Hi All,
I have read the when installing mains halogen spotlights, you need to have a dimmer rated to twice the actual rating of the load.
The range of switches we are using (the chrome crabtree ones from Screwfix) has a dimmer with a 400w maximum which isn't quite enough the arrangement we have (240w of normal light lightbulbs, plus 105w of Halogen) .. this would beed 445w capacity.
Can anyone explain why the 2x overrating is needed, and it a flexible rule (i.e +/- 20%)
Cheers Chris
There are a number of issues. There might be a slight inductive effect from any LV transformers.
There is a much higher inrush current on halogens as halogens warm up from cold, compared to incandescent. They also have particularly powerful ionisation shorts when they blow.
Christian.
It depends on the dimmer. It should say on the box or instructions. If it doesn't, it will be safe with any load (other than inductive) up to its maximum.
OKay, so as all the Halogens i plan to use are mains voltage there are no transformers, so the inductive load is very little.
So in my case 400w should mean I can dim 400w total of incandescent and halogen.
Sadly, the only was to read the instructions is to buy it :-( I could try Crabtree customer support i suppose...
Cheers Chris
Near enough non.
A quick glance at the Screwfix site shows downloadable instructions for the Crabtree dimmer I looked at. And it certainly was a modern 'any' load type with soft start and overload protection.
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