I'm about to buy the following item from Argos (430/8777) but I want to double check that light will work with a dimmer wall light switch.
Thanks.
If it'a mains voltage light, then yes.
Yes they are.
The case that one has to be careful about is low voltage since this depends in part on the transformer. Having said that, most of those seem to be dimmable.
Cheers for your help guys.
Yes but make sure you get a dimmer switch capable of taking the load. Halogen lights are different to normal lights. I burnt out my last dimmer switch even although it was well over the rating I'm sure someone will be along to explain it better in a minute.
Think GU10 means mains halogens so you should be ok - assuming your dimmer is suitable.
IIRC, it's down to the cold resistance of the filament which varies with the design of bulb. The dimmer instructions should say how much it has to be derated, but I'd guess at half. Could be modern dimmers can all cope with any type of bulb, though. Haven't bought one for a while.
The dimmer I'm getting should handle upto 400 so hopefully I won't burn it out!
Best to actually read the instructions etc to check it is suitable for your halogen loading.
This might be some use.
B&Q GU10s + properly rated dimmer switch = burnt out dimmer switch
I don't know how B&Q get their GU10s made, but they are nothing but trouble.
-- JJ
Check your dimmer specification. Most need to be de-rated by 50% because of the huge start current of these lamps. Also remember runnig dimmed massively reduces life span of halogen lamps. (gas/chemical reaction, not going into details; google for halogen lamp "halogen cycle")
OK, heres one:
Thanks for that link + info. What does 'de-rated by 50%' mean?
I'll also stay away from them B&Q GU10's!
Sorry, should have been clearer. If box says 400W dimmer, then (subject to operating instructions etc) if using GU10 lamps then only use 50% of its capacity, ie 200W. Hope that makes sense now ;)
Yes, that makes sense.. sorry for being a numpty!
Don't think they do cope. I know of a 1000w rated dimmer that was ruined within a month or so of being installed. It was controlling a dozen gu10 at 50w. All the bulbs were replaced by 35w and the new (1000w) dimmer seems to be doing ok. Your estimate that initial power flow can be twice as high as the rating seems about right.
Actually, it's very difficult to find halogen lamps where dimming reduces the life at all. Although the halogen cycle stops, this also coincides with massive reduction in filament evaporation as you reduce the filament temperature. Mostly, by the time the halogen cycle has stopped, filament evaporation is so insignificant that the filament life has already tended to infinity even in the absence of the halogen cycle.
No worries, if you have yet to buy a dimmer. Go to an electrical wholesalers and get an MK "Intelligent Dimmer"
(Cut from MK data sheet -
Intelligent Dimmer Switches incorporate the following advanced
features
? Suitable for dimming Low Voltage Halogen lamps via good quality,
fully dimmable electronic or wire-wound transformers
? Can be used with good quality mains voltage halogen lamps
incorporating GU10 bases. Please check with lamp manufacturer to
determine suitability
? Unidirectional current sensing
While being used with wire-wound transformers for low voltage
lighting, these dimmer switches continuously monitor the drive
conditions to the transformers, which require essentially, bidirectional
a.c. supply at their input terminals. If, due to some fault
condition, the supply to the wire-wound transformer is detected to
be unidirectional, which could result in over-heating and/or
damaging the transformer, the dimmer switches' circuitry
automatically stops supplying the transformer after a few cycles of
detected unidirectional supply
? Soft Start, which gradually increases the light output from the load
over 1 to 3 seconds after switch on. The Soft Start feature is also
particularly beneficial when used to dim Mains Voltage Tungsten
Halogen lamps which have inherent very high inrush current at
switch on
Standard Dimmer Switches
? Suitable only for use with fused GLS Tungsten Filament lamps to BS
EN 60064 and BS EN 60432-1
? One way dimmer switches incorporate manual soft start
? Incorporate thermal switches for protection against overload
It is when they blow and short-circuit that the dimmers tend to die. And if you buy GU10s from B&Q, it won't be long before one blows and short-circuits...
While investigating blowing bulbs a few years ago, it appeared that B&Q seem to hammer the suppliers costs down so much, that they produce special lines just for B&Q (though don't always label them as such). I suspect, in those sepcial lines, it is the long-life and safetly features that are sacrificed.
I bought two identical MK dimmers - identical ratings, model code etc. - one from B&Q and one from a local retailers. The local retailers version had extra components in it and a bigger heatsink, and a more robust connection between the heatsink and the thyrister. Of course, there could be other explanations for this, but it was enough for me not to touch B&Q electtical gear again (there was other evidence too, so this was not the only thing that led me to believe that their electrical equipment is inferior, even when it appears to be a big name).
-- JJ
I've got the dimmer already. I might just play it safe and just use 35W bulbs - might be a bit easier on the pocket too!
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