Random RCD's tripping

[Alessio imperato]

Hi to everyone, I'm new on the forum and a almost a new in this world too. I got my full qualifications done in April but never done any job yet.
So I'll try to explain the situation in the best way I can

3 double light holder on the outside of a wall are on a single way switch. The switch is on a 6 way gang for other inside light.
All the floor light are on B20 RDC, all the fuse board has been changed 5 years ago on 17th edition.

The problem become when, randomly, the lights outside are on and the RCD trips. Doesn't seem to be any particular time/load that let the RCD to trip. Can be all the lights on together or that one outside only on and the RCD trips. But not every time does happen. Same time happen once a day a some time 15.
I checked if the lights holder are in short somehow. Line and CPC are insulated correctly from each other. All the 6 bulbs are brand new and all correctly working too.
I tried to bypass the cable between the switch and the lights with a flying cable. No difference.
Tried to leave one bulb at time but no difference, still tripping.
Does anybody have any idea about it.
THANK YOU ALL

 

[Pete999]

What IR test result do you have?

 

[Alessio imperato]

I ordered a multifunction tester but I haven't received yet. I'll do the IR as soon as arrive.

 

[Pete999]

I ordered a multifunction tester but I haven't received yet. I'll do the IR as soon as arrive.

Comments anyone?

 

[DPG]

Comments anyone?

Early days, hasn't got all the kit yet. Possibly just helping a friend sort an issue put? Doesn't sound like he's installed anything so no testing needed as far as that goes.

OP, am I right?

 

[Baddegg]

Outside lights?...water ingress?

 

[ferg]

OP you are on a hiding to nothing without proper test gear TBH.

 

[Alessio imperato]

Outside lights?...water ingress?

I did detached all the light holder, open it, dry them out with hairdryer. Also changed the straight connectors because some got rust on the screw.
Thank you

 

[Alessio imperato]

OP you are on a hiding to nothing without proper test gear TBH.

May I ask you what OP means?
Thank you

 

[Pete999]

Maybe I ask what OP means?
Thank you

Opening post, Original poster

 

[Alessio imperato]

Early days, hasn't got all the kit yet. Possibly just helping a friend sort an issue put? Doesn't sound like he's installed anything so no testing needed as far as that goes.

OP, am I right?

Absolutely correct. I just replaced a like to like bulb, witch broke few weeks ago

 

[Alessio imperato]

Btw the cables are 5 years old. They don't carry more than 300W and I don't think they get degraded so quickly with so little load. They are 2 and E 1,5mm between the holders and the switch and 2 and E 2.5 to the MB.
Just my opinion.

 

[westward10]

I have deleted several posts from this thread. If you cannot offer helpful advice then don't post.

 

[James]

You say that you have dried lights with a hair drier,
I would be amazed if this fault has nothing to do with water ingress.
The fact you have dried them suggests they were wet.
Also, could there be a junction box somewhere full of water?

 

[ferg]

I still think that then OP would be be wise to wait for the delivery of his MFT before proceeding.

 

[Alessio imperato]

You say that you have dried lights with a hair drier,
I would be amazed if this fault has nothing to do with water ingress.
The fact you have dried them suggests they were wet.
Also, could there be a junction box somewhere full of water?

I use the hair dryer to dry out some potential moisture. No sign of water in.
Also no junction box. Straight from the switch to the holder. Each holder is connected to each other in parallel with the straight connectors, that I also changed with a brand new wago 221 ( I guess)

 

[James]

If you can disconnect 2 of the lights
L+N you will be able to see if the fault lies between the switch and 1st light or the other 2 lights

 

[Alessio imperato]

If you can disconnect 2 of the lights
L+N you will be able to see if the fault lies between the switch and 1st light or the other 2 lights

I did disconnected all of them and turn it on one at time with a brand new 2and E as flying cable straight from the switch. Is a really irritating situation. Also because people around are thinking that I'm trying my luck guessing something

 

[DPG]

I think the best plan is to wait for your tester to arrive. Do you have an experienced electrician that you can consult?

 

[Wilko]

Hi - if RCD only trips when the lights are on, then it’s likely there is some fault there. You’ve not seen a fault yet and as others have said you’ll need your tester (borrow one?).

Two thoughts in the meantime -
It is possible for a wonky switch that has contact bounce to trip an RCD, but you would always see that at switch on or off and it’s pretty rare.
As the RCD tripping is almost random, it may be the RCD is finally tripping due to added leakage from something else being used, kettle is a classic suspect .