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What is a chiller unit?

Chiller or water chilling unit – both terms are simultaneously used by the HVACR industry – but what kind of a device is it?


The task of the chiller is to prepare a medium with appropriate temperature parameters, which will be used to cool or heat rooms, for instance. Such a device operates in an indirect system – the chiller’s cooling system cools/heats the indirect medium which is then pumped to heat exchangers installed in areas where we need to collect or supply thermal energy.


The operating principle of this indirect system is illustrated in the diagram.

What is a chiller unit?

Chillers are available in air cooled or water cooled versions – depending on the unit’s design, the waste heat from the cooling process taken from the cooled medium is transferred to the outside air or to a specially prepared water system.


Optionally, there may also be a heat recovery exchanger, which allows the use of the waste heat from the cooling process, for instance, for preheating the hot water storage cylinder.


An interesting and energy-efficient solution is the FREE COOLING version of chillers – these are described in a separate article.


Due to “high” operating temperatures (+7°C÷+20°C), air conditioners often use water as the intermediate medium – which explains the name: “water chilling unit”. For cooling systems, which require lower temperatures of the intermediate medium, antifreeze mixtures of appropriate concentrations are used – most often ethylene or propylene glycols.