Outside light - tripping RCD

[hightower]

Went to a job last week, replace an outside light with another customer bought one. Straight swap, few extra holes in the wall for new mounting, job done. Photocell model.

Left the job with a working light. Now, I fitted this in the p***ing down rain, which in itself was a tad silly of me but I wanted this job out the way. I chalked it off as something damp inside and said I'd be back round to look in a few days when it dried up - not a problem as it has a switch so can be isolated leaving the rest of the electrics on and working.

When I went back it hadn't rained since fitting, so should have been nice and dry in there by now. I checked and there was no wires trapped or anything. I'd asked if they'd tried it since and "no", so flicked it on and it works. Left the job, 10 minutes later a message to say it's tripping again.

So the symptoms are the light works fine for a little while, but then starts tripping. Once it starts tripping it continues tripping until seemingly left a while.

Probably a simple one as "dodgy fitting" but wanted to double check on here if anyone had any more thoughts? He's asked me to stick his old one back up, which I'll be doing this weekend at some point, but wanted a second opinion....

 

[telectrix]

test the fitting as in pat.

 

[hightower]

test the fitting as in pat.

It'll likely pass though due to it not tripping for the first 10 minutes?

 

[DPG]

It'll likely pass though due to it not tripping for the first 10 minutes?

Not necessarily - the test will stress the insulation more, ie. 500VDC between neutral and earth.
Daz

 

[Bobster]

Could always be something a miss in the photocell electronics.

IR those an you'll likely break them.

 

[Richard Burns]

The light itself is unlikely to have any connection to earth in the circuitry so unless something is expanding whilst on and the circuit/lamp is then touching the body of the fitting I cannot see how the RCD would trip from the light fitting alone.
Where did those extra holes for mounting the fitting go? perhaps near the supply?

Also if the light had been changed before and there is a nice terminal block in insulation tape just inside the wall that got wet during fitting this may be a cause.
On site investigation is the only way, though it would be interesting to see if it still trips with the old light!

 

[hightower]

The light itself is unlikely to have any connection to earth in the circuitry so unless something is expanding whilst on and the circuit/lamp is then touching the body of the fitting I cannot see how the RCD would trip from the light fitting alone.
Where did those extra holes for mounting the fitting go? perhaps near the supply?

Also if the light had been changed before and there is a nice terminal block in insulation tape just inside the wall that got wet during fitting this may be a cause.
On site investigation is the only way, though it would be interesting to see if it still trips with the old light!

The cable is straight through so no chance of contact. Just finding it strange with it being a delayed trip rather than the second it's turned on

 

[Wilko]

Any chance it's them turning something else on that's under that RCD?

 

[hightower]

Any chance it's them turning something else on that's under that RCD?

One rcd for install. Definitely not anything else as the light trips as soon as turned on (after the initial delay) - it's that delay turned instant symptom that's making me think electronics of the photocell?

 

[Deleted member 9648]

There could be a N-E fault somewhere else on the installation, sometimes the tripping can be completely unrelated to the apparent cause. Test the whole lot.

 

[AyresomeBoro]

Another thought if all else tests out fine - Faulty RCD?

 

[sparksburnout]

No point looking for complicated solutions, it would be very co-incidental if it was something other than the light (assuming it actually was working OK before!). Just stick the old one back and see how it goes.

 

[hightower]

Thanks for replies everyone. Old one now back up and no issues, so had to be a faulty light

 

[Deleted member 9648]

I'd still of IR tested the install....would take 5 minutes to do a global. As it is you've made an assumption that may be correct but it's still an assumption.

 

[hightower]

I'd still of IR tested the install....would take 5 minutes to do a global. As it is you've made an assumption that may be correct but it's still an assumption.

I didn't explicitly say I didn't test the install. I did IR test it and returned fine. Also clamp tested to see but that returned nothing interesting