New extension - doing your own electrics.

[ban-all-sheds]

The building officer said that we (as an unqualified person) are not allowed to add a NEW CU.

He was wrong. Scarily so, given his job. I would go as far as to say he was so unfit to discharge his duties that his employment should be terminated.

He said however we can use the old one and do the rest of the electrics ourself.

And he was somewhat ignorant of electrical installation issues and the regulations which he is being paid out of the public purse to enforce if he thought that you could be competent to install new circuits but not a new CU.

[Our old CU was actually replaced not so long ago with a metal one].

So why did the question of replacing it ever arise?

 

[flux capacitor]

He was wrong. Scarily so, given his job. I would go as far as to say he was so unfit to discharge his duties that his employment should be terminated.



And he was somewhat ignorant of electrical installation issues and the regulations which he is being paid out of the public purse to enforce if he thought that you could be competent to install new circuits but not a new CU.



So why did the question of replacing it ever arise?

I'm afraid this is a case of Chinese whispers - I was not present when he came. This was remembered or mis-remembered by someone who knows even less than I do.

I was not there so I asked my sister to ask him are we allowed to do our own electrics and how much would the extra checks cost? And that what she said.

Having said that this was the same guy that was adamant that I could not use those rubber connectors with jubilee clips to repair clay pipes - Thames water came round to fix it and did exactly that (it had an extra metal jacket in the middle though).

 

[EFLImpudence]

something about cookers causing rcd's to trip unnecessarily and so to use MCB not protected by RCD.

I would agree with you but the regulations state that concealed normal cables in the usual installation methods have an RCD on the circuit.

(earth leak voltage current).

I guess RCBO as cable will be less the 50mm from the surface.

Yes.

 

[flux capacitor]

I would agree with you but the regulations state that concealed normal cables in the usual installation methods have an RCD on the circuit.

(earth leak voltage current).


Yes.

thanks for correcting my homework again.

 

[flameport]

Our old CU was actually replaced not so long ago with a metal one

There's only 2 rooms.

Why do you want to install another one?
Two extra rooms do not need a separate CU - just extend/relocate the existing circuits.

 

[flux capacitor]

Why do you want to install another one?
Two extra rooms do not need a separate CU - just extend/relocate the existing circuits.

Perhaps because of the induction cooker. If that needs a circuit of its own might as well do the lot.

The new cooker is far away from the main CU. It's a lot less destructive to route the cable outside the house (trench being dug anyway).

If I have to do that anyway, rather than put the cable in the back of the cooker, might as well put it in a CU and supply everything else, I don't have to try and tap into the existing electrics and disturb everything, 100 times easier.

The current CU is a nightmare. We once had this intermittent problem and it was plunging the house into darkness. Could not work out what was doing it - Faulty kettle? Faulty wiring? Rain getting into flood light? Faulty cooker? TV? It was impossible to track down. Lived with it for many weeks.

Finally called an electrician who swapped the CU for a new metal populated one - guess he thought the RCD could be faulty.

All was ok for a few days, then thwack, that dreaded breaker sound preceded by darkness. The fault was still there!

Eventually, I had enough - I bought one RCBO and swapped a few circuits into that. After a few days I was able to find the circuit that was doing it - the living room spotlights. Put a sticker over the living room light switch and never used it. Never had a trip after that. Months later called an electrician for something else and he had a look, one of the spotlights cables was worn, trouble is it never tripped the rcd as soon as you pressed the switch, so we never knew it was the cause. replaced that and all was fine.

Since that incident I vowed never to have a CU that was not a bank of RCBO no matter what the cost - makes fault finding a lot easier. I still have nightmares about that incident. Oneday I will swap out all the MCB's for rcbo's.

 

[JohnW2]

... Since that incident I vowed never to have a CU that was not a bank of RCBO no matter what the cost - makes fault finding a lot easier. ...

RCBOs obviously make it a lot easier to 'localise' the source of a fault. However, they can make it more difficult to determine the nature of the fault - since when a domestic RCBO trips, it gives no indication as to whether it has tripped because of overcurrent or residual current ('fault to earth').

Kind Regards, John

 

[flux capacitor]

RCBOs obviously make it a lot easier to 'localise' the source of a fault. However, they can make it more difficult to determine the nature of the fault - since when a domestic RCBO trips, it gives no indication as to whether it has tripped because of overcurrent or residual current ('fault to earth').

Kind Regards, John

Interesting.

 

[ericmark]

Soon after Part P came in we fitted a wetroom for my mother and we decided to do our own electrics, both my son and I are industrial electricians, when the building inspector arrived he said we needed to have it inspected by a third party, we objected to this, and in the end he did allow me to do my own inspecting and testing, however we had all the meters required and both of us have C&G2391 which shows we have the ability to test and inspect.

If a third party inspect and test they only issue an electrical installation condition report not an installation certificate, and the LABC issues a completion certificate on the strength of the EICR. Only the person in charge of the installation can issue an installation certificate, so if you wire it, unless under the control of some one else only you can sign the certificate.

It is rare to see an EICR without some notes as to work required, and if the LABC do not accept the EICR then it's a case of do it again and do it properly and pay another fee, although there is a fixed fee for the council, there is no fixed fee for third party inspectors, and we found there was a list of inspectors that the council would accept, so it's not a case of shopping around for a cheap one, seems council works on three strikes and out, so any electrical firm who works for council has to ensure no rejection so tend to cross all t's and dot all i's so slightest fault and it's a re-test job and pay the fee again.

Some councils have their own inspectors, and originally they were not allowed to charge extra, but I seem to remember that rule has changed, so to use the LABC to inspect and test is like signing an open cheque, unless they will accept you have the skill.

When it came to doing a full rewire, even as an electrician I decided anyone renting or buying the house seeing my name on certificate would be put off, and I would really need insurance and get all meters calibrated, it would likely take me 6 weeks to rewire in spare time, an electrical firm would take one may be two weeks, so I employed a firm to do the work. For the amount of work you need doing it is simply not worth going down the DIY route, yes it can be done, but £500 for test gear, and £200 for course and exam assuming you pass, simply not cost effective. Even the book of rules is around £70.

 

[ban-all-sheds]

does anyone think my idea of

4 radials (4x 20A RCBO/2.5mm2)
2 lighting circuits 2x 6A MCB
40A MCBO for induction cooker.
metal CU,
10mm2 armoured cable to supply CU

is fine?

So this was your idea?

How do you plan to install lighting circuit cables with no RCD?

 

[flux capacitor]

So this was your idea?

View attachment 151230

How do you plan to install lighting circuit cables with no RCD?

well spoted.

you often hear not to install lights on RCD as they are out of harm's way or some such and being plunged into darkness is worse.

from what I have recently learnt is that the cables (less that 50mm deep) coming down to the light switch create a need for having RCD (in case someone puts a nail in it?) - have I understood this correctly?

This would mean I need to revise that and use RCBO's to comply?

(how are some peoples lights not on RCD? or should they be? - change in the regs?) or protected in metal conduit?

 

[Taylortwocities]

@flux capacitor , mate, you don't have a scooby do.
Sorry but you have no chance of convincing LABC that you are competent to carry out the electrical works that you envisage.

This is so very basic and has been part of the Wiring Regulations since the 17th edition (got a copy? I thought not)

 

[ban-all-sheds]

flux - I don't know how advanced the build is, and what the schedule is, but I fear that you simply don't have the time to learn everything you need to know if you want to DIY the electrics.


You can't carry out work like this by asking whatever random questions happen to occur to you, what if you get something wrong because you have no idea your knowledge is wrong? What if you miss something because you simply have no idea it even exists, and just don't realise you don't know it?

Asking questions here can be a useful part of a learning process, but they are not a substitute for proper structured studying. The key term there is "learning process" - you cannot learn all the things you need to know just by asking questions here. It isn't structured enough - it won't provide you with a way to progress where each step builds on what you learned before.


Please have an electrician do the work.

 

[flameport]

(how are some peoples lights not on RCD? or should they be? - change in the regs?) or protected in metal conduit?

In the distant past, no circuits required RCDs.
Then regulations changed so that some circuits did in some circumstances
After that some circuits always required RCDs and others did not
Then all concealed cables required RCDs unless installed in certain ways - this is the situation in 2018.
From January 2019, all lighting circuits will require RCDs regardless of how the cables are installed.

At all times during the above it was entirely possible to install RCDs even if the regulations did not require them.

 

[ericmark]

@flux capacitor , mate, you don't have a scooby do.
Sorry but you have no chance of convincing LABC that you are competent to carry out the electrical works that you envisage.

This is so very basic and has been part of the Wiring Regulations since the 17th edition (got a copy? I thought not)

If my son and I, both electricians for many years, both with paper qualifications, including in my case a degree in electrical and electronic engineering, had a hard job to convince the LABC inspector that we had the skill to DIY, what chance do you really think you have to convince the LABC inspector? Oh and when he visited BS7671:2008 which was then the current edition was sitting on the table together with the three meters needed to do the testing, and my son had insurance as at that time he was a sole trader.

I think we can tell you loads on this forum, and you could possibly install it all, but if it costs as much to test and inspect as it would cost to do whole job, then what is the point? Don't get me wrong, electricians are no angles and we may break the rules exactly the same as you, but when self certified they don't have a problem. And with a building inspector about hardly likely to break rules.

As when I did the wetroom council already involved, they have their own rules, we had no intention of fitting an extractor, it had opening windows so rules say not required, however LABC inspector said must have an extractor as ground floor so we would no open window as some one could look in. OK fair comment, however hardly ever switched on, so I was right.

The same applies to RCD protection, you know where the cable runs to the shaver socket, you know the tiles are super hard and on one will try drilling them, and since the socket has an isolation transformer in it output is IT so any earth fault will not trip a RCD so totally useless, but you still have to fit one.

OK give the LABC inspector a go, and ask him, but I would be very surprised if he lets you DIY electrics, unless you use an electrician off his list to check it after and then the cost will be same as if you had whole job done.