Combining bathroom extractor fans

Discussion in 'Electrics UK' started by Markyuk5, 27 Oct 2021.

  1. Markyuk5

    Markyuk5

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    We have 2 bathroooms located near each other both with their own extractor fans but I've just noticed one of them is venting in to the roof space?! The other is venting through a roof tile vent.

    I'd like to combine both so they are venting out of the existing roof vent. I've seen 2 suggestions on how to do this - either add non return valves and a y piece (so when just 1 room is on it doesn't just blow in to the other room) or put the fan on the vent side of the y piece so it sucks from both rooms.

    I prefer the second option of a single fan but can't get my head around the wiring for it. They're both wired conventionally at the moment (switched live, isolator switch etc) but on 2 different lighting circuits.

    Any ideas on how I could could combine this in to 1 fan or will I need to go the 2 fan route?

    Thanks in advance!
     
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  3. winston1

    winston1

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    You need double pole switches in each bathroom. One pole does the local light and the other pole the fan. If the bathrooms are really on different lighting circuits you are going to have two different circuits on each pole of one of the switches.
     
  4. SUNRAY

    SUNRAY

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    First, let's try and assertain the detail;

    Are they on the same fuse/mcb in the consumer unit?
    If they are the answer is easy - inline fans are available with more than one switched line input and all that's required is a single conductor:
    upload_2021-10-27_12-15-3.png


    If they are on different fuses/mcb's and the wiring easily accessible, ie pull switches wired from the loft then winston's idea of double pole switches works, this method will also work insted of the multi input fan above:
    upload_2021-10-27_12-33-54.png

    Another, and OFTEN THE LEAST DIFFICULT/DISRUPTIVE, option could be to fit a relay,this doesn't require replacing switches or adding wiring to existing switches which may be chased into the walls:
    upload_2021-10-27_12-49-16.png

    I don't know your current installation methods or where the wiring loops in&out (switches or light fittings) so I've only sketched generic circuits I/we can help with more detail.
     
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  5. Markyuk5

    Markyuk5

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    Great thanks SUNRAY - really helpful. They are on different MCB's so I like the idea of the relay for simplicity. Any recommendations on stockist / brand of relay to go for that includes a mount?
     
  6. Taylortwocities

    Taylortwocities

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    Try these https://www.tlc-direct.co.uk/Products/SR501.html
    the base is detailed also.

    You will need to find an enclosure to put it all in.
     
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  8. SUNRAY

    SUNRAY

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    Thats rather OTT but purchasing anything different may incur an equal (If not more) amount of postage.
     
  9. Taylortwocities

    Taylortwocities

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    There are cheaper 230v relays, of course. but many will require the use of a soldering iron. For the OP I think these are an easy option, with screw terminals on the base.
     
  10. SUNRAY

    SUNRAY

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    yes the screw terminals are the only way to go for this.

    I would expect to pay around £6 for the following sorts of a relay with base but that's 50 at a time And to be honest I haven't purchased any for 3 years so I may be barking up the wrong forest let alone a single tree these days.
    [​IMG] [​IMG]
    Buying one at a time will incur delivery charges which will typically be around £5+VAT so the relay you linked to is not silly/unreasonable price.

    My initial comment about OTT was based on the 10A contacts (I assume & didn't check) despite only switching a mA or 3 for the fans SL input.

    Quite amazingly I've only ever purchased (or installed new) one octal relay and that was for my central heating back in 1984 but since then I couldn't begin to count how many control panels I've worked on containing them.
     
  11. bernardgreen

    bernardgreen

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    I recall that a DIN rail octal relay socket will fit into one of these enclosures with the relay case projecting slightly but safe as no Live parts are accessible.

    [​IMG]
     
  12. dannyboi2003

    dannyboi2003

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    I've had this situation before where multiple supplies have been an issue, the solution I proposed was a central fan unit with a ceiling PIR in each bathroom to activate it, all fed from single switched spur/isolator.
     
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