Question re extractor fan exhaust

Just trying to get a fix on what parts I need. lets say I buy a 125mm extractor fan. This will be fitted internally. Externally I will fit a gravity flap How critical are the dimensions of the flap unit as I am looking at one that has an overall size of 190 x 260 mm with the flappy part 150 x 220 so this would be larger than the extractor fan exhaust outlet. Also do I need to connect the extractor outlet to the flap unit with ducting tubing the distance being approx 220mm
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On 31/08/2015 21:06, ss wrote:

if you have a 125mm fan just get a 125mm duct kit such as https://www.tlc-direct.co.uk/Products/SLDK5.html and all will be fine.
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On 31/08/2015 21:28, Vortex11 wrote:

Yes that makes sense. thanks
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On Monday, August 31, 2015 at 9:06:20 PM UTC+1, ss wrote:


I'd connect the two with solid rather than flexible pipe if possible. Flexi ble pipe plays merry hell with the extraction performance.
Many years ago a 'qualified' kitchen fitter ran the cooker extractor fan in to the cavity with the vain hope that the adjacent vent would cope. It didn 't, with the result that all cooking smells were conveyed to my office on t he opposite side of the house. I could never understand why they were only apparent in that room rather than elsewhere.
Whole shebang was replaced with a Miele unit with a 150mm outlet which I to ok care to mate with plastic drainage pipe of the right dimension. All kitc hen smells are now well and truly under control.
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On 01/09/2015 14:06, fred wrote:

Thanks Fred I will order the extractor unit and then see best how to connect to the outside either pipe or a kit.
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