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IT equipment cooling: HVAC systems don’t suffice for climate control


Photo: Rittal

IT managers working in small and mid-sized businesses often find themselves searching their buildings for unused space to house the company’s IT enclosures.

Mailrooms, empty offices, janitors’ closets – all have been repurposed into data closets holding one to a few racks. This approach may be the right choice in terms of square footage needed, but when it comes to proper climate conditions for sensitive IT equipment, it could not be more wrong.

At best, these spaces are cooled using only the building’s AC system. At worst? An open window.

A building’s existing air conditioning system (or combined heat and air conditioning system) is designed to create comfortable environments for employees – the reason they are sometimes referred to as “comfort systems.” When IT racks need to be placed somewhere on site, it’s thought that “any old room” will do because AC ductwork usually terminates in these spaces.

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However, the reality is that even if you were to add ducts to supplement the building’s AC, relying on a system designed for humans is not a good solution for IT equipment.

Server rooms need more targeted cooling to keep the temperature within a specific range and prevent the servers from overheating. According to ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers), the appropriate temperature range for server rooms is between 64.4 and 80.6 Fahrenheit.

This requires a discrete cooling solution capable of monitoring and managing the temperature of both the equipment and the room. The same cooling system must also be capable of regulating humidity within the precise margins required by sensitive equipment.

Finally, building HVAC will not provide sufficient airflow volume for heat removal from installed appliances: the CFM requirements for comfort cooling are significantly lower than airflow required to remove heat from the IT devices.

Five enclosure climate control challenges

Still think your building AC is up to the task? Here are some of the hidden risks you will be vulnerable to:

  • Contaminants. A repurposed space can be exposed to airborne dust, gasses 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.
  • Reliability/redundancy. Even a short interruption in power supply to computer equipment can lead to loss of data, and the same is true for interruptions in cooling. Most buildings do not have redundant cooling in place and often an AC system breakdown can last hours – a costly risk for IT equipment.
  • Comfort systems cycle on and off. The temperature in the closet will decrease when the cooling system is on and increase when it is off, resulting in temperature swings throughout the day that can stress the equipment more than a consistent higher temperature.
    • Moreover, the issue is not only related to daily temperature swings, but more sustained periods that put the equipment outside the zone. Comfort cooling systems are often programmed for higher temperature set points on weeknights and weekends to conserve energy. The average temperature within a server closet will generally increase by the amount the temperature set point is increased.
  • Combined heating and cooling HVAC systems deliver heat in winter. The same ductwork that supplies cool air to the IT closet in warmer months will deliver heated air in colder months. This almost guarantees overheating of the equipment and increases the risk of equipment failure.
  • Inability to scale. Every kilowatt of power used by the IT equipment creates a kilowatt of heat that must be removed. If you were to add an additional rack and more equipment, the existing HVAC system would be even less capable of maintaining the ideal temperature.

Solutions for your climate control unit

So, what is an ideal option for supporting mid-size installations and 10-30kW thermal loads in a small space? A liquid cooling solution is one of the most effective options for data closets, IT rooms and other confined spaces that would otherwise rely on a building’s HVAC system.

An enclosure cooling solution should be adaptable to a variety of applications and locations, with closed-loop rack and open-loop inline options.

The closed-loop configuration maintains rack temperatures completely independent of room conditions, and the open-loop option maintains a constant room temperature, cooling the rack equipment as well as other equipment that may be in the room.

Cooling solutions should have a small footprint, be easy to maintain with tool-less fan replacement, and offer ongoing monitoring, variable capacity, and precise climate control.

Herb Villa is senior applications engineer at Rittal Corporation.