Halogen GU10s with Dimmer switch

[snagglepuss27]

Indeed that old chestnut!

I have a new room (garage conversion) and intend to fit 10 GU10 halogens in two rows of 5. So I'd need a 2 gang switch I would imagine.

Ideally I'd like to control each row of 5 with a dimmer switch. So the question is what dimmer switch do I need? Would 250W Halogen rated do the job or is that right on the limit?

Would it be better to use LEDs of Low voltage instead?



Kindest regards

Snagglepuss

 

[securespark]

So I'd need a 2 gang switch I would imagine.

If you want to switch them in two banks, yes.

Does the dimmer you are proposing need derating for use with TH loads?

That will determine its rating.

LEDS are more efficient. But again, is the dimmer capable of dimming these lamps?

 

[Steve]

All the websites claim LEDs are not suitable for dimming.

For dimming 250W halogen load you need a 500w dimmer. If you fit a 250w dimmer it'll be right on the limit and wont last long.

LEDs wont need dimming - they dont throw much light out unfortunately, very much a developing technology as far as general lighting goes. OK for feature or decorative lighting

Low voltage halogen have the same efficiency as mains voltage. For the sake of arguement, there is no noticable difference. But they are harder to dim - getting compatible transformers and dimmers can cause troubel, and transformers do fail.

Have a look at CFL GU10s (google it). These are available in dimmable forms now, and give a better light than halogen.

 

[snagglepuss27]

Thanks for the quick and helpful response guys!

Yes in two banks.

Understand the issues with LEDs. Spoke to a guy in a lighting shop who recommended Hamilton 12V light fittings, 400W dimmer, and one transformer for 2 lights. As I want to put them in two rows of three that will actually mean 6 txfrmrs. This solution would be OK but the cost is in excess of £200. That seems a bit steep to me but is probably to high water mark price in this project (at least I hope so).

I'll look up CFL GU10s but it still comes back to the rating of the dimmer switch because all I've found so far are 250W - reight on the limit.

 

[johnnykc]

Hi.... Varilight do a 2 x 400w dimmer which will be fine for this job....you don't have to de-rate for GU10 lamps you just have to make sure that you use quality lamps from one of the big lamp producers that have a fuseable link to protect the circuit WHEN the GU10 fails.......if you use an' inexpensive' imported GU10, the spike, when it fails will damage the circuit (dimmer)....

 

[RF Lighting]

you don't have to de-rate for GU10 lamps you just have to make sure that you use quality lamps from one of the big lamp producers

Thats not actually even a little bit correct.

Dimmers need derating for use with halogen loads because when the lamps are cold, the filament has a much lower resistance than an equivalent incandescent lamp.

The low resistance when cold means the lamp will use more power than its stated rating until it has reached operating temperature, This initial inrush current can overload a dimmer running lighting at its rated capacity.

More expensive dimmers often preheat lamps before they are switched on, or fade the lamps up over a second or so to prevent the initial inrush. This also greatly increases lamp life.

A quality fused lamp is a good idea, and may prevent a triac from being destroyed on lamp failure.

 

[johnnykc]

Hi all.....RF Lighting, i was talking about a Varilight dimmer when i mentioned that there was no need to de-rate for GU10 lamps. . I refer you to the Varilight website (dimmer selection guide)............ . .Not that i disagree with you....i never think that its a good idea to load a dimmer upto the gills!......

 

[RF Lighting]

Sorry, I think I mis-interpreted your post there

I thought you meant all dimmers.

I have a couple of varilight dimmers at home, which are fairly well loaded up, and displaying no problems.

I'm slowly starting to replace these with GET smart dimmers though, 'cause I love my gadgets