Kitchen cooker hood Extraction

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  • February 18, 2009 at 1:20 pm #43574
    newnhak
    Participant

    Hi

    I hope this makes sense to someone – basically my kitchen is a rectangle shape and the cooker is on one of the long walls. This wall is a dividing wall so the ducting for a cooker hood would need to run across top of units and out the end wall.

    However I have just been advised that I cant have a hole cut where I need it because there is a window lintel in the way. It also cant go further up into the ceiling cavity because it would mean cutting into the joists.

    I therefore thought a 90 degree bend might work to bring it across the ceiling (in the cavity) and out on the opposite long wall. But the designer said that putting a bend in would decrease the efficiency so much that you might as well just have it fitted to use as a recirculating extractor. I thought these were nowhere near as good but he has reassured me that will not be the case if I use it every time I cook and replace the filter regularly.

    But I have read the info on this site and that seems to be saying recirculation only is useless. Please can someone give me advice on what would be the best solution

    Thanks

    K

    February 18, 2009 at 1:25 pm #277738
    don
    Moderator

    Re: Kitchen cooker hood Extraction

    Hi

    This article should answer your questions on hoods and installs.


    HTH

    Don

    February 18, 2009 at 1:40 pm #277739
    newnhak
    Participant

    Re: Kitchen cooker hood Extraction

    Hi

    Thanks – i have read that article. That is saying reciculation is useless – so what should I do? Put the 90 degree bend in which means taking the ceiling out? Is that going to be the best solution? Becuse that is what the article seems to be saying.

    February 18, 2009 at 2:26 pm #277740
    don
    Moderator

    Re: Kitchen cooker hood Extraction

    Hi

    Most manufactrurers admit that ducted is better than recirculation, therefore if fitting a bend I would purchase a recognised brand of hood with a good extraction rate.

    What style of hood and size are you looking at purchasing?


    Don

    Glisten dishwasher cleaner

    February 18, 2009 at 2:40 pm #277741
    newnhak
    Participant

    Re: Kitchen cooker hood Extraction

    I need a 60cm – prefer a chimney hood style but to be honest I would take good extraction over aesthetics!

    The one I was considering was a Baumatic F60.2SS – has a good extraction rate of 500m3/h

    February 18, 2009 at 2:55 pm #277742
    don
    Moderator

    Re: Kitchen cooker hood Extraction

    Hi newnhak


    I would go for the BTC6720SS it`s half as much again on extraction for getting past that 90 degree angle. For the best quality, noise level and longevity of life have a look at Elica not cheap but it will outlast anything else out there.

    Don

    Appliance mobility rollers available here

    February 18, 2009 at 3:02 pm #277743
    newnhak
    Participant

    Re: Kitchen cooker hood Extraction

    Thankyou very much for your help – the BTC6720SS looks good and not much more in price either:-) I think I will go for that one but will find a local dealer to take a look at Elica too.

    February 18, 2009 at 3:07 pm #277744
    don
    Moderator

    Re: Kitchen cooker hood Extraction

    Glad to be able to help 🙂 .

    Let us know the outcome, you never know this thread may help someone else at a later date.


    Don


    ISE5 DW1 12 place AAA rated dishwasher loaded with features and a full five-year warranty

    February 18, 2009 at 7:13 pm #277745
    cockney steve
    Participant

    Re: Kitchen cooker hood Extraction

    A lot of these “designers” really don’t live in the real world!…..having read the thread, I assume the joists bridge between the two long walls, hence your need to site the extract between two joists and fit a 90* elbow.

    Now, unless I’m missing the blindingly obvious, you’d have to do this, irrespective of the joist’s direction…..the vertical extract STILL has to be turnes horizontal, wether it goes across the tops of the units, or between the ceiling and upstairs floor,or you box it into a false beam across the ceiling.

    General:- yes, bends do cause resistance….smooth ducting has lower drag than corrugated….ditto bends……a long, large-radius smooth bend is better than a length of flexible. you can reduce drag by making the cross-section larger …4″ pipe is about TWICE the SIZE of 3″. have a look at SCREWFIX…they do a range of rectangular,reducers, adaptors to round, etc.

    Remember that grease will collect in ducting, it has to be cleanable, and NO, you can’t rely on the hood-filters (one of the reasons that recirc. hoods are not that good)

    the outlet needs to be clear of brickwork, etc. otherwise you will get a stain on there.

    February 18, 2009 at 7:42 pm #277746
    admin
    Keymaster

    Re: Kitchen cooker hood Extraction

    Hi

    DONT use 3″ or 4″ ducting..Use 5″ or the equilivent square / oblong as it will work a lot better and quieter.You will also find that 90{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} of decent cookerhoods require 5″ to work correctly.

    Bryan

    February 18, 2009 at 9:44 pm #277747
    cockney steve
    Participant

    Re: Kitchen cooker hood Extraction

    Sorry , Bryan, i should have been clearer.
    What i really meant, was , “if you use a slightly larger diameter ducting, it’s CROSS-SECTION will be proportionately MUCH bigger.


    so, the biggest, smoothest duct with the gentlest curves , gives the easiest flow.


    but! you need to consider that if it’s TOO big,the airspeed can drop to the point that suspended grease and moisture drops inside the duct instead of being drawn out.

    February 18, 2009 at 11:45 pm #277748
    admin
    Keymaster

    Re: Kitchen cooker hood Extraction

    incase it helps anyone else Baumatic only recomment a max of 3 metres of ducting including only one 90 degree bend. I know from experience that anything longer really affects performance and increases noise…..

    February 22, 2009 at 11:22 am #277749
    newnhak
    Participant

    Re: Kitchen cooker hood Extraction

    cockney steve wrote: Now, unless I’m missing the blindingly obvious, you’d have to do this, irrespective of the joist’s direction…..the vertical extract STILL has to be turnes horizontal, wether it goes across the tops of the units, or between the ceiling and upstairs floor,or you box it into a false beam across the ceiling.

    Hi Steve

    Thanks for the comments – yes this was exactly what I thought because air going up has to turn somewhere to go along the ceiling whichever way you go – but being a girl i thought maybe I was being a bit dim – lol. I have no idea why the designer thought this – he’s done a good plan but I think I may ignore his technical comments!

    February 22, 2009 at 11:30 am #277750
    newnhak
    Participant

    Re: Kitchen cooker hood Extraction

    Hi – thanks everyone for the really helpful posts.

    I have bought the Baumatic BTC6720SS – 60cm. Designer has planned for a 70cm but I am not sure why. Anyway I think the one I have got will look fine. It should be arriving in the next few days.

    I am gathering from the posts that I need to buy the ducting kit separate – and that the general consensus is round 5″ ducting will be best. I guess if I wait for the hood to arrive it will give me some indication of what I need to buy.

    And if I go along the long wall the ducting will need to travel 2.2m so well within the recommended maximum. If I go across it will be shorter.

    Of course once I have it fitted I will let you know what I think

    Thanks once again

    K

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