Asko CW4951 Rangehood w poor Extraction

[DaleBlack]

I have a ASKO CW4951 Rangehood with poor extraction performance. Even basic fryups with high temp oils seem to result in smoke throughout the kitchen.



It has Airflow of 760m3/h though that may just be on the Boost Turbo function which is only 2 minutes before dropping back.
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The ducting is 150mm (I think) , flexi , about 1.5M long with 2 90 degree bends. The 2nd being as it goes horizontal to vertical up to the flue.
The 3 x filters have been cleaned in the washing machine and post cleaning there is no real difference.



See the images, you can see there is a 2 sided flap inside the unit, potentially that is not lifting ? but should I look to a ducting improvement, maybe rigid and possibly installation of a external motor in flue like this Fantech ECE152T
https://www.fantech.com.au/FanData.aspx?&Pid=ECE152T

(https://www.fantech.com.au/FanData.aspx?&Pid=ECE152T)

which I have in my bathrooms. Apparently pulling air from the very top of the ducting line instead of pushing it, is superior air extraction.
I guess I still want some sort of flaps that drop back down so there is not a direct opening to the sky when the ducted heated air is on.



Any suggestions?

[ErrolFlynn]

Presumably, you have checked for blockages. Right-angle bends would slow the airflow. A 1.5 m length of pipe seems rather long, but I’m no expert. The last extractor I fitted was on a flat roof meaning there was essentially no flex pipe involved. It worked a treat.

Have you seen this extractor working well? Ever. I’m wondering if you have recently bought the property and perhaps it has never been any good.

It also occurs to me that with all the oil fumes that are going up into the unit, the dirt and glug may have coated the fan blades making them heavy, perhaps the motor is struggling to spin as well as it used to. Perhaps the oil and glug had gotten into the motor (bearings) itself and slowing it down. Though, you’d want to hope the motor was a sealed unit. Are there any filters that seem blocked? Try it without the filter and see how it goes.

It is winter, after all. Heavy cold air pushing down and into the pipe would restrict outward flow. High winds may have an effect too.

I suppose you could disconnect the duct from the unit, in the roof space, to see how it goes. As a test. That would isolate any duct related issue. If with no duct fitted, no filter hooked up, and nice clean blades, and it still doesn’t work well it may be time to get a new one.

[r3nov8or]

With the rangehood on, can you observe that the flaps are lifting? Eg, take that photo when it's operating?

[DaleBlack]

Presumably, you have checked for blockages. Right-angle bends would slow the airflow. A 1.5 m length of pipe seems rather long, but I’m no expert. The last extractor I fitted was on a flat roof meaning there was essentially no flex pipe involved. It worked a treat.

Have you seen this extractor working well? Ever. I’m wondering if you have recently bought the property and perhaps it has never been any good.

It also occurs to me that with all the oil fumes that are going up into the unit, the dirt and glug may have coated the fan blades making them heavy, perhaps the motor is struggling to spin as well as it used to. Perhaps the oil and glug had gotten into the motor (bearings) itself and slowing it down. Though, you’d want to hope the motor was a sealed unit. Are there any filters that seem blocked? Try it without the filter and see how it goes.

It is winter, after all. Heavy cold air pushing down and into the pipe would restrict outward flow. High winds may have an effect too.

I suppose you could disconnect the duct from the unit, in the roof space, to see how it goes. As a test. That would isolate any duct related issue. If with no duct fitted, no filter hooked up, and nice clean blades, and it still doesn’t work well it may be time to get a new one.

Thanks for the replies from you both.

I had the unit put in during a 2015 renovation and it was brand new.


As for whether its a sealed unit

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The above 3 images are of the motor, is this a 'sealed' unit, i guess there has to be an opening somewhere to draw air through?

My update is

I took off the ducting completely (previously I had only dropped it from the flue 1.5m away), this time the ducting was taken off right above the motor and ran the unit on the lowest speed

The flaps as pictured all open

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Sucess - the sheet of paper holds on the lowest setting, and also at the outer edges of the units 3 filters. I say that as its strongest above the centre filter.

So if all I did was exhaust into the roof space directly above the flaps (320mm maybe) the unit is fine.

So next I decided to move the Flue and its lead covering down maybe 3 tile rows to directly over the unit
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above shows the duct at the flaps held tight by a screw clamp

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The ducting to the solid flue has several rounds of duct tape.

The new flexi duct (new leftover sitting in the shed from this install), say 500mm long but in a fairly stretched mode, to reach the bottom of the flue so maybe 320mm from bottom of flap to ceiling and then 100mm to the flue, then the rest was just up the outside of the flue to hold.

So I am probably operating on 420mm of stretched flexi ducting then transferring to a rigid flue to the outside, every so slightly not straight up.

I went back inside and tried the paper test again and it is still holding. So I will now try a few months of all my cooking and see if there is an improvement.

If not I suppose i attempt completely rigid duct and beyond that? a new inline motor.

[ErrolFlynn]

It seems as though you've fixed it. The paper test seems like a good check. Though, the real test will be when you do your next big fry-up. Though, you can't expect miracles. I replaced an old fan for a new one. One that sits in the centre of a window pane that is located above the stove, and when cooking and all the pots are belting out steam and fumes the exhaust fan can barely keep up.