Different type of extraction fan?

[shiva71]

Hi

Does anyone use these?

http://cgi.ebay.at/DOSPEL-Rohreinschub-Ventilator-Luefter-150mm-EURO-3_W0QQitemZ110432452103QQcmdZViewItemQQptZLüftungs_Klimatechnik?hash=item19b6497e07&_trksid=p3286.c0.m14

Most of you guys seem to use this type

http://cgi.ebay.at/Rohrventilator-UFO-Luefter-Luefter-VKMZ-100-270m-h-Grow_W0QQitemZ350242856634QQcmdZViewItemQQptZLüftungs_Klimatechnik?hash=item518c19deba&_trksid=p4634.c0.m14.l1262

Spec for 1st type, 164 cfm, 25W, 47dB, $31
Spec for 2nd type, 158 cfm, 60W, 47dB, $81

Is there any reason why the centrifugal type extractor is much better than the first type cos its way cheaper, to buy and to run....

Any thoughts?

Cheers guys!

 

[Nocturn3]

Axial fans are terrible under pressure. Pressure is created by long ducts, bends, and most importantly carbon filters. An axial fan will slow to a crawl with a CF (or stop completely), whereas a centrifugal fan won't.

CFM ratings are only part of the story for fans. The static pressure rating, measured in pascals (Pa),is just as important, particularly when a filter is needed.

 

[podunk421]

Axial fans are terrible under pressure. Pressure is created by long ducts, bends, and most importantly carbon filters. An axial fan will slow to a crawl with a CF (or stop completely), whereas a centrifugal fan won't.

CFM ratings are only part of the story for fans. The static pressure rating, measured in pascals (Pa),is just as important, particularly when a filter is needed.

Very true, it is also dependent on your focus of use with the fan. That fan would probably work well as an external air source for the plants but it just wont stack up to the chore of pressure. You either run an extraction or induction fan based on cab type this might cut it for induction because air is just pushed in, extraction has so many more features that while price may be cheaper now will leave you wanting a better fan within a week.

 

[shiva71]

Cheers guyz!

I plan to have a 250hps in a closet which will be 1.2/2 ft x 3ft x 5ft approx...i have a 120mm x 120mm pc fan which would pull in about 100cfm as incoming fresh air, then a centrifugal extracting 160cfm attached a carbon filter at the top, does that sound reasonable? Im a bit confused, some say you should have more air coming in than going out, others say vice versa...any thoughts?

cheers for the responses guys!