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Replacing ceiling rose with a halogen strip (problem)

Discussion in 'Electrics UK' started by joec_85, 12 Dec 2010.

  1. joec_85

    joec_85

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    Hi guys,

    Firstly, just wanted to say 'hello' and say how glad I am that I've discovered this forum in my hour of need!

    I've been replacing a ceiling rose with a halogen strip. The wiring is a standard loop system, I believe, so I followed these instructions, terminating the three red wires and identifying the switched live using a multimeter.

    Now the light appears to be working but the problem is that when the light is switched OFF, if the light in one of the rooms next door is switched on it causes the halogen lights to glow. Also, if they are on low setting (its on a dimmer but I've made sure I've got a double-wattage dimmer - 400W for 4x50W bulbs) and the light in the room next door gets turned on, it causes the brightness to increase quite a lot. Finally, if they are on maximum brightness, the light in the room next door won't work at all. I've tried it with other lights on the same circuit and they seem unaffected, it just seems to be this one.

    I was wondering if anyone had any suggestions of things to check, I've got a multimeter etc just short on ideas!

    I appreciate this is my first post so thanks in advance for your assistance :0)

    Regards,

    Joe
     
  2. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    Lets start with how many cables do you have coming from the ceiling?
    What colour cores are they?
    and did you also wire the switch?
     
  3. joec_85

    joec_85

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    There are three cables coming from the ceiling. Each cable has an earth (which are all sleeved together), a red and a black. The reds are terminated together, the switched live is in the connector which says 'L' and the other two are in the connector that says 'N'.

    Its identical to:
    [​IMG]


    At the other end there is 1 cable with an earth, red and a black. The earth is going to the edge of the dimmer (it has a metal fascia), the black is going to the 'LIVE' connector on the switch and the red is going to the 'LOAD' connector (yep, I wired that too...)
     
  4. riveralt

    riveralt

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    I would suggest that you first of all replace your dimmer with a normal switch and see if that solves your problem.

    Also is the wiring from this dimmer in some way linked to the other room switch?
    Just seen your latest...
    Edit:
    I think you may have the cables at the switch the wrong way around.
    Red will have come from the permanent live and black will be your switched live up to the load.
     
  5. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    Sounds like the terminations have been done correctly, so as riveralt has quite wisely suggested exchange the dimmer with a conventional switch to see if the problem still occurs.
     
  6. joec_85

    joec_85

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    Hmmm. I'm not sure if I still have the original switch (it had a different 250W dimmer on, previously) but I'll see if I can dig it out.

    As far as I'm aware, the two switches arn't connected directly - apart from via the loop system as described...

    I'll firstly try connecting the black to the LOAD and red to the LIVE and see if that makes a difference.

    Thanks guys :)
     
  7. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    If it's not to much trouble, you could always remove an exisiting switch of another light, just to see if it works or not.
     
  8. joec_85

    joec_85

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    Hello again :)

    RIGHT I've tried switching the LOAD and LIVE wires as suggested but this hasn't made any difference. I then took a switch from elsewhere in the house (so that it was on a different circuit) and tried using that instead of the dimmer but its still doing the same thing :oops:

    Looks like it must be a problem with the wiring in the halogen strip then...

    To clarify on how I found the 'switched live' in the ceiling wires:

    I used a multimeter to test each pair (red/black) of cores from each wire using the resistance function. Each of them had a resistence of 1, apart from one of the wires which had a resistence of 0.03. I therefore took this to be the switched wire and the black to be the switched live. Does this sound about right?
     
  9. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    Were any of the black core cables flagged or sleeved to identify them as the switch live?
    If not try swaping them about.
     
  10. bernardgreen

    bernardgreen

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    No it doesn't sound right.

    The cable to the switch should show less than 1 ohm with the switch ON and greater than 500 MegOhms with the switch OFF

    The other two cables should be more than 100 ohms ( the actual value will depend on how many other lights there are and whether their switches are ON or OFF.
     
  11. riveralt

    riveralt

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    Its going to take a bit more effort - simple sometimes works!! but not today

    How did you test to ensure that the switch live is as you say?

    If we assume that the red wire at the switch is permanent live.

    With the power off....

    Connect the black wire and the earth wire at the switch. Set your multimeter to low ohms.

    At the ceiling rose separate out the black wires and test them individually with the earth wire with you multimeter - on one of them you should get a low ohm reading on the others you will get an open circuit. The one with the reading is your switch wire - mark it.

    That goes into your live at the ceiling light.
    The other two black wires go to neutral.
    Incidentally, I do not agree with the way ultimatehandyman puts the reds into a separate terminal block. Most lighting manufacturers give you four terminal at the light three marked accordingly and the fourth can be used for the live loop. No need for an extra terminal block and no need for sticky tape.

    Once you have id the switch wire - mark it at the switch (red/brown tape) and put it in the L1 side of the normal switch or perhaps Load on your dimmer. The red cable goes in the C or the Live side.
     
  12. joec_85

    joec_85

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    Wow, riveralt, thanks for such a detailed troubleshooter.

    I'm shattered today but I'll give it a go tomorrow and get back to you.

    Thanks again :D
     
  13. joec_85

    joec_85

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    Hi Riveralt,

    I tried what you suggested - I used the multimeter in 20OHM setting and the readings were as follows:

    1 - 01.3
    2 - 00.5
    3 - 1

    (1) was the one that I thought was the switched live to start with.

    Not sure why two of them are giving me a reading though?

    Thanks
     
  14. riveralt

    riveralt

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    Its a bit difficult to interpret because I don't know what 200Hm setting is on your multi meter. If you connected the black and earth at the switch as I suggested and then tested between each of the black wires and earth at the ceiling rose area then I would expect one set to have a very low ohm reading and the others to be open circuit which you do not seem to have.
    Both your readings for 1 & 2 seem to be low ohms which is odd if you have conducted the continuity test properly.

    All I can suggest is that if you have already tried number 1 then I would suggest you try number 2 as your switched live.
     
  15. joec_85

    joec_85

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    Apologies - it should have read 20 Ohm :oops:

    I'm pretty sure I followed your instructions to the letter (connect earth and black at the switch end, then test each black with the earth at the other) and those were the readings I got... very strange :(
     
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