Hey all,

Having just finished making the conservatory weathertight, I am now up to the wiring up. I have decided to do the sockets as a seperate ring main on my consumer unit. I have fitted all of the boxes and wired up with two wires to the consumer unit.

As per photo I want to add another 32a RCD which there is space for on the buzzbar. Now to my question, do I need to uprate the switch on the left to a greater ampage ie 100a to take into account the extra RCD.

With thanks to the hive mind.

Marcel

I take it that you’re aware that Part P of the buildings regs require all new circuits installed in a domestic property to be inspected, tested and certified by a competent person, and a notification made to the local building authority???
It frightens me when DIY’ers think they can “do electrics” 😯

Putting that to one side, you need a 32Amp MCB, not an RCD. The double pole 63A switch is an RCD itself.
You don’t need to change it for a 100 Amp, because the total load on your socket circuits shouldn’t be anywhere near 63Amp.

Thanks for that, however I am no diy’er, I am a qualified joiner and do a fair bit of work on private sites, however, if there is a different way to wire up a ring main than wiring a ring please let me know. 😆

I also ‘think’ I can build conservatories, move doors, build guitars. But hey everyone has to start somewhere.

I love a my job is very technical kind of response.

Get an electrician In, you have probably made it more of a job than it would have been as he will have to check all of your work before connection which will probably take longer than him doing it himself in the first place

What 7 sockets in a ring to a consumer unit is a big job to check. Sometimes I despair at the mentality of some people. What did we do before all these regulations overtook the world.

I haven’t had my conservatory installed by an approved window installer either. Aren’t I naughty.

Why do I need an electrician before connection, I plan to connect myself as well.

From what you have said you are going to do you need an electrician

Lol, I love diy experts!
I’m a sparky, spent a 4 years apprenticeship learning the trade. I’ve seen countless bodges over the years and all from people that thought it looked easy.

How are you going to test and therefore verify that your circuit is safe? Earth connection snaps off behind a socket as you screw on the faceplate. Earth fault in your toaster but the mcb doesn’t trip. You just killed your wife/child, congratulations!

Get someone who knows what they are doing!

My 2p – if you have to ask on here for this sort of thing it is best to get someone in.

You must know someone who’ll do it ‘on the way home’ for a pint or two?

for gods sake, anyone can carry out electric work on their own home, and often don’t have to tell building control. they only have to be notified in particular circumstances, a quick google will confirm this. i’m not surprised the op feels confident if he’s worked on sites and met some electricians…i’ve worked with at least 10 and would only ever recommend one of them, same with plumbers….

I’m a sparky, spent a 4 years apprenticeship learning the trade. I’ve seen countless bodges over the years and all from people that thought it looked easy.

i’ve also seen countless bodges, from qualified sparkies…

It frightens me when DIY’ers think they can “do electrics”

Domestic electrics is actually incredibly simple and generally very safe. Even if you do get a shock, you have to be very young or infirm (or very unlucky) to be killed by a 230v ac. I’ve had hundreds in my life and don’t think twice about working on live stuff.

Part P is a ridiculous overkill reaction to a very small risk, all brought about because an MP’s daughter died. If the same risk-averse logic was applied to cyclists we’d be banned from all public roads and only let out on cycle paths in full body armour.

EDIT one of the many shocks I’ve had was caused by shoddy wiring from a ‘professional’ who’d taken some short cuts to save a few quid. The last two (last week) were in a hotel room in Nigeria where the mains sockets weren’t earthed and floating live, so you got a shock every time you plugged something in and then pulled the plug out. After the first few, I resorted to using a spare pair of socks as gloves to plug / unplug my laptop.

Times like this im glad im in scotland.

Me and my dad rewired my house with a spark mate popping in occasionally verrifying my work and dealing with any queries i had…. Not that many- its not rocket science biggest queries were about where i could and couldnt run wires. To be in the correct place.

Spent most of my time correcting really horrific bodges put in place when it was wired from the old bakelite switches and the old style plugs…..

To be in the correct place.

All on the web, you only have to Google:

Cable Safe Zones by brf, on Flickr

NB I have all the regs as PDFs, so if anyone wants a copy, drop me a mail and I’ll email you a Dropbox link to the files…

I did and i do but i have a few ambiguous routings i had to question due to not wanting to raggle my house into swiss cheese. I wasnt allowed one of them 🙁

This is what I love I only asked if I had to change the RCD I have already ordered the correct MCB as I can read the part numbers on the other ones.

Yes I can test the circuit by ‘borrowing’ a tester from work from one of the engineers there.

Oddly enough my wiring is very much like your diagram. Few holes in the ceiling to get wires to the consumer unit.

The only problem I have ever had with electrics, was at a customers house, whilst fitting a kitchen. Putting wall unit up, and bang tip of drill bit gone. Wire in wall in a diagonal from a socket. Oh yes and house had been rewired by a professional sparky.

Or for 8 quid one of these

http://www.screwfix.com/p/ced-plug-in-socket-tester/76975

i’m not surprised the op feels confident if he’s worked on sites and met some electricians..

Remind me to look for weekend work washing dishes in Nick Nairns kitchen, that’ll instantly make me a great chef!

I’ve had hundreds in my life and don’t think twice about working on live stuff.

Maybe you should think twice before you run out of luck. Don’t play down obvious risks, in case someone actually listens to you.

Always hear about dodgy tradesmen but in 15 years I’ve never seen any unsafe work. Untidy, plenty, but nothing unsafe.

Oh, and OP, a tester is only as good as the person using it. Maybe get one of the engineers to pop round and do it for you. If your rcd doesn’t trip in time then you are as well not having it. I presume you know the maximum permitted disconnection time?
You can’t also just order mcb’s based on whats already there. Your circuit could require a c or d type mcb and could need de-rated to 20A depending on the building fabric/circuit length etc etc

I would put in a radial circuit rather than a ring main as they are much safer.

No need to upgrade the isolator as your supply will be fused at 100A or less

So an existing ring circuit in brick and blockwork has an mcb of 32a, so if i create a new ring circuit in brick and blockwork and use an mcb rated at 32a I am wrong exactly how.

Sorry I do not know the exact millisecond for my circuit to trip, but when I press the test button I know its pretty damn fast.

For radial circuits read thicker wire.

My house has rings, my conservatory will have a ring.

I don’t get why the professionals get wound up. I fit the occasional kitchen for people, but never get wound up when people want to save money and do bits for themselves, or find I am just fitting the work surface, or replacing the work surface as they cocked it up.

I understand the regs, i merely asked a question, wished I waited till Monday, asked someone at work, borrowed the kit and got it sorted out that way.

Why do I need an electrician before connection, I plan to connect myself as well.

One of the reasons for an electrician is the need to make sure that the circuit, if a fault occurs, fails gracefully. It’s relatively easy to make a circuit work, but it’s possible for a working circuit to have a latent problem which might not manifest itself until it’s too late.

A ring circuit effectively overloads the cable because a 2.5mm cable has a current carrying capacity of 27amps but usually has a 32 amp MCB protecting it. A key test of a ring circuit is ring continuity which ensures that the ring is complete. Also, what is known as the Zs figure is important because the MCB needs to trip within a certain time and this is only possible if the earth fault loop impedence is low enough. Insulation resistance testing is also carried out to check that a cable hasn’t been damaged during installation. This would usually be picked up by the RCD but may not be the case in a N-E fault on TT earthing systems. Also, an RCD test should be carried out to confirm that the RCD trips in the required times – <300ms for 1x fault current and <40ms for 5x fault current. The test button only tests the mechanical operation, not the operation in fault situations.

A good electrician, and there’s plenty of poor ones out there, will undertake all these tests and be prepared to certify that it’s safe. They will have access to the test gear necessary to do the tests and the experience to interpret the results they find.

The part P/Building Control debate is a complex one. Like most things there are competent non professionals and incompetent professionals.

The important issue is that it’s safe for you and your family.

Rich.

(Edited for spelling).

Your right with a 32a MCB for a 2.5mm flat twin and earth ring its just a standard circuit out of the regs .

Officially it’s part p notifiable as it’s a new circuit from the consumer unit, but if you extended the existing ring its wouldn’t be. This is why the part p is a waste of time.

I personally wouldn’t do a ring because it’s more cabling and they are dangerous if the ring becomes broken. 4mm or 6mm radial is much better.

So an existing ring circuit in brick and blockwork has an mcb of 32a, so if i create a new ring circuit in brick and blockwork and use an mcb rated at 32a I am wrong exactly how.

Running the cable in brick and block is known as “clipped direct” and can dissipate the heat from the cable easily. The issue can come if you’v run the cable in the loft space and it’s been covered by insulation. Depending on the thickness of insulation and the way the cable has been run (ie touching the plasterboard or through the insulation) the effective capacity of the cable is lowered; sometimes by up to 50%. In reality it’s not likely to be a problem as the likelihood of the cable running at full capacity (and thus exceeding its temperature rating) is low. However, the regulations, which surprisingly are advisory rather than a legal requirement, would require the rating of the MCB to be reduced to a size that is lower than the effective capacity of the cable.

Rich.

psychobiker, as an electrician I’d obviously advise the use of a qualified person to do the checks for you to make sure all is ok. However, if you want to do the connection yourself I’d suggest that at a minimum you confirm that you have continuity between the two legs of the ring on all three conductors (L,N and E). With only 7 sockets I’d stick a 20a MCB on it rather than a 32. If the ring breaks it will give you additional resilience and unless you’re loading the circuit with heavy duty devices (dishwasher, tumble dryer) I would doubt you’ll have any tripping issues.
I’d like to see a proper RCD test but a mechanical test at least shows it’s capable of tripping.
Hope this helps.
Rich.

Good compromise rich

Sorry I do not know the exact millisecond for my circuit to trip, but when I press the test button I know its pretty damn fast.

Test button only tests the rcd, not the circuit.
If I fit a worktop and get it wrong I’m not going to fry my kids or burn my house down.

Typing on my phone, Rich explained in the post above about environment factors that require mcb derating.

At last some sensible answers thanks for that Rich.

If you follow guidence note 3 http://tinyurl.com/o7xlpv8 with an appropriate tester and the 17th edition http://tinyurl.com/p38op4r you should be fine. These are two essential books for electrical work IMO, no rocket science but provide you with all the best practice and requirments to assure asafe instailation. GN3 in particular is very clear and well layed out. (Not an electrican but hold some electric qualifications).

As a time served maintenance electrician and instrument tech. who is now no longer able to change the luminaire in his own kitchen… 👿

In answer to your actual question, the 60A RCBO will be fine – although the maximum current for each mcb is 32A, you can take into consideration the fact that you wouldn’t normally have three kettles plugged into each circuit at once. this is known in the trade as diversity.

Don’t worry about the ring either – assuming your conservatory doesn’t resemble kew gardens and you haven’t somehow gone into the loft on the run to the CU, you are unlikely to have exceeded the limits of cable resistance or floor area. 😉