rcds and rcbs - confused

[coopy]

I have a problem. I have a split board with common earth and neutral bars. The incomer is just a normal switch but the power side is covered by an RCD. The lighting side has rcbo units for each circuit. It all looks a bit of a mess but appears sound other than that.
I have added some outside lights on the lighting side via an mcb which feeds an rcd (the type with a 13A fuse in it). Problem is, when I power the circuit up the main power side rcd trips straight away.
I have also added some rcd sockets to the power side but have not actually tested them with a load yet, is this likely to cause me problems too?

 

[Steve]

If all the circuits are RCD protected at the CU, what do you think you'll accomplish by adding more RCDs?

 

[Taylortwocities]

I thought you said

The lighting side has rcbo units for each circuit

. Do you mean RCBOs or MCBs?
RCBOs have two terminals in and two terminals out and have a test switch.

If the RCD trips you've probably got the neutral from the new lighting side onto the Neutral busbar.

Send us a pic of your board.

 

[EdwardCurrent]

Hello Coopy.

An RCD will detect an imbalance (residual current) between L-N, but will not provide 'overload' protection. An RCBO will provide overload protection, and any imbalance between L-N.

Is there any chance you could post a piccy of your consumer unit please ?

Do you know what tests are required on your new 'power' circuit?

Is your 'N' bar not 'split' ??

Ed.

Looking like RCBO's on Mainswitch side, and 'other' circuits protected by an RCD ? To avoid unwanted tripping circuits dived between both ???

N in wrong bar , but testing is needed on your new circuits before you switch them on.

 

[coopy]

As I said, it is a split board in as far as it has two 'main switches' but common neutral and earth bars. I would say it is about ten years old from the 'test' stickers on it.
The lighting circuits all have rcbo units plus an mcb for the smoke detectors.
The power circuits are protected by an RCD 'main switch'.
I was asked to add two outdoor sockets which I have done but not as yet plugged anything into them.
I was also asked to add some outside lights, one 150watt PIR flood and two small columns with compact 15watt fleuro lamps. I decided it would be wise to install an rcd into the circuit to protect the residents but I am not now so sure this is necessary anyway. I have connected the new lighting circuit to the lighting side ie. the side with the 'normal' main switch via an mcb.
Now, when I power up the new circuit for the lights, the power RCD stips out. I ran out of time today but I can't work out why it trips anyway.
HELP ! ! ! !

 

[RF Lighting]

Are you suitably qualified and insured to be doing this work

 

[coopy]

Ok, I am rusty on some of this stuff hence asking for some help from folk who hopefully deal with this sort of problem more than I do. I can probably sort it out long term but I don't have the time to spend chasing a possible fault when I get the feeling I am missing something obvious that I should have spotted from the start.

 

[flameport]

If this is a split board, it must have at least 2 separate neutral bars.
The new circuit you have installed is not connected to the correct terminals/bars in the CU.

Adding RCD protected sockets to a circuit which already has an RCD is a waste of money, and will cause problems as there is no way to know which RCD will operate first.

If the board already has RCBOs, why add an MCB and a separate RCD? Why not just get another RCBO? And was a new circuit really necessary for 3 outside lights?

Socket outlets are not 'tested with a load', they are tested using test equipment, with most of the tests being done before power is applied.

Most of this work is notifiable (Part P), so unless you have already notified your local building control, you have broken the law.

 

[coopy]

Ok thanks folks, I think I have worked out where I going wrong now.
This IS a split load board and DOES have common neutral and earth bars, in the old fashioned way, which is part of the problem.
Thanks very much for all your input.

 

[Spark123]

A split load board has 2 Neutral Bars - one for the RCCB protected circuits and one for the Non RCCB protected circuits.
The RCBOs should be on the non-RCCB side, as should anything else on that side of the board.

edited for terminology
RCD = generic term covering RCCB, RCBO and some other stuff.
RCBO = MCB and RCCB in one package
RCCB = device which operates on earth leakage but no overcurrent protection.

 

[Taylortwocities]

So, if I understand correct. Its obvious to me.
All of the lighting circuits have RCBOs.
The rest is on the RCD side of the board.

You have introduced an MCB on the non-RCD side of the board and used the RCD neutral bar. That's the technical problem - how about your competence?
How will your new work comply with 17th edition?
Are all your 'residents'. instructed persons or something.

Good grief

 

[coopy]

PLEASE TELL ME WHY IT IS THAT NOBODY LISTENS ANY MORE ? ? ? ?
FOR THE LAST TIME OK! THERE IS ONE, REPEAT ONE EARTH BAR IN THIS SPLIT LOAD DB, AND ONE, REPEAT ONE NEUTRAL BAR.
STOP TELLING ME THERE 'MUST' BE TWO OF EACH, THERE ISN'T ! ! ! YOU HAVE NOT SEEN IT ! ! ! ! ! ! !
Ok, I have made mistakes on this one, all I was after was a little advice, a little help from fellow proffesionals in the field.
What do I get, abuse and disbelief. A few scraps of 'maybe' usefull information and a load of grief. What a waste of time.
I hope your moderators read this although it will probably not stay on the forum for long.

 

[ricicle]

It is not a proper split load board then

 

[coopy]

OK, so what is it then?
I have one earth bar, one neutral bar, one incomer and busbar with lighting circuits fed by rcbo's and another set and onther one under the control of an rcd main switch. All made by MEM.
What does that make it? Other than a pain!

 

[ColJack]

the very act of it being a split load board necessitates the need for a SPLIT neutral and earth bar..
the fact that it isn't indicates that you are an idiot.. it's not a split load board... it cannot possibly be..
at some point another idiot may have tried splitting it by putting in another RCD, but without splitting the neutral you would get trips all over the place..

if you don't like the advice you are given, feel free to not take it and to not come back to the board again with an attitude like that..

the fact that we have not seen it is not our fault, you are free to post pictures on here and would have had a diagnosis a lot sooner had you bothered..