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fuse for extractor fan

Discussion in 'Electrics UK' started by nick9one1, 12 Oct 2021.

  1. nick9one1

    nick9one1

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    I have two bathrooms with a triple switch (extractor, lightswitch, fuse) and another separate switch for the opposite room light.

    I've replaced the old extractor with an timed humidistat expelair that draws 7.7w max.

    I'm going to combine the bathroom light and extractor, and remove the separate switch, moving it to a new smaller double bathroom switch as the image shows.

    My question is about the fuse. Is it still needed for a 7.7w extractor? If so is there an inline fuse I can install behind the switch?
    20211012_114356.jpg
     
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  3. opps

    opps

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  4. nick9one1

    nick9one1

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    Yes youre correct. Should have read the manual!

    Capture.PNG

    This makes it a little more complicated.
    I think I will have to install a separate 2 pole isolator near the floor outside the bathroom.
     
  5. EFLImpudence

    EFLImpudence

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    It is up to you what you do but, if on the lighting circuit, the fan does not need a fuse nor an isolator.
     
  6. opps

    opps

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    You might have to install a fused spur as well given that it specifies a 5 amp fuse...

    ___________ edit__________ submitted before reading EFL's post

    That said, by using an isolator, if it decides to start running on a particularly humid night, you can turn it off if you have an isolating switch- the humidistat is on the permanent live, and not the switched live.

    Oh, and don't forget to earth the 4 core cable at the supply side. The device does not need the earth but the cable should be earthed (just in case).
     
    Last edited: 12 Oct 2021
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  7. winston1

    winston1

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    His lights won’t be on a ring. Rings are for UK socket circuits.
     
  8. winston1

    winston1

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    It doesn’t. It says MAX 5 amp fuse. It is wrong anyway as the fuse is to protect the cable not the fan which should be internally protected.
     
  9. opps

    opps

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    Yeah, my bad. they are (typically) radial. I made the mistake of saying ring, when in reality, I should have used the words lighting circuit.
     
    Last edited: 12 Oct 2021
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  11. opps

    opps

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    Sorry Winston, I do not understand. A MAX 5 amp fuse is less than the 6 amp MCB. The cable running to the device is protected by the MCB, the internal wiring? I have no idea. They specified 5 AMPs, not me.
     
  12. bernardgreen

    bernardgreen

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    Winston1 has been told several times that lighting circuits can be on a ring. He should not make statements which are not accurate for all installations.
     
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  13. opps

    opps

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    Perhaps, but in my case it was an error on my behalf.
     
  14. EFLImpudence

    EFLImpudence

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    [​IMG]

    Those instructions are quite interesting and one for Winston's "wrong instructions" collection.

    They are clearly written and drawn by someone who just thinks that is what one should do with no regard to the regulations.

    Usually such instructions call for a 3A fuse and people argue that there might be something in the fan that requires 3A protection rather that 6A on the circuit. If there is - there isn't - then the manufacturer should fit a fuse in the fan - that's why they don't.
    Not to mention the horrible rest of the world fitting the same fans on 10A or 16A circuits with no fused switches being available.

    There is no argument that a 5A fuse has any advantage over a 6A MCB so stipulating one is just pointless.


    As to the positioning of the double-pole isolator before the light: this negates even the convenience of having an isolator so that, with a fault, the lights will still work - or the silly "You can work on the fan with the light on".
    The Wiring Regulations do not require local isolation for any appliance; not even the cooker or shower.


    So, were one to fit a three-pole isolator after the light, would one then be not complying with the manufacturer's instructions.
     
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  15. Risteard

    Risteard

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    The cable does not need to be Earthed (and indeed most cable types can't be). A circuit protective conductor (cpc) must be run to and terminated at each point in the wiring (excluding some lampholders).
     
  16. EFLImpudence

    EFLImpudence

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    Not sure I understand that.

    A conductor will only be a CPC if it is Earthed. Does that not count as 'Earthing the cable'?
     
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  17. JohnW2

    JohnW2

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    I think Risteard's ('pedantic') point was that, although a cable may contain an ('earthed') CPC (and must, per regs, contain one if it is the only cable going to 'the point' in the installation), it is generally not possible to 'earth a cable' - unless it has armour or some conductive covering/sheathing/whatever.

    Kind Regards, John
     
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