Dix Dogfight:
Your building a device that will run off the 12V line from your cases PSU that will control your pelt and auto adjust to a specific temp to avoid condensation..... am I reading that correct? If so and if you get it to work correctly, I would be very interested in either borrowing your diagrams or purchasing a unit from you.
BTW if you case PSU is big enough (over 500W) and your 12V line is strong enough (over 20A) then you shouldnt have to worry too much about causing problems with the rest of the system. Even my system with 4 SCSI HDDs, 3 CDROMS, and lots of other goodies is barely using say 10A on my 12V line where my PSUs 12V line is rated at 24A. An 80W pelt running at say say 7-8A SHOULD not cause that much of a problem (it will just be running closer to its optimal effeicency mark).
Hence the reason why I wanted to use only a 56W pelt. Then I would only be drawing about 6A all the time BUT if I can control an 80W pelt with a setup that Dogfight is talking about, that would be even better (no guess work)
Keep me informed Dogfight.