hob extractors

Discussion in 'Kitchen Fitters' Talk' started by mojacar.kev, May 29, 2018.

  1. mojacar.kev

    mojacar.kev New Member

    i seem to get all the weird jobs, this one involves 3 extractors fitted in line above a 2.7 mtr cooking range,
    each extractor has a 150mm outlet i was thinking of running all 3 into one creating a kind of manifold then from that reduce to 100mm out through the wall using a "fit from inside" vent, as this building has no outside access at rear of building, now question being, do i run it in rigid 100mm round, 100mm flexi, or 100mm flat bearing in mind the run from each hood to wall is only around 450mm, or just scrap that idea and run each one to its own vent plus would it need an inline fan ?
    ;o; this is what happens when a brickie takes on a shop fitting lol
  2. Mr Rusty

    Mr Rusty Well-Known Member

    If they have a 150mm vent each, you need a 150mm for each of them (or poss 120mm if you can reduce just a bit). 3 x 150mm into a single 100mm will NOT work. The back pressure would mean you won't get a decent flow. All centrifugal fans have a flow curve that drops away quite rapidly as back pressure increases. Can't see it being much different for in-line. I'm no specialist in HVAC but if you did manifold together I think it would need to be into a single duct at least 300mm to ensure the back pressure allowed a decent flow. Maybe others will confirm.
    mojacar.kev likes this.
  3. mojacar.kev

    mojacar.kev New Member

    thanks, was thinking along those lines, deciding to go with 3 direct runs from hood to wall, it means a few extra holes to drill but much simpler :)
  4. kitfit1

    kitfit1 Well-Known Member

    As Mr Rusty said, the back pressure would make all the fans be next to useless. You could also add to that the huge increase in noise. If each fan has a 150mm outlet then that is what you should use. As the range is 2.7m long, i'm assuming this is a commercial kitchen ? If it is a commercial kitchen i hope each extractor is also a commercial extractor and not a domestic one ? Otherwise the local council will be down on the owner like a ton of bricks.
  5. CGN

    CGN Well-Known Member

    Are you in Mojacar now Kev?
  6. mojacar.kev

    mojacar.kev New Member

    wish i was matey, :)
    CGN likes this.
  7. CGN

    CGN Well-Known Member

    Me too. GF's mom lives in Turre, so go over at least once a year...usually just out of season, so not too busy. Was out there about 6 weeks back :(

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