Potentially dangerous - should I report this to someone?

[SammyG]

Greetings all,

I'm looking for a bit of advice. I'm not actually an electrician, but I am an electrical design engineer and I am aware of the regs.

I recently bought a new house which, after a few weeks developed an earth fault in the kitchen that kept tripping the RCD. No problem - I found the issue and fixed it.

However, whilst I was investigating this, I noticed that the sockets in my kitchen are not on a ring circuit, but rather in a radial circuit, with 2.5mm cabling, but the MCB in the consumer unit was a 32A. I believe that this was unsafe, so I replaced the MCB with a 20A.

Because I am a designer rather than an installer, I don't know how common this is and I don't really know how dangerous it is - theoretically, in fault conditions, the wire would likely melt before the MCB trips, but does it work this way in practice?

Also, I suspect that I am not technically supposed to tinker with my own electrics this way, so I am reluctant to go down any official channels.

I'd like to know if you folks here agree that this was dangerous, and if so, should I report the original installer to anyone (his name and number are printed on the consumer unit)?

Thanks in advance

Sammy.

 

[Darkwood]

Welcome to the forum Sammy

 

[Pete999]

Welcome Sammy

 

[TJ Anderson]

Hi Sammy and Welcome. Is there only a single conductor at MCB terminal and also are you 100% it is not 4mm csa cable?.

 

[Midwest]

Do you have a copy of the regs? If so appendix 15 gives recommendation for RFC & Radial, and suggests a 20amp ocpd for 2.5 tw&e on a Radial circuit . Table 4D5 gives current carrying capacities for insulated & sheathed flat cables, the highest rating for 2.5mm tw&e is 27amp clipped direct.

 

[telectrix]

echo post #4.

 

[Lucien Nunes]

From your description, it was non-compliant with BS7671 using the 32A MCB as the cable was not protected against overload, however I would not consider it to have been especially dangerous. Unless the cable installation method had drastically reduced its Iz, it certainly would not have melted and probably not got very much above rated temp even with the breaker at full load, which in itself would have been rare. Nonetheless, as it was a new installation, it should have been compliant and you could reasonably expect the installer to rectify at his cost. If the 20A radial arrangement does not provide an adequate supply given the expected use of the socket-outlets served, then rectification might include completing the ring or adding a circuit.

Edit, just realised it was a NEW house.

 

[Midwest]

Think the horse has bolted now, might have been better to get rectified by the company responsible for the new build, but I suppose at least its as it should, albeit you haven't the required competency (you said a much yourself) to do so. Are there any other 'noughties' in the installation? And are your neighbours in the same boat?

 

[Hawk]

I've seen this before on a number of premises, where a niceic registered electrical contractor had wired a 2.5mm radial and used a 32A breaker. Cowboys!

 

[Octopus]

I would recommend you find a local spark to confirm the cable size to start with......

 

[Pete999]

Echo posts 4 and 6

 

[LankyWill]

Get a spark in sammy, i understand your a designer but from an installer point of view, you dont know the ins and outs of the install side. Top marks on finding the fault but keep yourself safe and get a pro in.

 

[rapparee]

Was there no ring present at the cu i.e. was there one or two live conductors in the 32a breaker.. Perhaps there might be a spur off the ring for one or two sockets.

 

[Baker1988]

Have you got a copy of then electrical installation certificate that might help with a few of the questions.

 

[Adam W]

Echo posts 4 and 6

:iagree:

 

[Adam W]

Think the horse has bolted now, might have been better to get rectified by the company responsible for the new build, but I suppose at least its as it should, albeit you haven't the required competency (you said a much yourself) to do so. Are there any other 'noughties' in the installation? And are your neighbours in the same boat?

Same with any consumer issue - if you bought a television which developed a fault within a few weeks you could get it rectified for free under warranty, but probably not if you opened it up and tinkered around with it yourself. Had you given the original contractor the opportunity to rectify the fault you may have been able to start reporting people, but at this stage it's probably best to keep that one under your hat - I expect the last thing you want is them 'reporting' you for non-compliance with part P of the building regulations.

 

[Midwest]

OP could always pop the 32a mcb back in, then call the installer back in to explain

 

[Adam W]

I'm not sure I'd go to the effort personally, but it's an option for someone who's looking for an excuse to complain.

 

[SammyG]

Hi all,

Thanks for the welcomes and the advice.

In response to posts 4 & 6, it is definitely 2.5mm twin + earth.

It is not actually a new-build house, but the place had been completely renovated when I bought it and this circuit is in a fairly new extension.

There are two conductors in the MCB; It looks to me as though there used to be a ring around what used to be the kitchen, but when the extension has been done the ring has been broken into two radials, one going to the kitchen and the other to the utility room, and the two ends have not been connected back together to form the ring.

The overall floor area served by the circuit is slightly less than the 50m^2 stated in the regs. It seems to me that, with the 20A MCB in place, it is now safe. I plan to just leave it and see if the MCB starts tripping. If it does then I think I'll need to get a guy in to install a proper ring.

 

[davesparks]

How have you confirmed that this is a radial circuit and not a ring?
Can you post up a copy of the schedule of test results from the installation certificate so that we can see what information has been recorded there about the circuit?