GU10 bulbs - LED type

[Mentalguy2k8]

Friend has a 4-lamp ceiling light which takes the usual GU10 halogen bulbs,

2 of them blew so she went out and bought 2 replacements which were LED ones - same shape and fittings but have what looks like 3 LED lamps inside.

They're all fed via a dimmer switch directly from light circuit (no transformer), and with the dimmer turned up to max, the 2 LED lights went off after about 15 minutes, stayed off for about 10 minutes then came back on - the "normal" bulbs stayed lit throughout. The LEDs also made a buzzing noise with the dimmer turned down.

Are they overheating or just not suitable to use in this arrangement? Or is it not clever to have 2 LED and 2 halogen in the same fitting?

[Jethro_uk]

Are the LED bulbs dimmer-compatible ? I noticed (in Sainsburys !) a few weeks ago that theirs had "suitable for use with dimmers" on the box, which implies there are some which aren't.

[Roger Mills]

I've got a fitting which has a mixture of halogen and LEDs and that works ok - but it's not on a dimmer, so they're all fed with full mains voltage.

I would have thought that, assuming the LEDs are suitable for dimming (which they may not be), you would have wanted to use *all* LEDs rather than a mixture. Otherwise you might expect odd things to happen because the light output vs voltage for the two types is very likely not the same.

[Tim Streater]

Thass right, some don't work with dimmers. OP needs to check that.

[Mentalguy2k8]

I didn't see the packaging, I just got asked to fit them because she couldn't put them in the holders.

They seemed to dim down OK when I turned the dimmer knob, it was with max voltage (?) that they cut out after about 15 mins. I assumed that the dimmer turned right up would be roughly the same as the lights being on via a normal on/off switch. They did seem twice as bright as the existing lamps, is it possible that they are designed to run off a lower voltage from a transformer?

I'll see if she's still got the packaging.

[Mentalguy2k8]

That would have been ideal, but I was asked what bulbs she should get and I just said "normal GU10s" and she managed to find LED ones somewhere. I assumed they were all halogen types in the shops.

[Tim Streater]

There's plenty of LED ones in the shops. I got four from B&Q but then SWMBO pointed out that they had a spread of only 35deg, so I got some

120deg ones from:

[Tim Streater]

No, GU10s run at mains voltage. Wouldn't be a GU10, would it, otherwise?

[Mentalguy2k8]

No idea, I was just asked to put them in the holes.

[Geoff Pearson]

That site has dimmable LED GU10s - a different category to the main lot..

[Tim Watts]

The LEDs must be marked as "Dimmable".

It's not that intuitive as most of us are used to LEDs having simple resistors as current limiters - and these would be fine on any dimmer.

However, the high power LEDs have active current limiters (in effect little internal "dimmers") and it is this which does not like being fed by a dimmer

- unless it has been designed for it.

As for halogens and LEDs in the same feed - that's fine. In fact it would be a good thing if the LEDs alone might not provide enough load for the dimmer.

[Tim Watts]

Most aren't. Like CFLs and for much the same reason - they are full of electronics :-(

If they don;t say "dimmable", they aren't.

[Tim Watts]

Yes - that is the case.

You can get G4 LED bulbs if a 12V supply is desired (eg for safety reasons).

[Grimly Curmudgeon]

In light of my thread up there ^^^^^^^^^ I've been looking at recommended dimmers - some LEDs need leading edge and some trailing edge. This page explains why, and the pitfalls...

don't suppose it's totally comprehensive and there's bound to be someone who knows a bit more who can come along and illucidate further.

[Brian Gaff]

I strongly suspect theleds have a switch mode psu, which is not working correctly on a dimmer. Brian

[The Medway Handyman]

Did you have to push & twist or just push?

[Jim Hawkins]

Some American GU10.s are 220 volt

[Jim Hawkins]

Some American GU10.s are 220 volt