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Making a John Lewis Jensen 16 bulb light dimmable

Discussion in 'Electrics UK' started by Thrak, 16 Dec 2014.

  1. Thrak

    Thrak

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    Hi all,
    I'm working on a little lighting project and I was wondering if you guys could possibly help me out at all.

    Got the following light from John Lewis in a deal:

    http://www.johnlewis.com/john-lewis-jensen-dangle-cluster-ceiling-light-16-light/p276717

    It's great but we really want it to be dimmable to avoid blinding people at dinner. I saw the following review on the John Lewis website:

    Fitted by professional electrician who fitted dimmer transformers to great effect. Would be easy to have these provided at source however, at little extra cost. Would save many bad reviews. Very happy, look lovely.

    So, that's my mission. I didn't want to come to you empty handed so I've done a bit of research.

    The two existing non-dimmable (I assume) transformers are as follows:

    Anchorn AET-3202CL 10-60W

    http://www.globalmarket.com/product-info/electronic-transformer-101782.html

    Anchorn AET-3352CT 35-105W

    http://www.savemylight.co.uk/anchorn-aet-3352ct-electronic-transformer.html#.VJAroiusVrU

    The latter feeds 10 x 10W halogen bulbs, the former 6 x 10W, and they differ in size appropriately.

    To keep the wiring simple I am considering splitting the load as it is already setup i.e. straight replace both transformers. It's quite tightly wired so it might be a headache otherwise. However if needed I can look into a single transformer (I can't think why this would be an issue).

    Assuming straight replacements I was looking at the following for the smaller transformer:

    http://www.screwfix.com/p/halolite-low-voltage-electronic-transformer-20-60va/48058

    And this for the larger one:

    http://www.screwfix.com/p/halolite-electronic-transformer-35-105va/39220

    The dimmer switch I am looking at using is rated at 400W so should be sufficient even with derating for Halogien (if this is still required!):

    http://www.screwfix.com/p/lap-1-gan...itch-400w-400va-brushed-stainless-steel/45181

    I was hoping for some advice to see if I am on the right track - any and all comments appreciated :)

    Thanks,
    Thrak
     
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  3. ban-all-sheds

    ban-all-sheds

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    Dimmable would be a good idea.

    Although the implication is that people have given it bad reviews somewhere because it isn't dimmable. I think that anybody who gives a light described as not dimmable a bad review because it isn't dimmable already has enough dim things in their house.


    Yup - plus a slight enhancement would be my suggestion.

    Assuming you have access to the ceiling void there's no reason why the transformers have to go inside the base of the light. Plus for my idea you'd need to run another cable.


    Get both, connect one to the 4 lamps in the middle, and the other to the 12 around the outside, and put in separate supply cables to them, and a 2-gang dimmer.

    Halogen lamps don't like being dimmed by much - they go black and have their lives shortened, so you might find that it's still too bright sometimes. If you split them 4 + 12 you can run the light with 4, 12 or 16 lamps lit.
     
  4. ericmark

    ericmark

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    Start at the route of the problem quartz bulbs are not suitable for dimming.

    So step one is the bin the quartz bulbs so will a bulb looking like this [​IMG] work or does it look hideous? If I was getting a fitting to take those bulbs I would want the bulb covered not on view. This
    [​IMG] may look a little better but step one has to be select a suitable bulb.

    Once you have a suitable bulb then select the power supply to match.
     
  5. ericmark

    ericmark

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    If your not worried about bulb life then you need a power supply minimum 1/2 size of single bulb to maximum size of all bulbs so 3.5 - 112 VA dimable good look finding one.

    this would it seems work although never tried one. Note it says "Compatibility with TLC dimmer switches" so would need to buy dimmers from same place.

    Likely bulb life will be halved when using a dimmer so ensure you hold plenty of stock. One tungsten bulb is bad enough never mind 16.
     
  6. JohnW2

    JohnW2

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    As I've said many times before, that does not correspond to what I've read. My understanding is that, just as with any other filament bulb/lamp, the life of halogen bulbs/lamps is increased by dimming, but not to the same extent as the life of a non-halogen one's life would be increased. However, as I say, that's just what I've read - and we all know that one shouldn't believe everything that one reads!

    Kind Regards, John
     
  7. Thrak

    Thrak

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    Yeah I think I'm stuck with the bulbs since they are quite prominent.

    We might be going for a mixed height configuration so also not sure about 12/4/16 switch combination. If it was going to be in use more often it might be useful but we don't use the dining room much save for dinners (hence the timing, getting it all ready for xmas).

    Eric are you sure I need that low a limit on the transformers? As you mentioned they are very difficult to find.

    Thanks for all the help chaps

    T
     
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  9. ban-all-sheds

    ban-all-sheds

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    [​IMG]
    [​IMG]
    [​IMG]

    and many more.
     
  10. ban-all-sheds

    ban-all-sheds

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    The original source of this has gone to the great backup tape in the sky, but

    http://www.diynot.com/forums/viewtopic.php?p=154058#154058


    http://www.google.co.uk/search?q="halogen+cycle"+dimming
     
  11. ericmark

    ericmark

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    The idea is until the last bulb blows the lamp will still work as with say three 50W bulbs the power supply will be rated min 50 max 150W since when dimming it can takes as little as half the power if dimming those 50W bulbs then 25 - 150W clearly with so many bulbs the likely hood of wanting it work with one bulb is slim so you could look at 30 - 112W which would then still work with a few blown bulbs.

    The theroy with quartz is the envelope is so hot that the tungsten will not be deposited on the quartz also the thicker the element the more material has to be lost before it finally ruptures. So the idea of the electronic transformer is to ensure exactly the right temperature so a 12 volt version can last 1/3 again the time of a 230 volt version.

    Clearly defeating the careful voltage regulation using a dimmer will mean a shorter life. How much shorter is hard to say. One bulb lasting 32 weeks and we think this is reasonable. But 16 bulbs that means a bulb every 2 weeks on average. Most the life is lost while cold so switching them on just to pass through the room will shorten their life.

    Much larger lights on a building site 12 x 1500W on each tower crane and one tower crane timer went faulty so the lights were on 24/7 and they lasted longer than those only on at night.
     
  12. JohnW2

    JohnW2

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  13. Thrak

    Thrak

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    Cheers for all the help guys. I have a stack of tungsten bulbs that came with it and I think even with the modern style LEDs I'll lose some of the style (i.e. missus will tell me off).

    If I calc it correctly with the chosen transformers I should be OK to operate with at least 2 bulbs blown (worst case scenario with both on the smaller transformer).

    With the look of the light fitting I doubt the missus will let me get away with any more than that anyway.

    The better transformers are unfortunately too tall to go into the base of the unit so would require more rewiring. however i will take another look around and see if I can get a 10-60 for the smaller transformer.

    Will let you know how I get on!

    Cheers,
    T
     
  14. Thrak

    Thrak

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    Quick update - I double checked the available space and think I can squeeze in the high end transformers (one 0-70W and one 0-105W). I also got a good quality TE dimmer from the same place.

    thanks again for all the help - will report back on successful install and testing.

    Simon
     
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