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Fan/Light help please

goldenboy1818
Hi I fitted a new envirovent extractor in a bathroom, they had a 12volt one before but the zone position was ok for mains. Obviously removed the transformer.


However after leaving at night the customer has rang to say the light that operates when switched on with the fan, has a constant dim light. Bulb is a small 3watt led. It must be getting some slight back feed, only when the fan iso is on. Has anyone experienced this before, greatful for any input. Thanks
  • 0
    Low energy lamps flickering or dimly lighting when meant to be "off" is a common problem - usually due to capacitive coupling between the L and SL wires - especially where they run next to each other without a c.p.c. in between (so triple & earth cable on a 2-way switching arrangement can be worse when the switches are in a certain position).


    The fan complicates things a bit - the extra load on the SL line should if anything help reduce the problem. So perhaps there's some coupling between the perm L and SL lines due to the wiring layout changes, Or as you say perhaps a little current flowing back from the fan's electronics from L to SL.


      - Andy.
  • 0
    Thank you for the reply


    Not sure how best to resolve it. If the fan is isolated its completely fine.
  • 0
    As a quick check, see if the light goes out with a small load in parallel with the lamp (anything that consumes a few tens of watts should do)

    If that works, invest in a small capacitor and put it in shunt with the lamp in the back of the holder or in a small box.

    (you can buy one at exorbitant price with a label on it) or without once you know the value needed for far less..

    Mike
  • 0
    If the fan is isolated its completely fine.

    Is there a decent length of cable between the isolator and fan?


    Is it 3-core + earth?


    If so, are the L and SL in 3-core both to the same side of the c.p.c.? (with perhaps N on the other)


    If all of the above then perhaps swapping the cores around so L and SL are on opposite sides might help... (or might not..) Should be a relatively cheap experiment either way.


       - Andy.
  • 0
    Do you mean use the grey as S/L so swap the codes about ?


    I could revert back to a low voltage fan as the transformer will stop any back feed
  • 0
    Changing to ELV fan will not do much if there is only one transformer - the place that the steady live and the switched live meet and presumably cross-talk a few hundred microamps,  is at the over-run timer. The fact that the timer is driving a mains fan or an ELV one via a transformer is a secondary consideration.

    You may be lucky if the over-run timer is not the same design in the controller for the ELV one and for some reason has less cross-talk, but it is not the transformer or the fan voltage that is helping you.

    M.
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    The thing is the original low voltage fan never has this issue
  • 0
    OK - if you want, you can just swap the timer part.
  • 0
    How do you mean just swap the timer part ? I need to also add a transformer back in
  • 0
    The obvious answer is to swap the LED lamp for a small halogen.

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