underfloor duct for extractor

[dsharp7th]

in a new kitchen extension we're going for a downdraught extractor in a kitchen island, as it's clearly a neat solution, we've swallowed the cost, (our kitchen supplier has got the neff one way below cheapest list prices) and we have the opportunity to lay the duct under the new slab.

our builder is happy to do this, but hasn't done this before, so I'm wondering if there are any tips or pitfalls in the process.

So far I've got

- use pvc 150mm pipe with solvent welded joints

- use rigid elbows

- surround the pipe with sand

- cover the open ends as soon as it's in before any litter. dirt or other detritus gets in it.

- fit a back draught shutter (probably where it comes above the floor before it exits the exterior wall)

should anything be done to deal with condensation? any other tips?

 

[freddiemercurystwin]

If it ever got condensation in it, how would it ever be removed?

 

[dsharp7th]

I was hoping for advice rather than another question, but I would imagine the best way of removing condensation would be to slope the underfloor duct slightly towards the exterior wall and check/clear it from the wall vent and clean the duct like a drain now and again.

Anyone have experience of this?

 

[ree]

At its simplest: if you vent and then go down - run almost flat - and then come up, you will get condensation. You have built a condensation trap.

A tried method of cleaning out condensation and grease, must be worked out before any installation work.

Maybe, really powerful motors will almost eliminate condensation but they will be loud, and as they age get louder.

Downdraft extractors have generally had a bad press but some swear by them.

I've never installed one so i only report hearsay for what its worth.