RCD keeps tripping off

cherry76

My RCD keeps tripping off usually when I reset it works. On Monday I have to reset it three times and tripped off again after 10 mins. I decided to leave it a little longer and switched it back and it did stay on. Today it tripped off again. This has been an ongoing problem it can happen a couple of times in a year and then nothing for a long time. Told my husband I should contact an electrician to check but he does not want. Is it dangerous if do not do anything? Thanks

Jeepers_Creepers

This is the 'main' RCD in your CU, so that when it trips EVERYTHING goes off?

'Nuisance' tripping like this can be a 'mare. I posted on here myself a few months back as I started getting regular trippings at around 7 in the morning that couldn't be associated with anything. It then stopped doing it...

ALL circuits 'leak' to some small extent - every element in an oven, a teeny bit of damp in a light rose, a tiny bit of ditto in a mains socket - anywhere a tenny tiny path exists between the Live (or neutral) and the earth where a few milliamps of current can 'leak'. The problem with having a single main RCD switch is that all these wee leaks add up and something can then send it over the ~30mA tripping point.

If the RCD were to remain 'tripped' - ie there was a definite 'earth-leakage/imbalance' fault and you couldn't reset it - then that's easy; you flick off ALL the MVBs, reset the RCD and then switch on each MCB in turn until you find the one that causes the trip!

I suspect - like with mine - yours ain't like that?

How old is your house and wiring? Does it trip at any particular time of day? If it happened virtually every single day, then you could try a process of elimination by turning off unnecessary MCBs before you expect it to happen, and then see if that helps. Try and narrow it down that way. But that could be long-winded, pretty tedious and not even provide an answer.

Is it dangerous? That's not for me to say. I would hazard that it isn't - if you can reset it and it stays reset, then it's clearly hovering at around 30mA and not excessively above. But, it is a warning sign of something - so your call.

What did I do with mine? I couldn't find the circuit at 'fault', so assumed it was a general addition of teeny leaks in all which was then sent OTT by something - possibly even an external electrical spike (it was roughly around 7am, but there was nothing in the house that couldn't be blamed for that timing.) I was on the verge of thinking I'd need to replace my CU with one containing INDIVIDUAL RCBOs (MCBs with built-in RCDs) so that only the guilty circuit would trip in future, when........ it just stopped happening.

Too bludy annoying for words.

Yes, a sparky should be able to test each individual circuit for leaks and try and trace the cause, but if they find that no individual circuit is to 'blame', then they'll likely suggest a change over to RCBOs, at least for some main circuits. That might not be a bad thing, and if your CU is relatively modern, then you can get RCBOs for around £20 each, and they should pretty much slot straight in.

grumbler

I don't think it's dangerous - RCD does its job to protect you.

However, the problem does need to be sorted sooner or later. The sooner the better.

It can be either some appliance (more likely) or the wiring. I once had a laptop power supply that kept tripping my RCD.

cherry76

grumbler said:

I don't think it's dangerous - RCD does its job to protect you.

However, the problem does need to be sorted sooner or later. The sooner the better.

It can be either some appliance (more likely) or the wiring. I once had a laptop power supply that kept tripping my RCD.

Thanks the house is 46 yrs old. I had it replaced once. It happens usually at breakfast time when toaster is switched on. It used to happen at supper time when I used the rice cooker. All the lights work ok but not cooker or tv. Strange enough I could use the cooker switch to boil kettle. It does need to be checked but cannot persuade my husband I should get an electrician. He does not want anybody in the house now. 

Jeepers_Creepers

Sounds like you have a split CU, with the RCD protecting some circuits and not all. Ie, not the lights, and not the cooker supply, for example.

Bear in mind that if a device - eg the toaster - makes it trip, it might not be just that device's fault! Say you had a kettle running and a laptop (as Grumb experienced) and then you press down the toaster and the RCD goes 'pop' 20 seconds later, which appliance has the tripping 'leak'? Quite possibly all three to some degree, and the fridge, and the freezer and the...

It could be down to an accumulation of tiny leaks on a number of circuits, none of which are particularly 'faulty' on their own.

I went round our house and any sockets on cold outside walls were loosened and their backs given a spray of WD40 to displace any potential damp (this was a few months ago, during the coldest and dampest weather). This had no immediate effect, but the nuisance tripping did stop, seemingly all by itself a few weeks later.

It hasn't happened at all for a good whi...

Jeepers_Creepers

You understand the difference between the RCD and the MCBs?

The RCD detects any imbalance between the live and neutral (some might also detect earth leakage directly, I don't know). Whereas MCBs trip on current 'overload'.

The latter is of far more concern. That would indicate a short circuit either in an appliance or the wiring - and the fact an MCB trips means it's pulling a heavy current = worrying, and needs sorting asap.

The RCD is a safety device for the protection of peeps in the house - if you were to touch a live wire, there would be more current going through you than through the neutral, and the RCD would immediately detect that imbalance = trip!

It also detects leakages inside appliances, such as oven elements which have started to go but might still be 'working' ok (you might, for example, find the element is glowing very brightly in one spot where the actual element wire is sitting very close to the outer element casing and 'leaking' some current to earth.

Ganga

Mickey666 said:

Jeepers_Creepers said:

You understand the difference between the RCD and the MCBs?

The RCD detects any imbalance between the live and neutral (some might also detect earth leakage directly, I don't know). Whereas MCBs trip on current 'overload'.

The latter is of far more concern. That would indicate a short circuit either in an appliance or the wiring - and the fact an MCB trips means it's pulling a heavy current = worrying, and needs sorting asap.

The RCD is a safety device for the protection of peeps in the house - if you were to touch a live wire, there would be more current going through you than through the neutral, and the RCD would immediately detect that imbalance = trip!

It also detects leakages inside appliances, such as oven elements which have started to go but might still be 'working' ok (you might, for example, find the element is glowing very brightly in one spot where the actual element wire is sitting very close to the outer element casing and 'leaking' some current to earth.

I encountered this once with a toaster.  The toaster would start working but then cause the RCD to trip.  Turned out that one of the heating wires/filaments had (presumably) been bent such that it was very close to a bit of the internal metalwork of the toaster.  As the filament heated up it distorted slightly and touched the earthed toaster metalwork, whereupon the RCD did its thing correctly.

T'was a simple fix to bend the offending wire filament back into place and the problem has never recurred.

As previously mentioned, these sorts of faults can be very difficult to track down, even though they can be very simple to fix.  In my case, it was made easier because tripping only occurred within a minute of using the toaster so it was easy to locate the problem.

I know this is a MSE site but i think i would have got rid of the toaster and bought a new one for safety.

David713

Ganga said:

Mickey666 said:

Jeepers_Creepers said:

You understand the difference between the RCD and the MCBs?

The RCD detects any imbalance between the live and neutral (some might also detect earth leakage directly, I don't know). Whereas MCBs trip on current 'overload'.

The latter is of far more concern. That would indicate a short circuit either in an appliance or the wiring - and the fact an MCB trips means it's pulling a heavy current = worrying, and needs sorting asap.

The RCD is a safety device for the protection of peeps in the house - if you were to touch a live wire, there would be more current going through you than through the neutral, and the RCD would immediately detect that imbalance = trip!

It also detects leakages inside appliances, such as oven elements which have started to go but might still be 'working' ok (you might, for example, find the element is glowing very brightly in one spot where the actual element wire is sitting very close to the outer element casing and 'leaking' some current to earth.

I encountered this once with a toaster.  The toaster would start working but then cause the RCD to trip.  Turned out that one of the heating wires/filaments had (presumably) been bent such that it was very close to a bit of the internal metalwork of the toaster.  As the filament heated up it distorted slightly and touched the earthed toaster metalwork, whereupon the RCD did its thing correctly.

T'was a simple fix to bend the offending wire filament back into place and the problem has never recurred.

As previously mentioned, these sorts of faults can be very difficult to track down, even though they can be very simple to fix.  In my case, it was made easier because tripping only occurred within a minute of using the toaster so it was easy to locate the problem.

I know this is a MSE site but i think i would have got rid of the toaster and bought a new one for safety.

Why?
The fault was found and rectified at no cost so what reason would there have been to scrap a perfectly good and safe appliance?

TELLIT01

The OP has mentioned 2 devices which seem to be in use when the circuit trips.  Are these used on the same socket? or does the circuit only trip when one device or the other is in use?

Jeepers_Creepers

cherry76 said:

All the lights work ok but not cooker or tv. Strange enough I could use the cooker switch to boil kettle.

Hang on - when you say the RCD trips and the power goes off, the lights stay on (that's fine) but the TV goes off (that's fine) but the cooker also goes off but the cooker's wall control socket still works?

Can you confirm, please?