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Chilled Water Systems: What Are They and How Do They Work?

Updated: Oct 6, 2022

The foundation of HVAC (heating, ventilating, and air conditioning) cooling systems are chilled water systems. Chilled water systems are primarily used in industrial settings due to the lower cost of using water for chilling.

Applications that require significant cooling capacity, such hypermarkets, industrial processes, and commercial air conditioning, like offices and factories, frequently use chilled water air conditioning systems.

They operate on the same principles as other air conditioning systems that utilise normal refrigerant. Additionally, running water pipes instead of refrigerant lines over a sizable business space allows for more efficient water distribution to air handler evaporator coils.

Due to its affordability and lack of any safety risks associated with having refrigerant pipes running throughout the entire house, more and more households are employing this system to air condition their entire structure.

However, these systems are complicated and need to be maintained by well-trained personnel despite their cost-saving benefits.


How Do Chilled Water Systems Function?

Cooled water is used in chilled water systems to cool a building by absorbing heat from its interior spaces.

A chiller, the brain of the water-chilled system, uses a refrigeration cycle to extract heat from water. Heat is either transferred to the condenser water or the outside air in the chiller's condenser.

The refrigeration cycle of a chilled water system functions by eliminating heat from chilled water in the chiller's evaporator. The compressor powers the entire operation. In a chilled water system, it also consumes the greatest energy.

A building's chilled water is circulated via a chilled water loop, which comprises pipelines and pumps. The chilled water supply is the cold water that comes out of a chiller, its temperature is typically around 45 °F or 7.2 °C.

The building's air conditioning devices, such as air handling units (“AHU”) and fan coil units (“FCU”), are supplied with chilled water via a pump that travels through the chiller.

The chilled water is sent through a heat-exchanging coil in AHUs and FCUs to lower the coil's temperature and a fan circulates air through the coil to circulate cold air throughout the structure. AHUs and FCUs typically blow out supply air at a temperature of around 55 °F or 12.78 °C.

The chilled water returns to the chiller after leaving the heat-exchanging coil, where it is once more cooled, and the cycle is repeated. A single chiller and a single pump can make up a straightforward chilled water system setup.

More sophisticated or complex chilled water system layout can consist of numerous chillers, multiple pumps, cooling towers, heat exchangers, and various types of valves to reroute flow in accordance with the heat load inside the building.


Types of Chillers

Air Cooled Chiller

Almost often placed outside of a building or structure, air-cooled chillers exhaust heat from the condenser coil directly into the surrounding air. The outside air blows over the condenser coil as warm refrigerant runs through it, removing heat from the refrigerant.

The chilled water is subsequently cooled by the refrigerant as it travels through the evaporator and an expansion valve, where it rapidly cools. Then, the entire procedure is repeated.

Air Cooled Chiller designed by TCW Group

Air-Cooled Chiller in progress at TCW group’s manufacturing plant

Completed Air-Cooled Chiller assembled by TCW group

Water Cooled Chiller

Chillers that use water cooling are typically found inside of buildings. They operate nearly identically to air cooled chillers. The distinction is that they exhaust heat from chilled water to a second, separate water line known as the condenser water line.

Heat is absorbed by the condenser water as it passes through the chiller. The cooling tower then receives the condenser water. The cooling tower, which is typically situated outside of the structure, evaporates some of the condenser water into the atmosphere to remove heat.

Heat is removed from the condenser water as some of it evaporates, and the cool condenser water then flows back to the chiller. Then, the entire procedure is repeated.

Water cooled chillers are particularly energy efficient. However, they are frequently more expensive to install and maintain due to their complexity and numerous parts.

They are therefore typically only found in huge buildings. This is true since the system's installation and maintenance costs are offset or exceeded by the energy savings.

Different Water Cooled Chiller assembled by TCW Group


Types of Compressors

The effectiveness and dependability of a water chiller are often most influenced by the type of compressor that is utilised.

Reciprocating Compressors

For many years, the small chiller market's mainstay was the reciprocating compressor. A single chiller frequently housed many compressors.

Scroll Compressors

As a well-liked substitute for reciprocating compressors, scroll compressors are often offered in hermetic versions for use in water chillers. Like reciprocating compressors, a single chiller would frequently house numerous scroll compressors to accommodate bigger capacities.

Because they have roughly 60% less moving parts than reciprocating compressors, scroll compressors are often 10 to 15% more efficient than reciprocating compressors and have a track record of being very reliable. Smaller water chillers are frequently equipped with reciprocating and scroll compressors.

Helical-rotary (or screw) compressors

Helical-rotary (or screw) compressors have long been employed in low-temperature refrigeration and air compression in medium-sized water chillers. Helical-rotary compressors, like the scroll compressor, are more reliable and more efficient than reciprocating compressors because they have fewer moving parts.

Centrifugal compressors

Larger water chillers have long utilised centrifugal compressors due to its high efficiency, greater reliability, decreased noise levels, and relatively inexpensive price.



Chilled water systems are frequently a reasonable alternative to putting numerous distinct pieces of equipment in various locations since they function as a centralised cooling system providing cooling for a full building or multiple structures.

For example, there is a terrific approach to make it easier to reach the units for maintenance.

A chilled water system can be expensive up front, but the higher energy efficiency and cheaper maintenance costs typically make up for it.

A chiller is only a device that facilitates heat transmission from a building's interior to its outside, and the chilled water system can be set up in a variety of ways.

They can be put indoors or outdoors, and depending on the required cooling capacity and efficiency, they can have a variety of compressors and refrigerants.

In summary, chillers offer excellent customization choices. They may enable the selection of a wide range of choices and accessories that will allow the chiller unit to be completely adjusted to the requirements of a particular application.

Get a quotation from TCW group or contact our friendly experts to learn more about chilled water systems!

Custom built portable water chiller in progress at TCW group’s manufacturing plant

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