Server Room Cooling: What You Need to Know Before You Buy
Server rooms have very different cooling requirements from offices. Get the specification wrong and you risk equipment failure. Here's how to get it right.
A server room or network closet is one of the most demanding environments for air conditioning. Unlike an office, it generates heat continuously, the heat load is high relative to the space size, and the consequences of inadequate cooling — equipment failure and data loss — are severe.
Operating temperature requirements
ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers) publishes guidelines for data centre environments. The A1 class recommendation for most commercial IT equipment is 15–32°C. However, for maximum equipment life and reliability, most operators target 18–27°C.
Calculating the server room heat load
Unlike a domestic or office environment, the entire electrical power consumed by IT equipment becomes heat. A rack drawing 2kW of power generates 2kW of heat. The calculation is straightforward: sum the rated power consumption (or TDP) of all equipment in the room, add 10–20% for lighting and other small loads, and that is your cooling requirement.
A common mistake is sizing a server room system for the current equipment load without allowing headroom for growth. If you're planning to add equipment, size the system for your anticipated maximum load, not the current load.
24/7 operation requirements
Server rooms require continuous cooling — unlike an office that's unoccupied overnight, the heat load in a server room never stops. This has implications for system specification:
- •The system must be rated for continuous operation, not just the duty cycles typical of domestic installations
- •Service intervals need to be planned carefully to avoid any period without cooling
- •The system's compressor and components will work harder over its lifetime than a domestic unit of the same capacity
Redundancy
For business-critical environments, N+1 redundancy (one spare cooling unit) is the standard approach. This means installing two systems, each capable of handling the full load independently, so that maintenance or failure of one unit does not cause overheating. For a small server room, this might mean two 2.0kW systems rather than one 3.5kW system.
Humidity control
Both high humidity (leading to condensation on equipment) and very low humidity (creating static discharge risk) can damage IT equipment. Standard air conditioning systems dehumidify as they cool and are generally sufficient for most server room applications, maintaining relative humidity in the 40–60% range that IT equipment tolerates well.