Installing a shower extractor fan with 3 pole isolator switch and pull cord??

Discussion in 'Electricians' Talk' started by Wallace2017, Feb 6, 2017.

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  1. Wallace2017

    Wallace2017 Member

    I am looking to replace a previous in-line extractor fan; located in my loft however, it was clearly fitted by a cowboy DIYer before as there is only 2 core and earth.

    The problem arises with the wiring as the fan requires a switch live but there isn't one as the pull cord has a live, neutral and earth for both feed and source. The source comes from the main fuse box and the feed being the bathroom downlights.

    There is a 3 pole isolator switch located on the wall outside of the bathroom which I have fitted a 3 core and earth from to the extractor fan, however, the manufacturer instructions state a 3AMP FCU is required???

    It is causing some confusion as to how to wire this new extractor fan with timer into the lighting circuit. I am looking to locate the FCU with neon in the loft next to the extractor fan unit. How do I get a switch live for the extractor fan, FCU & isolator switch??

    There is no ceiling rose for the bathroom lighting circuit, just the 1.5mm cable running to/from each downlight. There is a junction box on the mains cable on to the junction boxes completing the upstairs radial lighting circuit.

    The extractor is needed as it is within an enclosed shower cubicle which steams up quickly during use.

    Ideally, would like to power this off the pull cord which operates the power shower and the downlight within the shower cubicle, and use the timer to have the extractor run on for at least 10mns after the shower usage. I don't really want the extractor to come on everytime the bathroom lights are used as this would be a problem at night particularly with noise for the over run.
     
    Wallace2017, Feb 6, 2017
    #1
  2. spaceman76

    spaceman76 Active Member

    QVS sell fused fan isolators,

    http://www.qvsdirect.com/excel-3-pole-fused-fan-isolator-switch-white

    only issue is just a single live terminal protected by the single fuse, which means wiring it in before the light (where theres only N and perm L).

    Bit of a daft design really cause if the fuse does go the fan, light, and in your case the shower pump aswell, will all go. Better to just use the unfused variety or find a fan that does not need fusing or is internally fused.
     
    Last edited: Feb 6, 2017
    spaceman76, Feb 6, 2017
    #2
  3. seneca

    seneca Screwfix Select

    I've been fitting Greenwood fans for a while now as they don't stipulate 3 amp fusing if wired into a 6 amp lighting circuit.
     
    seneca, Feb 6, 2017
    #3
  4. Bazza

    Bazza Screwfix Select

    This has been covered many times. The 3 amp FCU is only needed if you are powering the fan from a ring (socket) circuit. It's not necessary if power is from a 6amp lighting circuit.
     
    Bazza, Feb 6, 2017
    #4
  5. Wallace2017

    Wallace2017 Member

    Thanks for your reply, the manufacturer instructions state a 3amp FCU must be used.
     
    Wallace2017, Feb 8, 2017
    #5
  6. Bazza

    Bazza Screwfix Select

    Well fit one if it makes you happier, but unnecessary IMO.
    The QVS fused isolator (post #2) would save you having to fit a separate device.
     
    Bazza, Feb 8, 2017
    #6
  7. Comlec

    Comlec Screwfix Select

    From IET Wiring Regulations (BS 7671:2008+A3:2015) - Chapter 51 Common Rules

    510.3 Every item of equipment shall be selected and erected so as to allow compliance with the regulations stated in this chapter and the relevant regulations in other parts of BS 7671 and shall take account of manufacturers’ instructions.

    The assessment of suitability of equipment is made by the designer of an installation taking into account, among many other factors, information from manufacturers. Blindly following manufacturers instructions in not part of the regs.
     
    Comlec, Feb 8, 2017
    #7
    Bazza likes this.
  8. Wallace2017

    Wallace2017 Member

    Ok, with the fused 3 pole isolator, how would that be wired into the extractor fab and lighting circuit? The fan requires a switch live for the timer however, the pull cord switch only has a live, neutral and earth, there is a 3 core and earth from the 3 pole isolator to the extractor but what next???
     
    Wallace2017, Feb 8, 2017
    #8
  9. Bazza

    Bazza Screwfix Select

    No it hasn't. It has an earth a live and s switched live.
    The black (or blue) wire in a switch is NOT A NEUTRAL.!!!!

    All three plus an earth may be present at the light itself. Did you look there?
     
    Bazza, Feb 8, 2017
    #9
  10. Wallace2017

    Wallace2017 Member


    I have just looked and there is a feed side of L, N and earth, and the same on the source side
     
    Wallace2017, Feb 8, 2017
    #10
  11. Bazza

    Bazza Screwfix Select

    So, it's a double pole switch, with 4 terminals?
    I.e. Two cables each with 2 cores and earths?
     
    Bazza, Feb 8, 2017
    #11
  12. JP.

    JP. Screwfix Select

    Was the earth used for something else?
     
    JP., Feb 8, 2017
    #12
  13. Wallace2017

    Wallace2017 Member

    Yes, it has a feed and source side with 2 cores and earth on each.
     
    Wallace2017, Feb 8, 2017
    #13
  14. Wallace2017

    Wallace2017 Member

    Not sure as originally the bathroom had push switches for the lighting and that was changed to the pull cord.
     
    Wallace2017, Feb 8, 2017
    #14
  15. JP.

    JP. Screwfix Select

    If the 2c + e was used as 2c + e, how does this make the diy chap who installed it a cowboy Wallace?

    There are plenty of fans which require just 2c and e (e is normally parked on most fans) and my integral PIR through the wall fan is one of them..although I did use 3c + e in the wiring but just blanked off one of the unused cores..however I could have used 2c+e and I sure as heck aint no cowboy Wallace.
     
    Last edited: Feb 8, 2017
    JP., Feb 8, 2017
    #15
    Joe95 likes this.
  16. Wallace2017

    Wallace2017 Member

    So you took offence???

    The previous fan fitted was a timer one which had no run on time after the lights were switched off as the wiring was wrong.
    It was wired direct to a normal light switch in a bathroom which isn't right in itself. As it was, when the switch was removed and the terminals and wire connections had suffered from condensation.
     
    Wallace2017, Feb 8, 2017
    #16
  17. JP.

    JP. Screwfix Select

    Of course I didn't take offence Wallace - just pointing out stuff m8
     
    JP., Feb 8, 2017
    #17
  18. Bazza

    Bazza Screwfix Select

    Ok so you need to run 3c & E cable from the switch to the 3 pole isolator.
    L & N from the feed side into the switch
    Switched live from the live terminal on the load side of the switch.

    Then you'll have to decide what to go about this bloomin FCU. Use one of them QVS 3-pole isolator and it's all included. Otherwise you'll need to fit the FCU on the feed going into the pull switch. You don't need one though, as I said.
     
    Bazza, Feb 8, 2017
    #18
  19. Wallace2017

    Wallace2017 Member

    Thanks for this. I have ordered a 3 pole fused isolator switch to rid the FCU (as you advised).

    Can I run this switch from the pull cord powering the shower? I only ask as it is a 10mm cable on the source side of the switch?
     
    Wallace2017, Feb 8, 2017
    #19
  20. Bazza

    Bazza Screwfix Select

    Its a bit late in the day to ask about doing this!

    The way you asked is for the fan to operate when the light switches on.

    How would you expect this to work?
    Do you only want the fan to come on with the shower?

    Last question (for now). Does your bathroom have an opening window?
     
    Bazza, Feb 9, 2017
    #20
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