Bathroom extractor fan dilemma

Carnmore

I'm renovating the bathroom in a central (no window) mid-floor apartment with flat channel ducting and a long duct span (6-7 metres) to the external wall vent. I've removed the original centrifugal fan c.25 years old) and need to decide on a replacement. 

(The 1500mm x 700mm shower tray is fitted in the old bath recess with a fixed glass panel open at the end so shower tray not in an enclosure)

Inline fans seem to be the most effective but there is no room above ceiling level to install it. I'm considering installing the fan below ceiling level mid-way along the duct-which would be in a bedroom-with the existing flat channel ducting above ceiling level and boxing-in the fan. 

Other options I'm considering are a modern centrifugal fan or a dMEV (continuous running) fan.

Obviously having a fan boxed-in below ceiling level is not ideal!

Can anyone advise on the most suitable and effective option? 

Thank you in advance.

smuggler.ie

note that any type of fan you install will produce noise while in operation - not quite good in the bedroom. Box in the bedroom also seem... emm... well, you know....

Could you drop bathroom ceiling level or box there to accommodate the fan?

Carnmore

https://www.boards.ie/discussion/comment/121205718#Comment_121205718

Fan could be boxed in bathroom but would be within one metre of the ceiling inlet with 5-6 metres on the other side of it, which is not an effective way to set them up.

smuggler.ie

I might be wrong, but i think inline fan can be at whatever distance from either end as long it does not exceed recommended duct length. Duct shape/diameter/bends might effect the distance. Its performance/capabilities should be defined in specs.

antoinolachtnai

Closer to the bathroom end the better I think. It is easier for the motor to push than to pull.

would something like this work?

Xpelair C4HTSR Simply Silent... https://www.amazon.co.uk/dp/B08D9DLPVY?ref=ppx_pop_mob_ap_share

smuggler.ie

F all the difference . As long you have obstruction on either end it will put stress on motor.

Ideally you want 4" round hard duct and fan right half way - friction to walls same for suck and blow, but rarely you can have it. Grills either end are also obstruction, but you want "design", so you sacrifice.

Fan should be calculated to serve room volume, try something like

https://www.tlc-direct.co.uk/Technical/Ventilation/Ventilation4.html

kirk.

https://www.boards.ie/discussion/comment/121207122#Comment_121207122

I don't think I got an answer when I researched my inline fan ducted to soffit

Keep the ducting smooth and don't fit fan too close to inlet was all I figured out

smuggler.ie

you not mixing it with "air replacement source" (door, window) ? Inlet should be reasonably far from air supply source to avoid "short"

Some of the quiet extractor fans are great and very quiet in operation. Any one which has a humidistats is liable to premature failure when the humidistats inevitably fails. Installed one recently and it failed in two years. Relatively easy to replace the humidistat though so worth having a few in reserve for when it does.

smuggler.ie

Where i can see potential problem, is those flat ducts are short sections(~2m) and never sealed properly.

Powerful fan will create pressure and two things might happen, depending where fan is located:

where fan fitted in the bathroom, moist air will be forced into ceiling void in the bedroom through unsealed duct joints.

where fan fitted in the bedroom, air get suck from ceiling void thus reducing ventilation performance in the bathroom.

non of above is fan location problem, rather ducting issue, but should be considered

kirk.

https://www.boards.ie/discussion/comment/121207614#Comment_121207614

I think I read that having the inline fan upstream caused turbulence because the fan was blowing the steam out?

Don't think I got an answer on that and used round solid pipe covered with insulation and fan halfway