RCD Tripping for no apparent reason

[Sid____]

Hi All,
Just recently our 100mA RCD in our home consumer unit has started to trip for no apparent reason.

On Thursday around lunchtime it tripped 3 times in the space of 1-2hrs. We were just using the kettle and microwave in the kitchen at that time. After I re-set it for the 3rd time I unplugged all our electrical appliances and switched off the outside lights. I gradually re-introduced them one at a time and all was well until around 3.00am this morning when I woke to find that the bedside clock was no longer illuminated. I got up and re-set the RCD then went outside to check if triggering the outside lights would cause it to trip. It didn't, but a few minutes later the RCD tripped again. I re-set it, turned the outside lights off and went back to bed. It hasn't tripped since.

Any idea of what could have gone awry? It's the same RCD that we have had for over 30 years. The outside PIR LED lights I fitted in December and have worked just fine. Everything else is as it has always been. I did wonder if anything on the mains supply side could be causing the RCD to trip. Is this possible?

 

[Murdoch]

To be honest as a homeowner there is little you can do other than keep notes about when it trips and what you were doing / using.

Turn on the new outside lights .......... and see if the tripping returns

Supply issues can trip RCD's

If it bugs you get a competent spark in to test your RCD - these do start to fail or become more sensitive.

 

[Geoff1946]

One possibly worthwhile guess is to closely inspect the outside lights for any sign of water ingress. Also anything else outdoor such as sockets, whether or not in use.

 

[Richard-the-Ninth]

Doesn't have to be water ingress, in this cold weather it can also be condensation

 

[Sid____]

Thanks to you both for your suggestions.

I've just been up the ladder and given the outside lights a close inspection. The 2 new ones are sealed units with short leads which are connected to the existing wiring using plastic terminal blocks which I wrapped in self-amalgamating tape like you use on satellite dishes. No sign of water ingress there. The other long standing PIR light has a built-in waterproof housing where the existing wiring connects directly to the light unit. That also looks OK.

I do have a sauna in the basement which hasn't been used in years. This has its own RCD on a separate circuit which I have now set. It will be interesting to see if this one trips as well if there is a next time.

The one that has been tripping is a Proteus 80/2/100T. I suppose if I can find a new one or equivalent for a reasonable price it could be worthwhile swapping them over myself before involving a sparky.

 

[Sid____]

Sorry Richard was busy replying. Didn't see your post until just now!

 

[SPECIAL LOCATION]

I suppose if I can find a new one or equivalent for a reasonable price it could be worthwhile swapping them over myself before involving a sparky.

From my past experience I find that randomly swapping components is a bit of a hit-n-miss method that typically proves nothing...

I normally start with some tests on the RCD to verify it is still operating within spec..
Then some insulation resistance tests on all relevant circuits supplied from that RCD..

And keeping in mind that it may not be one single thing causing the RCD to operate..
Cumulative leakage from multiple items/circuits could be the reason..

 

[jackiekennedy]

I have found in the past that it could be the motor on your fridge/freezer causing it, especially if is happening at different times. I had a client where this was found to be the issue.

 

[ELECTRICMEN]

As you state the RCD is 100mA, It may be prudent and compliant to remove and change with one with a 100A\30mA rating, Then if the New RCD\RCCB Keeps tripping then try to leave off one circuit at a time, but remember you could have a combined earth leakage on say 2 or 3 or 4 combined circuits greater than 100mA

But on a more technical note, imagine an RCD\RCCB Like a bucket that holds water, 30mA before it is full and tips over, you could have items on the circuits that are leaking say 5mA, 15mA, or 20mA, These leakages all safe leakages, but combined these items total more than the max rating of 30mA and hence you might just need a tech to establish your total earth leakage per circuit.

Hope that helps a bit.

All the best.
Mr Spence Eng (retired)

 

[Sid____]

Thanks everyone. I'm retired too and need all the help I can get!

 

[Radiotowers]

Hi All,
Just recently our 100mA RCD in our home consumer unit has started to trip for no apparent reason.

On Thursday around lunchtime it tripped 3 times in the space of 1-2hrs. We were just using the kettle and microwave in the kitchen at that time. After I re-set it for the 3rd time I unplugged all our electrical appliances and switched off the outside lights. I gradually re-introduced them one at a time and all was well until around 3.00am this morning when I woke to find that the bedside clock was no longer illuminated. I got up and re-set the RCD then went outside to check if triggering the outside lights would cause it to trip. It didn't, but a few minutes later the RCD tripped again. I re-set it, turned the outside lights off and went back to bed. It hasn't tripped since.

Any idea of what could have gone awry? It's the same RCD that we have had for over 30 years. The outside PIR LED lights I fitted in December and have worked just fine. Everything else is as it has always been. I did wonder if anything on the mains supply side could be causing the RCD to trip. Is this possible?

Without testing circuits its a bit hit and miss . In addition to all the above, in all my years working with a REC as a first response I can honestly say its very rarely the incoming supply thats the issue

 

[Sid____]

Without testing circuits its a bit hit and miss . In addition to all the above, in all my years working with a REC as a first response I can honestly say its very rarely the incoming supply thats the issue

Agreed.

Was watching a Terminator Chronicles DVD in bed with my wife last night and at around 11.00pm the main 100mA RCD tripped again. The 30mA RCD on the sauna which I had set did not trip so it sound as though the RCD is either doing its job or is faulty.

I've isolated the 1 dedicated flood light circuit for front and back floods & the basement lighting circuit for the flood over the garage and see what happens.

I may end up having to get a local Electrician to come and do tests. A ramp test on the RCD and insulation tests on individual circuits as mentioned earlier by Trailer Boy. It's a shame that decent test equipment is so expensive.

 

[Sid____]

Excluding Megger, is there any specific test equipment that anyone can recommend?

 

[SPECIAL LOCATION]

I may end up having to get a local Electrician to come and do tests. A ramp test on the RCD and insulation tests on individual circuits as mentioned earlier by Trailer Boy. It's a shame that decent test equipment is so expensive.

You can hire test equipment e.g... https://national-instrument-hire.co.uk/rcd-testers

Could be worth a bit of googling to check for any local to you...?>

 

[binky]

Excluding Megger, is there any specific test equipment that anyone can recommend?

You can get some reasonably priced gear off the likes of Amazon, but how good it is I really don't know.

 

[Radiotowers]

Excluding Megger, is there any specific test equipment that anyone can recommend?

Well the first thing I did as a first response from the REC was check incoming supply voltage to make sure it was within spec , if it was high incoming volts , this would be normally be overnight and very early in the morning.The transformers are very lightly loaded and the volts will creep up .
So a voltage indicator initially.

 

[Leigh Winspear]

Agreed.

Was watching a Terminator Chronicles DVD in bed with my wife last night and at around 11.00pm the main 100mA RCD tripped again. The 30mA RCD on the sauna which I had set did not trip so it sound as though the RCD is either doing its job or is faulty.

I've isolated the 1 dedicated flood light circuit for front and back floods & the basement lighting circuit for the flood over the garage and see what happens.

I may end up having to get a local Electrician to come and do tests. A ramp test on the RCD and insulation tests on individual circuits as mentioned earlier by Trailer Boy. It's a shame that decent test equipment is so expensive.

sounds like that pesky cyberdine systems is taking over one rcd at a time......

 

[Sid____]

Very funny!!

 

[dj.reynolds.]

Hi. Sid. I would want to place my bet on your fridge or freezer as the culprit. I have just come up with the same problem at my neighbours establishment. He has a shed with an egg dispensing self serve machine in it.
My checks of the supply found it to be clean, but when the fridge starts the leakage volts start to creep up and when a certain pump in it starts up there is more than a good chance it trips at this time. Still it is fairly new , he should be able to get the machine repaired for nothing under its warranty. I need do nothing more.

 

[SPECIAL LOCATION]

Fridge / Freezer compressors failing are a common cause of random RCD tripping events...

Regular fixed time of day faults are generally easier to track down..

Other random operating time component failures can include;
boiler/heating controls, valves, pumps...
outdoor PIR sensors / lights...
water penetrating external wiring/accessories...
mice/rats chewing through wiring, internal or external!