fixng outlet pipe to cooker hood

[sm_jamieson]

Bosch cooker hood has 150mm outlet and I have a 150mm vent pipe to connect. However, a normal pipe connector that fits inside the tube does not fit inside the hood outlet, since it is profiled and with a seam in the moulding. But the outside of the outlet is the metal casing and the 150mm pipe does not fit over this either, since it is too large and slightly tapered. It appears the only way is to butt the pipe to the outlet and fix it with loads of gaffer tape. Is this acceptable ? Simon.

[John Rumm]

They invented duct tape for a reason ;-)

[DerbyBorn]

John Rumm wrote in news: [e-mail]:

Thought it was for tapeing Ducks.

[Tony Bryer]

I've just fitted two hoods here using rigid duct which has a slightly reduced profile at one end and enlarged socket at the other. Neither fits the hood outlet properly - the solution is to cut the duct at an appropriate point leaving the normal section which does fit. May not be relevant to your case though.

[sm_jamieson]

My duct is plain ended, but where did you get yours - is it aluminium ? It may be that your enlarged end (sorry) fits my outlet duct (doubly sorry ;-)

Simon.

[John Rumm]

Its going to be a long way to go to get you hands on Tony's enlarged end ;-)

[fred]

Dear me, no need for innuendo, the enlarged piece is simply known as the bell end, adaptors available from all goo ducting suppliers.

Back to it, I'm ok using short flexibles in the vertical as long as it changes to smooth for long horizontals (falling to the outside). An alu based flexible can be crushed down onto a smaller outlet using an extra long jubilee type strap or tightened wire. Best silicone sealed on the inside if condensation is expected to run back with duct tape on the outer as a double measure.

[sm_jamieson]

Not having any luck finding such a thing for 150mm plastic ducting. Can you post a link ?

Simon.

[Tony Bryer]

Here in Australia you're not allowed to use plastic for cooker hood ducting (fire risk allegedly). You can use flexible aluminium (as used for flue liners in UK) or rigid metal which presents less resistance to airflow.

[fred]

Sorry mate I was indulging in stores counter humour, "can I have a left handed screwdriver, a tin of tartan paint and a bell-end adapter pls".

I missed the winkie smiley and moved on to the actual helpful bit that was to use flexible aluminium instead that could be conformed onto the outlet spigot. I was also thinking of the issue that Tony mentioned about not having flexible plastic in the duct where flames from a pan fire could be sucked in by the extractor.

[charles]

a bit pointless when my whole fan assembly is made of plastic, except for the metal cover to which the trim is fixed.

[fred]

Valid point and the ongoing non flexible ducting or drainage pipe will also be susceptible but my main concern was fire transfer to hidden areas like a ceiling void or boxed in area. PVC flexibles would be gone in a flash leading to spread of fire but the non-flexible may take a bit longer to breach. More important if the duct path passes in a void to other room s but that doesn't appear to be the case here.

I'm quite cautious about these sorts of things.