A couple of RCBO questions

[mightyoakbob]

Hi,

I have a Crabtree split board CU which has 'B' type MCBs in it. My Shower, upstairs and downstairs ring mains are RCCB protected but the rest is not. I was advised that I could replace the two 6amp lighting MCBs with RCBOs for extra protection and I would like to do it. I do understand how RCBs etc. work by comparing the current on the live and the neutral and looking for an imbalance. So I realize that the unmonitored neutral will also need to be connected to an RCBO as will the returning neutral from the lights. I am also aware of the borrowed neutral on the landing light problem, I will run another neutral for it.
Now my questions...

There appears to be a blue and a white wire. Which is which and where do they connect? The white wire looks too thin to carry the neutral. Can't find a spec for these devices on the net just people selling them.

Also, what doe this 'B' mean as opposed to A and C? Something to do with size?

Cheers guys.

Bob.

 

[ColJack]

the blue one is the neutral and goes to the neutral bar, the circuit neutrals then connect straight to the RCBO..

the white one ( with the green/yellow tag on it ) is the functional earth and goes to the earth bar..
A, B, C and D are the curves of the breaker..


a breaker will operate within a given time as long as a given current is flowing.
the higher the letter the more current is needed to operate in the same given time.
it is usefull for when you have things like motors or transformers or lots of discharge lighting to have a higher letter to handle the inrush currents.

 

[rebuke]

Note that if you're in England or Wales changing the protective device for a circuit is notifiable under Part P of the building regs to your LABC *before* doing it. They'll probably charge you £100+ for the privilege, so it's almost certainly going to be cheaper to get an electrician in to do it.

An electrician can also test the existing circuits, and the RCD part of the new RCBO to verify it's all working properly...

 

[mightyoakbob]

Note that if you're in England or Wales changing the protective device for a circuit is notifiable under Part P of the building regs to your LABC *before* doing it.

I was aware that there were heavy restrictions on what you can do in your own home these days. I was working on the assumption that if/when I sell the house I will have to pay someone to examine/test and provide me with a safety certificate. I can't work out how anyone will know if I do this and what differnce it will make other than making changing a bulb safer. I certainly do not have any certificates of any sort for electric or gas at the moment.

They'll probably charge you £100+ for the privilege, so it's almost certainly going to be cheaper to get an electrician in to do it.

Not your fault I know but that really goes against the grain, having to pay someone a large wedge to do something I can do myself. If there's no alternative it means it wont be done at all.

An electrician can also test the existing circuits, and the RCD part of the new RCBO to verify it's all working properly...

Yes, I can see the advantage of that.

Thanks for your help.

 

[rebuke]

I was aware that there were heavy restrictions on what you can do in your own home these days. I was working on the assumption that if/when I sell the house I will have to pay someone to examine/test and provide me with a safety certificate. I can't work out how anyone will know if I do this and what differnce it will make other than making changing a bulb safer. I certainly do not have any certificates of any sort for electric or gas at the moment.

According to the building regs (which are legally enforceable), you have to notify before doing the work, unless you're a member of a self certification scheme. If you don't, then if you're lucky you might just need to get a PIR done, but if the buyer's solicitor is being thorough, you may have to pay a large regularisation fee to the LABC (and risk them telling you to rip things out etc).

 

[sparkyspike]

Something to consider: When fitting an RCBO without actually testing it, you can't be sure that it is tripping as it should. Even new RCBOs sometimes do not meet trip times or other functional tests.

Without testing, you also won't know whether the condition of the circuit (or even the supply) is acceptable. Obviously, you won't be making things any worse, but in this case it appears that, although you seem to understand the basic theory behind RCDs, you do not know your way around a consumer unit.

I would guess, having read your posts, that you probably can fit this RCBO yourself without too much trouble. But to be sure that it has been fitted correctly and that it actually works, you do need to test it.

Are you happy to not test the RCBO or the wiring and save money?