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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, 2013 at 19:56
  • Immediately - less than a second
    – rf_wilson
    Dec 10, 2013 at 9:10

4 Answers 4

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The LEDs do not light up (ie conduct) for a brief time after switch on. During that time there is current in the Live wire but not in the Neutral. The rcd reacts to this imbalance (residual current) by breaking the circuit. Neither the rcd nor the LED lighting system is faulty.

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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, 2013 at 12:14
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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, 2014 at 23:29
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    @FiascoLabs: That does seem to be the most likely explanation. Worth complaining to the manufacturer -- you may not get a refund, but you'll be helping them improve the product for the next buyer. Also, you may want to experiment with keeping one halogen and see if that buffers this noise enough to make the RCD happy; it's not a great answer but it could be a stopgap solution.
    – keshlam
    Sep 22, 2014 at 22:59
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    how about a less sensitive rcd?
    – Digital Lightcraft
    Dec 22, 2014 at 9:27
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    @DigitalLightcraft -- what's really needed here is a more-EMI-resistant RCD.
    – ThreePhaseEel
    Nov 22, 2015 at 2:06
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This problem is probably due to EMI from the LED bulb driver/ballasts tripping the RCD. One suggestion to try would be wiring a lamp debuzzing coil in series with the fixture -- this should provide at least some EMI suppression.

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The LED bulbs emit electricity from only one side, unlike fl which are two sided. Your LED bulbs are shorting out. you have to remove the ballast in your fixture (or just cut the wires) and to replace the sockets in your fixture (from shunted to non-shunted). suggest you find an electrician experienced with LED or look on youtube for how to install linear led tubes

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  • OP indicated these are GU10 sockets, originally with halogen bulbs, see topbulb.com/q35fr-gu10-bulb-35w-120v-djd-halogen-frost . These are not linear fixtures nor are they fluorescent, and are very likely not ballasted. I didn't downvote you myself, but it looks like others have made similar observations.
    – Doktor J
    Feb 13, 2017 at 19:53
  • You may be thinking of G13 sockets, i.e. those used in standard T8/T12 linear fluorescent fixtures?
    – Doktor J
    Feb 13, 2017 at 19:54

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