Rodrigues, when you say load, what exactly do you mean?
When i tested my TEC chiller i ran prime95 small and furmark stability xtreme test at the same time for 2 hours (and got temps in the 20s cause room temp went up).
19-20 water temps, right?

Justfire,
is 16C the lowest it can handle or is it just the temp you feel comfortable with?
What pump are you using?
have you tried some serious load testing (like i mensioned)?

and how in the world did you get 3 280s to run at 810/1620!!!? i cant get to run a single card t over 783! i tryed 2 (one in my sig and one evga) and 756 seem to be the limit for both(even overvolted to 1.3). luck of the draw? cap mod? what is your secret?