OK, you asked for it.
I have a similar server room (similar to the FL server Rm that started the "War and Peace" thread). The difference is that it is in a basement and it is in upstate NY. We plan on using a Trane TWE AHU with a thermo expansion valve and TTP cond. unit with a 0F low ambient electronic head pressure control. We are putting the server cabinets up on blocks with sheet metal to create a plenum under them (there are two cabinets) and ducting about 50% of the air to the plenum. The rest of the air will be discharged behind the cabinets (the AHU return is in front of the cabinets). The fan will run continuously.
Does anyone think we need anything else. Hot gas bypass? Freezestat?
Actually the first question is what is the heat output of the servers. They are Dell rack mount with a power supply rated at 700W. I have heard 33% and 66%. There is a big difference with 22+ servers.