Spotlights switching off

[Floorboard_Killer]

I recently installed 10 spotlights into the kitchen ceiling and relaxed happily in the knowledge that they were working fine.

An hour later they switched themselves off, with an audible click at the dimmer switch. 5 minutes later they came back on.

This appears to do with reaching a certain temperature as they do not switch off at all if the dimmer is down low.

Any ideas on where the problem lies? The audible click on the dimmer switch makes me suspect that but how and why?

 

[Lectrician]

Overloaded dimmer. 10 lights? 50watt or more?? 500watt.

Most dimmers from DIY sheds only rate upto 250watt

 

[securespark]

If they are GU10's you need to derate the dimmer. If you have SELV lighting, you may need a special dimmer.

 

[andemz]

If they are GU10's you need to derate the dimmer.

Hi spark can you explain what you mean by derate the dimmer. I thought that the dimmer would need to be a higher rated one say 1000w rated dimmer.

Am i missing something here.

 

[ban-all-sheds]

That's what derate means. It means to reduce the rating of the dimmer, not install a dimmer with a lower rating.

So if a dimmer has a capacity of 500W, and you're using it for mains halogens, you have to derate the dimmer to 250W, i.e. regard it's capacity as 250W.

It;s the same with cables. 2.5mm T/E is rated at 27A clipped to a wall, but if you install it in conduit in insulation, you have to derate it to 20A.

 

[andemz]

so then if you have 10 mains GU10 downlights 50w each = 500 w you would need a dimmer which as a capacity of 1000w which would then be derated to 500w?

Is this right and if so why does it need to be derated like this?

 

[plugwash]

yeah

the think with halogens is they have a much lower cold resistance than normal lamps of the same power rating