by ericmark »
Mon Aug 11, 2025 8:25 am
I find the changing of a fuse box to a consumer unit is so often done on the cheap, one needs to be careful that it is a like for like quote.
My consumer unit is all RCBO populated with a surge protection device, so I have 14 circuits, all independent, a fault on one will not stop any other working.
However, I have seen boards with two RCD's feeding MCB's and one is far more likely to have an earth leakage fault to an overload fault, so in real terms one only has 2 circuits.
We should divide into circuits, as necessary, to: (iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit (iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced
by equipment in normal operation plus some others, but these means should we do something when causes the RCD to trip that should not plunge one into darkness.
So we tend to split ring circuits side to side of the house, not up/down, as side to side uses less cable, so we have a better loop impedance and volt drop, and the two rings are more even loaded, plus with a fault one can run an extension lead without it going up/downstairs, but with lighting we tend to wire upper and lower floor, so to split into two groups means all sockets on one group and all lights on the other, which in turn means an uneven load, and should anything go wrong with a socket circuit you lose the lot.
So there is no way to split the load with two RCD's which really complies with the regulations, unless as with a caravan one has battery backed 12 volt lighting.
I had a trip about a month ago, I as so pleased we had all RCBO's as freezers still working so could wait until morning to find the fault. Anoying fault never found, unplugged items until fault cleared, tested the last few items, tested the RCBO no fault found and power returned to all. Maybe a slug or a spider in some electrical equipment, we will never know.
