[Kaliv]

It would seem that your setup is fine...your problem seems to lie with A/C technicians that work like doctors. They aren't sure what the problem is so the take a guess and fix one thing at a time until something works without really knowing what's causing the problem...being out there for the 3rd time when you haven't had issues in 5 years.

I've worked in server rooms for quite a few years, but I can't say that I've ever inquired about how the A/C system works. But I do know when working in the server room, it alway seemed windy. The main issue isn't really cooling the air, it's the transfer of air. Just as inside the computers themselves...they don't run cool air over the heat sinks, they just run plain air to move the hot air away. Ambient air will always be cooler than what the systems are generating. So you mainly just need a flow going to push the hot air out. Adding in cold air is just a bonus for extra cooling.

Case in point, I was working in a server room once when the fan to the A/C unit broke. We went from 68 degree to about 100 degrees in less than an hour. By the time we got a bunch of huge fans in the area to circulate the air, the temperature dropped to low 90s, high 80s...and that was without cooling and our crappy quick fix circulation.

Guess the point here is...seems like you have a working layout solution. Just keep the air circulation going.