This well-cremated consumer unit (home distribution board) was sent by Nick Bundy for our entertainment. You can see the video where he replaces it with a new one here:-
https://www.youtube.com/watch?v=I_VHEBGMHEI
From 2016 all new consumer units in the UK tend to be metal cased ones to reduce the risk of incidents like this. This may have been influenced by a number of recalls related to Wylex circuit breakers with contact burning issues.
Under fault conditions a circuit breaker in the UK can potentially have to break a fault current of several thousand amps, so I've never really been comfortable with the value engineering that has been applied to them. £3 or less seems just too low for something so important to electrical safety.
It's possible that the root of this fault was either a faulty isolator or poor termination. There's a lot more to terminating a cable than just stuffing it into a hole and clamping it with a screw. With rigid cables like the tails shown, it's especially important that the rigidity of the cable doesn't result in a twisting force on the terminal, as it can potentially affect contact positioning.
It's also important to recheck that terminals haven't loosened when cables are moved.
It's interesting to note that both RCDs were in their tripped state, but while they isolated all wiring leading from the fire they couldn't isolate the cause itself.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
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18 thoughts on “Plastic consumer unit fire autopsy.”
  1. Avataaar/Circle Created with python_avatars Kim Sleep says:

    As a N.American, I find European wiring fascinating, in the fact that everything is so DIFFERENT!

  2. Avataaar/Circle Created with python_avatars Bob Lewis says:

    And all for the sake of a contactor and a thermal trip switch set for 65°C!🤔🙄🥴👎👎

    One of these days my erstwhile fellow members of the IET who draw up the regs will wake up to the fact that without a source of fuel, electricity initially then the plastic breaker cases, a fire CANNOT spread!

    The plastics are good to at least 120°C so a temp cut out of 65° TOTALLY PREVENTS fire automatically, since ABS doesn't melt and burn until 3-5 times that temperature. If you don't reach the flammability point … No fire!
    No power = No fire! It's NOT rocket science now is it?

    A metal casing does NOT prevent fire and since the vast majority of electrical fires apparently occur in the CU which is loaded with fire fuelling ABS encased breakers, why not STOP a fire BEFORE it starts?

    Overtemp can be indicated early with a 20° higher trip out temp so say 65° lower (alarm) and a 20° higher 85° to trip completely.

    I, for one, don't ever recall my garage (where my CU lives) getting above 38°, so a minimum safety headroom of over 40° before tripping would be a FAR safer and cheaper approach to PREVENT fires rather than try to contain them in a metal box. It doesn't work anyway since the breakers (flammable!!) can be permanently exposed just by leaving the metal cover up! Thereby allowing the fire to escape and …!!!🤔🙄😲😢😢

  3. Avataaar/Circle Created with python_avatars Roy Tellason says:

    Things are rather different in the US… 🙂 What you're calling an isolator I'd call a main breaker. In this old house there wasn't one, but instead a separate box with a couple of huge cartridge fuses in it, rated at 150A I think. Some time back our power got weird, some stuff worked and other stuff didn't. It looked like we had one phase of the two that were coming in off the pole transformer. On contacting the power company we were told that the smart meter was seeing both connectiojns but they sent someone out anyway. It turned out that the weatherhead-meter-ingress stuff had leaked moisture into the fuse box which was in the basement, which caused it to blow. After a while an electrician came out and replaced the whole setup, from the weatherhead on in and including the breaker box, so we now have a main breaker instead of that box and it's all well sealed to keep the weather out of the wiring and we presumably won't have a problem again. I've never seen anything other than metial used for a breaker box, including the one in the house, one in the garage, and a load center in an outbuilding (which I installed). Plastic? No thank you!

  4. Avataaar/Circle Created with python_avatars Michael Skelton says:

    I remember my partners rear demister was intermittently working. I opened the fuse box and wobbled the fuse and it was sparking and the fuse was extremely hot from this. The pin in the fuse box was bent inwards so it was an easy fix but was also a potential fire hazard as the fuse had spot weld type marks on it

  5. Avataaar/Circle Created with python_avatars Alex Attis says:

    I agree that our electrical system is mostly inferior to yours, and this is an example of why I always say mostly inferior. We also have better testing laboratories like Underwriter's Laboratories with certifications that have a clear indication of the certification number, rather than just a CE mark. Correct me if I'm wrong.

  6. Avataaar/Circle Created with python_avatars Scott K says:

    "not very conducive to isolation by the time it finished." 😂😂

  7. Avataaar/Circle Created with python_avatars Derek Christenson says:

    I've long admired the well-thought-out lamp / appliance plugs that the UK now uses (as we still use an evolved version of a very, very old design here for our lamps and small appliances), but compared to the heavy, all-metal breaker box on my house here in Arizona, that plastic box looks like a (terrifying) toy! 😲 I'm not an electrician, so I've never personally installed a breaker box (and have no expertise, of course), but I've seen it done here, and every working part of it looked much more heavily built, aside from the housing of the unit, too.

    Very interesting! I'll still give points on the UK's fancy lamp plugs, though; very well-engineered.

  8. Avataaar/Circle Created with python_avatars Xanda_uk says:

    Hi guys
    As a experienced electrician, most consumer unit belt downs and fires are caused by badly terminated MCB,s and badly terminated cables. MCB,s can be incorrectly fitted to the Buzz bar resulting in arching and heating. But mostly electricians who do not double over terminations for improved conductivity or simply lose connections are the cause.

  9. Avataaar/Circle Created with python_avatars Robin Wells says:

    Using non contact thermometer to verify the screw clamp terminations temperatures under load is a precaution worth considering or better still have a video thermography survey done to look for hot spots. These are sometimes used in industry to ensure equal sharing of load across circuits. Make sure that load is present to provide the heat source obviously.
    I’m erring toward the neutral bus bar as a resistance fault heat source perhaps. Forensic Clive at your best. 👍

  10. Avataaar/Circle Created with python_avatars Go Away says:

    Non solid core wires: screw them up and move them around. Tighten and repeat untill they stay tight.

  11. Avataaar/Circle Created with python_avatars wayne p says:

    I wonder if it would be when an electrician comes out for any reason if it would be a good idea to tighten all the screws.
    At the video section of the unburned unit the far right pair of wires going in the bottom seemed to have been installed straight in and tightened then the cables bent 180 degrees causing the conductors to slip. On the burned section. The RCD power wires into it were probably the cause of the heating as the copper wires heated and cooled with changes in the load causing deformation and coming loose causing the hot spot. Time to add a mini smoke detector to the fuse box to trip the RCDs but it might be too late..
    Perhaps inspections might be required to tighten the screws and to bring on the loads and use a thermal imaging camera to look for hotspots.

  12. Avataaar/Circle Created with python_avatars Niki Bretschneider says:

    The main question is WHY both RCDs and almost all fuses are melted with levers in OFF position? They could be manually operated in attempt to isolate output of that unit, which would lead us to the conclusion, that someone had a really big trouble to operate the main switch, which then leads us to the conclusion, that all that began at the main switch. There is also one fuse, that was not in off position. This is also important, because this has its own cause. Maybe, it was not possible to turn it off, so it was somehow defunct, or just did not trip for some reason. Yes, there is possibility that both RCDs and fuses was tripped, not manually operated and that is something, that would lead me to conclusion, that some high voltage surge or something like that came from somewhere outside the house, that tripped all that fuses, both RCDs and caused arcing, that ignited that fire. Loosy joints prove nothing due the fact, that copper softens when temporarily exposed to the high temperature, which is something, that happened during that fire, so loosy joints after the fire doesn't mean they were loosy before that fire.

  13. Avataaar/Circle Created with python_avatars Arno Seitzinger says:

    Don't touch the burnt mess with bare hands please. Dioxines and other nasty stuff builds when PVC insulation burns…

  14. Avataaar/Circle Created with python_avatars ANTHONY BOOTH says:

    that cable is 6mm2 at best… – I have two samples of 6mm2 cable; – each are different diameters of copper! …now I understand towering inferno (the movie)…
    …was that mess extracted from a new build house?

  15. Avataaar/Circle Created with python_avatars Mike PXG says:

    Rule 1 always cut the seal at the cutout. 😎

  16. Avataaar/Circle Created with python_avatars artifactingreality says:

    i have a metal one so i am better than you are

  17. Avataaar/Circle Created with python_avatars The BrainlessSteel says:

    Oh.. the rising clamp should be mandatory.. a few days back that almost cost a farm to burn down…

  18. Avataaar/Circle Created with python_avatars The BrainlessSteel says:

    oh our breakers switch Live and Neutral. 🤔interesting. so each system has it's ups and it's downs. (so hear if the breaker is off you can just safely work on the installation.)

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