Garage cu - discrimination

[swc]

Hi
Am currently doing my 17th edition. Our teacher gave us a question to split typic domestic loads amongst the 10 way mcbs.
This is what I come up with


However one of my more experieced course mates said "All garage circuits protected by 2 x 30mA RCDs - no discrimination"
I know idscrimination is when the protective device closest to the fault operates. But am confused as to whats wrong with the way I did my consumer unit

 

[Richard Burns]

the rcbo has a neutral wire where can i put that when i only have two spare ways in neutral bar which are for the two unprotected ways.

Okay what you need to do is to be able to think about what you are going to do and how this will affect the circuit you are wiring up.
As you are in training (or possibly not) you still have some way to go with the understanding of circuits and how they are connected and how they will interact.

If you are using an RCBO then the neutral wire for the circuit goes into the RCBO and the neutral lead from the RCBO goes into the neutral bar, so you will not have a problem with too many neutral cables, even so, if you are thinking about it, you will see that you could put two neutral cables in to the same neutral termination.

 

[Deleted member 26818]

the rcbo has a neutral wire where can i put that when i only have two spare ways in neutral bar which are for the two unprotected ways.

When you use an RCBO, the circuit neutral is connected to the RCBO, rather than the neutral bar.
The neutral lead on the RCBO then goes to the neutral bar instead.
An RCD/RCBO detects any difference in current between the Line and Neutral.
As such the neutral has to be connected to an RCD/RCBO in order for the device to detect the difference.