Garden Lights Tripping

[sl1210]

I went to see a job today where the garden gu10 spike lights trip out the rcd after an hour. i done an insulation resistance test from the switch and was getting a short between line and earth.

All the spikes and connecter boxes look ok and can't see any signs of water getting in. I disconnected the right hand side lights to see if i could narrow down the fault, and it tripped at some point again after i left. It has an rcd weather proof fusebox in the garden which seems to come of an rcd off the main house fusebox. now i've heard 2 rcd's could counteract each other, but it can't be this as they have worked fine for 19 months.

Strange thing is when i tested a couple of the lights individually with the lamps removed i was getting readings of 0.44 mega ohms line to earth, 0.55 mega ohms neutral to earth and 0.26 mega ohms line to neutral with the lamps removed. is this right for these lights? as i tested about 3 or 4 and most were giving this low readings.

Got to go back at some point and rectify this. Really baffling my brain.

Cheers

 

[Octopus]

If both of the RCD's are on the same circuit and they are both 30mA, the first thing you need to do is remove the one in the garden.

Your IR readings are on the low side.

 

[Strima]

You've either got water ingress on the JB's or a cable damaged somewhere. What's the cable type and installation method?

 

[sl1210]

its all run in armoured. i've opened up all the junction boxes and no sign of water. i'm slightly confused with the readings on the individual lights

 

[Strima]

How's the armoured run, buried, surface, clipped etc. Just laid under paving slabs, sharp stones etc can damaged the cable.

 

[sl1210]

mainly buried in soil and under paving stones

 

[Contently8413]

I have been in this exact situation, but it was 3 outdoor GU10 spotlights. Gel boxes and buried cables.

Regardless of weather, it had varying trip patterns: RCD did not even arm at times, sometimes triggered after a few seconds, sometimes after a few minutes, sometimes after a few months and sometimes while switching off the breaker. At some point, depending how many of the 3 spotlights were connected to the circuit, it would trip something like 3/20 times turning on the circuit. Tried replacing the GU10 bulbs with others that worked on another circuit connected to the same RCD and the trip pattern was only slightly different.

Even had to replace the RCD after it broke probably because it tripped far too many times.

My solution: replaced the 3 bulbs with Osram Parathom 16. This was the 3rd ou 4th different brand I tried. All previous ones resulted in random trips. No issues since. The problem existed for 2 years after building remodel. 2 different electrician teams tried to fix the issue without success.