Ring Final Circuits ... each leg into a separate MCB!

[GB.Kayak]

I was inspecting the electrical installation in a large 5-bed late Victorian or early Edwardian property that I am considering buying in Scotland when I came across the 'socket circuits'; 3 32A MCBs so I expected 3 Ring Final Circuits. Each MCB only had one wire so adjust assumptions - they must be radials, jumper lead earth to live and search out sockets with continuity to measure R1 + R2. No easy task with ~12 rooms to check, and by the time I find that only one double socket is on this circuit I am beginning to wonder at the installer's logic. So on to the next MCB checking every socket ... this time all other sockets with the exception of a single socket on this circuit. Now running short of time I test the last circuit and one by one the same sockets as those on the second circuit show continuity! What had the installer done? What risks does this installation present to those occupying the house in their day-to-day use of electricity?

 

[woko]

2.5 radials on 32A MCBs are not safe, the cable will overload before the MCB will trip.
The simplest solution is to de-rate the circuit by installing 16 or 20a MCBs depending on the zs on each circuit.

 

[telectrix]

first thing is to establish if part of it is, in fact , a RFC. if so, after doing e-e on all conductors, bang 'em in the same MCB. if they are radials the downrate the MCBs. look out for a RFC with cross connections into other circuits.

 

[ackbarthestar]

The cpcs are likely to have been cross bonded between the rfcs another circuits and extraneous pipework. Often find this on lighting circuits. So by measuring from a common earthing terminal to each of the lives you will get continuity.

Try using the standard method of testing for a separated rfc, by removing all the circuits and doing an end to end test then to confirm or not that there are rfcs installed by the other two tests.

It is not that dangerous, albeit non standard, to have a B32A covering a 2.5mm2 radial circuit with one socket on it.

 

[Octopus]

Sounds to me as if there was one RFC and a couple of storage heaters and some muppet has installed sockets rather than the heaters and then used 32A MCB's rather than 16 or 20A

 

[oldtimer]

Yep think Murdoch has a point it will not been the first time that someone has chucked a 32A breaker at a 2.5 radial thing is if you are moving in now is the chance whilst empty to rewire it why ? I have just went to a job where the owner was advised 20 years ago to rewire the property he is now renting it out and has problems but the property for want of a better word is cluttered so if you get it take the chance and rewire lots of savings in the longrun

 

[SirKit Breaker]

Definitely a DIY Charlie job here somewhere.

 

[Marty203]

Left the ring main when I left the UK, only radial circuits here, 16 amp CB for 10 amp sockets with limits on how many per cir and 16CB for 15 amp sockets but only 1 allowed per cir, no fuses in plug tops only CB or fuse at switcboard