I have two 6-way strips of halogens (50W GU10's) that I want to control via a 2-gang dimmer. Most dimmers I have seeen say they are rated at 400W, but when you read the small print they say they are only rated at about 250W if using hologen's. Given that I need 300W per dimmer can any one recommend a dimmer for the job? I have heard you can get 600W two-gang dimmers on a double face-plate, but they sound very expensive. The last company I contacted (Hamilton's) said their policy with 400W dimmers was to de-rate them by just 25% (i.e. giving me the 300W I need), but they didn't sound confident. Any help gratefully received.
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- Thread starter bodgerd
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The usual rule of thumb is to derate by 50%. Given that you have 300W per gang, this gives 600W.
So you need a dimmer that will handle 600W, and preferably a 2 gang one at that. You may have to install 2 x 1g side by side.....
So you need a dimmer that will handle 600W, and preferably a 2 gang one at that. You may have to install 2 x 1g side by side.....
MK Logic Plus Intelligent dimmers are rated at 2 x 300W continuous for halogens.
I think the derating rules-of-thumb came from early experiences with dimmers never designed to cater for the high inrush currents that LV halogens generate. Nowadays, manufacturers are making products designed to cope without derating.
I think the derating rules-of-thumb came from early experiences with dimmers never designed to cater for the high inrush currents that LV halogens generate. Nowadays, manufacturers are making products designed to cope without derating.
Thanks for that - just looked at the MK Logic Plus datasheet at http://www.tlc-direct.co.uk/Technical/DataSheets/MK/Logic_Plus_Dimmer.pdf and I am now confused. I see they are OK for mains powered halogens and rated at 40 to 300W, but they are described as 1-gang double dimmer switch. I thought 1-gang meant there was only one dimmer on the face plate, or have I lost the plot? I also notice they do a 1-gang single rated at up to 500W, would I be better off with 2 of these rather than a double rated at 300W each just in case - any thoughts?
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Maybe the point they are trying to make is that the double switch fits a single-gang box.
And yes - if you don't mind two singles you'd be better off as they'd be lightly loaded, which is always a good thing. Even if they are quite happy, dimmers can get warm. I've got a DIY 4-module (assembly of the accessory is DIY, not the actual dimmers) on a 2-gang plate in my living room, total load 600W, and all 4 are often on, at a dimmed setting, for several hours. The dimmers are fine, but over the years the rising heat has left dark marks on the wall above. (Yes it's way past time for a re-dec...)
And yes - if you don't mind two singles you'd be better off as they'd be lightly loaded, which is always a good thing. Even if they are quite happy, dimmers can get warm. I've got a DIY 4-module (assembly of the accessory is DIY, not the actual dimmers) on a 2-gang plate in my living room, total load 600W, and all 4 are often on, at a dimmed setting, for several hours. The dimmers are fine, but over the years the rising heat has left dark marks on the wall above. (Yes it's way past time for a re-dec...)
Cheers - Just phoned MK Technical Support. They recon the Intelligent Dimmer 1 gang, double dimmer rated at 40 to 300W each will do the job, although we are at the maximum limit with our two 6-way GU10 halogen strips. They say that "1-gang" to them just means it fits on a single face plate, but confirmed it causes much confusion with their customers! The only problem is - they cost £52! I think I'll go for it, and if I get worried about using them at their limits of power rating I will replace the 6 x 50W GU10's for 35W. Thanks again for your help with this.
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Just a little warning.
MK dimmers used to have fuses to protect the dimmer from toasting if the lamp blew.
No longer. MK put a warning in the dimmer boxes that you should ensure the lamps have internal fuses to prevent any damage to the dimmer. And at £52.00, you want to protect that investment...
MK dimmers used to have fuses to protect the dimmer from toasting if the lamp blew.
No longer. MK put a warning in the dimmer boxes that you should ensure the lamps have internal fuses to prevent any damage to the dimmer. And at £52.00, you want to protect that investment...
I'm actually having second thoughts, and I might well go for 2 single dimmers, rated at 500W, price-wise it works out the same (it just won't look so neat having to have two single back-boxes). On the protection fuse front, if my halogen strips don't have them built in, where can I put them?
Use a dual one:bodgerd said:
Have you looked at the grid systems available from manufacturers like MK ( http://www.mkelectric.co.uk/products/ranges/rangelist.asp?RangeID=1026 ) or Crabtree ( http://www.electrium.co.uk/download.asp#pos_crabtree ) etc?
A grid system lets you make up a single plate containing either a mix of different things and/or a large number of things.
You buy individual modules, which can be switches, fuses, dimmers, neon indicators etc, a frame to fix them to, which then screws to a flush or surface mount box (conventional ones for the smaller sizes of frames) and then a plate to cover the whole lot up, e.g :
Where they come into their own is when you want a lot of switches on one neat plate, as you can get quite big ones
Unlikely to want one as big as that in your house though, but you do see 8-12 way ones in kitchens with a mix of switches and fuses supplying and controlling socket or flex outlets under worktops for appliances - you can get switches engraved with legends like Fridge, Dishwasher, Tumble Drier, Boiler etc etc.
In your case you could use a grid to get 2 high capacity dimmers onto a single plate which would fit a normal (deep) 2-gang flush box.
Probably safe to say that the price would be higher than non-grid....
You buy individual modules, which can be switches, fuses, dimmers, neon indicators etc, a frame to fix them to, which then screws to a flush or surface mount box (conventional ones for the smaller sizes of frames) and then a plate to cover the whole lot up, e.g :
Where they come into their own is when you want a lot of switches on one neat plate, as you can get quite big ones
Unlikely to want one as big as that in your house though, but you do see 8-12 way ones in kitchens with a mix of switches and fuses supplying and controlling socket or flex outlets under worktops for appliances - you can get switches engraved with legends like Fridge, Dishwasher, Tumble Drier, Boiler etc etc.
In your case you could use a grid to get 2 high capacity dimmers onto a single plate which would fit a normal (deep) 2-gang flush box.
Probably safe to say that the price would be higher than non-grid....
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