RCD
    7. 8. 531 – Fault protection by automatic disconnection of supply An RCD supplied direct from the origin of an installation forming part of a TT system
    8. 9. 532 – Devices for protection against fire <ul><li>Where it is necessary to limit the consequence of fault currents with respect to the risk of fire , an RCD should be installed, which: </li></ul><ul><ul><li>complies with Regulation Group 531.2 for fault protection and </li></ul></ul><ul><ul><li>is installed at the origin of the circuit to be protected and </li></ul></ul><ul><ul><li>switches all live conductors, and </li></ul></ul><ul><ul><li>has a rated residual operating current ≤300 mA. </li></ul></ul>
    9. 10. 533 – Devices for protection against overcurrent <ul><li>Section 533 provides further information relating to the selection of devices for : </li></ul><ul><ul><li>Overload and </li></ul></ul><ul><ul><li>Fault current </li></ul></ul><ul><li>(To be read in conjunction with Chapter 43) </li></ul>
    10. 11. 536 – Co-ordination of protective devices <ul><li>Where co-ordination of series protective devices is necessary to prevent danger and where required for proper functioning of the installation, consideration should be given to selectivity and/or any necessary back-up protection. </li></ul><ul><li>Where selectivity between overcurrent devices or RCDs is necessary to prevent danger and where required for proper functioning of the installation, the manufacturers’ instructions must be taken into account. </li></ul>
    11. 12. 537 – Isolation and switching <ul><li>The term ‘ isolation and switching ’, relates to four distinct operating functions which are defined in Part 2 of BS 7671 : </li></ul><ul><ul><li>Isolation (537.2) </li></ul></ul><ul><ul><li>Switching off for mechanical maintenance (537.3) </li></ul></ul><ul><ul><li>Emergency switching (537.4) </li></ul></ul><ul><ul><li>Functional switching (537.5) </li></ul></ul><ul><li>Firefighter’s switches (537.6) are also covered in this section. </li></ul>
    12. 13. 537 – Isolation and switching <ul><li>Table 53.2 of BS 7671 provides guidance on the selection of protective, isolation and switching devices </li></ul>
    13. 14. 537 – G eneral requirements <ul><li>Each installation to have provision for disconnecting supply </li></ul><ul><li>A main linked switch or linked circuit-breaker is required as near as practicable to the origin of every installation as a means of switching the supply on load and as a means of isolation </li></ul><ul><li>Where an installation is supplied from more than one source, a main switch is required for each source of supply or alternatively, a suitable interlock system must be provided. </li></ul><ul><li>Exercise: What are the requirements relating to switching or isolating devices in PEN and protective conductors? </li></ul>
    14. 15. 537.1.4 – General requirements <ul><li>A main switch intended for operation by ordinary persons e.g. of a household or similar installation, should interrupt both live conductors of a single-phase supply </li></ul>
    15. 16. 537.2 – Isolation <ul><li>Isolation is the function that allows operatives to work safely on electrical equipment, and is defined as: </li></ul><ul><li>‘ A function intended to cut off for reasons of safety the supply from all, or a discrete section, of the installation by separating the installation or section from every source of electrical energy .’ </li></ul>
    16. 17. Isolation <ul><li>Items to be considered in relation to isolation devices include: </li></ul><ul><ul><li>Numbers of poles to be isolated </li></ul></ul><ul><ul><li>Isolation of groups and inconvenience </li></ul></ul><ul><ul><li>Devices designed and/or installed to prevent unintentional or inadvertent closure </li></ul></ul><ul><ul><li>Isolation devices to be clearly identified and indicate the installation or circuit it isolates </li></ul></ul>
    17. 18. Isolation <ul><li>Where an isolating device is placed remote from the equipment to be isolated, provision must be made to secure the device in the open position. </li></ul>
    18. 19. Isolation <ul><li>Where there is more than one source of supply a durable warning notice is required </li></ul>
    19. 20. Isolation requirements for TN-S systems Single-phase Three-phase
    20. 21. Isolation requirements for TN-C-S systems Single-phase Three-phase
    21. 22. Isolation requirements for TT & IT systems Single-phase Three-phase
    22. 23. 537.3 – Switching off for mechanical maintenance <ul><li>Switching off for mechanical maintenance is not necessarily intended to provide protection against electric shock. </li></ul><ul><li>Switching off for mechanical maintenance is to enable non-electrical maintenance to be performed safely without the risk of burns or injury from mechanical movement. </li></ul><ul><li>Mechanical maintenance is defined as: </li></ul><ul><li>‘ The replacement, refurbishment or cleaning of lamps and non-electrical parts of equipment, plant and machinery.’ </li></ul>
    23. 24. 537.3 – Switching off for mechanical maintenance <ul><li>The replacement of a belt from an electric motor to a machine may be able to be undertaken after switching off for mechanical maintenance </li></ul>
    24. 25. Exercise: Switching off for mechanical maintenance <ul><li>Refer to Regulation Group 537.3. </li></ul><ul><li>Where should such a device be inserted? </li></ul><ul><li>How should the device be operated? </li></ul><ul><li>What is its capability for cutting off current? </li></ul><ul><li>Could such a device be intentional switched back on? </li></ul><ul><li>Do such device have to be identified </li></ul><ul><li>How does one know when such a device is off? </li></ul>
    25. 26. Switching off for mechanical maintenance <ul><li>A shower or cooker switch may perform the function of switching off for mechanical maintenance </li></ul>
    26. 27. 537.4 – Emergency Switching <ul><li>Where, in case of danger, there is necessity for immediate interruption of supply, an interrupting device must be installed in such a way that it can be easily recognized and effectively and rapidly operated. </li></ul><ul><li>Emergency switching is defined as: </li></ul><ul><li>‘ An operation intended to remove, as quickly as possible, danger, which may have occurred unexpectedly.’ </li></ul>
    27. 28. Emergency Switching <ul><li>The means for emergency switching must consist of either: </li></ul><ul><ul><li>a single switching device directly cutting off the incoming supply, or </li></ul></ul><ul><ul><li>a combination of several items of equipment operated by a single action and resulting in the removal of the hazard by cutting off the appropriate supply. </li></ul></ul>
    28. 29. Exercise: Emergency switching <ul><li>What are the requirements for emergency switching in relation to: </li></ul><ul><li>(1) Full load current </li></ul><ul><li>(2) hand-held devices </li></ul><ul><li>(3) identification of emergency switching devices </li></ul><ul><li>(4) Positioning and accessibility </li></ul><ul><li>(5) Positioning and identification </li></ul><ul><li>(6) Further danger </li></ul>
    29. 30. 537.5 – Functional switching <ul><li>Functional switching is provided for the users of electrical installations for normal operating purposes to control items of current-using electrical equipment. The equipment may be controlled either individually or in groups and via a manual or automatic operation. </li></ul><ul><li>Functional switching is defined as: </li></ul><ul><li>‘ An operation intended to switch ‘on’ or ‘off’ or vary the supply of electrical energy to all or part of an installation for normal operating purposes’ </li></ul>
    30. 31. Functional switching <ul><li>Examples of functional switching devices include: </li></ul><ul><ul><li>a switch in a socket-outlet </li></ul></ul><ul><ul><li>a contactor switching the supply </li></ul></ul><ul><ul><li>Push buttons </li></ul></ul><ul><ul><li>a thermostat </li></ul></ul><ul><ul><li>a pressure switch </li></ul></ul><ul><ul><li>a microswitch </li></ul></ul>
    31. 32. 537.6 – Firefighter’s switches <ul><li>A firefighter’s switch is a device intended for use by the fire service, although not exclusively so. </li></ul><ul><li>Its purpose is to de-energize designated parts of an installation that operate at a voltage in excess of low voltage ( e.g. neon lighting ) </li></ul>
    32. 33. Exercise: Firefighter’s switches <ul><li>What are the requirements for firefighter’s switches relating to: </li></ul><ul><li>Colour and labelling </li></ul><ul><li>Visibility and position of the ON and OFF indication </li></ul><ul><li>Accessibility, where there are more than one firefighter’s switches </li></ul><ul><li>Maximum height </li></ul>
    33. 34. 538 – Monitoring <ul><li>Section 538 of BS 7671 provides the requirements relating to monitoring. </li></ul><ul><li>Within Section 538 there are two types of monitoring: </li></ul><ul><li>Insulation monitoring devices (IMDs) for IT systems (538.1), </li></ul><ul><li>and Residual current monitor (RCM) (538.4) </li></ul>
    34. 35. 538.4 – Residual current (RCM) monitor <ul><li>An RCM permanently monitors any leakage current in the downstream installation or part of it; such a device is NOT intended to provide protection against electric shock </li></ul><ul><li>In supply systems, RCMs may be installed to reduce the risk of operation of the protective device in the event of excessive leakage current of the installation or the connected appliances. </li></ul><ul><li>Where an RCD is installed upstream of the RCM, it is recommended that the RCM has a rated residual operating current not exceeding a third of that of the RCD . </li></ul>
    35. 37. Protective Earthing <ul><li>Is provided for reasons of electrical safety, and is divided into two parts. Briefly discuss each, before moving on </li></ul><ul><li>1. Source earthing 2. Electrical equipment earthing </li></ul>
    36. 38. 542.1 – Main earthing terminal (MET) <ul><li>The main earthing terminal (MET) of an installation should be connected with Earth by one of the following earthing systems: </li></ul><ul><ul><li>TN-S, to the earthed point of the source of energy (part of the connection may be formed by the distributor’s lines and equipment), </li></ul></ul><ul><ul><li>TN-C-S, where protective multiple earthing is provided, to the neutral of the source of energy, </li></ul></ul><ul><ul><li>TT and IT, via an earthing conductor to an earth electrode. </li></ul></ul>
    37. 39. Types of earthing arrangement
    38. 40. 542.2 – Types of earth electrode <ul><li>Seven distinct types of earth electrode are recognized in BS 7671. </li></ul><ul><li>Exercise: </li></ul><ul><li>Identify all suitable earth electrodes recognized </li></ul>
    39. 41. Earth rods and pipes <ul><li>Although suitable for many, if not most, earthing applications, Solid rod or pipe earth electrodes are not particularly well suited to situations where rock or other hard strata prevent deep driving </li></ul>
    40. 42. Earth plates <ul><li>Earth plates are usually of copper or cast iron, and normally not more than 1.2 metres square. They should be set vertically, as shown. </li></ul>
    41. 43. 542.3 – Earthing conductor <ul><li>The earthing conductor of an electrical installation is the protective conductor connecting the Main Earthing Terminal (MET) of the installation with the means of earthing (the external earthing system). </li></ul>
    42. 44. Table 54.1 – Minimum cross-sectional area of a buried earthing conductor * Note: The covering of a green-and-yellow single-core cable is not a sheath . Protected against mechanical damage NOT protected against mechanical damage Protected against corrosion by a sheath* 2.5 mm 2 copper 10 mm 2 steel 16 mm 2 copper 16 mm 2 coated steel NOT protected against corrosion 25 mm 2 copper 50 mm 2 steel
    43. 45. 542.4 – MET connecting the earthing conductor to installation protective conductors
    44. 46. Main earthing terminal (MET) <ul><li>To facilitate measurement of the resistance of the earthing arrangement, a means of disconnecting the installation earthing conductor will be required. This provision may be combined with the main earthing terminal. </li></ul>
    45. 47. 543 – Protective conductors <ul><li>Regulation Group 543 provides information on the selection of both, type and cross-sectional area of protective conductors. </li></ul><ul><li>Protective conductors are conductors provided for the purposes of safety, for example protection against electric shock. </li></ul><ul><li>Exercise: </li></ul><ul><li>What types of conductors are covered by the generic term ‘ protective conductors ’? </li></ul>
    46. 48. Cross-sectional areas of protective conductors <ul><li>There are two methods that may be employed when choosing a protective conductor as required by Regulation 543.1.1. The cross sectional area (csa) of every protective conductor (other than protective bonding conductors, which are discussed later) must either be: </li></ul><ul><ul><li>Selected (in accordance with Regulation 543.1.4) or </li></ul></ul><ul><ul><li>Calculated (in accordance with Regulation 543.1.3) </li></ul></ul>
    47. 49. Exercise: CSA of protective conductors <ul><li>Except where a protective conductor is an integral part of a cable, formed by a conduit, ducting or trunking or contained in an enclosure of a wiring system what is the minimum csa for a copper protective conductor if: </li></ul><ul><li>protection against mechanical damage is provided, and </li></ul><ul><li>mechanical protection is not provided. </li></ul>
    48. 50. Selection of protective conductor (reference to the related line conductor and Table 54.7 Exercise: What is the csa of a protective conductor selected from Table 54.7 where a line conductor csa is (1) 6 mm 2 , (2) 25 mm 2 , and (3) 50 mm 2 (same material as the line conductor)
    49. 51. Calculation of protective conductors (adiabatic equation) <ul><li>Where the “selection” method has not been utilized, every protective conductor, other than a protective bonding conductor, will need to be verified by use of the calculation method. </li></ul>Ah yes, I remember the ‘good-old’ adiabatic equation
    50. 52. Example question <ul><li>Calculate the minimum c.s.a. for a circuit protective conductor for a circuit protected by a 40 A BS 88 fuse (assume maximum Z s ( refer to Table 41.4 of BS 7671 ) and 5 s disconnection time). The cable is 70 0 C thermoplastic single insulated with copper conductors, bunched with cables. The nominal voltage is 230 V. </li></ul>
    51. 53. Step 1 <ul><li>I (current) = V/ Z s = 230/1.35 = 170 A. </li></ul><ul><li>t (disconnection time) for a 40 A BS 88 fuse with 170 A flowing is 5 seconds ( refer to Appendix 3 Table 3.3B ). </li></ul><ul><li>k (from Table 54.3) 115 (cable assumed to be less than 300 mm 2 , for a 40 A device). </li></ul><ul><li> S = 3.3 mm 2 . Consequently, a 4 mm 2 cable would be required. </li></ul>
    52. 54. Exercise: Types of protective conductor <ul><ul><li>Apart from metallic protective conductors (e.g. swa, conduit etc.) what is the minimum size of a protective conductor if it is not made of copper? </li></ul></ul><ul><ul><li>W hat types of extraneous-conductive-part cannot be used as a protective conductor? </li></ul></ul><ul><ul><li>What Regulation outlines the requirements where extraneous-conductive-parts are to be used? </li></ul></ul><ul><ul><li>BS 7671 lists seven types of protective conductor, Apart from a single-core cable (coloured green-and-yellow), identify four others . </li></ul></ul>
    53. 55. Metallic enclosures used as a protective conductor <ul><li>Where a metal enclosure or frame of low voltage switchgear or controlgear is used as a protective conductor, its electrical continuity must be assured, either by construction or by suitable connection. </li></ul>
    54. 56. 543.2.7 – Earthing tail requirement <ul><li>Where metallic conduit, trunking, etc. is used for a protective conductor, the earthing terminal of each accessory is required to be connected by a separate protective conductor to the earthing terminal incorporated in the associated box or other enclosure </li></ul>
    55. 57. Exercise: Protective conductors <ul><li>What is the specific requirement for the connection of circuit protective conductors of a ring final circuit (where they are not formed by the metal covering or enclosure of a cable)? </li></ul><ul><li>What are the three specific external influences that BS 7671 requires protective conductors be protected against? </li></ul><ul><li>What are the requirements for the insulation of circuit protective conductors? </li></ul>
    56. 58. 543.7 – Earthing requirements for the installation of equipment having high protective conductor currents <ul><li>When energized and in normal use, some electrical equipment can cause current to flow in the circuit protective conductors. Equipment having such currents may include: </li></ul><ul><ul><li>Information technology equipment , </li></ul></ul><ul><ul><li>Industrial and telecommunications equipment with radio-frequency interference suppression filtering, </li></ul></ul><ul><ul><li>High frequency luminaires, and </li></ul></ul><ul><ul><li>Certain types of heating elements </li></ul></ul>
    57. 59. 543.7 – Earthing requirements for the installation of equipment having high protective conductor currents <ul><li>Any equipment or circuits having a protective conductor current greater than 3.5 mA may increase the risk of electric shock. There are therefore, additional requirements stipulated for these circuits. </li></ul>
    58. 60. Exercise: High protective conductor currents <ul><li>(1) What are the two alternatives for connection to a piece of equipment having a protective conductor current exceeding 3.5 mA, but less than 10 mA? </li></ul><ul><li>List three of the five options for protective conductor connections in final circuits and distribution circuits intended to supply an item (or items) of equipment, where the total protective conductor current is likely to exceed 10 mA </li></ul>
    59. 61. 543.7.1.4 – Where two protective conductors are used … NOTE: The ends of protective conductors to be terminated independently; the same is true at distribution boards
    60. 62. High protective conductor current - Labelling <ul><li>A label (shown) or similar information, should be provided at the distribution board, indicating those circuits having a high protective conductor currents. </li></ul>
    61. 63. Cross-sectional area of main bonding conductors <ul><li>The purpose of main equipotential bonding was discussed previously in Chapter 41 (Section 411) </li></ul><ul><li>The requirements for the minimum cross-sectional area (csa) of a main protective bonding conductor are given in Regulation 544.1.2 and (for PME conditions) Table 54.8. </li></ul><ul><li>Main bonding conductors buried in the ground are subject to additionally requirements. (Refer to Regulation 542-03-01 for earthing conductors.) </li></ul>
    62. 64. Where Protective Multiple Earthing (PME) conditions do NOT apply <ul><li>Where PME conditions do not apply , a main bonding conductor should have a csa of not less than half that required for the earthing conductor of the installation, and not less than 6 mm 2 . </li></ul><ul><li>NOTE: The csa need not exceed 25 mm 2 if the bonding conductor is made of copper, or, if of other metals, a csa affording equivalent conductance. </li></ul>
    63. 65. Where Protective Multiple Earthing (PME) conditions apply … <ul><li>the main bonding conductors should be selected in accordance with the neutral conductor of the incoming supply and Table 54.8. should be followed. </li></ul><ul><li>Exercise: What would be the minimum csa of a copper main protective bonding conductor where the neutral of the incoming supply is: </li></ul><ul><li>25 mm 2 </li></ul><ul><li>70 mm 2 </li></ul><ul><li>(3) What are the requirements relating to the location of the main equipotential connection to an incoming service (gas, water etc), and where should the connection be made if there is an insulating section? </li></ul>
    64. 66. Connections to extraneous-conductive-parts <ul><li>Main bonding connections to metal pipework should normally be made using bonding clamps complying with BS 951: Specification for clamps for earthing and bonding purposes . Clamps should be selected to suit both the pipe diameter and bonding conductor size . </li></ul>
    65. 67. Supplementary bonding <ul><li>Supplementary bonding was covered in Section 415 (Additional protection). </li></ul><ul><li>Its use may be required where disconnection times cannot be met or where required due to the special nature of the installation . </li></ul>The above diagram is meant as an example only and is not necessarily a requirement
    66. 68. 544.2 – Supplementary bonding conductor sizes
    67. 69. 547.2.5 – Supplementary bonding to a fixed appliance <ul><li>Where a short flexible cord is used to connect a fixed appliance, the protective conductor can provide both circuit protective conductor and supplementary bonding conductor functions </li></ul>
    68. 71. 551 – Low voltage generating sets <ul><li>Section 551 applies to both low voltage and extra-low voltage installations which incorporate generating sets intended to supply, either continuously or occasionally, all or part of the installation. </li></ul>
    69. 72. Additional requirements where a generating set provides a supply as a switched alternative <ul><li>To prevent parallel operation, suitable precautions may include: </li></ul><ul><ul><li>an electrical, mechanical or electro-mechanical interlock between the operating mechanisms or control circuits of the change-over switching devices </li></ul></ul><ul><li>Exercise: </li></ul><ul><li>Study Regulation Group 551.6 to identify three further acceptable precautions </li></ul>
    70. 73. Additional requirements where a generating set may operate in parallel with other sources <ul><li>Several additional requirements are required for installations where the generating set may operate in parallel with the system for distribution of electricity to the public . </li></ul><ul><li>Exercise: Study Regulation Group 551.7 </li></ul>
    71. 74. 551.4.4 – Low voltage generating sets <ul><li>Where the installation and generating set are NOT permanently fixed, an RCD with a rated residual operating current of not more than 30 mA should be installed in accordance with Regulation 415.1 … </li></ul>The RCD is to protect every circuit!
    72. 75. 552 – Rotating machines <ul><li>Motors require additional consideration in relation to their starting currents and control equipment. </li></ul><ul><li>The starting, accelerating and load currents of a motor must be considered when assessing the suitability of the equipment and cables carrying these currents. </li></ul><ul><li>Every motor should be fitted with means to prevent automatic restarting after a stoppage due to a drop in voltage or failure of supply, where unexpected restarting of the motor might cause danger. </li></ul>
    73. 76. 552 – Rotating machines <ul><li>Every electric motor having a rating in excess of 0.37 kW should be provided with control equipment incorporating means of protection against overload of the motor. </li></ul>
    74. 77. Exercise: Accessories (553) <ul><li>What are the requirements of BS 7671 relating to the mounting height of socket-outlets? </li></ul><ul><li>What are the requirements relating to the provision of socket-outlets to ensure that the length of flexible cords are not excessive? </li></ul><ul><li>For requirements relating to: cable couplers, see Regulation Group 553.2; for plugs and socket-outlet types, see Table 55.1 </li></ul>
    75. 78. 554 – Current-using equipment <ul><li>Electrode water heaters or boilers </li></ul><ul><li>Used to heat water or raise steam in certain domestic, commercial and industrial applications. They can be either single-phase or three-phase </li></ul><ul><li>Typical applications include saunas, central heating, humidifying, cleaning and sterilizing. Electrode boilers can be low voltage, high voltage,. </li></ul><ul><li>Special requirements must be complied with relating to: Earthing and bonding, Overcurrent protection, and Isolation and Switching </li></ul>
    76. 79. Electrode water heaters and boilers Single-phase & three-phase uninsulated electrode boilers
    77. 80. Electrode water heaters and boilers <ul><li>Where an electrode water heater or electrode boiler is not piped to a water supply or is in contact with any earthed metal, it is said to be ‘insulated’ and different requirements apply </li></ul>Single-phase insulated electrode boiler
    78. 81. Water heaters having immersed and uninsulated heating elements <ul><li>A single-phase water boiler or heater having an uninsulated heating element immersed in water is deemed not to be an electrode water heater or electrode boiler . </li></ul><ul><li>The difference in this case is that the resistive element between line and neutral is continuous and the current does not flow through the water. ( Specific requirements apply to these type of boilers (Regulation Group 554.3 refers). </li></ul>
    79. 82. 554.4 – Heating conductors and cables <ul><li>Heating conductors and cables are specifically designed to generate heat. </li></ul>Exercise: (1) State typical applications where heating conductors and cables might be used (2) What other section of BS 7671 refers to these installations? (3) When installing such systems, what must be prevented from happening?
    80. 83. 555 – Autotransformers and step-up transformers <ul><li>Where an autotransformer is connected to a circuit having a neutral conductor, the common terminal of the winding must be connected to the neutral conductor. </li></ul>Exercise: What are the switching requirements relating to a step-up transformer? Auto-transformer
    81. 84. 559 – Luminaires and lighting installations <ul><li>Section 559 applies to luminaires (lighting fittings) and lighting installations intended to be part of the fixed installation and to highway power supplies and street furniture. </li></ul><ul><li>The requirements include: </li></ul><ul><ul><li>Fixed outdoor lighting installations </li></ul></ul><ul><ul><li>Extra-low voltage installations supplied up to 50 V a.c. or 120 V d.c. </li></ul></ul><ul><ul><li>Lighting for display stands </li></ul></ul><ul><ul><li>Exercise: List the types of lighting installations that Section 559 does not apply to (or are excluded within outdoor lighting installations) </li></ul></ul>
    82. 85. 559.3 – Outdoor lighting Installations <ul><li>Lighting installations for roads, car parks, parks, gardens, sporting areas, places open to the public, illumination of monuments and floodlighting are included within BS 7671 . </li></ul>
    83. 86. 559.3 – Outdoor lighting Installations <ul><li>And so are … </li></ul><ul><li>Lighting arrangements in: </li></ul><ul><ul><li>telephone kiosks, </li></ul></ul><ul><ul><li>bus shelters, </li></ul></ul><ul><ul><li>advertising panels, and </li></ul></ul><ul><ul><li>town plans </li></ul></ul>
    84. 87. 559.3 – Outdoor lighting Installations <ul><li>As too are … Road signs and traffic signal systems </li></ul>
    85. 88. Selection of symbols used in Section 559 (Table 55.2) 5 2 1 3 Exercise: What do the above symbols ( 1 to 5 ) relate to? 4
    86. 89. 559.5 – Protection against fire <ul><li>When selecting luminaires, consideration should be given to the thermal effects of radiant and convection energy generated by a luminaire with respect to the surroundings. </li></ul><ul><li>Exercise: What are the three main effects that need to taken into account to provide protection against fire when selecting or erecting a luminaire? </li></ul>
    87. 90. Connection of luminaires to the fixed wiring <ul><li>At each fixed lighting point or position, one of the connection devices listed in Regulation 559.6.1.1, such as a pendant set or luminaire supporting coupling (LSC) should be used. </li></ul><ul><li>Exercise: List four other devices for the connection of a luminaire </li></ul>Luminaire supporting coupling Pendant set
    88. 91. A typical pendant and ceiling rose arrangement <ul><li>Ceiling roses should only be used for one outgoing flexible cord unless they are designed for multiple pendants. </li></ul><ul><li>Their use is also restricted to circuits not exceeding 250 V. </li></ul>
    89. 92. 559.6.1.5 – Fixing of luminaires <ul><li>Luminaires must be fixed securely, and the means of fixing must be able to support the weight of the luminaire. </li></ul><ul><li>Cables and cords between the fixing means and the luminaire should be installed to accommodate any expected stress in the conductors or terminals so as not to impair the safety or operation of the luminaire. </li></ul><ul><li>Exercise: </li></ul><ul><li>What is the minimum mass a fixing for a pendant luminaire should be able to support? </li></ul><ul><li>What should be ensured if the weight exceeds the minimum mass specified? </li></ul>
    90. 93. Exercise: Fixing of luminaires (559.6.1.5) <ul><li>What should be the temperature rating for bayonet cap lampholders B15 and B22? </li></ul><ul><li>Except for E14 and E27 lampholders, when using ES or centre bayonet cap type lampholders which part of the lampholder should the neutral be connected to? </li></ul><ul><li>Lighting circuits incorporating B15 (SBC), B22 (BC), E14 (SES), E27 (ES), or E40 (GES) lampholders should be protected by an overcurrent device having a rating not exceeding …? </li></ul>
    91. 94. 559.6.2 – Through wiring
    92. 95. 559.10 – Requirements for outdoor lighting, highway power supplies and street furniture <ul><li>There are several specific requirements relating to street furniture including: </li></ul><ul><ul><li>Access doors </li></ul></ul><ul><ul><li>Intermediate Barriers </li></ul></ul><ul><ul><li>Access to lamps </li></ul></ul><ul><ul><li>Earthing </li></ul></ul><ul><ul><li>External influences </li></ul></ul><ul><ul><li>Isolation & switching </li></ul></ul><ul><li>(see Section 559.10 of BS 7671 </li></ul>
    93. 96. Exercise: Outdoor lighting installations, highway power supplies etc. <ul><li>(1) What is the minimum size copper earthing conductor permitted for street electrical fixture? </li></ul><ul><li>(2) What is the maximum disconnection time for all highway power supplies feeding fixed equipment? </li></ul><ul><li>(3) A door in street furniture giving access to electrical equipment must be locked with a key or a tool if it is located less than what height above ground level? </li></ul>
    94. 97. 559.10.3.2 – Requirements for outdoor lighting installations, highway power supplies etc. <ul><li>Recommendation for additional protection in the form of an ≤30 mA RCD to be provided for lighting installations within: </li></ul><ul><ul><li>telephone kiosks, </li></ul></ul><ul><ul><li>bus shelters </li></ul></ul><ul><ul><li>town plans </li></ul></ul>
    95. 98. 559.11 – Extra-low voltage lighting installation <ul><li>Protective measures and supplies </li></ul><ul><li>FELV is NOT to be used as a protective measure. </li></ul><ul><li>Extra-low voltage luminaires installed without a provision for the connection of a protective conductor should only be installed as part of an SELV system. </li></ul><ul><li>Exercise (1) What symbol should marked on the device where an electronic convertor is used for an extra-low voltage lighting installation? </li></ul>
    96. 99. 559.11 – Extra-low voltage lighting installation <ul><li>Protective measures and supplies </li></ul><ul><li>Safety isolating transformers for extra-low voltage lighting installations tocomply with BS EN 61558-2-6 , and meet at least one of the following requirements: </li></ul><ul><ul><li>the transformer must be protected on the primary side by a protective device with the characteristics detailed in Regulation 559.11.4.2 or </li></ul></ul><ul><ul><li>the transformer must be short-circuit proof and marked with the symbol: </li></ul></ul>
    97. 100. 559.11– Extra-low voltage lighting installation <ul><li>A typical recessed downlighter </li></ul>
    98. 101. Extra-low voltage lighting bare conductors <ul><li>If the nominal voltage does not exceed 25 V a.c. or 60 V d.c., bare conductors may be used provided the conductor csa is not less than 4 mm 2 , and the conductors are not placed on combustible material. </li></ul><ul><li>Regulation 559.11.5.3 refers. </li></ul>
    99. 103. 56 – Safety Services <ul><li>A Safety Service is defined as: ‘ An electrical system for electrical equipment provided to protect or warn persons in the event of a hazard, or essential to their evacuation from a location ’ </li></ul>Such services are commonly employed in buildings open to the public and general commercial and industrial premises
    100. 104. 560.1 – Safety services - Scope <ul><li>Additional specialist systems classed as safety services also include Fire pumps, Fire fighting lifts, Fire evacuation systems, smoke ventilation systems, CO detection etc … </li></ul>Sprinkler pump house Smoke vent supplies and controls Detection CO2 Detector
    101. 105. 56 – Safety Services <ul><li>The requirements for the general characteristics relating to these systems are specified within Chapter 35. </li></ul><ul><li>Four distinct sources are recognized as being suitable for use as the safety service. </li></ul><ul><li>Exercise: </li></ul><ul><li>What are the four recognized sources for use as a safety service supply? </li></ul>
    102. 106. 560.4 – Classifications <ul><li>An electrical safety service supply is classified as either: </li></ul><ul><ul><li>A non-automatic supply </li></ul></ul><ul><ul><li>An automatic supply </li></ul></ul><ul><li>Automatic systems are further classified by whether they offer a continuous “no-break” supply, or are based on their maximum change-over time duration. </li></ul>
    103. 107. 560.7 – Circuits of safety services <ul><li>In addition to the requirements relating to cables, specific requirements also relate to: </li></ul><ul><ul><li>Overload protection </li></ul></ul><ul><ul><li>Switchgear and controlgear locations </li></ul></ul><ul><ul><li>Routes of wiring systems </li></ul></ul><ul><ul><li>Drawings and information relating to all (safety service) current-using equipment </li></ul></ul>
    104. 108. Chapter 56. Safety Services <ul><li>Batteries used as the supply for safety services are classified into two categories: </li></ul><ul><ul><li>“ central power supply sources” and </li></ul></ul><ul><ul><li>“ low power supply sources”, the low power source being limited to 1500 watt-hours. </li></ul></ul><ul><li>Exercise: What is the minimum declared life of a battery for (1) a central power supply source and (2) a low power supply source? </li></ul>
    105. 109. 560.6.11 – Uninterruptible power supply sources (UPS) <ul><li>These type of devices maintain a continuous supply to connected equipment by supplying power following the failure of the primary source. </li></ul><ul><li>They can be either static (delivering an output voltage from a stored source through a convertor) or rotary (for example a diesel driven generator). </li></ul>
    106. 110. Circuits for safety services. <ul><li>To ensure a high integrity supply and to minimize disruption (electrical faults, maintenance or modification to other systems) a safety service should employ a dedicated independent circuit that is ideally run through areas of low fire and risk. </li></ul><ul><li>Where impracticable, a circuit should be run using a fire-resistant cable system. </li></ul>
    107. 111. 560.7 – Circuits for safety services <ul><li>In addition to the requirements relating cables specific requirements also relate to: </li></ul><ul><ul><li>Overload protection </li></ul></ul><ul><ul><li>Switchgear and controlgear locations </li></ul></ul><ul><ul><li>Routes of wiring systems </li></ul></ul><ul><ul><li>Drawings and information relating to all (safety service) current-using equipment </li></ul></ul>
    108. 112. Well that was part 5 <ul><li>Does this make sense? </li></ul><ul><li>GOOD – We will carry on - - - - - - - - </li></ul><ul><li>What do you think of the show so far? </li></ul><ul><li>Sorry you had to do some investigation for yourself. </li></ul>