Rapid Fire AIT Practice Exam

In a closed HVAC system, glycol is added to water for protection primarily against freezing and overheating. Glycol, particularly ethylene glycol or propylene glycol, lowers the freezing point of the fluid, making it essential in climates where temperatures can drop significantly. This prevents the water in the system from freezing, which could cause pipes to burst and lead to costly damages.

Additionally, glycol helps to inhibit corrosion within the system's components, such as pipes and heat exchangers, which can be especially important in systems operating over long periods. Its properties also enhance heat transfer, making the HVAC system more efficient in regulating temperatures.

Chlorine is typically associated with disinfection in swimming pools and may not provide the protective benefits necessary for HVAC water systems. Calcium is often present in water as a mineral but does not offer the same protective qualities against freezing or overheating. Salt is used in some water softening processes but is not suitable for closed HVAC systems due to potential corrosion issues.