chimney extractor hood

[jumbo55]

decided to use my old chimney breast that has been blocked up for years to vent my extractor hood into, drilled me pilot hole and it went through to a void, so drilled me 125 mm hole, and got through to something, a small void, but im worried that it is blocked off, cos when i put my hand in and then up, all i feel is brick, i put a piece of flexible conduit in hole and it only goes up about 300mm and seems no further, do you think im missing something, is it a small hole im missing, i put a smoke pellet in there and a little bit came back out through hole but not that much, has anybody had experience of this, any suggestions.

 

[cmother1]

You may be better off moving this problem to the 'building' forum where you're more likely to find people who know how flues are constructed. After all, there's nothing wrong with the hood, is there?
Could just be that you're hitting brick as the flue steps sideways (most of them do). You could try the torch and the angled mirror trick, if there's room, to see if the way out is visible.

 

[Richard C]

This dodge comes up fairly frequently; apart from the fact your flue appears to be restricted, it’s not a good idea as domestic fans won’t generate enough air velocity to clear the stack & moisture/grease laden air will cool & condense inside the duct/stack; 5 meters is the maximum for many fans & some won’t even do that. If your kitchen refurbishment (or other associated work) is subject to inspection, Building Control won’t approve it either as it wont meet current Building Regs. requirements for forced extract.

 

[jumbo55]

thanks for replying lads, very interesting points you bring up, looks like i did a lot of work for nothing, oh well you live and learn, gonna fill the hole back up and just recirculate, have a powerful fan on the exterior wall anyway, just that instructions point out its not much good unless ventillated to outside. my mistake, should have thought it through.

 

[Richard C]

gonna fill the hole back up and just recirculate, have a powerful fan on the exterior wall anyway, just that instructions point out its not much good unless ventillated to outside. my mistake, should have thought it through.

Sorry to tell you but recirculation hoods do not comply with current Building Regulations requirements but if you have an external extract fan anyway it should not matter, you just have to more or less double the extract rate.

See here:
http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADF_2006.pdf
Read it through but page 10 is the one you’re interested in.