Wiring Extractor Fan... Fuse and Switch requirements...

Discussion in 'Electricians' Talk' started by themissingelf, Oct 6, 2018.

  1. themissingelf

    themissingelf Member

    Hi,

    I bough one of these extractor fans to use in my (home) garage workshop; to extract airborne dust, fumes etc. It will be fitted high up on a wall or to the ceiling and ducted to outside.

    I'd planned to wire it to some flex with a 3-pin plug fused at 3amps and simply plug it into a socket. However... the instructions tell me:
    • "a flexible cord must not be used"
    and go on to state:
    • "A double pole fused spur having a contact separation of 3mm in all poles must be used and fitted with a 3A fuse"
    Two questions...
    1. Is this really necessary given the intended use (i.e. NOT for a bathroom and NOT controlled via the light etc. NOT in a loft space)?
    2. If I have to comply... I'd like to use MK Metalclad (same as the rest of the garage) but it seems they don't have fused isolator switches in the range... Any suggestions?
    Thanks in advance!
     
  2. peter palmer

    peter palmer Well-Known Member

    I'm sure it will be fine on a plug and socket, considering these usually go in lofts and would maybe have an isolator next to them it would make perfect sense to go from the isolator to the fan in a bit of flex, why would you use twin and earth in that situation.
     
  3. dobbie

    dobbie Well-Known Member

    If in a garage, I would run a plastic conduit from the metalclad spur to a metalclad flex outlet next to the fan.Run a piece of flex from the outlet to the fan,a nice tidy job then.
     
  4. themissingelf

    themissingelf Member

    I did wonder about this approach. The only addition I would need is a switch. The fan will be up quite high so a switched flex outlet would not be practical, however I had thought about using a "normal" switch near the spur (perhaps with a neon light to remind me to switch the fan off when I leave!). I understand the difference between double and single pole switches but not the reason/s why a fan would need the double pole with 3mm gap (and therefore whether any of the reasons are relevant to what I am doing)?
     
  5. Bazza

    Bazza Well-Known Member

    Don't worry about that. It is intended when the fan is intended to ventilate a bathroom. Your plug with a 3amp fuse is just fine.
     
  6. dobbie

    dobbie Well-Known Member

    The switched spur at the lower level would be the switch for the fan,with neon if you so choose.
    The flex outlet at high level does not have a switch and is kind of junction box to go from twin and earth to flex.
    If using mk you will need a grid module,box,grid and front plate.
    http://www.sparkydirect.co.uk/produ...lus-16-Amp-Cord-Outlet-Grid-Module/index.html

    You could also have a 20amp dp switch at low level and an unswitched spur with flex outlet at high level, which would probably be cheaper in materials.
     
  7. Bazza

    Bazza Well-Known Member

    Or change it for a timer fan…
     
  8. themissingelf

    themissingelf Member

    I'm going with a plug end on some flex for the time being. It's the least disruptive if the fan turns out not to achieve the results I'm looking for in terms of clearing the air of dust. I may leave it if there's no reason to change or switch to a conduit, switched solution.

    As mentioned, the instructions say don't use flex etc and state the cable to the fan should be 1mm2 minimum. I already have some 0.75m2 flex and believe this will be fine for a 3amp fused appliance. Am I being naive thinking they're stating 1mm2 because that's the smallest fixed cabling option you can get, it's overkill for a fan, and I'll be fine with 0.75mm2?
     
  9. Bazza

    Bazza Well-Known Member

    They probably say 1mm as that is the smallest size used on lighting circuits.
    .75mm + 3A fuse will be fine.
     
  10. themissingelf

    themissingelf Member

    Thank you!
     

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