Simon Barker:

It's a bit difficult with only one light circuit, but it's common to put the upstairs lights and downstairs sockets on one RCD and the downstairs lights and upstairs sockets on the other.  That way, if one trips, things don't go totally black.


Perhaps put the lights on their own RCBO?

There are future proposals to install a UPS next to the consumer unit for use during power cuts. The intention is that the lights will all be LED. My own proposal is to have a separate RCBO.


Circuit 6 might be taken out following a central heating upgrade.

Morgaine Dinova:

If someone could post links to online standards and advice for wiring up domestic consumer units both large and small, that would make very interesting reading.  It's somewhat embarrassing to be well acquainted with many advanced areas of E&EE yet lack basic knowledge of what is standard practice for every electrical installer. :-)


Morgaine.

The 17th edition Wiring Regulations contains useful information as all new installations (should) comply with it but implementing them in practice often requires knowledge and experience of an electrical installer. Split load consumer units are new beasts as they are not directly drop-in replacements for old school fuse boxes like single load consumer units are. An installer will have to answer the question about which circuit should be connected to which particular bank of MCBs under the control of an RCD, and which circuit would be best provided with its own RCBO, to ensure that the consumer unit is wired up optimally. Modern consumer units accomodate a number of control and switching devices - such as time switches, contactors, kWh meters etc. - as well as MCBs so these also have to be taken into account.


University engineering departments aren't generally very good when it comes to teaching undergrads about the basics of building electrical systems. I suspect that very few lecturers know much about the subject as they do not come from an electrical installation background.

Simon Barker:

You will have trouble finding anything even semi-official for free on-line.  The IET will quite happily sell you everything you need to know https://electrical.theiet.org/

Alasdair Anderson:

You may want to consider putting the kitchen sockets on their own RCBO as kitchen items are one of the more common sources of earth faults (with kettles and irons being particularly guilty).

Alasdair

Would it be a good idea to put Circuit 4 and Circuit 5 on the same RCD? If so, then should Circuit 7 or Circuit 9 also be added?

Simon Barker:

If you don't mind paying for it, the best option would be to lose the RCDs entirely, and put everything on RCBOs.  But that would be more expensive.


The two RCD solution is a bit of a compromise, but still perfectly OK for most homes.  It's really not that critical - just spread the load across the RCDs to avoid overloading them, and try to minimise the inconvenience if one trips.

You could argue that RCDs are purely cost saving and the optimal solution is to pay extra and have every circuit on its own dedicated RCBO. If there are no hard and fast rules how to allocate a particular circuit to a particular bank of MCBs under the control of an RCD then are there any conventions or recommendations from amongst the electrical installation community?