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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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Products: 12v 50w GU10 replacements

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  1.  
    • CommentAuthorRobinB
    • CommentTimeJan 8th 2013 edited
     
    I'm wanting to buy 12v GU10 to replace 12v 50w halogen downlights, each having a small transformer. I am scared by this statement on the retailer's website. How can I know if transformers are magnetic? If I buy one to try and it seems to work can I assume it's safe? I need about 15 in total. Any suggestions for nice bright LED (at least as bright as the 50w's) s at reasonable price welcomed.

    "Many electronic transformers require a minimum load which is greater than that provided by LED bulbs. LED bulbs will usually not work properly (no light output, flickering, and strobing) in fixtures that have integral electronic transformers in each fixture. We recommend changing the power LED power supply which can be purchase in our website. In addition, many standard Track Light power supplies will produce voltages as high as 16 with little or no load (LED bulbs provide little load). You must make sure that the voltage of your existing power supply does not exceed 14 Volts with the LED bulbs installed. "

    thanks!
    ps Are the 12v ones still called GU10s?
  2.  
    How about running several lamps off a single transformer to bring it up to minimium load ,
    how are they wired to the 'small transformer' ?
    • CommentAuthorRobinB
    • CommentTimeJan 8th 2013
     
    mmm I don't really know, I just know each one has a transformer and they each make a massive hole in the ceiling through to the loft.
    • CommentAuthorjamesingram
    • CommentTimeJan 8th 2013 edited
     
    probably each wired to a 50W tranformer like http://www.tlc-direct.co.uk/Products/LTYT50.html
    which are pretty standard for 12v halogen lamps . Try linking several lamps to one , cant think of reason
    why not , though there may be a obvious one I've completely missed . I'll get back to you.
    or could swap them out for something like these http://www.tlc-direct.co.uk/Products/SK153753.html
    or http://www.energylightbulbs.co.uk/products/6w-led-driver-transformer

    By they way MR16/11 are 12V , GU10 are 240V
    • CommentAuthorSprocket
    • CommentTimeJan 8th 2013
     
    Like James says, you want "MR16" rather tha GU10.
    And yes, you can run lots of them off one transformer. Just connect them all in parallel.
    To match light output from a 50W halogen you will need a decent 7W LED lamp. Just make sure your transformer is big enough to power 15 * n Watts.

    It gets a little more fiddly if you need to dim them but still doable - just need the right power supply.
    • CommentAuthorRobinB
    • CommentTimeJan 8th 2013
     
    Posted By: jamesingramBy they way MR16/11 are 12V , GU10 are 240V


    Thanks,
    I did wonder, its not for me and I'm just going on what I was told. I saw them at the weekend but didn't take the lamp out to have a look. If I can't do a straight swap of LEDs for halogens we'll need an electrician.
    • CommentAuthorocean
    • CommentTimeJan 8th 2013
     
    transformers can create electro magnetic fields (EMF) I would minimize there use if given the option,
    just a thought:surfing:
    • CommentAuthorwookey
    • CommentTimeJan 9th 2013 edited
     
    By they way MR16/11 are 12V , GU10 are 240V


    Usually, but not always. 240V MR16s exist as do 12V GU10s. Best to check.

    The designation simply defines the physical shape/size and the connection pins. Voltages are just convention. The most obvious difference is the shape of the pins. (Flanges on the end of GU10s')
    • CommentAuthorowlman
    • CommentTimeJan 9th 2013 edited
     
    If you are intending to use the existing 12V halogen transformers and simply insert an MR16 LED lamp into the fitting I would advise against it. As your retailer says, don't run LED lamps off standard low voltage transformers. LED lamps usually require a special power supply,-( driver ), which is optimised/modified for LEDs, otherwise flickering and loss of brightness may occur. IMO you are going to have to buy new LED 12V drivers or ditch the 12V system altogether and go for a 230V system and use GU10s, this will also involve new fittings.

    P.S. LED drivers are DC not AC
  10.  
    <blockquote><cite>Posted By: wookey</cite><blockquote>By they way MR16/11 are 12V , GU10 are 240V</blockquote>

    Usually, but not always. 240V MR16s exist as do 12V GU10s. Best to check.

    The designation simply defines the physical shape/size and the connection pins. Voltages are just convention. The most obvious difference is the shape of the pins. (Flanges on the end of GU10s')</blockquote>

    Are you sure - link please - I'd always assumed that the different connectors were in part a safety feature so that you couldn't connect 12v bulbs to 240v supply.

    Robin - I might have a use for your 'spare' 50W halogens. Borrowed workspace while we're building needs higher rated bulbs (and we wont be using it enough/there long enough to justify swapping out to LED). just need to check 12v vs 240v first.
    • CommentAuthorEd Davies
    • CommentTimeJan 9th 2013
     
    MR16 designates the shape of the whole bulb assembly: “Multifaceted Reflector”, 16 eighths of an inch (i.e., 2") across:

    http://en.wikipedia.org/wiki/MR16

    So both the bulbs usually called MR16 and the ones usually called GU10 are basically MR16 by the definition. Sort of - as MR16 also includes the use of the GU5.3 pins on the bottom.

    Often 12 V but not necessarily. There are 24 V versions and here's a 240 V one:

    https://www.bltdirect.com/product.php?pid=11070

    GU10 designates the form of the connectors on the bottom with two pins with a twist lock - pins like little metal mushrooms.

    http://en.wikipedia.org/wiki/Bayonet_mount#Light_bulb_bayonet_mounts

    They're usually used on MR16 format bulbs but not always:

    http://www.amazon.co.uk/TP24-GU10-Energy-Light-Bulb/dp/B0044BCMJS/ref=pd_bxgy_light_text_y

    AIUI, the numbers (10 and 5.3) designate the nominal pin spacing in mm.
    • CommentAuthorCWatters
    • CommentTimeJan 9th 2013 edited
     
    If you can get to the transformer take a photo and post here with a transcript of any text on it. The weight is likely to be your best clue. Electronic transformers feel light and almost empty. A magnetic transformer will feel like there is something heavy in it for it's size. That will be the iron core of the transformer.

    Typical electronic transformers...

    http://images01.olx.co.za/ui/12/84/46/1346069420_432697846_1-220v-to-12v-downlight-transformers-Kyalami.jpg

    Typical magnetic..

    http://www.lulusoso.com/upload/20110717/12v_downlight_transformer.jpg

    You mention you may need 15 but is that one array of 15 bulbs in a kitchen or ? What's the spacing between them and what's the ceiling height?

    Many LEDs have a wider beam angle than halogen - so when you compare one of each the LED can look dimmer even if it's producing the same light output. That's because it's spread out over a larger area. If you replace an array of say 3 x 5 lamps on a 1m spacing this issue goes away because the beams overlap and reinforce each other.

    However ... Are they really 50W 12V MR16 halogens or could they be 20W or 35W? A 50W MR16 is quite a bit brighter than a 50W 230V GU10.

    You can replace 50W 230V GU10 halogen with LED and get a brighter result reasonably cheaply (Ă‚ÂŁ7-11 each), however I question if you can do the same with 50W 12V MR16 halogen so easily/cheaply. Check if they really are 50W or if they are 20W or 35W.

    If in doubt post photo of bulb as well and a transcript of any writing on it (usually hard to see).
    • CommentAuthorRobinB
    • CommentTimeJan 9th 2013
     
    Thanks for the helpful and educational replies. Unfortunately they are not in my house so I can't get at them for a while.
    • CommentAuthorCWatters
    • CommentTimeJan 9th 2013
     

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