Aye, thingemajib's right, so:
Well, rearranging the old equation, a 30W channel at 12V gives:
P=IV . . . thus I=P/V.
Plug in the numbers (P=30 W, V=12 Vdc)
I=30/12
I=2.5 Amps per channel
So, in theory, if you are using the 0.4amp fans you mentioned, you should be able to run a maximum of about 6 of them (2.5 amps divided by 0.40 amps)...
(since 2.5A/0.40A = 6.25)
But remember that fans need more juice to spin up at start up than they do when they're already running... so 6 might be pushing it a little - if you overdo it, at best the fans may not start and at worst you could burn out something .... but if you only need to run 3 of those 0.40amp fans on the 2.5amp channel... it should handle that ok.
If their RPMs aren't monitored by the mobo or controller, your best bet is to try starting up with 3... and if it works and you need a fourth, try that... but keep your eye on it for the first dozen or so times to make sure they all spin up, and later on in a few weeks or months when it might have some dust in it, check again that all the fans are still spinning up at startup.
Just be glad you're not running 3amp Delta fans... ahh, the old days of overclocking before watercooling was common.
Hope this helps.
