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I have had some re-plastering and re-decorating work done in my kitchen. I had a new light fixture installed which takes 6 GU10 type bulbs. When the light fixture was first installed I placed 6 LED bulbs into it. The bulbs are Aurora branded and consume 7W of power each.

When I switch on the light it trips out the power on the Residual Current Detector (RCD) in my house. We assumed the problem was with the old wiring - perhaps it got damaged when the work was being done. So we ran a new wire to the fixture from a new light switch.

The power still tripped out. Next we assumed the light fitting itself was faulty, so we returned it and got another.

Still the power trips out.

Then I thought it might be the LED bulbs, so I swapped them out for the 6 Halogen bulbs that came for free with the fixture - it works perfectly!

So the problem seems to be with the LEDs, but how can LED bulbs cause electrical problems? I paid £10 per bulb so wouldn't expect them to behave this way.

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With all 6 bulbs, how long after turning them on does the RCD trip? –  wallyk Dec 8 '13 at 19:56
    
Immediately - less than a second –  rf_wilson Dec 10 '13 at 9:10

1 Answer 1

Definitely sounds like faulty bulbs. The LEDs ought to consume less power than the halogens they are replacing (which typically consume 20-50W each in GU 10 size), and since you said you can run the fixture with all six halogens installed with no problem, your problem is not simply that six 7W LEDs were too much for your circuit in combination with all the other loads.

See if you can isolate the problem to one specific bulb out of the six by only installing one bulb at a time. It could be a short in one of the bulbs due to a manufacturing defect.

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So I have tested all 6 LED bulbs individually and none of them seem to be at fault. Through a lot of trial and error I have found that with just 3 LEDs the fixture works fine. As soon as I add a 4th LED then it trips the power. I have even tried a different brand (and lower power) LEDs and they too trip out the power when there are 4 or more in the fixture. –  rf_wilson Oct 14 '13 at 12:14
    
I am wondering if LEDs cause a short burst of power when they first switch on? Or maybe the fixtures I am using are not suitable for LEDs for some reason. –  rf_wilson Oct 14 '13 at 12:15
    
LEDs won't draw anything like the surge current at switch on that a halogen lamp draws; a cold halogen lamp is pretty close to a short circuit until the filament warms up. –  John May 25 at 23:07
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Their power supplies must be reflecting some sort of hash noise into the power wiring that the RCD detects as an arc fault. –  Fiasco Labs Jun 24 at 23:29

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