Fan Thoughts

[Luke Skywalker]

You would be well served to get an oversized fan for the application you intend it for.

 

The axial bathroom style fans are excellent at moving high volumes of air, but any back pressure on them (including long lengths of duct, particularly if it's not stretched as tight as possible and has bends in it) will severely curtail it's flow.

 

If you have to use ducting, keep the lengths to a minimum and ensure that you stretch the duct as smooth as possible. This will ensure that you don't have a massive drop off in flow.

 

Axial fans, those which run like a propellor blade, (bathroom and axial inline fans) are good for rooms which don't require a carbon filter, (those using ozone gens or venting high into the air where there is no problem with neighbours) but will not operate under carbon filter loads.

 

A centrifugal fan, which scoops the air around and then spits it out, is designed so that air cannot backflow, and there is high pressure generated. They do cost more, but are highly efficient, and work excellently in situations where long duct lengths are required, and for a carbon filter they are the only way to go. They aren't necessarily going to move more air than an axial, and quite often don't, but they do generate the required pressure for the applications we require of them, and are sturdier IMO.

 

Ideally, you should vent your room's volume each minute, but airflow is one of the few things where it's very hard to overdo it. Unless you have a jet engine in there you'll rarely be harmed by having excess exhaust power.

 

I would recommend you invest in the centrifugal fan if possible, or if you can only afford a quality continuous rated axial, go with one for the moment but save or layby a centrifugal for the future.

 

One thing to note is that the bathroom fans available from places like bunnings which are exactly that, bathroom fans, are not suitable. They have to be rated for continuous use, or you could end up with a fire on your hands, or at the least a failed fan when you least need it. They also put out pitiful amounts of airflow compared to the continuous ones like the air-xpress and hydro-turbo.

 

The airflow of the air-xpress is about 220litres per second, and the hydro-turbo about 250liters per second. Which does work out to about to around the 880m3/hr figure given. This will drop when you put duct on it, but it should still be adequate for most small rooms.

[Ozzy420]

Spot on as all ways young jedi with your info.

 

I only have a aveage sized robe and the air-express fan i use dose more then the job i want to going through 2 meters ducting hooked up to an ozone gen with a 120mm fan in the end of the ducting to help a bit with the air flow through the ducting...

[Stoney]

ahhh sweet as lads thanks for the info i may just go with a bathroom style fan and just fit it to the roof of me wardrobe and have no ducting attatched just vent straight into the garage

 

you guys that use the bathroom jobbies do you have them on all the time when lights are on or do you have them set to a timer or do you have a thermerstat set up

 

thanks again

[Ozzy420]

I have mine set to startup when my light comes on and turns off with lights off.

 

As it is only a small area like a robe the heat can build up a bit quicker then larger areas so i have my fan going all the time the light is running....

Edited July 19, 2006 by ozmade

[stonedstump]

Whoops I think I meant to say thc24 but I saw ozmades name just there and must of typed it accidently. Oh well

[Gazza2001au]

few people have talked about the air-xpress fans and posted pics/links im using one just as an exhaust in a 12x9 foot room (i think its that size) two 600's room temps sitting on 21.5c handels 1000w heat no problem

 

you guys that use the bathroom jobbies do you have them on all the time when lights are on or do you have them set to a timer or do you have a thermerstat set up

atm i just leave my fans running 24/0

[stonedstump]

I'll be leaving my fans running 24/7 but I want to get a speed controller so then I can slow them down to half speed during lights off.