Understanding Makeup Water in Air Cooled Chillers
Author : Climaveneta India | Published On : 27 Mar 2026
At first glance, Air Cooled Chillers appear to operate completely without water. Since these systems use ambient air to remove heat, many professionals assume they are entirely water-free.
However, during installation or inspection, the presence of a makeup water connection often raises questions. If the system is air cooled, why does it still need water?
The answer lies in understanding how the internal hydraulic circuit works. While Air Cooled Chillers rely on air for heat rejection, they still depend on a stable chilled water loop to deliver consistent cooling performance.
This article explains why makeup water is essential, how it supports system stability, and why Scroll Chillers follow the same principle.
Air Cooled Does Not Mean Water-Free Operation
The term Air Cooled Chillers refers specifically to how heat is rejected from the refrigerant. Instead of using cooling tower water, condenser fans push ambient air across coils to release heat.
However, the cooling process still involves a closed chilled water circuit that transfers cooling capacity to the application.
This hydraulic loop typically includes:
• Water tank or buffer vessel
• Circulation pumps
• Piping or flexible hoses
• Air vents and drain valves
• Safety and pressure control components
Even in a closed loop, small amounts of water loss occur naturally over time.
Common causes include:
• Minor evaporation through vents
• Air purging during commissioning
• Small leaks from joints or connections
• Water loss during maintenance or reconnection
• System draining during relocation
If water levels drop too far, the pump may begin drawing air instead of liquid, leading to operational instability.
Why Makeup Water is Important in Air Cooled Chillers
Makeup water helps maintain the correct volume inside the chilled water loop. Without it, even minor losses can gradually impact system efficiency.
When water levels fall below the recommended threshold, the following issues may occur:
• Pump cavitation affecting circulation stability
• Fluctuating chilled water temperature
• Reduced heat transfer efficiency
• Low pressure safety alarms
• Unexpected system shutdowns
Maintaining proper water volume ensures steady flow rates, accurate temperature control, and reliable performance.
Makeup water acts as a preventive measure, helping Air Cooled Chillers maintain consistent cooling capacity without manual monitoring.
Portable Air Cooled Chillers Experience Higher Water Loss Risk
Portable Air Cooled Chillers are frequently used in dynamic environments such as:
• Industrial testing facilities
• Temporary process cooling
• Equipment commissioning
• Event cooling applications
• Emergency backup installations
Because these units are regularly transported and reconnected, they experience higher chances of minor water loss.
Typical reasons include:
• Hose disconnection and reconnection
• Air removal during startup
• Small spills during transport
• System draining between applications
• Variations in operating conditions
Makeup water helps ensure the system remains ready for operation without unexpected interruptions.
Do Scroll Chillers Also Require Makeup Water?
A common misconception is that Scroll Chillers operate differently in terms of water requirements. While scroll compressors affect refrigerant compression efficiency, they do not change the behavior of the chilled water loop.
Like other Air Cooled Chillers, Scroll Chillers rely on stable water volume for consistent heat exchange.
Water loss may still occur due to:
• Air release during commissioning
• Small leaks at connection points
• Maintenance procedures
• Normal evaporation within the tank
Because hydraulic principles remain the same, Scroll Chillers benefit equally from makeup water connections to maintain steady operation.
Impact of Low Water Levels on Chiller Performance
Reduced water volume does not always cause immediate system failure, but it can gradually affect performance.
Some noticeable effects include:
Unstable Flow Conditions
Air entering the pump can create turbulence, reducing circulation efficiency and affecting cooling consistency.
Reduced Heat Transfer Efficiency
Inconsistent flow through the evaporator can lower heat exchange performance, reducing overall system efficiency.
Increased Mechanical Stress
Irregular pressure conditions may place additional load on internal components, potentially affecting long-term reliability.
Inaccurate Temperature Control
Variable water flow can lead to fluctuating sensor readings, causing uneven cooling output.
Maintaining correct water levels helps ensure predictable and stable operation across varying load conditions.
Do Air Cooled Chillers Consume Water?
Unlike evaporative cooling systems, Air Cooled Chillers do not continuously consume water during normal operation.
Instead, makeup water compensates for small, unavoidable losses within the hydraulic circuit.
This process is similar to maintaining coolant levels in a closed automotive cooling system. The fluid remains within the system, but occasional top-up ensures optimal performance.
Conclusion
Although Air Cooled Chillers rely on ambient air for heat rejection, their chilled water circuit still requires a stable fluid volume for reliable operation.
Makeup water helps maintain hydraulic balance, ensuring consistent flow, efficient heat transfer, and stable temperature control.
The same principle applies to Scroll Chillers, as compressor technology does not alter the physical behavior of water within a closed loop system.
Understanding this small yet important detail can help improve system reliability, reduce operational disruptions, and support long-term performance.
Want to explore air cooled chillers for your needs? Climaveneta India brings the best of them for you.
