The Difference Between an Air Cooled Chiller and a Water Cooled Chiller

Chiller systems are often the ideal way to keep large buildings, warehouses, industrial spaces, construction sites and equipment cool and dry. To decide whether you’d be better served by an air cooled chiller or a water cooled chiller, learn how they work and what the differences are.

What is a chiller system?

An industrial chiller system uses a chemical refrigerant to collect heat and reject it through a transfer of energy to water or air. There are two common types: air cooled chillers and water cooled chillers. Both use an evaporator, compressor, condenser and expansion device to create a closed loop refrigerant cycle and maintain a preset temperature.

The evaporator collects the heat and transfers it to a liquid refrigerant. As the heat transfer takes place, the refrigerant is changed into a gas. The gas flows into the compressor, where it is pressurized. The condenser receives the gas and, using water or air, rejects its heat and condenses the gas back into a liquid. The expansion unit regulates the flow of the liquid refrigerant into the evaporator, which starts the process over again.

How are chiller systems rated?

The cooling capacity of a chiller system is rated by how many tons of heat it removes. A ton is defined as the amount of heat needed to melt 1 ton (2,000 pounds) of ice in 24 hours. One ton of cooling capacity can remove 12,000 BTUs (British Thermal Units) of air per hour.

Industrial chillers range in cooling capacity from a 10 ton air cooled chiller to a 500 ton air cooled chiller to a 2,000-ton cooling tower used in water cooled systems.

Air cooled chiller vs. water cooled chiller: What are the differences?

Air cooled chillers, as their name implies, are cooled by environmental air and require free-flowing air. The condenser typically sits outside, either on the roof or at ground level. Fans blow ambient air over a wall of condenser coils that contain the refrigerant and reject the heat into the environment.

Water cooled chillers require a constant water supply. They also require a cooling tower system (water tank, water pump, tower fan), which sits outside. The condenser, which looks like a large tank, sits inside. Condenser coils containing process water surround pipes containing the refrigerant gas. The process water absorbs the heat and is then pumped into the cooling tower, which slowly releases the heat into the environment.

Air cooled chiller vs. water cooled chiller: Pros and cons

These general guidelines can help you decide which type of chiller system to choose. Every situation is different, so ask a knowledgeable equipment vendor such as United Rentals to recommend a cooling system that’s right for your application and budget.

When to consider an air cooled chiller

Air cooled chillers are commonly found in commercial and industrial facilities such as restaurants, data centers, manufacturing plants, hotels and medical centers with heat-intensive MRI and CT scanning equipment. Portable units can also be used for sporting events, large pop-up events and emergency situations.

Since they don’t require water, air cooled chillers can be an excellent choice in regions prone to drought or water restrictions. They also have lower upfront installation costs, take up less interior space and require less maintenance than water cooled chillers.

The trade-offs: They generally have shorter lifespans, require a large, open, outdoor space with continuous access to fresh air, are loud and are less efficient than water cooled chillers.

Air cooled chillers should be used only in areas where heat discharge does not pose a danger to the surrounding environment.

When to consider a water cooled chiller

Water cooled chillers are common in medium to large facilities such as airports, shopping malls, office buildings and hospitals. They’re also used to cool equipment with precision cooling needs, such as plastic-injection molding devices and laser equipment. They require access to a steady supply of water and are not ideal for drought stricken regions.

Water cooled chillers cost more upfront and require regular maintenance due to their reliance on cooling towers, condenser water pumps and other parts that air cooled chillers don’t have. The upsides include a longer lifespan, quiet operation and greater energy efficiency.

Chiller systems are complex and you should always consult with an expert regarding the specific circumstances, applicable rules and regulations related to your site and to your situation. To learn more about United Rentals’ offerings, contact your United Rentals representative or visit our online marketplace to browse our selection of chiller systems.