100 mm fans :in-line centrifugal and axial

[mointainwalker]

I wonder if anybody can recommend products as above ?

a) In-line centrifugal :Ideally I would just want the fan as I have a
timer and will be feeding into 100 mm PVC pipe approx 4 m long.

I know nothing about fans, expected life-time etc, just want one for domestic use ( shower 1 x 8 m3) .

On-line I see Vent-Axia etc can be 80 -100 pnds and others including Manrose around 30 pnds.

b) Axial : Would this type vent a shower ( 5 m3 ) with following exhaust .
straight 60 cm, 90 degree elbow, 1 m straight. as before just need fan.

Grateful for comments and recommendations, thank you.

 

[stem]

The recomended ventilation rate for a bathroom is 20 changes per hour, so work out the volume of the area you wish to ventilate then multiply it by 20. Then find a fan that gives the appropriate extraction rate in m3/hour.

As with most things you get what you pay for. I know of two Xpelair fans I installed in 1980 that are used daily and are still going strong and without any rattles or rumblings. I've fitted a couple of Greenwood Airvac's too and haven't had any problems.

Axial fans can't generate enough pressure to overcome the pressure drop in long lengths of ductwork, so the air flow falls off. Axial fans are best limited to absolute maximun duct lengths of 3 metres. For longer runs use a centrifugal fan which can generate a higher pressure.

Any fan located in Zone 1 of a bathroom or shower room will need to be rated for such a location and be RCD protected. An in line remote fan is a better solution really.

 

[mointainwalker]

Stem - thanks for your reply and apologies for not replying sooner.

Picking up on the axial again, do you feel that I could use one of this type in the situation described in my b) ( will be in Zone 3) as I don't know what "length" you calculate for an elbow ?

 

[stem]

You will be running beyond the capability of most axial fans. If possible I would suggest that you use a centrifugal. An added advantage is that they are less effected when it's windy.

Keep the duct run as straight as possible after the bend, and slope it downwards towards the outlet slightly to avoid any condensation running back inside. As a rule of thumb, I believe the 'equivalent length' of a 90 degree bend would be in the region of 2 metres.

If you do go down the axial route, you could get a good quality fan with a higher extraction rate than you need, this may help offset some of the duct losses, but I wouldn't recommend it.