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How to wire up a consumer unit

Arran Cameron

A semi-detached house has a prehistoric fuse box with rewirable ceramic fuses. It will shortly be replaced with a modern consumer unit. The existing circuits are:



 



1. Lights



2. Upstairs sockets



3. Downstairs sockets



4. Kitchen sockets



5. Cooker



6. Shower



 



The following circuits will be added to the consumer unit:



 



7. Central heating



8. Burglar alarm and CCTV



9. Outside lights



 



I have been informed that the best choice is a split load consumer unit with two RCDs and space for RCBOs. My intention is that circuit 8 has its own RCBO but what is the optimal way to allocate circuits to RCD A and RCD B? Also, should any other circuits have their own RCBO?


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    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?



     

Reply
  • 0

    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?



     

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