House RCD intermittent trip

[Tiggie]

2nd day in a row I've come home to find left hand side of consumer unit has tripped. Haven't added anything new electric wise recently so looks like I'm going to have to spend some time investigating 

 

The side that trips has the kitchen sockets, ground floor lights and upstairs sockets on it so that narrows it down a bit. Visually everything plugged in looks fine, nothing overheating etc etc. I'm doubting its the lights as they have all been off when it happened. 

 

Any tips welcome 

[bonio]

Ours started tripping unexpectedly. Turned out that the kettle we'd had for years was causing it - enough of a short to trip the box but not enough to blow the fuse in the plug. It was intermittent, but happened often enough to make it easy to track down. I'd say start by removing things one by one from the sockets and see if it still happens; it it does, then it's not the thing you've removed. 

[Guest]

Kettle did this to my ma and pa some years back.

[Bender]

Fridge/freezer usual culprit followed by toaster,  kettle microwave etc. 

 

If it starts doing it regularly it's easier to find,  you can't just switch something off at socket or wall,  if you have a neutral to earth fault it will still trip,  you need to un plug everything you can and start from there. 

 

Could be a faulty rcd too in which case it's not the things at fault . 

[manxie49]

I had a similar issue a few years ago, drove me mad!  I ended up getting an electrician, he found the fault in a couple of minutes, and it was as Bender alluded to, faulty RCD.

[Tiggie]

Wife and kids away till tomorrow night so I've switched off everything in kitchen until I get home from work. Will do same with upstairs tomorrow if it hasn't tripped.

 

Kettle wasn't even plugged in so I can rule that one out at least 

 

Sods law it'll be the washer or the fridge 

[Tiggie]

Think I might try swapping the RCDs around on the unit. Then I'll be able to tell if it's that or not 

[Bender]

5 minutes ago, Tiggie said:

Think I might try swapping the RCDs around on the unit. Then I'll be able to tell if it's that or not 

Yup if it's split circuit swap it over. 

 

 

[Mississippi Bullfrog]

Our used to that and it turned out to be the fridge. 

[Bender]

Is boiler on said circuit? 

[EX GASMAN]

It could be almost anything, you have to disconnect everything apart from the fridge freezer which has to be on, if it doesn't trip keep adding one at a time until it does. The problem is it's not always the last thing that has the fault. Most likely things are those that have water and electricity kettle immersion heater washing machine dishwasher etc. It may pay to call in a sparkly they have equipment to test the RCD and the resistance of appliances.

Edited August 19, 2022 by EX GASMAN

[Mickly]

We get an occasional trip - the main switch turns everything off, probably once every couple of months, I have learned that when I switch it back on to turn the central heating off as it resets to ‘auto’ which is only used in the very depths of winter 

[bonio]

Yes we get this after a power cut. Boiler switches to "auto" and "eco". "Eco" is German for never hot enough.

[keith1200rs]

Off topic,  but a bulb in my Neff oven tripped the main fuse when it blew. It also vaporised the main circuit board in the oven. The spare part has been discontinued. Fortunately an internet search showed where the damaged PCB tracks would be so I have fixed it and saved £1k+

[keith1200rs]

2 minutes ago, bonio said:

Yes we get this after a power cut. Boiler switches to "auto" and "eco". "Eco" is German for never hot enough.

I have an electric radiator in my bathroom and have to agree. I have also had to add a correction to the temperature sensor to make it heat the room up properly.

[Tiggie]

@Bender Boiler isn't on that side.  I turned off upstairs instead before going to work and it had tripped again when I got home so I figure it has to be kitchen related.

 

Strangely my ring doorbell is running from kitchen and it switched off both times between 8pm - 9pm.  I don't have anything running on a timer so might just be a coincidence 

 

 

[Bender]

4 minutes ago, Tiggie said:

@Bender Boiler isn't on that side.  I turned off upstairs instead before going to work and it had tripped again when I got home so I figure it has to be kitchen related.

 

Strangely my ring doorbell is running from kitchen and it switched off both times between 8pm - 9pm.  I don't have anything running on a timer so might just be a coincidence 

 

 

How did you turn off upstairs? 

[Tiggie]

unplugged everything and flicked the upstairs sockets mcb off

[Bender]

19 minutes ago, Tiggie said:

unplugged everything and flicked the upstairs sockets mcb off

To do that properly you need to remove the neutral from the bar that goes with the mcb,  turning off the mcb only removes the live,  if its a fault on something you missed or a cable it will still trip,  you must remove the live and the neutral when trying to locate or rule a circuit out. 

 

Rcd just acts like a balance, its watching the electric and expects the same on live and neutral,  you could have a situation when you get earth leakage that you didn't think possible ie tv with no earth but a fault that sends voltage via aerial cable to earth and rcd goes,  I know,  I've had that before.

 

Usually it's something obvs like outside light, fridge toaster,  sometimes it's a mare,  we had a fault on a ring main a mate of mine couldn't find it (proper lecy) and we had to split the circuit and loose a couple of sockets,  I found it when I did our bedroom last year and the feckers before us buried a joint in a plaster wall. 

[Tiggie]

I just know it's going to end up being the fridge or the washer    another good possibility could be an outside socket which is a spur from the kitchen. I've had a quick look and it seems fine, will take apart tomorrow for a better look.

 

Got the afternoon off so can have a better look at it.

[Bender]

Just now, Tiggie said:

I just know it's going to end up being the fridge or the washer    another good possibility could be an outside socket which is a spur from the kitchen. I've had a quick look and it seems fine, will take apart tomorrow for a better look.

 

Got the afternoon off so can have a better look at it.

Make sure it's got a drain hole in the bottom of the back plate,  even condensation can cause enough of a nuisance to trip. 

[Tiggie]

Definitely not the outside socket. Bone dry inside. 

 

It hasn't knocked off again yet since I came home last night which is annoying!! 

[EX GASMAN]

My daughter had this in her kitchen and only when I went and was able to check the resistance to earth with my test set (I used to do this as part of my work) I traced the fault to some bad wiring behind the kitchen units. I disconnected that part of the circuit leaving 1 socket not working and it was all ok until I replaced her kitchen and rewired the socket.  But without a test set it's very hard to locate the fault. As others have said the first thing to do is swap the RCD's over to try and confirm it is a fault on the circuit and not a faulty RCD.

[EX GASMAN]

1 hour ago, Tiggie said:

Definitely not the outside socket. Bone dry inside. 

 

It hasn't knocked off again yet since I came home last night which is annoying!! 

It's not just damp, if any socket looks slightly heated or burnt it could be that.

[Tiggie]

Swapping the RCD's over this afternoon 

 

I was reading an interesting story on a sparkies forum about a person who had a very intermittent fault. Would trip the breakers every couple of days or so, owners couldn't see what could be causing it so got electrician in. Turned out the owner had added some more nails to one of the floorboards in the toilet to stop it from squeaking, one of those nails had missed the joist and the end of it was resting on top of a cable. Whenever someone stood in just the right spot it would push very slightly into the cable and cause the trip.