Data Center Temperatures

The primary heat load is from the processors in the servers (rack, case or main frame).

If you check out the manufacturer's data sheets, you will likely see that the units can operate with no problem in temperatures as high as 30C and relative humidity of over 70%.

The main issue is that the RATE OF CHANGE of any of these parameters must be very slow to keep the internal resistance of the circuit boards from changing quickly- as it would if the temperature or humidity changed rapidly- because such a change will cause the equipment to "read" an internal signal incorrectly and generate bad output data or trigger a shut-down error. The other issue is that there must be enough air movement to keep equipment INSIDE the box below its "critical" temperature- typically below 40C- to avoid excessive growth (causing same problems as noted above) and/or system shut-down.

The reason that most data centers are run so cold is that it requires a very competent designer to lay out the HVAC system so that all equipment receives adequate cooling to keep below critical temperature, and a cold room covers a lot of design "sins of omission".

The other reason that the rooms are kept cool is the fact that they are "dynamic"- meaning that equipment comes and goes, or internal capacity (and heat load) grows so often that even the best designer could not keep up with the constant changes so a cold room solves a lot of "operating sins".

If you want to minimize the operating cost of the room, look into available "free cooling" during cold weather and also look into redesigning your equipment for an alternate operating approach. Several years ago, I designed a system that puts 2-speed fans in the HVAC equipment, controlled by the humidity.

Normal operation is about 16 CuMtr/min per ton of cooling with moderately cool air supply (17C-18C). If room Relative Humidity (RH) climbs above set-point, the unit begins to cool the air down to around 13C, nearly doubling the cooling load (and energy) to remove moisture and then reheating the overly cool air to prevent over-cooling the space.

By using the 2-speed fan, set to run on high in "Normal" operation, to drop to Low Speed when the humidity rises, the cooling system will automatically increase the cooling capacity to reduce the air temperature to about 13C to maintain room temperature as called for by the thermostat. However, that reduced temperature will be applied to 2/3 of the airflow, so the only actual added load will be the moisture removal energy. The 13C air at 2/3 volume will provide the cooling effect as the 17C air at full volume, so NO REHEAT will be required. Room humidity can be maintained with only about 15% more cooling energy than normal without the added energy load of the reheat AND the reduced fan speed will SAVE nearly as much electrical energy as the added cooling (water removal) load adds- essentially giving you a zero-sum room conditioning energy package. When humidity is under control, the fans return to full speed and the cooling will return to 17C discharge.

The retrofit cost is very low and the control modification is very easy to set up. Pay back is usually less than 4 months.

Thank you very much for your detailed reply. I think all of us should strive to conserve power by following available best practices.

Try APC's Data center university. They have short courses in everything related to data centers including all types of cooling necessary. Typically the worst offender for heat are loaded blade servers. They can produce up to 20 times the BTU's that a lightly loaded rack will. When in doubt use 70 degrees or less for your ideal temperature. Remember that all electronics ages quicker the hotter it runs.