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Two switches for a bathroom fan??

Discussion in 'Electrics UK' started by peterb20, 5 Feb 2018.

  1. peterb20

    peterb20

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    Hi all,

    Looking at the attached photo, the fan I have for my bathroom needs the normal double pole switch, but also another connected to a 2nd live called T.

    Surely this could simply be hardwired to the live and use the dp pull switch to turn the fan on and off?
     

    Attached Files:

  2. EFLImpudence

    EFLImpudence

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    T is the timer control.

    If you switch off the permanent live as well the timer function will not work.
     
  3. peterb20

    peterb20

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    Ahh ok, so this switch is the actual light switch so the fan comes on with the light, and the permanent live into the main fan will keep it running on timer after the light has gone off? Confusing way of drawing the schematic if this is correct!
     
  4. EFLImpudence

    EFLImpudence

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    That is correct.

    The diagram may be confusing but it is correct.
     
  5. JohnW2

    JohnW2

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    Well, not necessarily. that switch could be a separate one, either instead of or as well as the light switch - so if it was 'as well as' you could use it to switch on the fan when the lights were off (in which case you would have to use the switch to manually switch the fan off, with a delay) (but also coming on when the lights came on) or, if it was 'instead of' it would be the only way of turning the fan on/off (i.e. it wouldn't come on with the light).

    Kind regards, john
     
  6. EFLImpudence

    EFLImpudence

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    I don't follow that, John, the way Peter has phrased it, he is correct.

    It is a way of fusing both line feeds (is that necessary?) to the fan with one fuse and isolating the fan and light with the FCU.

    The light switch will operate the light and fan and the timer will work.


    There are other ways of doing it.
     
  7. ban-all-sheds

    ban-all-sheds

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    May it be?

    In what possible way?

    It doesn't show a sensible way of wiring it, but it really, really should not confuse anybody.
     
  8. EFLImpudence

    EFLImpudence

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    To people who are not used to diagrams.

    Should I have used might be?
     
  9. ban-all-sheds

    ban-all-sheds

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    May/might/could be/whatever - all the same and all questionable.

    The diagram is not confusing. If somebody is confused by it then that is entirely because of their shortcomings, and not in the slightest because of a problem with the diagram.
     
  10. JohnW2

    JohnW2

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    The way he's phrased it is certainly one way (the most common way) to do it, and one way of interpreting the diagram.

    However, that switch is labelled "recommended to incorporate an indicator if lamp not fitted" - so, as per the "instead of" option I mentioned, they are presumably at least considering the possibility that it is not 'the light switch' but, rather, a standalone fan switch (with timed run-on after manually switching off).

    The thing about the diagram that would probably confuse a good few is that (although it's by far the most common situation) they don't show a light (other than the optional indicator, for when there is no light connected to the switch).

    Kind Regards, John
     
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  11. EFLImpudence

    EFLImpudence

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    Ah right, I didn't see that.
    I assumed it was the room light. I've never come across that before.

    I said the diagram may be confusing.
     
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  12. ban-all-sheds

    ban-all-sheds

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    It really would not be sensible to have the bathroom light on the same fuse as the fan, and downstream of the fan isolation switch.

    They should not be considering the possibility that it is the light switch, and nobody installing it should be considering doing it that way.
     
  13. JohnW2

    JohnW2

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    I've just looked in a dusty drawer, and its seems that good few (all pretty old) diagrams in wring instructions for timer fans are just like that one.

    Kind Regards, John
     
  14. ban-all-sheds

    ban-all-sheds

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    This surely is the FCU providing the (dubious) fused supply for the fan:

    upload_2018-2-5_23-46-7.png

    A good few diagrams in wring instructions for timer fans tell you to have the room light on that same FCU?
     
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