Department for Communities and Local Government Research Report:

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1 Department for Communities and Local Government Research Report: BD 2890 Investigation of real fires - Electrical consumer unit fire experiments (E3V2) CPD/04/102/027 Prepared for: Brian Martin Department for Communities and Local Government Building Regulations and Standards Division Zone 2/J6, Eland House Bressenden Place London, SW1E 5DU 10 th April 2014

2 1 Research Report BD 2890 (E3V2) FIRE BD 2890 Investigation of real fires Research Report on Electrical consumer units fire experiments Prepared for Brian Martin Prepared by Ciara Holland, Martin Shipp, and David Crowder BRE output ref (E3V2) Approved on behalf of BRE Name Dr Corinne Williams Position Deputy Lot Manager Date 10 April 2014 Signature BRE Bucknalls Lane Garston Watford WD25 9XX Tel : Fax : hollandcm@bre.co.uk Website :

3 2 Research Report BD 2890 (E3V2) Executive Summary BRE Global carries out fire investigation activities, under contract, on behalf of the Department for Communities and Local Government (DCLG) Building Regulations and Standards Division (BD 2890). In addition to the continued investigative work carried out by BRE Global, this contract includes an element of experimental work to allow further analysis of issues arising from investigations of incidents. The overall aim of the current experimental project was to assess the performance of typical, commerciallyavailable, domestic electrical consumer units from an ignition originating within the unit, and provide a report of findings from the experiments to inform DCLG. This work was intended as a scoping study and assumed that a fire had already been established; this study was not intended to replicate ignition scenarios from an electrical fault in a consumer unit or replicate ignition scenarios used in standard testing methods. Four experimental fires were carried out using two different types of consumer unit and two types of backing board. Two metal and two plastic consumer units were wired up as typical domestic systems with the openings in the top but without connection to power. The consumer units were fixed to an 18mm thick plywood backing board or an 8mm thick vinyl faced plasterboard sheet fixed to 18mm thick plywood. These backing boards were 600mm by 600mm in area. A hot wire loop energised by a variable power source was used to ignite the consumer units from within the units. This hot wire loop was capable of generating 0.5kW of heat with an estimated temperature of 1000 C. For the conditions studied, the conclusions of this scoping study are as follows. Both plastic consumer units caught fire and their casings became involved in the fire. It was necessary to use a water hose reel to extinguish both fires in the plastic consumer units. It should be noted that the plastic unit mounted on the plasterboard backing was more difficult to ignite than that mounted on the plywood backing, taking 19 minutes for established flaming. It is BRE Global s opinion that this delay in ignition was due to the non-combustible backing board. However, once the fire was established in that unit it burned more rapidly and more of the unit s casing became involved in the fire. With the plastic unit on the plywood backing, the fire, once established (after nine minutes), involved the plywood board above the unit and less of the plastic unit below in contrast with the plastic unit on the plasterboard backing. Both metal consumer units contained the fire within the unit; the casings did not become involved in fire except for the front plastic cover and this only melted away from the heat. The backing board did not make any difference to the performance of these units. Smoke was emitted from all four units as soon as the ignition source was energised. The smoke exited the units through openings where the wiring passed into the units. It is BRE Global s opinion that the suggested test method in the proposed amendment to BS 7671:2008, for the verification of resistance of insulating materials to abnormal heat and fire due to internal electric effects, whilst relevant to consumer units, is not severe enough to verify the resistance of the casing material to abnormal heat and fire when considering a resistive heating fault from within such units which could be a prolonged event.

4 3 Research Report BD 2890 (E3V2) Table of Contents 1 Introduction Project objectives 4 2 Methodology Materials Instrumentation Experimental method 6 3 Observations and findings Experiment 1 Plastic consumer unit on plywood backing Experiment 2 Metal consumer unit on plywood backing Experiment 3 Plastic consumer unit on plasterboard backing Experiment 4 Metal consumer unit on plasterboard backing 19 4 Discussion 21 5 Conclusions 22 6 Summary of the potential impact/implications for regulation and/or policy 23 7 References 24 Appendix A Publishable summary 25

5 4 Research Report BD 2890 (E3V2) Electrical consumer unit fire experiments 1 Introduction This work is part of the project commissioned under the Department for Communities and Local Government Building Regulations Research and Development Programme Framework Agreement with the BRE led consortium under contract reference CPD/04/102/027, BD 2890 titled Investigation of Real Fires. An important element of this contract is to ensure that findings from fire investigations are made available to the fire community, and other stakeholders. In addition to the continued investigative work carried out by BRE Global, this contract includes an element of experimental work to allow further analysis of issues arising from investigations of incidents. The current experimental work is in response to a request from the Department for Communities and Local Government (DCLG) Building Regulations and Standards Division to submit a proposal against their specification for a project titled Electrical consumer unit fire experiments. 1.1 Project objectives The overall aim of this project was to assess the performance of typical commercially-available, domestic electrical consumer units from an ignition originating within the unit and provide a report of findings from the experiments to inform DCLG Building Regulations and Standards Division. This work was intended as a scoping study and assumed that a fire had already been established; this study was not intended to replicate ignition scenarios from an electrical fault in a consumer unit or replicate ignition scenarios used in standard testing methods (see Section 6). 2 Methodology 2.1 Materials Two types of wall mountable electrical consumer unit were used; two metal and two plastic. These consumer units were wired up as a typical domestic system without connection to power by a qualified electrician. The plastic consumer units used were both from the same manufacturer and the same model and were 12 way split load insulated with 24 Miniature Circuit Breakers (MCBs). The metal consumer units were both from the same manufacturer and the same model and were 8 way with 16 MCBs. Two types of backing board were used; a plywood backing and a plasterboard backing. Both were 600mm by 600mm in area, the plywood was 18mm thick, the plasterboard was vinyl faced and 8mm thick, fixed to a sheet of 18mm thick plywood. Each type of unit was tested on each type of backing board. The consumer units and backing boards were sourced from an electrical suppliers by the electrician and came pre-assembled to BRE Global. For the experiments, the consumer unit complete with backing board was held on a metal support so that it was a free standing unit (see Figure 1). Each of the units had four openings in their top portion; for the plastic units all the openings were along the top, for the metal units there were three openings along the top and one at the side near the top (see Figure 2). There was one further opening at the bottom of the unit, used to insert the ignition source and a thermocouple but this opening was sealed up with tape for the experiments.

6 5 Research Report BD 2890 (E3V2) Figure 1 Typical setup for the experiments; consumer unit with backing board clamped to a metal support 2.2 Instrumentation Each opening in the consumer units had a Type K 1.0mm diameter steel sheathed thermocouple which was suspended approximately 20mm into the opening to measure the temperature of any smoke or flame escaping from the openings. Figure 2 Layout of thermocouples within the consumer units; the openings were labelled anticlockwise, stars indicate approximate locations of thermocouples and the cross indicates the approximate location of the ignition source. Opening 5 was sealed with tape but a thermocouple was introduced close to the hot wire loop to record temperatures near the source of ignition. The ignition source for the experiments was a 20 standard wire gauge (normally referred to as SWG) ferritic iron-chromium-aluminium alloy hot wire loop (see Figure 3) which was energised using a variable power source. This power source was rated at 5 amperes (A) output current with a variable voltage up to 100 volts (V). The hot wire loop was capable of generating 0.5 kilowatts (kw) of heat energy. The temperature of the hot wire loop when energised to 100 V was estimated at 1000 C. The performance of the consumer units was monitored during the experiments with visual observations and using video equipment and a stills camera.

7 6 Research Report BD 2890 (E3V2) Figure 3 Hot wire loop, indicated by red arrow, used as the ignition source. The loop was connected to the power source using ceramic blocks and was positioned appropriately within the consumer unit 2.3 Experimental method The consumer units were ignited from within the closed unit using the hot wire loop. The fire was allowed to develop and, using a grid on the backing board, flame heights from the top of the units were measured and temperature measurements were taken at each opening in the units. The hot wire loop ignition source was fitted inside the consumer unit in contact with wiring and plastic components (see Figure 4). Figure 4 Location of hot wire loop in a plastic consumer unit indicated by a red arrow The hot wire loop was left powered on until flames continuously extended out of the top of the consumer unit at which time the power was removed. In cases where flames did not extend beyond the consumer unit the hot wire loop remained powered on until termination of the experiment. Where necessary the fire was extinguished using water from a hose reel. Table 1 outlines the four experiments which were carried out.

8 7 Research Report BD 2890 (E3V2) Table 1 Order of experiments listing type of consumer unit and backing board Experiment Consumer unit type Boarding type 1 Plastic, 12 way split-load insulated with 24 MCBs 2 Metal, 8 way with 16 MCBs 3 Plastic, 12 way split-load insulated with 24 MCBs 4 Metal, 8 way with 16 MCBs 18mm plywood 18mm plywood 8mm vinyl faced plasterboard fixed to 18mm plywood 8mm vinyl faced plasterboard fixed to 18mm plywood 3 Observations and findings 3.1 Experiment 1 Plastic consumer unit on plywood backing This experiment was carried out on a plastic consumer unit mounted on a plywood backing (see Figure 1). Trial and error was used to determine the optimum voltage required for ignition using the hot wire loop. The power source was initially at 70 volts (V); this generated very light wispy smoke within 15 seconds. The generation of smoke continued for seven minutes, after which time it was decided by BRE Global to increase the voltage to the ignition source. The voltage was increased to 100V, the maximum voltage possible, seven minutes after the start of the experiment. Almost instantly more smoke was visible from the top of the consumer unit and also a flash of flame. The hot wire loop remained energised for a further two minutes to allow flames to develop after which time (nine minutes after start of test) the power was switched off (see Figure 5). Figure 5 Early stages of flaming approximately nine minutes into the experiment after switching off power to the ignition source The fire, now established, continued to grow and three minutes after the first sign of flames, 10 minutes into the experiment, flames were extending ~0.3m from the top of the consumer unit (see Figure 6). Flames reached a maximum of 0.5m from the top of the consumer unit, extending beyond the height of the backing board.

9 8 Research Report BD 2890 (E3V2) Figure 6 Plastic consumer unit on plywood backing board approximately 16 minutes into the experiment The fire was extinguished approximately 18 minutes into the experiment because it was considered that no further data would be gained. It was clear that the fire size, immediately prior to extinguishing, would have been sufficient to ignite any combustible items that might be present nearby. An interesting observation was that the flames did not initially extend out of the openings at the top of the unit but instead burned through the plastic between Opening 3 and Opening 4. The maximum temperature recorded, as shown in Figure 7 and Figure 8, was 901 C at Opening 4. The area approximately 20mm below the ignition source recorded a maximum temperature of 790 C. See Section 4 for comparison with other experiments. Figure 7 Temperature-time curve for Experiment 1; plastic consumer unit with 18mm plywood backing board

10 9 Research Report BD 2890 (E3V2) Figure 8 Temperature-time curve (x-axis normalised for comparison with other experiments) for Experiment 1; plastic consumer unit with 18mm plywood backing board Figure 9 and Figure 10 shows the damage to the consumer unit after the fire was extinguished and also shows the damage to the backing board. The plywood backing board did not burn through during the fire but was charred. Figure 9 Damage caused to plastic consumer unit and plywood backing board by the fire started within the consumer unit Figure 10 Damage to plywood backing board after Experiment 1 after removal of burned plastic consumer unit

11 10 Research Report BD 2890 (E3V2) Experiment 2 Metal consumer unit on plywood backing This experiment was carried out on a metal consumer unit mounted on a plywood backing (see Figure 11 and Figure 12). Having established the ideal settings for the ignition source in Experiment 1, the decision was made by BRE Global to go straight to 100V on the power source for the remaining experiments. Given the layout and construction of the metal units, the ignition source was placed closest to items most likely to burn to assess a worst case scenario. The position of the ignition source is shown in Figure 11; the loop was in contact with an MCB and also close to the plastic gap filler (see Figure 12). Figure 11 Location of hot wire loop in metal consumer unit Figure 12 Location of hot wire loop with cover on metal consumer unit showing plastic gap filler, red arrow. Also of note are the locations of the openings in the metal units with this unit having one opening to the side and three at the top. White wispy smoke was visible 55 seconds after switching on the hot wire loop. After approximately four minutes, the plastic gap filler, shown in Figure 12, started to melt and at approximately five minutes, the hot wire loop was visible and glowing (see Figure 13). It was possible to view into the part of the consumer unit at this time and it was noted that the MCB in contact with the hot wire had started to melt.

12 11 Research Report BD 2890 (E3V2) Figure 13 Glowing of the hot wire loop after the plastic gap filler had melted away due to the heat After 7½ minutes, the outer screen of the unit was showing signs of heat damage and there was discolouration of the metal above this area (see Figure 14). A small hole formed in the outer screen after 14½ minutes and this ventilation allowed for a very small flaming fire centred around the MCB. Figure 14 Outer plastic cover has been damaged by the heat and some small flames can be seen within the metal consumer unit with some discolouration of the metal The flames did not reach more than 25mm in length throughout the experiments and were contained inside the metal unit. After 25 minutes, the flames became smaller. The power to the hot wire loop, which had remained switched on for the duration of the experiment, was switched off at 30 minutes. Some small flames (20mm in length) were still evident but the fire had self-extinguished by 2¼ minutes after switching off the hot wire loop power. The maximum temperature recorded, as shown in Figure 15, was 269 C approximately 20mm below the ignition source. The maximum recorded temperature at the openings was 66 C. See Section 4 for comparison with other experiments.

13 12 Research Report BD 2890 (E3V2) Figure 15 Temperature-time curve for Experiment 2; metal consumer unit with 18mm plywood backing board Figure 16 and Figure 17 show the damage to the metal consumer unit after the fire was extinguished. The fire was contained within the unit and hence the damage is also contained to within the unit with the exception of the plastic outer cover which became heat damaged. Figure 16 Damage to metal consumer unit after Experiment 2; the fire was contained by the unit and centred around the hot wire loop which remained energised throughout the experiment Figure 17 Damage to metal consumer unit after Experiment 2; the front casing has been removed to show the extent of the damage within the unit which was minimal after 30 minutes exposure

14 13 Research Report BD 2890 (E3V2) Experiment 3 Plastic consumer unit on plasterboard backing This experiment was carried out on a plastic consumer unit mounted on a vinyl faced 8mm plasterboard backing which was mounted onto an 18mm sheet of plywood (see Figure 18). This experiment was split into three parts (phases) as the consumer unit did not catch fire after the initial experiment and the purpose of the experiment was to assess the performance of these units to the most severe conditions. This required optimising the position of the hot wire loop to create such conditions. As with Experiment 2 the optimum setting for the power supply for the ignition source of 100V was used for all three parts. Figure 18 Plastic consumer unit on vinyl faced plasterboard backing board for Experiment 3 Parts 1 to 3 The location of the hot wire loop for Part 1 and 2 is shown in Figure 19. Figure 19 Location of hot wire loop in plastic consumer unit for Experiment 3 Part 1 and Part 2 Part 1 White, wispy smoke was visible from the unit approximately 10 seconds after energising the ignition source and it was possible to see a glow from the hot wire loop on the backing board after 35 seconds. There appeared to be a flicker of flames after one minute but this did not develop any further or extend beyond the unit. Approximately four minutes after starting the experiment the volume of smoke had reduced and there were no flames. No change was apparent up to 25 minutes from the start of the experiment at which time it was decided by BRE Global to terminate the experiment.

15 14 Research Report BD 2890 (E3V2) The hot wire loop was de-energised at 25 minutes. After allowing the hot wire loop to cool down, the front cover of the plastic consumer unit was removed to assess the damage. There was minor discolouration of the wiring close to the hot wire loop but no damage was apparent on the consumer unit itself. It appeared as though the loop may have moved after installation. It was decided to re-position the hot wire loop and run the experiment again under the same conditions. The maximum temperature recorded, as shown in Figure 20, was 170 C at Opening 3. The area approximately 50mm below the ignition source recorded a maximum temperature of 36 C. See Section 4 for comparison with other experiments. Figure 20 Temperature-time curve for Experiment 3 Part 1; plastic consumer unit on plasterboard backing. (There were no flames visible outside the unit for this experiment). Part 2 The hot wire loop was re-positioned after becoming dislodged from its original position as shown in Figure 19. The hot wire loop was in more contact with the wiring for Part 2 than Part 1. The same conditions as with Part 1 were then applied. Dark grey smoke was visible approximately 32 seconds after energising the hot wire loop. Looking into the unit from above, it was possible to see the glow of the hot wire loop and some of the insulation on the wiring burning with a glow but no flames were visible. As with Part 1, the smoke volume reduced after the initial few minutes and remained low until the experiment was terminated at 20½ minutes. The maximum temperature recorded, as shown in Figure 21, was 114 C at Opening 3. The area approximately 50mm below the ignition source recorded a maximum temperature of 32 C. See Section 4 for comparison with other experiments.

16 15 Research Report BD 2890 (E3V2) Figure 21 Temperature-time curve for Experiment 3 Part 2; plastic consumer unit on plasterboard backing. (As with Part 1, no flaming was observed for this experiment.) Figure 22 to Figure 24 show damage caused by the hot wire loop within the plastic consumer unit after carrying out the experiment twice (Part 1 and Part 2). There is some discolouration of wiring; parts of the plastic MCBs have charred and a small area of the plastic back of the unit has melted, exposing the plasterboard backing board behind. Figure 22 Damage to the top exterior of the plastic consumer unit after Part 1 and Part 2 of Experiment 3. There is some evidence of heat damage but the unit did not become involved in fire. Figure 23 Damage/discolouration to wiring after Parts 1 and 2 of Experiment 3; red arrow indicates location of hot wire loop which is behind the wiring.

17 16 Research Report BD 2890 (E3V2) Figure 24 Damage to back of plastic consumer unit after Parts 1 and 2 of Experiment 3; part of the plastic has melted away to expose the vinyl face of the plasterboard behind. Some damage to the MCBs is also evident. The unit was left to cool overnight before attempting Part 3 of this experiment. Part 3 After Parts 1 and 2, the unit was examined and it was clear that the hot wire loop had created heat damage inside the unit and also to the back of the unit. The decision was made to re-position the hot wire loop so that it was in direct contact with the plastic back of the unit rather than the wiring. The hot wire loop was turned around and moved slightly to an undamaged part of the back of the unit. The same conditions as with all other experiments were used again; 100V power to the hot wire loop. Approximately 18 seconds after energising the hot wire loop, dark grey smoke was visible rising out of the unit through the openings at the top. The volume of the dark grey smoke continued to increase and began to discolour the plasterboard backing (see Figure 25). Figure 25 Dark grey smoke issuing from top of plastic consumer unit for Experiment 3 Part 3 After approximately 12 minutes, the first flames were observed extending outside the unit, out of Opening 1, and were approximately 20mm in length and grew to approximately 50mm. This flame died back after approximately 20 seconds. At this time, the top of the unit was showing signs of heat damage and was distorting (see Figure 26).

18 17 Research Report BD 2890 (E3V2) Figure 26 Distortion of plastic consumer unit during Experiment 3 Part 3 After approximately 17 minutes, there were some small flames extending from Opening 4, again the flames were only approximately 20mm in length. Opening 4 at this point had been distorted and large section of the plastic top had melted away from the opening. Approximately 10 seconds after these flames emerged the length increased to approximately 150mm above the top of the unit but only briefly. The flames died back again, with only smoke visible above the top of the unit. At approximately 18 minutes, flames started to pulse out of Opening 4, reaching a height of 150mm. This pulsing flame turned into a continuous growing flame after a few seconds, reaching a height of 200mm. The fire then spread to the right hand side of the unit with flames extending out of Opening 1 (see Figure 27 and Figure 28). Figure 27 Flames extending from openings at the top of the plastic consumer prior to deenergising the hot wire loop Figure 28 Side view of the plastic consumer unit showing flames having melted the plastic backing travelling along the backing board

19 18 Research Report BD 2890 (E3V2) The power to the hot wire loop was switched off at 19 minutes and the fire was allowed to develop and involve the unit. The fire was extinguished after approximately 21 minutes since the unit had started to detach from the backing board. The maximum temperature recorded, as shown in Figure 29, was 819 C at Opening 2. The area approximately 50mm below the ignition source recorded a maximum temperature of 427 C. See Section 4 for comparison with other experiments. Figure 29 Temperature-time curve for Experiment 3 Part 3; plastic consumer unit on vinyl faced plasterboard backing board Figure 30 and Figure 31 show damage caused by the hot wire loop and resulting fire within the plastic consumer unit after carrying out the experiment three times (Part 1 to Part 3). As noted previously, during Part 3 of this experiment, the consumer unit caught fire. It can be seen that the vinyl facing of the plasterboard backing was damaged in a localised area and that the plastic casing of the consumer unit has been significantly damaged by the fire. Figure 30 Damage to plastic consumer unit and backing board after Experiment 3 Part 3

20 19 Research Report BD 2890 (E3V2) Figure 31 Close up of damage to plastic consumer unit and backing board after Experiment 3 Part Experiment 4 Metal consumer unit on plasterboard backing This experiment was carried out on a metal consumer unit mounted on a vinyl faced 8mm plasterboard backing which was mounted onto an 18mm sheet of plywood (see Figure 32). As with Experiment 2, the optimum setting for the power supply for the ignition source of 100V was used. The hot wire loop was installed in the same location as with Experiment 2 with the plastic gap filler placed over it. The openings in this unit were slightly different to Experiment 2 as the side opening was on the right hand side in this unit but there were still three openings in the top (see Figure 32). Figure 32 Metal consumer unit for Experiment 4 Approximately one minute after switching on the hot wire loop, the plastic gap filler had started to melt (see Figure 33). After 5.25 minutes very small flames (~20mm) were visible around the MCB in contact with the hot wire loop (see Figure 34). As with Experiment 2, the hot wire loop remained energised for 30 minutes after which time the power was switched off. Flames were still apparent but self-extinguished approximately one minute after the hot wire loop was de-energised.

21 20 Research Report BD 2890 (E3V2) Figure 33 Plastic gap filler melted away showing the glowing hot wire loop in the metal consumer unit Figure 34 Flames visible behind the melting plastic outer cover of the metal consumer unit The maximum temperature recorded, as shown in Figure 35, was 162 C at Opening 3. The area approximately 20mm below the ignition source recorded a maximum temperature of 88 C. See Section 4 for comparison with other experiments. Figure 35 Temperature-time curve for Experiment 4; metal consumer unit mounted onto a vinyl faced plasterboard backing board which was fixed to a sheet of plywood Figure 36 shows the damage to the metal consumer unit after the fire was extinguished. The fire was contained within the metal unit and did not spread to involve the plasterboard backing board. Some discolouration of the cables outside the unit was evident but this was due to the hot gases and not flame.

22 21 Research Report BD 2890 (E3V2) Figure 36 Damage caused by fire to the metal consumer unit on vinyl faced plasterboard backing after Experiment 4 4 Discussion Comparison of the four experiments helps demonstrate the differences between each of the units and their backing boards. Table 2 compares the maximum recorded temperatures for each of the units and notable observations from the experiments. Table 2 Comparison of maximum recorded temperatures and notable observations from the experiments Experiment Conditions Maximum temperature at openings ( C) Maximum temperature near ignition source ( C) Flame height above unit (m) Time to established flaming from power on (minutes) Time fire extinguished (minutes) 1 Plastic consumer unit with plywood backing 2 Metal consumer unit with plywood backing 3 (Part 3) Plastic consumer unit with vinyl faced plasterboard backing 4 Metal consumer unit with vinyl faced plasterboard backing 901 (Opening 2) 66 (Opening 1) 819 (Opening 2) 163 (Opening 3) (selfextinguished) (selfextinguished)

23 22 Research Report BD 2890 (E3V2) Same units, different backing board For the metal consumer units, the fire was contained within the unit so the backing boards were unaffected by the fire and did not contribute to the fuel load. For the plastic consumer units, there was a difference in the way the units burned. The plastic unit on the plywood backing burned for approximately six minutes before it was extinguished by BRE Global staff. The plastic unit on the plasterboard backing only burned for two minutes before it was necessary to extinguish the fire. The fire in the second plastic unit (Experiment 3 Part 3), while reaching flame heights of ~0.4m, had a lot of material dripping or dropping from the base of the unit. Most of the damage to the first plastic unit (Experiment 1) was to the upper portion of the unit with minimal dripping from the base. The hot wire loop in both experiments was located near the top. It also took three attempts to ignite the plastic unit mounted on the plasterboard backing (Experiment 3) and when it eventually did ignite, it took 10 minutes longer than it had with the plywood backing. It is BRE Global s opinion that the difference in the backing boards account for this difference in burning characteristics due to the plywood backing board being involved in the fire. Same backing board, different units It is clear from the experiments that the metal units, regardless of the backing board, contained the fire within the unit and the plastic units did not contain the fire and their casings became involved in the fire. While the fire was contained within the metal units, smoke did escape from the units through the openings as it did with the plastic units. Due to the typical location of these units in domestic premises, a fire in an electrical consumer unit could go undetected for some time leading to the smoke itself being enough of a hazard in a property prior to it being detected. 5 Conclusions This report has summarised the results of four experiments carried out to assess the performance of typical commercially-available, domestic electrical consumer units from an ignition originating within the unit This work was limited to assessing the performance of two different types of consumer units. Two plastic units and two metal units each mounted on either a plywood backing or a plasterboard backing. Furthermore this work assumed that a fire had already been established within in the unit. In conclusion, both plastic consumer units caught fire and their casings became involved in the fire. It was necessary to use a water hose reel to extinguish both fires in the plastic consumer units. It should be noted that, of the two plastic units, the unit mounted on the plasterboard backing was more difficult to ignite and it is BRE Global s opinion that this delay in ignition was due to the non-combustible backing board. However, once the fire was established in that unit it burned more rapidly and more of the unit s casing became involved in the fire. With the plastic unit on the plywood backing the fire, once established, involved the plywood board above the unit and less of the plastic unit below in contrast with the plastic unit on the plasterboard backing. Both metal consumer units contained the fire within the unit; the casings did not become involved in fire except for the front plastic cover and this only melted away from the heat. The backing board did not make a difference to these units. Smoke was emitted from all four units as soon as the ignition source was energised. The smoke exited the units through openings where the wiring passed into the units.

24 23 Research Report BD 2890 (E3V2) It should be noted that this was a simple scoping study. This study has only looked at two types of wall mounted consumer units; there are several other types of domestic consumer unit available, e.g. flushmounted consumer units, which have not been addressed in this work. Further work would be required to establish the performance of other types of consumer units not covered by this study. 6 Summary of the potential impact/implications for regulation and/or policy Amendment No 3 of BS 7671:2008 [1] has recently been available for public consultation and there are several proposed changes to the current standard [2]. The proposed wording, relevant to consumer units, for inclusion in BS 7671:2008 incorporating Amendment No 3 Chapter 42 Protection against thermal effects, and due to be published in 2015 is as follows: Switchgear assemblies including consumer units shall: (i) have their enclosure manufactured from non-combustible or not readily combustible material, or (ii) be enclosed in a cabinet or enclosure constructed of non-combustible or not readily combustible material. NOTE 1: Ferrous metal e.g. steel is deemed to be an example of a non-combustible material NOTE 2: For the purposes of this regulation insulating material e.g. plastic meeting a 960 ºC glow-wire flammability test as defined in BS EN is considered to be an example of a not readily combustible material. The findings of the consumer unit experiments here support the proposed amendment regarding noncombustible and not readily combustible material. However, BRE Global questions whether the glow-wire flammability test BS EN [3] will be sufficient for the conditions under which a consumer unit may become involved in fire. This glow-wire test (BS EN ) is based upon exposure of the test specimen to the wire at the relevant temperature for 30 seconds. As noted from the experiments carried out here, exposure of the plastic consumer units to the hot wire loop, at an estimated temperature of 1000 C, took between nine and 19 minutes for flaming to be established outside the consumer unit. It is BRE Global s opinion that this 30 second exposure is not severe enough to verify the resistance of the casing material to abnormal heat and fire when considering a resistive heating fault from within such units. It is BRE Global s experience that undetected resistive heating faults can continue over prolonged periods beyond that of 30 seconds as tested by the standard. Furthermore, BS EN :2009 [4] would appear to be a more relevant standard to use in this proposed regulation. This standard does make reference to BS EN but also includes specific criteria for enclosures of switchgear. Paragraph Resistance of insulation materials to abnormal heat and fire due to internal electric effects states: parts which might be exposed to thermal stresses due to internal electric effects, and the deterioration of which might impair the safety of the ASSEMBLY, shall not be adversely affected by abnormal heat and fire and shall be verified by the glow wire test in NOTE: The glow wire test in refers to BS EN :2001, IEC :2000 Fire hazard testing. Also of note is that while Approved Document B [5] refers to Approved Document P [6], it does not refer to BS 7671:2008 directly. Inclusion of reference to BS 7671:2008 in Approved Document B perhaps should be considered given the proposed amendments relevant to fire safety.

25 24 Research Report BD 2890 (E3V2) References [1] BS 7671:2008 incorporating Amendment No 1:2011 Requirements for electrical installations. IET Wiring Regulations Seventeenth Edition, and British Standards Institution, [2] Private communication between BRE Global and Mr Ken Bromley of the Department for Communities and Local Government, 7 th March [3] BS EN :2001, IEC :2001 Fire hazard testing Test methods. Glowing/hot wire based test methods Glowing-wire flammability test method for end-products. British Standards Institution, [4] BS EN :2009 Low voltage switchgear and control gear assemblies General rules. British Standards Institution, [5] Approved Document B: Fire Safety Volume 2: Buildings other than dwellinghouses edition incorporating 2007, 2010 and 2013 amendments. [6] Approved Document P: Electrical safety Dwellings. P1 Design and installation of electrical installations edition.

26 25 Research Report BD 2890 (E3V2) Appendix A Publishable summary BRE Global carries out fire investigation activities, under contract, on behalf of the Department for Communities and Local Government (DCLG) Building Regulations and Standards Division (BD 2890). In addition to the continued investigative work carried out by BRE Global, this contract includes an element of experimental work to allow further analysis of issues arising from investigations of incidents. The overall aim of the present experimental project was to assess the performance of typical commerciallyavailable, domestic electrical consumer units from an ignition originating within the unit and provide a report of findings from the experiments to inform DCLG. This work was intended as a scoping study and assumed that a fire had already been established; this study was not intended to replicate ignition scenarios from an electrical fault in a consumer unit or replicate ignition scenarios used in standard testing methods. Four experiments were carried out to assess the performance of typical, commercially-available, domestic electrical consumer units from an ignition originating within the unit Four experimental fires were carried out using two different types of consumer unit and two types of backing board. Two metal and two plastic consumer units were wired up as typical domestic systems with the openings in the top and without connection to power. The consumer units were fixed to an 18mm thick plywood backing board or an 8mm thick vinyl faced plasterboard sheet fixed to 18mm thick plywood. These backing boards were 600mm by 600mm in area. A hot wire loop energised using a variable power source was used to ignite the consumer units from within the units. This hot wire loop was capable of generating 0.5kW of heat at an estimated temperature of 1000 C. Both plastic consumer units caught fire and their casings became involved in the fire. It was necessary to use a water hose reel to extinguish both fires in the plastic consumer units. It should be noted that the plastic unit mounted on the plasterboard backing was more difficult to ignite than the one mounted on the plywood backing, taking 19 minutes for established flaming. It is BRE Global s opinion that this delay in ignition was due to the non-combustible backing board since it did not become involved in the fire. However, once the fire was established in that unit, it burned more rapidly and more of the units casing became involved in the fire. With the plastic unit on the plywood backing the fire, once established (after nine minutes), involved the plywood board above the unit and less of the plastic unit below in contrast with the plastic unit on the plasterboard backing. Both metal consumer units contained the fire within the unit; the casings did not become involved in fire except for the front plastic cover and this only melted away from the heat. The backing board did not make any difference to the performance of these units. Smoke was emitted from all four units as soon as the ignition source was energised. The smoke exited the units through openings where the wiring passed into the units. It is BRE Global s opinion that the suggested test method in the proposed amendment to BS 7671:2008, for the verification of resistance of insulating materials to abnormal heat and fire due to internal electric effects, whilst relevant to consumer units, is not severe enough to verify the resistance of the casing material to abnormal heat and fire when considering a resistive heating fault from within such units which could be a prolonged event and may need another review.