Socket Ringmain RCD isolation issue

[Gert_Lush]

Last night, i went to isolate an upstairs socket to replace the faceplate as it had cracked.
I flicked the RCD marked 'Sockets Up' and the socket i was working on went dead as expected. However, some other sockets upstairs were still live as a stereo was still on, but a few sockets went dead downstairs.

I flicked off the 'Sockets Down' RCD as well and all the sockets up and down went dead.

The problem as i see it is the RCD for sockets upstairs only turns off half of the sockets upstairs but also half of the sockets downstairs.
The RCD for sockets downstairs only turns off half of the sockets downstairs but also half of the sockets upstairs.

The house is 6 years old, and otherwise i have had no other problems with the electrics.

Any ideas what the fault is?

 

[Adam_151]

MCBs? (An RCD has a test button, an MCB doesn't, we'll ignore RCBOs for now )


The labeling is clearly wrong, you could got a couple of colours of stickers, stick one on each fuseway, and then go around testing what doesn't or does work and sticker it accordingly

Do you have an EIC (electrical installation certificate) for the house?, I'm just worried that if they are muddled up in the way that you describe, whether anyone has actually verified that the ring final circuits are actually in proper ring formation (as clearly no one has checked the labeling... they should have... its a tick box on the inspection schedule 'Labelling of protective devices, switches and terminals'!)

 

[Gert_Lush]

MCBs i mean!

I thought there could be a cross connection in the fusebox, not sure how common that is...

 

[Adam_151]

The circuits will quite likely be wired as ring final circuits where a cable leaves the distrubution board, connects to a string of outlets and returns to the distribution board after the last one. If the ends of the circuits were muddled up, you'd have to flick off both MCBs to cut the power to anything as it'd be interconnected (which would be a very dangerous situation, as it would severly compromise the protection abilities of the MCB!)

What could have happened in your case is the guy doing the wiring of the final circuits decided to split it into back and front sockets instead of up and down, someone else fitted the board, they didn't talk to each other and the thing got confused, and no one tested the installation and no certificate was issued! (as you don't mention having the EIC I asked about?)

I'd recommend taking it up with NHBC and pushing for a PIR (periodic instpection report) to be carried out

 

[Gert_Lush]

I don't have an original EIC from when the house was built. I do have an installation certificate from when an electric shower was installed about 9 months ago though.

 

[Gert_Lush]

If it is cross connected in the consumer unit, is it a simple job for a qualified sparky to rectify - if so, how long should i reasonably expect it to take?

 

[RF Lighting]

It will not be cross connected.

It was probably deliberatly wired like it is, but merely labelled incorrectly.

 

[kai]

It could have been wired as a Front of House and Back of House ring set up, so that some types of failure of the ring circuit (i.e. short circuit or overload fault) will leave half the sockets in working order per floor. (earth faults will pop the RCD though.)

 

[Gert_Lush]

i thought that but when i flick the upstairs mcb, some sockets at the front of the house upstairs go dead, as do some at the back of the house downstairs...

 

[Pensdown]

It sounds a bit messy

I would get a lead light and sort out which ones go off with which breaker and if need be label the sockets with the MCB number.