Internally Installed Extractor Fan Ducting.

Mornin',

                  it appears that nobody has any personal experience with these new devices, or they are not prepared to share their experience with them. So, how do you practically ensure a three degree slope downwards to the outside when drilling the hole for the duct tube? If the tube slopes at more than three degrees the outer flexible collar will not fit snugly up against the outside wall.


Z.

Morning, we fit these quite often. Never really had any issues with getting them to seal as long as the angle isn't too steep.


Nick

If the tube slopes at more than three degrees the outer flexible collar will not fit snugly up against the outside wall.

Not tried that one, but I doubt the angle is that critical - most outside walling (even machine made brick) is far smooth & flat - there'll be far more than 3° variation from vertical in individual bricks, never mind the natural stone blocks that are favoured around here - if the system is going to work reasonably it'll have to be able to accommodate much more variation than that. (Likewise the horizontal angle between the axis of the hole and the outer wall surface - which won't practically be judged by anything other than eye).


  - Andy.

You are right, the internal fans are a very snug fit, and thin walled housing means they will bind up with even the smallest misalignment. Something of a mismatch between fan designers utopia and real life. 

Spirit level on the drill  (plus a bit)  if you are worried. Installing a new fan to old wonky duct is the trickiest, I recently had to grind out plastic inside the duct wall to allow one in without binding. 

The manufacturers specify a 3 degree drop of the ducting to outside to allow water to run outwards and not back into the room, and also to give a good seal to the flexible outer seal on  to the outside brickwork. Any angle greater than 3 degrees may cause a poor external seal. Fans will run in almost any orientation, vertical or horizontal or anything in between in my experience. See original post please.


Z.