Kitchen extractor duct running under suspended floor and back up. Drawing attached.

ToastyToes · 16 May 2019

Just wondering if there could be potential problems with running the kitchen extractor from the island under the suspended floor across the kitchen, back up through the floor and then out the wall?

Drawing below - The ducting is drawn in red.

Lower · 16 May 2019

From a practical perspective, any build up of grease will just sit in that pipe rather than dripping back out. But i have no idea if that is just accepted with an extraction system of that type.

ToastyToes · 16 May 2019

Lower said:
From a practical perspective, any build up of grease will just sit in that pipe rather than dripping back out. But i have no idea if that is just accepted with an extraction system of that type.

Makes sense, but any installation using a flexible duct will have a build up of grease in each of the ridges surely? It'd be impossible to 'drip out'.

Lower · 16 May 2019

If the ducting is higher than the extractor, grease or condensation will drip back down into the extractor and out into the kitchen if it builds up to a significant level. It happened in our old kitchen and made us realise that the grease filters hadn't been fitted properly and the fan was lifting the filter off its seat when the extractor was turned on.

In the your drawing it would just pool in the bottom of the duct.

As i said before, i don't know if that's an issue in a domestic kitchen.

ToastyToes · 16 May 2019

Lower said:
If the ducting is higher than the extractor, grease or condensation will drip back down into the extractor and out into the kitchen if it builds up to a significant level. It happened in our old kitchen and made us realise that the grease filters hadn't been fitted properly and the fan was lifting the filter off its seat when the extractor was turned on.

In the your drawing it would just pool in the bottom of the duct.

As i said before, i don't know if that's an issue in a domestic kitchen.

Thanks for your advice. I'm concerned more about condensation then anything else but not sure if i need to worry about it as I'm not too sure how it works with extractors .

JP_ · 16 May 2019

Better than nothing. Any reason why it can't go across the ceiling?

foxhole · 16 May 2019

I could see the low discharge point attracting vermin, rats would chew thru any external vent to get at the attractive smells coming from it.

ToastyToes · 16 May 2019

jonbey said:
Better than nothing. Any reason why it can't go across the ceiling?

It's a vented induction hob as we dont have space in the ceiling void above to extract... thanks

foxhole said:
I could see the low discharge point attracting vermin, rats would chew thru any external vent to get at the attractive smells coming from it.

If that's the only issue, I can prevent entry so it doesn't bother me too much. Thanks

JP_ · 16 May 2019

Curious so googled it. Not many people support the idea: https://www.mybuilder.com/questions...wnwards-and-towards-the-outside-under-a-floor

Issues as already mentioned - rodents, grease build up, as well as potential fire risk if grease and oils, water accumulating etc.

Charcoal filters?

Lower · 16 May 2019

ToastyToes said:
Thanks for your advice. I'm concerned more about condensation then anything else but not sure if i need to worry about it as I'm not too sure how it works with extractors .

Condensation you could avoid by insulating the pipework in the floor but you'll still get some condensation at the end of the pipe.

What will happen is that the extractor will extract the hot, moist, steam laden air from the cooking area. When that moist air hits gets in contact with the cold pipe you'll get condensation forming.

You way be able to get a condensation trap to fit into the duct under the floor that you can then run to a drain or a soakaway.

Ian H · 16 May 2019

Could you run it straight out in solid pipe without the turn up at the end?

ToastyToes · 16 May 2019

Ian H said:
Could you run it straight out in solid pipe without the turn up at the end?

No the ground level outside is not low enough.

jj4091 · 16 May 2019

Your drawing suggests that there is not going to be an extractor above the hob. As heat & steam rise I doubt it will extract the condensation out efficiently anyway if it has to drag it side ways first. You could go across the ceiling with flat ducting thus avoiding going into the ceiling void unless you would find that intrusive, but I think it would be much more efficient on smells & fumes.

ToastyToes · 17 May 2019

jj4091 said:
Your drawing suggests that there is not going to be an extractor above the hob. As heat & steam rise I doubt it will extract the condensation out efficiently anyway if it has to drag it side ways first. You could go across the ceiling with flat ducting thus avoiding going into the ceiling void unless you would find that intrusive, but I think it would be much more efficient on smells & fumes.

Correct there is no overhead extraction. The latest hob extractor tech is really good. Youtube some of the Elica hob demos. They are very effective. We had one years ago at my parents home and it was fantastic.

foxhole · 17 May 2019

ToastyToes said:
Correct there is no overhead extraction. The latest hob extractor tech is really good. Youtube some of the Elica hob demos. They are very effective. We had one years ago at my parents home and it was fantastic.

Checked out a demo and it was computer graphic, not a real hob in a real kitchen, doubt it would perform very well in the real world, and can imagine a mess if a pan boils over or is spilt into the fan.

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Kitchen extractor duct running under suspended floor and back up. Drawing attached.

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