Open-loop systems are exposed to the atmosphere, making them prone to contamination and requiring more frequent maintenance. An example of an open-loop system is the condenser water loop in a chiller system.
Closed-loop systems, on the other hand, are sealed and not exposed to the atmosphere, making them less susceptible to contamination but still requiring treatment to prevent corrosion and scaling. An example of a closed-loop system is the chilled water loop in a chiller system.