Wiring bathroom extractor fan from lighting circuit

Discussion in 'Electricians' Talk' started by Mack Eater, Sep 14, 2006.

  1. Mack Eater

    Mack Eater New Member

    Bathroom has the light switch outside of the room, switch cable going up to a junction box in the loft, bathroom light connected to the junction box, all 1mm twin & earth cable. Extractor fan is double insulated and has live, switched live and neutral connections - can I wire this up directly to the junction box so that the fan turns on with the light switch? If so, do I need to use 3 core and earth?
  2. dont forget the fan isolator!
  3. JP.

    JP. Screwfix Select

    Aye three core and earth plus a TP Fan Isolator Switch made especially for isolating the fan whilst maintenance is being carried out on the unit....:D
  4. ShortCircuit48

    ShortCircuit48 New Member

    do I need to use 3 core and earth?


    Why do you think you need 3c + earth?
  5. JP.

    JP. Screwfix Select

    Is it Part P notifiable?.... don't ask me I dont give a hoot.....:^O
  6. Mack Eater

    Mack Eater New Member

    bloke at work suggested 3 core and earth being part of the solution - wanted to run it past the experts.
  7. Mack Eater

    Mack Eater New Member

    fortunately for me it's not part p notifiable cos building control approved the drawings in 2003.
  8. Ripped Off

    Ripped Off New Member

    You need three core, the perm live allows the fan to run on after the light has been turned off.
    The isolator as said is to allow maint on the fan, so the live, switched live and neutral are all isolated from the fan
  9. ShortCircuit48

    ShortCircuit48 New Member

    By asking the question it gives an idea of your depth of knowledge.

    If you only want the fan to run when the light is on, then 2 core is adequate, simply link is fan.
  10. JP.

    JP. Screwfix Select

    bloke at work suggested 3 core and earth being part
    of the solution - wanted to run it past the experts.

    And if he suggested T + E what would have been the modus operandi behind his thinking....with regards to the CPC....
  11. Mack Eater

    Mack Eater New Member

    i have to have a second switch (3p) dedicated to the fan? Is that that essential or just good practice? Can i locate the switch in the loft, out of view?
  12. Ripped Off

    Ripped Off New Member

    By asking the question it gives an idea of your depth
    of knowledge.

    If you only want the fan to run when the light is on,
    then 2 core is adequate, simply link is fan.

    Why the link. Fan will come on with the light, go off with the light, no run on
  13. ShortCircuit48

    ShortCircuit48 New Member

    Sorry 2c+earth
  14. ShortCircuit48

    ShortCircuit48 New Member


    Why the link. Fan will come on with the light, go off
    with the light, no run on


    fan is double insulated and has live, switched live and neutral connections

    ???????
  15. Mack Eater

    Mack Eater New Member

    forgot to mention the fan has overrun facility, which i would like to utilise - if that makes a difference?
  16. JP.

    JP. Screwfix Select

    forgot to mention the fan has overrun facility, which
    i would like to utilise - if that makes a difference?

    Which is why I asked if the chap had suggested T + E what was he proposing to do with the CPC?....
  17. Ripped Off

    Ripped Off New Member


    Why the link. Fan will come on with the light, go
    off
    with the light, no run on


    fan is double insulated and has live, switched live
    and neutral connections

    ???????


    OK education time.
    In general use the fan will run without the perm live ie no link required. The switch live will put the fan ON and OFF without a timer function. The link to the permanent live which would normally keep the fan running would be dead once the light was switched off so it'll be as much use as a chocolate fire guard.
    Double insulation means chuff all for a control circuit.

    Clear as mud now
  18. Ripped Off

    Ripped Off New Member

    Which is why I asked if the chap had suggested T + E
    what was he proposing to do with the CPC?....

    Had just that the other week, guy even put the test certs into LABC. They came out and bounced the job - surprise surprise
  19. Mack Eater

    Mack Eater New Member

    well i didn't realise it would work without the perm live, so i have indeed been educated.

    the chap happened to mention that 3 core & earth 'might' be needed to do the job, that's all - hence the query on here.

    so what wiring do i need to make the overrun work - twin & earth from jb to triple pole switch then 3 core & earth from the 3p switch to the fan?
  20. Ripped Off

    Ripped Off New Member

    Need 3 core from the jb.
    Perm live, the live that goes to the light fitting itself ie the live from the switch, & neutral. Then 3 core to the fan

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