Changing light fixture, RCD issues after

cryptoparrot · Mar 8, 2021

Hi all,

Over the weekend I swapped out a light fixture in a bedroom that had a Loop-in ceiling rose to a modern pendant light that had a choc block style terminal only.

I used Wago connectors and Wago box to wire everything up and put it in the ceiling. Before doing any work I flipped all the breakers for all circuits in the house off and also the main switch in the Consumer unit (possibly overkill I know but I'm a pessimist when working on this sort of thing!). I turned everything back on and everything in the house is working OK as far as I can tell, including the new light.

The issue is that the RCD switch for a circuit labelled "Sockets" (I'm not sure which socket circuit this is actually, I didn't label them and I haven't been in this house long) will no longer lock back in the "On" position. It's just hanging limp, in a position between on/off. It will lock into "Off" though if I push it down. Despite this, all sockets and lights in the house are working as far as I can tell, which is a bit unsettling.

To be safe I removed the new light fitting for now and just left the old cabling in the Wago blocks in the box - I'm going to have someone come take a look at this but I just wanted to have some opinions in the meantime.

Thanks!

littlespark · Mar 8, 2021

Could we possibly have a photograph of the board, showing the tripped rcd. Strange for domestic to have a mid position rcd like that.
I dont think this is in relation to the light you changed, unless you did something in the board as well.

All sockets and lights still working when rcd is off? This suggests nothing coming off this rcd, possibly because itself is faulty, and previous owners moved circuits off it onto a good rcd.
Have you checked any outbuildings that this circuit might feed?

There is a possibility that 2 socket circuits have been interconnected in the board or elsewhere which would mean 2 breakers need to be turned off to isolate. Might never have been found until work was needed on either circuit.

cryptoparrot · Mar 8, 2021

Thanks for the reply. Yeh, sure, here's a picture showing the mid-position switch attached. I'm really not an expert on this, the best description I have is that it's "flappy" or "limp" in that middle position and when moved upwards to the "On" position. It will lock into "Off" though.

I didn't do any other electrical work, so didn't touch the board other than to flip the power off. I was lead to believe the unit itself was pretty new and was installed just before we moved in. I think the last one might have been in violation of some regulations so was replaced.

All sockets, lights and the extractor fan in the bathroom are working. It's a small house, don't think I've missed any.

If there's any other troubleshooting I can do then I'm happy to do so when I'm home tonight.

Timbo · Mar 8, 2021

Being a 20A RCBO would suggest a radial circuit. Is there an outside socket, or a socket for a single appliance, or an immersion heater?

cryptoparrot · Mar 8, 2021

Timbo said:
Being a 20A RCBO would suggest a radial circuit. Is there an outside socket, or a socket for a single appliance, or an immersion heater?

There's no immersion heater and all of the appliances are still working, I just did a quick check.

There is some outdoor lighting but it doesn't work. There's a floodlight above the back door (currently no bulb, looks ancient) and a series of hard wired lights that you can stake in the ground. Just from looking at them, they seem to be powered by a piece of flex that just comes out of the wall around the first-floor level.

The guy who checked the place out for us electrically when we first moved in didn't mention them, so I just assumed everything looked OK RE wiring etc... and that the lights themselves didn't work.

I guess that could be the mystery circuit?

cryptoparrot · Mar 8, 2021

Just an update to the above:

I had a look at the outside lighting and where it comes back into the house, it's run off a couple of plugs that come in behind a cabinet in the corner. They're not plugged in currently and the socket they are close to is working fine.

That still doesn't account for the floodlight. I just had a closer look at that, it's in bad nick really. The casing is cracked and it has no bulb, definitely not water tight.

That's the only thing that's left that I can't test and confirm as fully working.

Timbo · Mar 8, 2021

Switch off the consumer unit and remove the cover. See if anything is connected to the faulty RCBO.
Post a pic, we like pics.

littlespark · Mar 8, 2021

Sorry, but I would advise not to take the cover off the board unless you feel confident doing so or have an isolator BEFORE the consumer unit that can be turned off.

Just turning off the board at its own mainswitch still leaves accessible live parts.