Sequencing of RCDs and MCBs

[OzziAussie]

Hello sparkles,
I have a question in relation to sequencing the RCDs and MCBs in the CU.
I called an electrician to come to my house and upgrade the CU. Because it was hard to re-arrange the sequencing, an additional RCD was installed and the corresponding new MCB after it, but one old MCB is also now connected to the same RCD and location wise it stays several places before this RCD.
The electrician told me that he can re-arrange the whole install and shift the second MCB staying after the RCD but this would require shifting several MCBs and this is inconvenient.
I know that in some countries there is a requirement that all corresponding MCBs should be installed after the RCD they are linked to. Is this a compulsory requirement here in AU?
Personally I don’t mind, it’s just if someone else comes in to me next time, will it be convenient for this person to work?
Thanks
P.S. just to avoid unnecessary discussions, I am not touching anything or re-arranging anything. This question is for understanding of how RCDs and MCBs should be physically located and if it is compulsory to arrange them in a specified sequence.

 

[Mike Johnson]

Don't know the AU regs, but a MCB without RCD protection seems a bit daft if the RCD is already there, the MCB is just overload protection, the RCD prior to it provides a degree of short circuit protection in addition.

 

[OzziAussie]

Don't know the AU regs, but a MCB without RCD protection seems a bit daft if the RCD is already there, the MCB is just overload protection, the RCD prior to it provides a degree of short circuit protection in addition.

Thanks. I think there was some misunderstanding.
I will change the text to clarify.

Two MCBs are now connected to one RCD. One MCB is staying in the CU well before the RCD it is connected to, the second MCB is staying right after the RCD it is connected to.

My question was if all MCBs that are connected to the same RCD are required to be physically located to the right of that RCD, or they can be located anywhere in the CU.

 

[Mike Johnson]

Your explanation is still not clear to me, but In Europe MCB's are usually connected to the RCD by a busbar witch dictates the distance between the two: British General 21-Way Busbar 366mm - Screwfix -

 

[OzziAussie]

Your explanation is still not clear to me, but In Europe MCB's are usually connected to the RCD by a busbar witch dictates the distance between the two: British General 21-Way Busbar 366mm - Screwfix -

Ok, I’ll explain in more detail.
The switchboard has multiple RCDs and multiple miniature circuit breakers /MCBs/. If I look at the switchboard, to the left I’d see the main switch. Then, going from the main switch to the right, in sequence I’d see the MCB for switching the oven, then the MCB for switching the aircon. They are not connected to any RCD. Then I would see the MCB Power 1, then several others, then RCD1, then MCB Power 2. Power /active/ to both MCBs Power 1 and Power 2 comes from RCD1.

Following the logic of appearance, the RCD1 should be the left device and then MCB1 and MCB2 should stay after it to the right. It is just easier to understand the functionality of connections and dependencies. This is not the case, as I described above.

My question was about wiring rules and if this document specifies the visual appearance of switchboard and if it is allowed to have some randomness of installations

 

[Mike Johnson]

A photograph would make it much clearer, but in general in the UK the main switch is on the right, have been known to be on the right, but most consumer units have the large knock outs for the main cables on the right.

 

[littlespark]

From following the description, it may be that the feeds to the RCDs and mcb are on flexible cable rather than a static busbar… like how the UK in a dual rcd board where there is flex to the two RCDs and then busbar onward.

Aussie must be flex looped from device to device.

Electrically, it won’t matter, but for common sense and very possibly the Oz regulations, it should be laid out in a sensible order.

 

[Taylortwocities]

the MCB is just overload protection, the RCD prior to it provides a degree of short circuit protection in addition.

Not quite.
An MCB provides overload (or short circuit )protection. The RCD provides protection for EARTH FAULT current, not short circuit protection.