rcbos

[dainesekid]

Wonder if any sparkies can help - Doing my own self build and bld control will test on completion through their part p third party. Job was started on 16 edition but Im told it would be better to upgrade with rcbos for to comply with 17th. Have a split contactum c unit with layout as follows. Ring mains on 32 amp mcbs on rcd side ( including the bathroom shaver sockets ) Electric oven into cooker plate (2.5 flex) and up to cooker switch and back to c unit (10mm cable) on 16 amp mcb on rcd side (gas hob) Outside pier lights on 6 amp mcb rcd side. Immersion not in yet but would mcb side be correct? If so what rating and is it ok on 2.5 cable?
Kitchen lights downstairs lights upstairs lights (including bathrooms) and smoke alarms on 6 amp mcbs. 1st fix has been passed and second fix inspected and connection cert issued.(waiting for meter) Have purchased 4 rcbos (6 amp B6 contactum) to change from the lighting and smoke mcbs to rcbos but being an old tart have never seen them before. Does the top blue cable with made off end go into the neutral bar and then live and neutral into the top connectors? Also should the 2 smokes be on their own runs or ok to 3 core and earth one to tother. Sorry for essay but want to get it right. Any replies greatly appreciated

 

[ColJack]

as you said..
blue fly lead to neutral bar, L+N into the rcbo..
smokes are best connected together and interlinked so if one goes off they all do..

 

[Steve]

And we want photos of your self build!!!

 

[Taylortwocities]

Please be aware that Contactum is in administration and has ceased
trading. Buy your rcbos, and spares while they are still available!

See www.contactum.co.uk

 

[sparkyspike]

You seem to be doing pretty much everything correctly (which makes a nice change!). You don't have to wire to 17th if you started to 16th, but you clearly understand it's worthwhile to do so, which it is.

Immersions are normally put on a dedicated 16A breaker (in this case an RCBO) and wired with 2.5mm.

Shaver points are usually wired into lighting circuits to avoid having to fuse down.

 

[ColJack]

wouldn't changing the mcb's require further notification if the building notice has already been completed and the certificate issued?

you're changing circuit protective devices after all..? albeit for the same rating and curve, just with the RCD part attatched?

 

[dainesekid]

Many thanks to all - Bld control not signed off untill test cert issued - only connection cert for meter issued at present so changing board to suit part p company shouldnt be a problem as they will finall test anyway. Didnt know contactum were going down the pan so thanks for that. As for the shavers I thought all bathrooms now (except lighting) had to be rcd protected (they have transformers in anyway) so I think they will have to stay as allready tiled in. Will put 16ml earth wire and 25ml tails in for meter boys today. Have a 10ml earth from gas and water mains to the board and 6ml earth linked on clamps to boiler copper tails. Sounds like Ive done the smokes right then. Presently got the board rigged up to a geny and everthing works but does that mean it will test ok ? Will sort a photo out when Ive finished. Would have got a sparky in to do the whole job but the last one I had on another job drilled my new joists in the wrong span without a right angle drill and cost me shed loads of grief from the Bld inspector also found chaffed cable down to the copper so had to rip half of it out. That was just before part p came in so I guess he might be a window cleaner now !!!

 

[ColJack]

ALL circuits in a bathroom need to be RCD protected now, lights included..

 

[dainesekid]

So does not the bathroom lighting on an rcbo not comply ?

 

[securespark]

Yes.

 

[dainesekid]

I thought an rcbo was a kind of combined rcd and mcb plus overload but Im probably wrong. I understand the dicrepency over 30ma trips the rcd but what happens inside an rcbo or what scenario would make it trip where an mcb wouldnt - It were all fuse wire and silver foil when I was a leckeys mate.

 

[ColJack]

RCBO's are MCB's with RCD's built in..

As for the shavers I thought all bathrooms now (except lighting) had to be rcd protected

is the reason we mentioned rcd protection of the lighting in the bathroom..

 

[Space cat]

what happens inside an rcbo or what scenario would make it trip where an mcb wouldnt

The live and neutral wires pass through a ferrite ring on which is also wound a coil of fine wire. What you have is a transformer with two, single-turn primaries and a multi-turn secondary. As long as the live and neutral currents are equal, their magnetic fields cancel out and no voltage is induced in the secondary. If a mismatch occurs, this residual current DOES induce voltage in the secondary.

What happens next may vary between brands. A little over twenty years ago, I helped design one for MK. The secondary voltage went through some electronics which triggered a triac that tripped the MCB part of the device. It was, in effect, a standard MCB with an extra circuit board inside and it was a tricky business getting all the bits to fit. Happy days!

 

[dainesekid]

Many thanks for explaining - Theres a lot packed in to them little critters - ofcourse I knew all that just needed reasurance Ha - Why are the neutral leads coming out the top so long - Ive managed to squeeze them into the board that I bought last year but only just - they fit the rail allright but not much room left up the top - dont want to change the board now - Tlc reckon they should be ok.

Thanks again

 

[Steve]

They are made long enough for big 3 phase boards where they have to reach fom the top MCB right down to the neutral bar at the bottom.