you want to find out what Power your fans take (Currect) and what AMperage they are (Amps) ex.. Most Pc fans are 12V DC and somthing mA ex. .62mA

THis means any 12 V DC Power supply with atleast 620 MillAmps will power this,, So more Amps More fans.. be careful not to have too much power though if your not running Mulitple fans

heres a good example I have 2 PC fans each rated at

12VDC .32 mA

So that means I need atleast a 12V DC 320mA Adapter to run ONE FAN,

But wait I have 2 fans I dont want to take up two power sockets only 1 cuz im growing in a box and space is tight.

So If I get a power supply that is 12V DC 1 Amp. That will be able to run 2 fans no problem. Also leaving mee enouugh power to run a third fan rated at the same mA If I want to. .320 + .320 + .320 = 960mA

1 Amp equals 1000mA

Hope thius helps... I can answer more questions later Im at work so I typed this fast......

kd_special