RCCB as main switch?

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Noob2013

Hi all,

I have been to a property where the tails come out of the meter and into an RCCB which then feeds the main switch of the consumer unit. All circuits are protected by MCBs.

If I'm adding a new circuit, is it best put in an RCBO instead of an MCB?

Thanks
 
There should not be a 'front end' RCD installed at all. Circuits should be separated so that if a fault occurs the whole installation does not trip.
 
UKESRail said:
There should not be a 'front end' RCD installed at all. Circuits should be separated so that if a fault occurs the whole installation does not trip.
Click to expand...

Yes lets rip it all out and start from a fresh.. and then also get rid of the 100mA time delay RCD's from them old installs lol
 
Noob2013 said:
Hi all,

I have been to a property where the tails come out of the meter and into an RCCB which then feeds the main switch of the consumer unit. All circuits are protected by MCBs.

If I'm adding a new circuit, is it best put in an RCBO instead of an MCB?

Thanks
Click to expand...
Hi Noob,

A new circuit would need notifying under Part P of the building regs. As your profile shows that you're an apprentice you could maybe undertake this job with one of the electricians that you work with.

Also, if you don't already have it, get yourself access to the trainees forum.
 
UKESRail said:
There should not be a 'front end' RCD installed at all. Circuits should be separated so that if a fault occurs the whole installation does not trip.
Click to expand...
cobblers. this was most likely to regs. when installed. there's no requirement to bring it up to current regs. although any work done on the installation must comply to 17th.
 
telectrix said:
cobblers. this was most likely to regs. when installed. there's no requirement to bring it up to current regs. although any work done on the installation must comply to 17th.
Click to expand...

"most likely"

good enough for you. Not good enough for me.

As soon as he disconnects the tails to the existing he must be happy with the current installation before he reconnects it.

Just my opinion.
 
UKESRail said:
"most likely"

good enough for you. Not good enough for me.

As soon as he disconnects the tails to the existing he must be happy with the current installation before he reconnects it.

Just my opinion.
Click to expand...

as long as it's safe for continued use. the fact that it was installed to a previous version of the regs. is no reason to condemn it. that's like condemning a 1990's car because it doesn't have abs or airbags.
 
ImpeededLoop said:
Hi Noob,

A new circuit would need notifying under Part P of the building regs. As your profile shows that you're an apprentice you could maybe undertake this job with one of the electricians that you work with.

Also, if you don't already have it, get yourself access to the trainees forum.
Click to expand...

Can't we have an "Apprentice" badges Mods?
 
telectrix said:
as long as it's safe for continued use. the fact that it was installed to a previous version of the regs. is no reason to condemn it. that's like condemning a 1990's car because it doesn't have abs or airbags.
Click to expand...

Not condem but advise and make sure it is on the cert if the home owner does not want it.
 
Simlec said:
Should this question not be on the Screwfix forum ?

You would use a MCB. But do you know why ?
Click to expand...
I would use an MCB as I believe there would be a level of RCD protection.

Obviously not the best situation as it would take out the whole consumer unit.

I've also read the affects of having an RCBO and RCD/RCCB together.

If I'm wrong, could you please explain?

Much appreciated
 
Noob2013 said:
I would use an MCB as I believe there would be a level of RCD protection.

Obviously not the best situation as it would take out the whole consumer unit.

I've also read the affects of having an RCBO and RCD/RCCB together.



If I'm wrong, could you please explain?

Much appreciated
Click to expand...

ideally, you'd upgrade the board to give circuit division between 2 RCDs or, better still, RCBOs. but you can only do as much as the customer is prepared to pay. in this case, a MCB for the new circuit is the most cost effective solution.
 
Noob2013 said:
I would use an MCB as I believe there would be a level of RCD protection.

Obviously not the best situation as it would take out the whole consumer unit.

I've also read the affects of having an RCBO and RCD/RCCB together.

If I'm wrong, could you please explain?

Much appreciated
Click to expand...

Your thinking along the correct lines. We're guessing to some degree as we don't know all the details but it seems ok.....if operation is satisfactory
 
Noob2013 said:
Can you tell bt the front on an RCD if it is time delayed??
Click to expand...

Yes it would be an S type RCD. Also, I can't see on here what rating (ma) the Main Switch RCD is. If it is 30ma then a RCBO (30ma) in series would be rather pointless. If it was a 100ma then it may be required dependant on circuit.
 
UKESRail said:
It will have a 'S' in a square.

But it if this is installed this will not give your circuit appropriate RCD protection.

whole DB change is what I would recommend.
Click to expand...
Thank you.

So if the customer would not pay for that, and it was a time delayed rccb, could a new circuit not have an rcbo so it is protected?
 
Noob2013 said:
Thank you.

So if the customer would not pay for that, and it was a time delayed rccb, could a new circuit not have an rcbo so it is protected?
Click to expand...

Yes you will need to RCBO it. If the main is time delayed you will achieve the required discrimination between the RCBO & the RCCB.
 
davesparks said:
Your crystal ball is obviously working better than mine! I can't quite see what the earthing system is or what rating that up front RCD is.
Click to expand...

I am going on the info I have. As in my signature. Everything I say the installer should be happy within their own mind that it is correct.
 
TJ Anderson said:
As I posted before, It may be a 30ma RCD upfront already, he has not stated rating.
Click to expand...

I know but we were specifically talking about if the RCCB is time delayed. In this case it would not give his new circuit the required protection so a 30mA non time delayed RCBO will be required.
 
Yes Noob you should not have 2 of the same mA RCDs in line, unless your RCCB is 100mA & time delayed.
As you have not given a mA for the RCCB which would normally be on the front, are you mistaking it for a ELCB?
You may need to take a pic of it so members can check.
 
UKESRail said:
Yes you will need to RCBO it. If the main is time delayed you will achieve the required discrimination between the RCBO & the RCCB.
Click to expand...

From the description , and without looking at it !
I would say that the installation is likely to be TT , hence the up front rcd ( probably an 100mA S type ) so why or how could it possibly be failing any regs if the new circuit was to be just installed on a new rcbo ( even then if needed ? ) , instead of a whole new board !?
 
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