I have a potential customer who is leaving it up to me to decide the amount of a/c and type of a/c to put into a future room where all his controlling "server" equipment etc. is going to be located.

If you posted that comment over at the HVAC forum you would be able to hear them laugh all the way over here! Pretty much what we do when we look at their electrical work.

Computer room environmental control is a specialized field, even being an HVAC guy doesn't mean you are qualified. If I were you I would act as a consultant on this. Hook your customer up with a company like Liebert, charge for your time and tack on a percentage. You will come out ahead, believe me.

-Hal