Dimming LED downlighters

Discussion in 'Electricians' Talk' started by RolandK, Feb 22, 2018.

  1. RolandK

    RolandK Screwfix Select

    I've had four LED downlighters knocking around for a while that I'd like to use. (They are Franklite RF 257's).
    Each one comes with it's own small led driver and 3 x 1W LEDS connected in series. The drivers are not dimmable. If I get a dimmable driver and compatible dimmer should I be able to dim these? If so is it a driver per fitting or one to do all four?
    Cheers
    Roland
     
  2. Bazza

    Bazza Screwfix Select

    Hmm.

    You will certainly need dimmerable drivers. And an LED dimmer. The Varilight V-Pro are probably the best ones. Available from our host.,
     
    KIAB likes this.
  3. RolandK

    RolandK Screwfix Select

    Thanks Bazza.
    Is it one driver per fitting or one for all 4 do you reckon?
    Cheers
     
  4. Bazza

    Bazza Screwfix Select

    I have no idea what a Franklite RF 257 is.

    You could wire them with separate or combined to one driver. Make sure its the right driver for the LEDs and enough for the total load, and decide if you need a constant voltage or constant current driver....... this electric stuff isn't simple you know.
     
  5. RolandK

    RolandK Screwfix Select

     
  6. RolandK

    RolandK Screwfix Select

    No it sure ain't simple these days !!
    Constant voltage or constant current ? Dunno I'll do some more digging. The fittings themselves look really simple with just the 3 leds in. They were pretty pricey so I'd like to use them if poss.
    Thanks again
     
  7. Bazza

    Bazza Screwfix Select

    Constant voltage basically means that the LEDS are wired in parallel. So if they are 12v LEDs then you need a 12v LED constant voltage driver. This is the most common method.
    Constant current basically means the LEDs are wired in series. Popular sizes are 350mA or 700mA. It will depend on your LEDs.
     
  8. DIYDave.

    DIYDave. Screwfix Select

    Just think the idea of using 1 transformer per light fitting is when and if transformer blows, you only loose that 1 light fitting (until a replacement fitted)

    Like those horrible MR16s that were/are popular still ?

    You can have 1 light per transformer or buy higher output transformer and have 1 per multiple fittings - but when transformer blows, again you loose 4/5/6 lights

    Can certainly get 1 transformer to power all 4 lights, especially as with led, load is so much less then halogen

    Depends on accessibility of transformer as well - needs to be accessible as these don’t last forever

    Although with led, they probably last longer as a blown halogen can also knock out transformer (im only guessing here tbh on this point) :)
     
  9. Sparkielev

    Sparkielev Screwfix Select

    Be easier to change whole fitting with driver included and not much cheaper
     
  10. RolandK

    RolandK Screwfix Select

    Thanks all for the replies.
    The 3 leds in each fitting are definitely wired in series so constant current driver it is then. The supplied driver is 12v so I'll get the new one with the same output. So then I know to check the dimmer is compatible. For ease of wiring I'll probably go with a single driver/transformer with plenty of spare capacity. I guess I can 'daisy chain' the output to each fitting. The fittings are going in the landing ceiling so plenty of access to them and the wiring if needs be. Good point about the single driver failing but in situations like this I tend to keep spares so will do so with the driver. I was thinking of the option of just going for something else but these fittings are just right for the job (apart from the fact that they don't dim!) and beautifully made. I was surprised when I wired them up to test them how much light came out of each one with just the 3 x 1W leds, hence the need to dim them! And if my memory serves me correctly the four cost me about £320! So reluctant to bin them!!
    Cheers all.
     
  11. unphased

    unphased Screwfix Select

    Roland I would offer a word of caution. All components in a dimmable system need to be dimmable. The LED lamps themselves must be dimmable as well as the driver. I am not sure that these LED lamps are dimmable. You could try their website for contact details and see if they can help you. www.franklite.net
     
  12. RolandK

    RolandK Screwfix Select

    Good point unphased. Tried to get some techie help from them earlier but not too successful!
    I'll try again with this specific question. Else the leds will need changing at which point is it worth it !?
    Thanks
     
  13. unphased

    unphased Screwfix Select

    Exactly, Roland. I know you paid a premium for that fitting, so I agree that its tempting to try to keep it. I suppose the reticence on the part of manufacturers to 'help' is they don't like people modifying their products. I hope they would be willing to divulge whether the LEDs used are dimmable, though, its a bit selfish if they don't, or won't. Good luck!
     
  14. RolandK

    RolandK Screwfix Select

    Just been thinking about this dimmable led business........
    The leds in the fittings are on a mini circuit board and are the only component. They are therefore connected directly to the low voltage input. So if the driver is dimmable then should the led be dimmable to? What I'm trying to say is is there any such thing as a dimmable led at the component level? I've used quite a few leds in the past for various projects and have never seen the option to buy dimmable v non-dimmable ones.
    Following earlier advice from this thread I've ordered a dimmable constant current driver (works with a standard triac type dimmer alledgedly) so I guess my next step is to try it and see what happens. What have I got to lose!
    Cheers
     
  15. RolandK

    RolandK Screwfix Select

    Hi
    just a quick update in case it's of use to anyone else...........
    I got one dimmable constant current driver to drive all three fittings. It's one that can be dimmed by a standard TRIAC type dimmer, so I go one of those too. Connected everything up on the workbench (the three dimmers connected in series) and lo and behold all works fine! Only thing is the LED's don't dim below about 15% but that's OK for me. Below that you'd probably turn them of anyway and it means when they are on there is always some light on the landing and stairs for safety.
    Thanks for all the help and tips that pointed me in the right direction folks.
    Cheers
    Roland
     

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