Kitchen extractor issue

[Jupiter01]

I have an AEG extractor that is ducted to the outside. After 7 years, it failed earlier this week. I did the "tissue test" and there was no suction. Everything else seems to be fine: controls, fan noise. I assumed the motor is knackered and booked an engineer from AEG to come out and have a look at it.

The engineer, also did the "tissue-test". Same result.
He then disconnected the foil duct connected to the extractor and repeated the tissue test. We have suction!

There is obviously some sort of issue with this duct. This foil/aluminium flexible duct travels around 3 metres above the living room ceiling and then exits at the side of the house. There is a bend where it comes through the kitchen ceiling and then connects into the hood.

I am at a loss as to what is causing this (other than the fact that it appears to be the duct) and how I should replace this, given the nature of its route through the living room.

I would be grateful for any advice that you can provide. Thanks in advance.

 

[Harry Bloomfield]

There is obviously some sort of issue with this duct. This foil/aluminium flexible duct travels around 3 metres above the living room ceiling and then exits at the side of the house. There is a bend where it comes through the kitchen ceiling and then connects into the hood.

The duct has rotted/collapsed. Remove it, and replace it with rigid pipe, of a similar size.

 

[Jupiter01]

The duct has rotted/collapsed. Remove it, and replace it with rigid pipe, of a similar size.

How do I replace this given that it runs above the ceiling for around 3 metres and also, the run may not be completely straight and hence, not lend itself to a rigid pipe?

 

[aveatry]

I found a useful guide a while ago but cannot find it now, it something like the max length should be lets say 6m but for every 90 degree turn you need to add 1m. so if your straight run is 3m with 1- 90degree bend your total length is calculated at 4m. Like I say those are not the exact figures - its just from memory. Also that refers to 150mm rigid and not flexible.

 

[aveatry]

How do I replace this given that it runs above the ceiling for around 3 metres and also, the run may not be completely straight and hence, not lend itself to a rigid pipe?

There must be a shorter exit to outside, poss run along the top of cabinets and box it in.

 

[Ivor Windybottom]

The bendy duct gives waaaaay more air resistance than rigid. Not so much as it's bendy, but because it has bumps all along its length. For the air, it's like driving on a cobbled road instead of a motorway.

You need to access the ducting by whatever means, and completely replace it. With rigid ducting, carefully put together by someone who actually cares about what they're doing (i.e. not a builder or property developer).

Unless you're very lucky and it can be done from the ends, you will probably need full access to the whole length. This may require removal of plasterboard, it could be a pretty destructive process. But once it's done properly it should last for decades, unlike the rubbish that was used previously. Patch up, paint, done.

 

[Jupiter01]

Is there any merit in getting one of those mobile Cameras and having a look inside the current duct?

 

[Harry Bloomfield]

Is there any merit in getting one of those mobile Cameras and having a look inside the current duct?

Probably a waste of money, better spent on doing the job, which you know has to be done. You know it's blocked, likely the duct has collapsed.

 

[aveatry]

Probably a waste of money, better spent on doing the job, which you know has to be done. You know it's blocked, likely the duct has collapsed.

If it has collapsed,then how. You can get a cheap usb camera scope in amazon or ebay. like this https://www.amazon.co.uk/Lightswim-...2115079&sprefix=3+m+scopes,aps,77&sr=8-5&th=1

 

[foxhole]

Have you checked the outlet for blockage , could just be a build up of greasy fluff .