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.

 

[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?

 

[Midwest]

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.

From what you've said here, and what you said in your original post, I think you need to get a competent electrician to inspect & test this circuit. Its possible that circuit in question was originally installed a as Ring circuit, and either has become faulty or was not correctly installed in the first place. It sounds as if the property has been renovated and in the process rewired.

You originally said the RCD was tripping, suggesting some kind of fault. The only way to investigate this is by testing, this will also clarify whether the circuit is an RFC or two radials in one MCB.
If the original installer cannot be located, then I would suggest using the services of a local electrician.

 

[sparksburnout]

As above. For saying you are an electrical design engineer you don't seem to have much of a clue about this! How do you know it's not an RFC???

 

[Octopus]

My money is on the fact its a ring but with spurs off spurs in the kitchen.

Matey - you need to get somebody competent with a MFT to confirm what exactly is going on...... before doing anything.

 

[andyb]

Echo post 11

 

[SammyG]

Ok, to post 21, yes initially the RCD was tripping, so I investigated this by going around the room, isolating each socket in turn and checking the live-earth resistance . I tracked the problem to a leaky junction box plastered into the wall (which I'm pretty sure was wrong as it should have been accessible for maintenance. That junction was just joining two lengths of cable so I replaced it with a new, single length of cable which I chased into the plasterboard. It was in carrying out this investigation that I noticed that when I isolated any one socket, a lot of the rest of the sockets would stop working, which is what started me wondering about the integrity of the ring.

So I spent my saturday mapping out all the socket connections - isolating absolutely everything and then testing the connections between each socket. I now have a complete drawing of the circuit in question, I know exactly what is connected to what, and I can assure that it is definitely two radials.

I did do the work myself but, being aware of my lack of experience of installation work, I checked all my plans with the electricians at work before I did anything, and got them to inspect everything I did, either in person or by photograph.

 

[gazdkw82]

It sounds like it could have been a ring prior to extention and then when that was done the ring was separated into 2 radials

 

[Bobster]

I've got to ask, how are you designing circuits without the basic knowledge of the tests required to ensure they are safe to be use.

 

[Midwest]

Ok, to post 21, yes initially the RCD was tripping, so I investigated this by going around the room, isolating each socket in turn and checking the live-earth resistance . I tracked the problem to a leaky junction box plastered into the wall (which I'm pretty sure was wrong as it should have been accessible for maintenance. That junction was just joining two lengths of cable so I replaced it with a new, single length of cable which I chased into the plasterboard. It was in carrying out this investigation that I noticed that when I isolated any one socket, a lot of the rest of the sockets would stop working, which is what started me wondering about the integrity of the ring.

So I spent my saturday mapping out all the socket connections - isolating absolutely everything and then testing the connections between each socket. I now have a complete drawing of the circuit in question, I know exactly what is connected to what, and I can assure that it is definitely two radials.

I did do the work myself but, being aware of my lack of experience of installation work, I checked all my plans with the electricians at work before I did anything, and got them to inspect everything I did, either in person or by photograph.

OP, please don't be offended, but I don't think you are qualified enough to be carrying out this work.

An RCD can also trip when there is a neutral to earth fault, and also when there is a fault on another circuit. When an RFC is installed, there are a series of test to be carried out to establish it has been correctly installed.

It would be unusual, but not uncommon, to find two radial circuits (for socket outlets) to be connected into one mcb. Hence the suggestion, that your circuit in question, was installed as a RFC, but somehow part of the ring has been disconnected, and you think you have two radials, especially as the original mcb was 32amp. I might be wrong. Unless the installer, forgot or missed part of the installation? Do you have two sockets with only one cable at each, but has continuity with the origin of the circuit (s)? This can be complicated by 'spurs' from your circuit. It is practice by some local councils, to turn a RFC into two radials, if a leg of the ring develops a fault. But the faulty cable would be isolated, and the two legs turned into two separate radials, in two separate mcb's.

When carrying out the installation work yourself, it should be properly tested before being bought into being. Having your plans checked by people at work, either in person or by photograph, will not facilitate this. Failure to carry out proper testing, sometimes ends with the predicament you find yourself in.

As you do not have the proper test equipment or sufficient experience, I would ask the 'electricians at work' to come and assist you, and rectify this problem.

 

[Octopus]

I've seen quite a few 32A mcb's with 2 cables but they are not a ring.

Only somebody with a MFT and competence can really tell you!

 

[Midwest]

I've seen quite a few 32A mcb's with 2 cables but they are not a ring.

That sounds quite Freudian to me, but I'm no Sigmund. :smilewinkgrin: