Canadian Consulting Engineer

Climate control for data closets

February 2, 2022
By Herb Villa

Server rooms need targeted cooling.

liquid cooling

Image courtesy Rittal.

Information technology (IT) managers working for small and medium-sized businesses (SMBs) often find themselves searching their buildings for unused space to house their server enclosures. Mailrooms, empty offices, janitors’ closets—all have been repurposed as data closets, holding one to a few racks.

This approach may be the right choice in terms of the needed square footage, but when it comes to proper climate conditions for sensitive equipment, it could not be more wrong. At best, these spaces are cooled using only the building’s air-conditioning (AC) system; at worst, an open window.

A building’s heating, ventilation and AC (HVAC) system is designed to create a comfortable environment for tenants. When IT racks need to be placed somewhere on-site, it’s thought that any room will do, because AC ductwork usually terminates in these spaces. However, even if engineers were to add ducts to supplement the building’s AC, relying on a system designed for people is not a good fit for IT equipment.

Server rooms need more targeted cooling to keep the temperature within a specific range and prevent the equipment from overheating. According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the appropriate range for server rooms is between 18 and 27 C (64.4 and 80.6 F). This calls for a discrete cooling system, capable of monitoring and managing the temperature of both the equipment and the room.

A system designed for people’s comfort is not a good fit for IT equipment.

The same system must also be capable of regulating humidity within the precise margins required by the sensitive equipment. A building’s HVAC system will not provide sufficient airflow volume for heat removal from the installed appliances; the requirements in cubic feet per minute (CFM) for comfort cooling are significantly lower than the airflow required to remove heat from the IT devices.

The following are some of the hidden risks of relying on HVAC:


A repurposed data server space may be exposed to airborne dust, gases and moisture that seep into the room and compromise the quality of the air and the performance of the equipment. These may not be adequately removed from the room using only the existing AC.


Even a short interruption in power supply to computer equipment can lead to loss of data. The same is true for interruptions in cooling. Most buildings do not have redundant cooling in place. An AC system breakdown can last hours, posing a costly risk to IT equipment.

Cycling on and off

The temperature in the data server room will decrease when the building’s comfort cooling system cycles on and increase when it is off, resulting in temperature swings throughout the day. These fluctuations can stress the equipment more than a consistent, higher temperature would.

This issue is not only related to daily temperature swings, but also to more sustained periods that put the equipment outside its own comfort zone. By way of example, HVAC systems are often programmed with higher temperature set points on weeknights and weekends to help conserve energy, but server temperature should be kept more consistent.

Winter heating

The same HVAC system’s ductwork that supplies cool air to the IT closet in the warmer months of the year will deliver heated air in the colder months. This almost guarantees overheating of the equipment and increases the risk of equipment failure.

Inability to scale

Every kilowatt (kW) of power used by the IT equipment creates a kW of heat that must be removed. If the IT manager were to add an additional rack and more equipment, then the existing HVAC system would be even less capable of maintaining the ideal temperature.

Most buildings do not have redundant cooling in place.

Liquid cooling

To support midsized installations and 10 to 30-kW thermal loads in a small space, liquid cooling has proven one of the most effective go-to options for data closets, IT rooms and other confined areas that would otherwise rely on the building’s HVAC system. Rather than mixing massive amounts of cold air with the heat emitted from the IT equipment to achieve the appropriate temperature, liquid cooling is targeted and wastes less energy.

A closed-loop configuration can maintain rack temperatures completely independently of room conditions, while an open-loop configuration can instead maintain a constant room temperature by cooling both the rack equipment and other equipment in the same room. A set point temperature is maintained as heat loads vary, ensuring precise climate control.

These server rack cooling units are adaptable to a variety of applications and locations, require only a small footprint and are generally easy to maintain. Optional features include ongoing monitoring, remote notifications, tool-less fan replacement and variable capacity for heat loads.

Herb Villa is a senior applications engineer with Rittal. For more information, visit


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