Chillers 101: System Overview


Commercial chiller unit.

This Chiller blog post is part of a series of blog posts that explores how Veris Industries products can be used to monitor and regulate heating, ventilation, and air conditioning (HVAC) applications.

It is important to note that a chiller does NOT create cold. A chiller removes heat.

In large, multi-story buildings it simply isn’t practical to pump coolants around the building to multiple air handlers. Long runs of refrigerant pipes would increase the probability of leaks. Coolant leaks would create a potentially hazardous environment for employees; pollute the environment, and waste money. Instead, a chiller provides a centralized location for the coolant to be put to work to remove heat from water.

Chillers circulate chilled water to air-handlers in order to remove heat from the air by transferring the heat to water, i.e. condition the air.


A chiller has two separate systems (or sides):

  • The condenser / cooling tower side where water removes heat from the coolant.
  • The chilled water / air handler side where coolant removes heat from water.

Warm water from the air handler returns to the chiller where heat is passed from the water to a liquid refrigerant. The heat from the air handler water turns the liquid coolant into a gas. The spent refrigerant enters the compressor where it is turned into a hot vapor. Upon leaving the compressor, the refrigerant vapor enters the condenser side of the chiller where heat is transferred from the hot vapor refrigerant to water that is on its way to the cooling tower. This heat removal condenses the refrigerant back into a liquid. The now liquid coolant is reused to chill more water for the air handler.

The coolant remains contained in the chiller. It is the heat exchange between the coolant and water that both cools the water to condition the air in the handler and removes heat from the refrigerant for reuse.

There are a wide variety of types of chillers that utilize varying pressures, different numbers of tanks and chambers, etc., however the fundamental application is the same as the closed-looped cooling system in your home. Coolant expands to a gas as it removes heat from the water. The now chilled water is pumped to air handlers. The heated gaseous refrigerant is condensed into a liquid for reuse.

In the United States, chiller capacity is measured in terms of tons or ‘tons of refrigeration.’ One ton of refrigeration is roughly equal to the cooling power of one ton (2,000 pounds or 907 kilograms) of ice melting in a twenty-four hour period. Chillers can also be measured in British Thermal Units per hour (BTU/h) and Watts (W). For perspective, an average residential air conditioning unit can be 1 to 5 tons (3 to 20 kW) in capacity. However, a commercial chiller can be from 15 to 150 tons (53 to 5,275 kW) in cooling capacity.

A facility manager and / or building owner may decide to monitor temperature, pressure, liquid flow rate, and electrical power to help maintain an efficient chiller.


Veris Industries has a complete line of sensor and flow metering products for cooling tower applications. Visit our website or call our sales team at 1-800-354-8556 or +1 503.598.4564 for more product details.

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