Your feedback on regulation issues

Farmboy, the IET may appear rather passive in the wiring regulations but this is not the case. Any defects, difficulties or suggestions for changes are looked at very carefully, and whilst we follow the IEC, CENELEC, etc. on many issues, checking what this means to UK installations is very important. If you look in the front of the BBB you will see that Graham Kenyon (who uses his own name on the Forum) is part of JPEL/64 as well as several other IET Members. The IET has a policy committee which decides the IET view on wiring regulation matters with several more of the posters here as members, chaired by Graham. The discussions on the forum provide a very useful background to the committee, and keep up with some of the installers' thoughts and problems directly, which is much more useful than a trade body view. The Regulations are a very important part of keeping the UK infrastructure both safe and up to date. The various countries have considerable freedom to control their own regulations if they wish, and you will see this if you travel around the World, although many are members of the IEC and other common bodies.

Yes Mike, it is interesting that the diversity method seems to have been copied straight out of the Onsite Guide, and I agree that it does not really work in many instances. Primarily this is because one cannot make skilled Engineering Judgement into a simple rule, and the problem is really a chaotic one anyway meaning there is no analytic solution! I see that there is no BEAMA advice on CUs with local generation or EVC, in the provided documents. Perhaps they have some convenient rule of thumb there too?

David that does seem strange that metal CUs were seen to be the answer to preventing fires caused by loose connections in plastic CUs. At the time I seem to recall that there was a school of thought that not removing the fire retardant from the plastic used for the case, going back to tunnel terminals with 2 screws or being able to use smaller diameter strands in the meter tails would have been just as good a solution. Of course none of the solutions cater for poor installation practice which I'm sure we have all seen. Were the various comments on forums like these not taken into account as regards the change?

Hi BusterK


That is a good and fair question. There was very considerable pressure to "do something" from the London fire brigade who had seen a lot of incidents. It was never ascertained the complete cause of the fires, they were loose connections, but why did they occur? Fire investigation of small non-fatal fires is not good in a number of ways, but a consensus idea was that they may have been related to smart meter installations in some way, as the installers moved the tails around, but did not or actually were not allowed to check the connections for tightness! Whether this is true or not was never investigated. The decision was therefore to make non-inflammable enclosure a regulation (although some aspects are still not very clear, eg external RCDs in TT installs). A metal case immediately makes the CU identifiable, is hardly more expensive, and much more fire-resistant. The CUs without the fire retardant, are difficult to identify, and the problem seems to have largely gone away. I have tried to follow up on the terminal problem with tails cables, suggesting that a crimp spade type terminal would improve the terminations, with a couple of manufacturers, but so far none have taken the idea up. I hope that is helpful and sufficient to satisfy the feedback you would like.

How much longer does a metal consumer unit contain a fire for? I imagine the building still burns down, admittedly it might give the occupants a bit longer to escape. But if your asleep and your board catches fire its not going to make much difference surely? The real issue, like you say Dave, is the cause of the fire that should be addressed, not the containing the problem for a bit longer before it breaks out and burns the house down

This reply is to farmboy.

The ESF report commissioned to test meter tail connections is useful, but in my view flawed. It did find difficulties with tails connections in many designs of main switch or RCD, but really made no useful recommendations or conclusions except that connection followed by tails movement was, in general, bad and led to a movement, disconnection under tension or lack of tightness in the screw.

Here is a prototype of the answer to all that messing about inside the CU. I estimate that a manufactured 25mm version could sell for £1.00 fairly easily. Note this design is copyright David Stone 2020. I have tried a couple of manufacturers of CUs but no interest yet. They obviously don't care about ease or safety!

The result is neat and much better than trying to bend that tails cable at the top. (25mm2)