NHXSB20AFD

Arc Fault Detection Devices 

18th Edition - We’re ready 

## **ARC FAuLT DETECTION DEvICES & THE WIRING REGuLATIONS** 

The 18th edition wiring regulations (BS7671) sets out requirements for electrical installations in the UK, including requirements for protection of persons, livestock & property against the risk from fires that may be generated & propagated in electrical installations. 

Designers & installers are required to ensure that installations are arranged so that the risk of ignition from high temperatures or electric arc is minimised, and protection from harmful thermal effects is provided during normal operation and under fault conditions. Protection requirements include protecting against fire caused by insulation faults, arcs & sparks & high temperatures[(1)] . 

Installing arc fault detection devices is recognised in the 18th Edition of the wiring regulations as a means of mitigating the risk from fire in final AC circuits due to arc faults. 

## **MCBs & RCDs & THE SAFETY GAP** 

Although the wiring regulations permit the use of RCDs as a measure for protection against insulation faults, & require the use of other circuit protection devices such as MCBs to provide protection against short circuit & overcurrent conditions etc, those devices cannot detect or disconnect arc faults. Neither of those devices is capable of detecting serial arc faults, and parallel arc faults will go unnoticed due to the fact that the magnitude of an arc fault is insufficient to operate an RCD or MCB. 

## **COMBINED TECHNOLOGY - AFDD, MCB & RCBO** 

In order to provide for all of the above requirements Wylex AFDDs are combined with Miniature RCBOs as a single protective device that includes overcurrent protection, short circuit fault protection, earth leakage protection, and arc fault protection, with two pole isolation as standard. 

Wylex combined technology AFDDs provide for the requirements of BS7671 including additional protection against fires caused by arcs. Closing the safety gap & providing additional safety measures. 

(1) Requirements in BS7671 can be found in Chapters 13 (Protection For Safety) and Chapter 42 (Protection Against Thermal Effects) other chapters are also be applicable. Readers should refer to BS7671 for full details. 

**2** 

## **BS 7671 WIRING REGuLATIONS 18th EDITION** 

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DANGER<br>  DEFINITIONS Risk of injury to persons from:<br>fire, electric shock, burns, arcing and explosion arising from the use of electrical energy<br>PROTECTION FOR SAFETY<br>The requirements are to provide for the safety of persons, livestock and property against dangers that may arise<br>from reasonable use of electrical installations including risks of injury from:<br>  CHAPTER 13<br>shock currents<br>excessive temperatures likely to cause burns, fires and other injurious effects<br>arcing or burning, likely to cause blinding effects, excessive pressure and/or toxic gas<br>PROTECTION FOR SAFETY - THERMAL EFFECTS<br>  CHAPTER 13 Installations should be arranged so that the risk of ignition of flammable materials due to high temperature or<br>electric arc is minimized and risk of burns should be minimal.<br>PROTECTION AGAINST FIRE CAuSED BY ELECTRICAL EquIPMENT<br>Requires people livestock and property to be protected against harmful effects of heat or fire that may be<br>  CHAPTER 42<br>generated or propagated in electrical installations.<br>Harmful effects from heat or fire may be caused by insulation faults, arcs, sparks and high temperature particles<br>PROTECTION AGAINST THERMAL EFFECTS<br>Electrical equipment shall be so selected and erected that its normal temperature rise and foreseeable<br>  CHAPTER 42 temperature rise during a fault cannot cause a fire.<br>This shall be achieved by the construction of the equipment or by additional protective measures taken during<br>erection of installation<br>PROTECTION AGAINST THERMAL EFFECTS<br>Arc Fault Detection Devices are recommended as a means of providing additional protection against fire<br>  CHAPTER 42 caused by arc faults in AC final circuits e.g. in buildings with sleeping accommodation, in places with a risk of<br>fire involving stored or processed materials, wooden/combustible buildings, fire propagating structures and<br>premises with endangered or irreplaceable items<br>DEvICES FOR THE PROTECTION AGAINST THE RISK OF FIRE<br>Where specified. Arc fault detection devices shall be installed at the origin of the final circuits to be protected,<br>  CHAPTER 53<br>and in AC single phase circuits not exceeding 230V.<br>Arc fault detection devices shall comply with BS EN 62606<br>**----- End of picture text -----**<br>


For reference - 131.1, 131.3.1, 131.3.2, 420.1, 421.1.1, 422.1.2, 421.1.7, 522.6.1, 522.6.2, 526.1, 532.1, 532.6, Appendix 6 schedule of inspections & schedule of test results. Not exhaustive, other requirements may also apply. 

## **ELECTRICAL FIRES** 

Government statistics for 2016/17 show a high number of incidents where the source of ignition is recorded as electrical distribution or electrical appliance, these two categories amount to more than 13,000 fires in total[(2)] 

**Year                        Total                        Electrical distribution             Other electrical appliances                  Combined total** 2014/15                    71,116                                    7,812                                             5,834                                            13,646 2015/16                    73,477                                    7,719                                             5,634                                            13,353 2016/17                    74,803                                    7,822                                             5,525                                            13,347 

(2) Government statistics for England, fire statistics table / data sets 

## **AFDD EXPERIENCE** 

Arc Fault Detection Devices (AFDDs) have been proven to reduce the number of incidents of electrical fires in countries where these devices are used. AFDDs detect & automatically disconnect arc faults that occur in damaged or crushed cables, in loose terminations, and in ageing installations where the insulation quality degrades over time. 

Arc faults cause overheating and the temperatures that are generated from such overheating can be high enough to ignite flammable materials and cause fires. AFDDs monitor the condition of a circuit for unusual conditions that are indicative of a series or parallel arc. These arc fault conditions can occur in electrical installation circuits and in cords & leads and in equipment / appliances connected to those circuits. AFDDs detect arc fault conditions & automatically disconnect the power to the circuit with an arc fault. With the government statistics revealing so many fires involving electrical distribution & appliances the use of AFDDs on final A.C. circuits would address some of these issues, including those associated with cords & leads. 

**3** 

## **ARC FAuLT DETECTION DEvICES (AFDDs)** 

Arc fault detection devices offer extremely effective protection against fires that are started by electrical faults. Typical causes include loose connections, damaged cables, crushed cables or where aged insulation allows current to leak between conductors. 

AFDDs detect electrical arcing faults that MCBs, RCDs and RCBOs cannot detect. 

## Types of Arc Fault: 

## **Serial arcing faults:** 

These are typically caused by a loose connection or a damaged conductor.  In this arc fault condition current flow is always lower than the operational load current. Miniature Circuit Breakers and Residual Current protective devices will not detect these electrical faults. 

## **Parallel arcing faults between conductors:** 

These are caused by electric arcs resulting from damage to the insulation that permits minimum contact between the two live conductors. MCBs or RCBOs may trip if the fault current is high enough. However AFDDs are extremely sensitive and will disconnect parallel arcing faults from 2.5A 

## **Parallel arcing faults between phase or neutral/protective conductor:** 

AFDDs will detect arcing faults against the protective conductor and provide adequate fire protection where no RCD is used. However Wylex AFDDs are combined with 30mA Miniature RCBOs that reliably detect and shut down this type of parallel arc fault. 

AFDD with Miniature RCBO provides the highest levels of protection for the installation and its users. 

**4** 

AFDDs & Consumer Unit Busbars 

## COMBINED RCBO AFDD 

CURRENT       RCD B CURVE                C CURVE                RATING      RATING    POLES   MODULES NHXSB06AFD       NHXSC06AFD           6A            30mA          2              2 NHXSB10AFD       NHXSC10AFD           10A           30mA          2              2 NHXSB16AFD       NHXSC16AFD           16A           30mA          2              2 NHXSB20AFD       NHXSC20AFD           20A           30mA          2              2 NHXSB25AFD       -                                 25A           30mA          2              2 NHXSB32AFD       NHXSC32AFD           32A           30mA          2              2 NHXSB40AFD       NHXSC40AFD           40A           30mA          2              2 

Select consumer unit and appropriate busbar from following information 

## AFDD NMX BUSBAR 

CAT REF                                                                   DESCRIPTION NMBBX18AFDD01                                                  1W AFDD NMX busbar NMBBX16AFDD02                                                  2W AFDD NMX busbar NMBBX14AFDD03                                                  3W AFDD NMX busbar NMBBX12AFDD04                                                  4W AFDD NMX busbar NMBBX10AFDD05                                                  5W AFDD NMX busbar NMBBX08AFDD06                                                  6W AFDD NMX busbar NMBBX06AFDD07                                                  7W AFDD NMX busbar NMBBX04AFDD08                                                  8W AFDD NMX busbar NMBBX02AFDD09                                                  9W AFDD NMX busbar NMBBX00AFDD10                                                  10W AFDD NMX busbar 

## AFDD NM FLEXIBLE BUSBAR 

CAT REF                                                                   DESCRIPTION NMBB17AFDD01                                                     1W AFDD flexible busbar NMBB15AFDD02                                                     2W AFDD flexible busbar NMBB13AFDD03                                                     3W AFDD flexible busbar NMBB11AFDD04                                                     4W AFDD flexible busbar NMBB09AFDD05                                                     5W AFDD flexible busbar NMBB07AFDD06                                                     6W AFDD flexible busbar NMBB05AFDD07                                                     7W AFDD flexible busbar NMBB03AFDD08                                                     8W AFDD flexible busbar NMBB01AFDD09                                                     9W AFDD flexible busbar 

**5** 

For further information please contact Wylex technical 01543 438321 

## NMX & NM Flexible Consumer Units 

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NMX16<br>**----- End of picture text -----**<br>


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—<br>NM1406LFLEX<br>**----- End of picture text -----**<br>


## MAIN SWITCH - WITH KNOCKOUTS ALL SIDES 

CAT REF              RATING        MODULES           WAYS            KNOCKOUTS NMX16                 100A                 16                     8                All sides NMX20                 100A                 20                    10               All sides 

## MAIN SWITCH - PLAIN SIDES 

## FLEXIBLE MAIN SWITCH 

CAT REF                     MS RATING               MODULES               AFDD WAYS NM506FLEX                    100A                           5                                2 NM806FLEX                    100A                           8                                4 NM1106FLEX                  100A                          11                               5 NM1406FLEX                  100A                          14                               7 NM1906FLEX                  100A                          19                               9 

CAT REF              RATING        MODULES           WAYS            KNOCKOUTS NMX16P               100A                 16                     8                Rear only (plain sides) NMX20P               100A                 20                    10               Rear only (plain sides) 

Select appropriate AFDD busbar 

## DIMENSIONS 

CAT REF                     HEIGHT mm             WIDTH mm                DEPTH mm NMX16                             235                          372                            125 NMX16P                           235                          372                            125 NMX20                             235                          445                            125 NMX20P                           235                          445                            125 

## DIMENSIONS 

CAT REF                     HEIGHT mm             WIDTH mm                DEPTH mm NM506FLEX                     261                          188                            121 NM806FLEX                     261                          241                            121 NM1106FLEX                    261                          292                            121 NM1406FLEX                    261                          343                            121 NM1906FLEX                    261                          438                            121 

**6** __ 

## NM Duplex Consumer Units & Accessories 

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NMD1112 EIU NMTG32 NMCE1<br>**----- End of picture text -----**<br>


## MAIN SWITCH DUPLEX 

CAT REF                     MS RATING               MODULES               AFDD WAYS 

NMD89                           100A                          17                               8 NMD1112                        100A                          23                              11 NMD1415                        100A                          29                              14 NMD1920                        100A                          39                              19 

## NM ACCESSORIES 

CAT REF               PRODUCT                                                            MODULE NMMB                 Metal blanking plate - Twist fit                                       1 NHB1PP               Blanking plate - Busbar & cover                                    1 NH00PP               Blanking plate - Twist fit                                                1 NHET25              25mm Earth Terminal **-** NMLDK               Angled visor locking kit NMTLK2              Curved visor locking kit MCBLDX             MCB locking device WPL                    Padlock for NHLDK & MCBLDX 

## MAINS TAILS GLAND 

## DIMENSIONS 

CAT REF                     HEIGHT mm             WIDTH mm                DEPTH mm NMD89                             500                          241                            127 NMD1112                         500                          292                            127 NMD1415                         500                          343                            127 NMD1920                         500                          438                            127 

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|||||||
|---|---|---|---|---|---|
|EIU                       Moulded cable gland kit for metal consumer unit to provide|
|additional support and supplementary insulation similar to Class|
|II construction for the incoming cables.|
|Suitable for 16mm|[2]|or 25mm|[2]|double insulated cable and 16mm|[2]|
|earth cable|
|32mm knockout|
|NMTG32              Flush ‘push fit’ moulded cable gland for metal consumer unit to|
|provide additional support and supplementary insulation similar|
|to Class II construction for the incoming cables.|
|Suitable for 16mm|[2]|or 25mm|[2]|double insulated cable and 16mm|[2]|
|earth cable|
|32mm knockout|

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## FIRE RETARDENT MEMBRANE CABLE ENTRIES 

NMCE1                Membrane cable entries kit 1 

3 x 32mm & 7 x 20mm 

NMCE2                Membrane cable entries kit 2 10 x 20mm 

## FLUSH MOUNTING KITS FOR NM FLEXIBLE 

NM07FLA             7 module flush kit assembly NM10FLA             10 module flush kit assembly NM13FLA             13 module flush kit assembly NM16FLA             16 module flush kit assembly NM21FLA             21 module flush kit assembly 

Not suitable for meter cabinet units 

## NM CONSUMER UNIT PATTRESSES FOR NM FLEXIBLE 

CAT REF                         LEFT/RIGHT                      ENCLOSURE TOP/BOTTOM                CABLE ENTRY                  WIDTH                  DEPTH MNSPE-6462/BNR          MNSPE6668/7NR             7 Module               16mm MNSPE-6462/CNR          MNSPE6668/10NR           10 Module              16mm MNSPE-6462/DNR          MNSPE6668/13NR           13 Module              16mm MNSPE-6462/ENR           MNSPE6668/16NR           16 Module              16mm MNSPE-6462/FNR           MNSPE6668/21NR           21 Module              16mm 

For use with NM consumer units.  Allows surface cable entry through rear knockouts and automatically maintains enclosure IP rating to comply with BS7671 and BSEN61439-3 

**7** 

• Cable entry slot may be positioned top or bottom, or left/right Not suitable for meter cabinet units 

## **ELECTRIuM SALES LIMITED A SIEMENS COMPANY** 

Commercial Centre, Lakeside Plaza, Walkmill Lane, Bridgtown, Cannock WS11 0XE. eMail: info@electrium.co.uk 

## **www.electrium.co.uk** 

## **uK SALES** 

Telephone:  01543 455020 Facsimile:    01543 455021 eMail: wylex.sales@electrium.co.uk 

## **TECHNICAL** 

Telephone:  01543 438320 Facsimile:    01543 438321 eMail: wylex.technical@electrium.co.uk 

## **EXPORT SALES** 

Telephone:  +44 1543 455049 Facsimile:    +44 1543 455048 eMail: export@electrium.co.uk 

## **DuBAI OFFICE** 

Telephone:  +971 4 3660684 Facsimile:    +971 4 3660676 eMail: export@electrium.co.uk 

@ElectriumNews or download the APP 

Although every effort has been made to ensure accuracy in the compilation of the technical detail within this publication, specifications and performance data are constantly changing. Latest details can be obtained from Wylex. 

Publication No. WY2440 8/18 Printed in England.