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How do Server Room Air Conditioning Units Differ from Evaporative Coolers ?

Traditional Data Centre/Server Room Air Conditioning

Traditional server room air conditioning units or as they commonly known CRAC units use a refrigerants system to cool the air that is recirculated through the data centre. They usually contain high powered centrifugal distribution fans as well as refrigeration systems that contain powerful condenser units. These all mean that the systems use vast amounts of electrical energy. These conventional units differ drastically to evaporative EcoCoolers which are explained below.

EcoCooling/Evaporative Coolers

A standard Ecocooling evaporative cooling unit takes the external air and still passes it under the floor void but the EcoCooling unit is mounted externally to the building.

For the vast majority of the year, over 95%, the EcoCooling units deliver filtered external air tempered with internal warm air to maintain the required delivery temperatures in the cold aisle.

When the external temperature rises above 16° C, although this figure can be easily altered, the EcoCooling unit utilises the evaporative cooling section on the system to further cool the external air. Hence the EcoCooling units can provide comfortable correct temperatures throughout the year for your data centre at a vastly reduced cost.

All data centres can now utilise EcoCooling units due to the more robust nature of the equipment contained within modern data centres. The temperature envelope in which the Racks now operate is usually between 10° and 30° C and the relative humidity is now no longer as important as it once was, typically they can withstand an upper level of 85% and a lower level of 15% or as many manufacturers now quote non condensing conditions.

It really is legacy thinking to keep data centres at 20° C +/- 1° C and 50% RH +/-5% when the equipment within the data centres now no longer requires these tight tolerances of operating conditions, as it is very expensive to maintain.


The amount of air is dictated by the kilowatt rating of the servers in the racks inside the data centre for every 100 kW of IT load 8.6 m3/s of air at the right conditions (temp and humidity) is required.

We often find the conventional systems employing server room air conditioning units deliver air at the right conditions but not in the correct volumes. Unlike CRAC units, EcoCooling evaporative coolers deliver a larger volume of air at a lower Delta T but this still gives the same overall cooling capacity. The main benefit of this is that there are less hotspots in data rocks with evaporative coolers when compared to CRAC systems.

ASHRAE compliant conditions

Our evaporative EcoCoolers can also maintain 100% temperature compliant ASHRAE conditions within your data centre. As well as this, it can also maintain 95% RH compliant ASHRAE conditions in your data centre when used with the EcoCooling atemperation system. This simply recirculates some of the internal warm air entering the area in the cooler months.

For further information on how evaporative coolers work please click here.

Alternatively, if you would like a no obligation quote for an evaporative air EcoCooling solution, then make sure you contact us today. You will save thousands on energy costs in the long run and dramatically increase the efficiency of your data centre!

Article by Jim Jackson

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