What's tripping my switch?

Flashy

Distinguished Member
A couple of times a week for the past couple of weeks, something trips an RCD. The one that's going is one of two main ones (with a test button, as opposed to any of the ones next to it labelled 'oven, 'kitchen sockets' etc.) and is the same one that tripped when using one side of the old toaster, which we identified as the cause and replaced.

It always goes between roughly 5.45am and 6.15am. It happened this morning at 6.10am, which is roughly the same time it went the last time, a few days ago.

I know little about electrics, but is it likely to be the fridge-freezer that's to blame? It's an integrated Lamona one, was there when we moved in and is probably about eight years old, if that helps at all.

That's the only thing I can think of that could be suddenly switching on and using a significant amount of power at that time of day. The only other thing I can think of is the combi boiler doing something, but we don't have any timers or anything like that set on it so can't see what it would be doing.

To my uneducated mind, the fridge-freezer makes sense, but surely it does what it does and goes through its motions throughout the day, so why would it only cause a problem at a fairly specific time, roughly ten hours after one of the two doors was last opened? (Though maybe that's the key – it hasn't needed to keep cooling because the door's shut for the longest period?)

If I need a new fridge-freezer I need a new fridge-freezer, but don't really want to get one if I don't have to and it's something else causing the issue.

Is there any way to test whether or not it's the culprit which doesn't involve turning everything off at the wall and turning on one appliance at the time? That's not really going to be practical given the fridge-freezer's contents, and complicated further by it not doing it all the time. The toaster was easy to identify and replicate – push down, toaster heats up for a bit, RCD goes. This is a bit different.

Happy to call out an electrician, but would rather solve myself if I can and save him the trouble of not finding anything and suggesting I try the process of elimination. Unless it sounds like something hugely dangerous/a disaster waiting to happen, of course.

Any ideas?
 

noiseboy72

Distinguished Member
I doubt it would be the fridge freezer, as they tend to have a fairly constant load throughout the day and night. Can you run an extension lead and run it from a socket not on that RCD? Depending on the configuration of the board, you may find that sockets elsewhere in the house are on a different RCD, but many older installations only have one to protect all circuits.

I would get the trip tested to make sure it has not become overly sensitive. The electrician can also do an insulation test on each circuit and see if the fault can be identified. RCDs work by sensing a difference in the current between the live and neutral, so all sorts of thing can cause enough leakage to trip out the breaker. Damp in a cable, loose and arcing cables and connections, failing cable insulation, rodent damage and of course a faulty appliance.
 

adam-burnley

Distinguished Member
My main RCD started tripping a few months ago, but at random times (usually in the evening), and mostly for no obvious reason. At first I thought it was something external as there has been occasional problems with the supply (so much so that I purchased a couple of UPS battery backup blocks for the NAS and Sky boxes a couple of years ago), however, the neighbours have not reported any problems so was probably internal to my house.

As mentioned, most of the time it would just trip for no obvious reason, i.e. nothing turned on immediately before the RCD tripped, but in the past few weeks it has tripped just as the kettle has been turned on, or the Induction hob. In fact I couldn't reset the RCD until I turned off the hob supply, which has its own breaker, but after about 24 hours I tried it again and it's worked fine since.

At the moment I don't know whether there is a faulty bit of equipment, or whether the system is being overloaded, but as it's so intermittent and doesn't appear to be caused by any one single bit of equipment I don't know how to troubleshoot it.

House was built 18 years ago, so the wiring and consumer unit is not that old really. Do RCDs need replacing after so long?

I need to get a sparky out to sort the sockets and lights in my new cinema room so will ask him to take a look at the same time, but if anybody has any ideas then I'm all ears.

@Flashy - if my electrician comes before yours I will report back on his findings.

Edit: sparky is hopefully coming tonight
 
Last edited:

Flashy

Distinguished Member
I doubt it would be the fridge freezer, as they tend to have a fairly constant load throughout the day and night. Can you run an extension lead and run it from a socket not on that RCD? Depending on the configuration of the board, you may find that sockets elsewhere in the house are on a different RCD, but many older installations only have one to protect all circuits.

I would get the trip tested to make sure it has not become overly sensitive. The electrician can also do an insulation test on each circuit and see if the fault can be identified. RCDs work by sensing a difference in the current between the live and neutral, so all sorts of thing can cause enough leakage to trip out the breaker. Damp in a cable, loose and arcing cables and connections, failing cable insulation, rodent damage and of course a faulty appliance.
It's integrated so can't get behind it easily but will get the step ladder out and have a nose around later. I'm assuming it's going to be like the oven (single oven) and dishwasher – plug from fridge to wall behind, which can be isolated using the fused switch on the wall. Hopefully the plug's high and I can get to it, in which case I'll try an extension lead overnight.

From memory, the board's in two halves, and the half that's tripping has all the sockets on it. There are umpteen things on but not in use. Normally I know it's gone because I'll wake up and there's no wifi on my phone when I go to turn off the alarm. Aside from things being on stand-by, nothing that's plugged in, barring the baby monitors, is 'active'.

But this morning I was actually up and watching TV, as I'd been awake since 3am (little one woke me up coughing, I just couldn't get back to sleep), hence me knowing when it went. So, Sky was on and TV was on, but that was it.

Just seems so odd that when it goes it's within the same half-hour window every time, hence me thinking fridge cooling kicking in after a longer break because the fridge-freezer doors have been shut and nights are cooler than days, meaning it's taken longer to warm up enough for it to fire up. I did turn down the temperature on the fridge after this morning's episode, whether that'll make a difference or not, who knows?

I need to get it looked at, better to be safe than sorry. Though when I mentioned the toaster tripping the RCD to the guy when we had the boiler serviced last year he said newer boards do err on side of caution as it were, and are far more sensitive than older ones. That's when he also mentioned how hard it can be to identify sometimes, hence me wanting to make a head-start if I can.
 

Showoff

Distinguished Member
Long shot!
I've had this issue before and it turned out to be the tundish for the central heating that was installed above a motorised value.

The water pressure was too high and the tundish was leaking into the value and tripping the RCD.

Could your water be coming on around that time?
 

Flashy

Distinguished Member
Long shot!
I've had this issue before and it turned out to be the tundish for the central heating that was installed above a motorised value.

The water pressure was too high and the tundish was leaking into the value and tripping the RCD.

Could your water be coming on around that time?
No timers set for central heating and it's a combi boiler so no timers for water (and not even a water tank anywhere). Definitely no taps/water-using appliances on at the times it's happened, either.
 

adam-burnley

Distinguished Member
Sorry I forgot to update this thread after my electrician came. He primarily came to discuss the requirements for the new cinema room, but we did talk about the RCD tripping issue. He said it was more likely to be the RCD had become overly sensitive, but didn't want to rule out the possibility of something being faulty.

As it turns out I'm possibly going to take the opportunity to replace the consumer unit, and get additional RCDs fitted to protect all of the circuits rather than just some of them, so will see if the issue continues after then. This is penciled in for the 13th or 14th July.
 

Flashy

Distinguished Member
Sorry I forgot to update this thread after my electrician came. He primarily came to discuss the requirements for the new cinema room, but we did talk about the RCD tripping issue. He said it was more likely to be the RCD had become overly sensitive, but didn't want to rule out the possibility of something being faulty.

As it turns out I'm possibly going to take the opportunity to replace the consumer unit, and get additional RCDs fitted to protect all of the circuits rather than just some of them, so will see if the issue continues after then. This is penciled in for the 13th or 14th July.
My house is just coming up to ten years old so a relatively new everything, but will get mine looked at in the near future.

But touch wood, since turning the dial down on the fridge (think the wife may have nudged it from less than 4 to nearly 4.5 out of 5, which explains why the cucumber was half frozen the other day) it's been okay.

So maybe it was the fridge. Or maybe it was something else. Or maybe I've jinxed it and it'll happen again tomorrow.
 

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