Computers don't operate well in extreme heat conditions. We had the misfortune of having the air conditioning go out in the computer room of our old building. It was cooler in the hall. We propped open the doors and had a series of fans blowing to pull the heat out. I recommend never letting temperatures approach 90 degrees, as it did that day for us. A computer room should be cooled to 6570 degrees, depending on the type and volume of equipment that you have running. Midframe and mainframe computers typically generate more heat than PC servers, and cooling should be adjusted accordingly. Propping open the computer room door also circumvents the security system you have protecting access to that door.
With the overheating problem vivid in my memory, I vowed to avoid that problem in our new computer room. When I worked with the HVAC contractor to design the cooling system in the computer room, I told them that we needed backup. We installed a primary air conditioning (AC) unit with a failover mechanism with support from another AC unit. Here's how it works. A sensor in the computer room monitors the temperature; if it ever rises above 80 degrees, the system automatically powers a motorized damper that opens to another AC unit. We also installed a manual override switch on the wall to open the support unit whenever we deemed it necessary. It's my sincere hope that this system will keep the computer room cool at all times.