Outside Security Light Causing Rcd To Trip

[PeteDel]

About 6 months ago I installed a light outside my kitchen door. this was wired from the fused spur for my extractor fan and I performed all tests required for a minor works cert.

All was well until a few weeks ago when the rcd started to trip, this seems to happen at random times, however it stops if I turn the fused spur off to isolate the light and fan.

please ignore the pun but can anyone throw any light on what might be causing this?

 

[binky]

water in fitting, or spider has nested in there

 

[Doc Hudson]

RCD's will trip, (should trip), when a small amount of current is flowing to earth. Assuming your RCD is a 30ma device a continuity of around 7666ohms or less between a live conductor and earth will allow a current large enough to trip the RCD. A continuity test between line and earth and neutral and earth may start you in the right direction (Remember that neutral is also a live conductor). As Binky has pointed out water ingress, insects, rodents or mechanical damage from installation could all cause an earth leakage path. However assuming it was all installed correctly, and all of the appropriate tests as per BS7671 were carried out, I would think it unlikely that deterioration of the cables or the accessory should have occurred within 6 months.  The RCD could be over sensitive, what is the rating of the outside light? What else is on the circuit besides the fan? What other circuits is the RCD protecting. Some further testing is needed to isolate various parts of the installation out of the equation.

Doc H.

 

[PeteDel]

Binky, water getting in was my first thought as well. No signs of condensation or moisture in the lamp and looked bone dry inside the enclosure where all the cables are connected as well, just to make sure I did apply some silicone sealant around the incoming cable and where the screws are, however hasn't made any difference.

Doc, the light and fan are part of the kitchen ring.  rcd also covers another ring and a lighting circuit. outside light is rated at 120w

 

[septiclecky]

Are you sure it is the light and not the fan if they are both off the same FCU

 

[Blue Duck]

Sounds like its the fridge! I mean seriously anyone ever heard of an rcbo?

Done about 10 security lights in the last 2 weeks must be the cold contracting the plastic? Mostly full of water some faulty internal switch.

If you have the eqipment IR it

 

[steptoe]

Binky, water getting in was my first thought as well. No signs of condensation or moisture in the lamp and looked bone dry inside the enclosure where all the cables are connected as well, just to make sure I did apply some silicone sealant around the incoming cable and where the screws are, however hasn't made any difference.

Doc, the light and fan are part of the kitchen ring.  rcd also covers another ring and a lighting circuit. outside light is rated at 120w

you do realise silicon reacts with PVC cable?  :|

 

[SPECIAL LOCATION]

If you have the equipment IR it

I believe he bought a tester back in February....

http://talk.electricianforum.co.uk/topic/22250-choice-of-two-testers/

Maybe its still in the box ...

Or the IR test isn't working...?

Can't be that difficult to Test RCD verify its ok....

IR test all circuits supplied by the RCD....

If intermittent

Maybe swap a circuit to another RCD

Or install a temporary RCBO

or any other logical step to isolate elements out of the equation to work out the cause...

:coat

 

[Steve3948]

you do realise silicon reacts with PVC cable?  :|

I would'nt worry too much Steps, I've been using it for years, gone back after 10 years to change fitting, cable fine more than can be said for fitting which the UK weather had destroyed..

 

[binky]

in that case check a screw hasn't snagged a cable in FCU causing intermittent short to back box - so easy to do!

 

[steptoe]

I would'nt worry too much Steps, I've been using it for years, gone back after 10 years to change fitting, cable fine more than can be said for fitting which the UK weather had destroyed..

I know,

but, I have also seen other types of 'silicon' that are very aggressive towards cables,

I dunno why  :C

 

[SPECIAL LOCATION]

I know,

but, I have also seen other types of 'silicon' that are very aggressive towards cables,

I dunno why  :C

That silicon in those dodgy breast implants was a bit aggressive from what I have heard...

opcorn

 

[kerching]

That silicon in those dodgy breast implants was a bit aggressive from what I have heard...

opcorn

I blame them fully and squarely for the cause of my wrist problem

Just saying

 

[samson337]

Well it's also affected my eyesight, luckily my wrist is still going strong

 

[Bruspark]

Bathroom sealer "AKA silicone bathroom sealant' may contain acid to accelerate setting and that can definitely affect metals and some plastics while it cures (the smell is the warning)

"Silicone grease" e.g. google   "Servisol 50g Silicone Grease" is a different thing : specifically intended to seal small cable gaps and connector threads and does not set.  I've not seen any bad side effects besides that It also gets everywhere and ruins your trousers but that's another story