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Replacing MR16 transfomer

Discussion in 'Electrics UK' started by vegasgo, 15 Jun 2016.

  1. vegasgo

    vegasgo

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    Our bathroom has 10 MR16 halogen lights. I've been replacing them with LED's and after a short while 5 of them stopped working. I've taken up the floorboards to reveal as shown in the pic. I resume the white box is the transformer and the black box is the junction box? Would it be a simple case of replacing the transformer? There's 4 wires coming out of it which is a bit confusing as I thought it would either be one to feed the junction box or five to feed the lights. Thanks for listening.
     

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  3. ban-all-sheds

    ban-all-sheds

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  4. ban-all-sheds

    ban-all-sheds

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    Good grief - how big a bathroom do you have that it needs 10 lights to light it up properly? :eek:


    Given that mess, I would not try replacing anything until it is all sorted out and properly connected up.

    OOI, what is the room above the bathroom?


    Looks like it.


    That might or might not be why the lights have stopped working.

    Even if you find a wiring fault, the transformers might not be suitable for driving LEDs anyway.


    Can't see that in the photo.


    So what goes into the JB?

    Are the lights split 5+5 between two supplies, or 6+4?
     
  5. Taylortwocities

    Taylortwocities

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    If your lights are ELV then you should replace the grey box (can't remember what they are called just now:sneaky:) and install a proper LED driver instead.

    How many wires are there will depend on the wiring, so you'll need to deduce that. There may just be another greyboxthing serving the other lights.

    General point 1. The wiring there is a right horlicks. You need to spend some time and get some proper junction boxes. All of the connections should be enclosed inside enclosures, you should not be able to see any inner conductor wires and choc block wrapped in sticky tape is a sure sign that John Wayne has galloped through there.

    General point 2. It would have been a lot easier if you had gone for 230v LEDs, then you could have dispensed with greyboxthingies.
     
  6. ericmark

    ericmark

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    Oh dear what a mess. There has been a lot of debate on running 12 volt G5.3 based MR16 equivalent LED lamps, my bathroom also has 4 x 12 volt lamps, but unlike yours I have a real transformer not a switch mode power supply, so in theroy I should be able to change to LED without any mods. However I bought cheap LED spots which only lasted about three months.

    Else where in the house I had GU10 based 230 volt MR16 equivalent LED lamps and these are all still working, so what you have to decide is which route to take.
    1) Use a 12 Vac power supply and cross fingers.
    2) Use a 12 Vdc power supply.
    3) Move to 230 Vac lamps.

    Since the wiring is such a mess to me the last option is the way to go, rip out the existing wiring and do it again and do it properly.
    Note MR16 is the size of the lamp and fact it has a reflector it has nothing to do with voltage or base, since most LED's don't have a reflector they are compatibles rather than really a true MR16.
     
  7. vegasgo

    vegasgo

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    Only bought the house this year so don't blame me for the wiring chaos! It is a large bathroom but 10 lights is excessive. The junction box has five ports where the wires shoot off through the joists. I presume there is another one of these feeding the other five lights. The four wires coming out of the transformer also shoot off through the joists and not into the junction box. The bathroom is downstairs, only one half is accessible though the floorboards upstairs as the other half is under the roof. I think I will disconnect the transformer and if the other five lights still work then I will replace it, the only transformer I can find with four ports has a minimum load of 100VA though which is no good for LED's, unless I stick with halogen.
     

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  8. ericmark

    ericmark

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    Careful if you look for an LED driver, a true driver controls current, however the lighting industry seems to call anything designed to power an LED a driver, so you have to forget the name and look as the specs. 340 mA 0 ~ 12 volt is a true driver these are no good for what you want. 0 ~ 2000 mA 12 volt is a fixed voltage rather than current that will do the job. Likely it would actually say 2A rather than 2000 mA but kept units same for both examples.
     
  9. ericmark

    ericmark

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    Only just read your reply, what you have to consider is that the lamps already bought may be damaged, so staying with 12 volt you could be putting good money after bad, also with LED versions of the 50mm round lamp often only 25mm is lamp, with massive cooling fins, I would look as other LED lamps first and decide if you really want to keep what you have. I find a 3W spot behind my bed head works well, but my son tried 7W LED lamps and although very bright they don't light the room very well because the light is so concentrated. 7W over a 100mm would work very well, but over 25mm it is a failure.
     
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  11. vegasgo

    vegasgo

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    So I disconnected the white transformer ... now only one light works. Confusing. So I'm guessing the transformer powers four of the lights, the black junction box powers five (could this have its own in-built transformer?), and there's a rogue one with a life of its own. Thanks for all your replies.
     
  12. EFLImpudence

    EFLImpudence

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    It doesn't really matter, does it?

    It needs redoing properly. Starting again.
     
  13. vegasgo

    vegasgo

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    Further probing... The black junction box (called a MF300) is dated 1998 - is kaput. The white transformer is dated 2013 and it works. Took one connection from the black box and inserted it into the transformer and that light worked again. So will need a new transformer to replace the black box, and job done.
     
  14. ban-all-sheds

    ban-all-sheds

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    How can a junction box go kaput?

    Why do you want to replace a junction box with a transformer?

    Why do you want to install a transformer when you are using LED lights?

    1 out of 10, or 1 out of the 5 which were working?


    Indeed.

    And the rats nests of cables, junction boxes and transformers isn't helping.

    Take it all out and start from scratch.


    You must not do electrical work on the basis of guessing.


    No.

    All the old halogens were the same were they, all 12V?


    You really do need to get access to that.

    Given the quality of the work we can see, there might be potential danger lurking where we can't.

    And I can guarantee that the numpty who installed them will not have put properly sealed enclosures over them, so warm moist air from the bathroom will be getting into the roof space, where it might well condense and cause the roof timbers to rot.
     
  15. vegasgo

    vegasgo

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    I guess that's the same for every bathroom in the world!
     
  16. ban-all-sheds

    ban-all-sheds

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  17. Iggifer

    Iggifer

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    The MF300 is a toroidal transformer no? Not a JB.

    I would suspect, a 300va transformer at that, thus powering 5 lights quite happily
     
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