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Wiring a Fused Fan Isolator

Discussion in 'Electrics UK' started by AzK, 25 Dec 2020.

  1. AzK

    AzK

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    Hi

    I am installing an extractor fan that has a built-in humidstat and timer. I ordered a
    '10A 3 Pole Fan Isolator Switch with 3A Fuse' to combine having both a fan isolator switch and a FCU.

    Has anyone wired one of these up before or would they have a good idea how to do it? It's more the 'L in' and 'L out' element on the back of the fuse that I am not sure about.

    The fan is a Xpelair CV4SR that has 3 connections.

    I am planning to wire:

    L1: Black (Switch live) to 'T' (within the fan unit)
    L2: Brown (Permanent live) to 'L'
    L3/N: Grey (Neutral) to 'N'

    That being the case, where do L in and L Out wire into?

     

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  3. EFLImpudence

    EFLImpudence

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    It depends where in the circuit you fit the Switch, how it would be wired.
    If you are just locating it between the light and the fan, then -

    The Lin and Lout are the fuse connections so Permanent Live to Lin, then a link from Lout to L2 (as you have stated).
    However, this will mean that the Switched Live is not fused.

    Some say it is not necessary to fuse the SL, but as the fan is on the lighting circuit then it is not necessary to fuse the PL either.
     
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  4. SUNRAY

    SUNRAY

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    Various schools of thought on this.
    MI's usually require te fitting of a 3A fuse, however the blowing requirements of a BS1362 3A fuse are not a lot different to a B6A MCB therefore it's almost a 50:50 chance which of the 2 will break first.

    The only sensible way I've found to use a single fuse to protect L & SL is to also include the light it's associated with on the fuse.
     
  5. securespark

    securespark

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    The downside is that if you then need to isolate the fan, you are in darkness in the bathroom.
     
  6. SUNRAY

    SUNRAY

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    I made my post then went to bed, I avoided using the bathroom light so the pull switch so as not to wake 'er in bed and thought how difficult it would be to service a fan in the dark.

    Also adding a fused switch to include the existing bathroom light is potentially messy/fiddly.

    Follow EFL's advice.
     
  7. plugwash

    plugwash

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    No you don't, you can put the fuse before both the fan and the light, but the fan isolator only in the feed to the fan.
     
  8. plugwash

    plugwash

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    Incoming live to Lin
    Incoming neutral to bottom N
    Link wire from Lout to bottom L1
    Permanent live to switch from Lout
    Switch live from switch to bottom L2
    Live to light from bottom L2
    Neutral to light from bottom N
    Permanent live to fan from top L1
    Switched live to fan from top L2
    Neutral to fan from top N
     
  9. SUNRAY

    SUNRAY

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    Yes I was thinking more about the fuse blowing and taking both out.
     
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  11. eveares

    eveares

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    If it was my house and assuming the fan and light in the room were switched separately, I would:

    • Permeant line to L in
    • Neutral in to the bottom N
    • L out to the bottom L1 and Bottom L2
    • Top L1 to fans permeant line
    • Top N to fans neutral
    • Top L2 to the every day switch for the fan
    • From the every day switch for the fan to the switched line of the fan.

    Obviously and of course all CPC's of the circuit would be connect as well.
     
  12. winston1

    winston1

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    Just an example of MI being wrong.
     
  13. SUNRAY

    SUNRAY

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    No they are not wrong! in this instance the MI give a requirement to provide overcurrent protection for the product.

    What on earth is wrong with that.

    And for all of our sanity sake please don't start your incorrect bleating on about the protection is only for the cable or 16A circuits in Europe.
     
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  14. EFLImpudence

    EFLImpudence

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    If it were required then the manufacturer should/must fit integral protection - as they do.

    I have to say that asking a question and precluding the correct answer seems to be somewhat futile.
     
  15. bernardgreen

    bernardgreen

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    Having a removable fuse provides a means to ensure that the fan is safe to work on should someone flick the switch back ON.
     
  16. winston1

    winston1

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    But that is not what the fuse is for. It to protect the cable. If the product required protection it will be internally fitted.
    You are the one with a sanity problem if you don’t believe the purpose of the fuse is only for protection of the cable. And yes the same product sold in Europe would only have a 16 amp MCB and no lower in line fuse.
     
  17. winston1

    winston1

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    What about if someone should replace the fuse?
     
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