HVAC - EPA Certification Practice Exam

A filter drier should be replaced anytime a system is opened for servicing to ensure the system's integrity and efficiency. When a refrigeration or air conditioning system is opened, there is a risk of moisture and contaminants entering the system, which can lead to corrosion, reduced efficiency, and potential failure of components.

Replacing the filter drier at this time helps to eliminate any moisture and debris that may have infiltrated the system during maintenance. It acts as a safeguard, ensuring that the system operates smoothly and extends the lifespan of the components within the system. Furthermore, filter driers are designed to absorb moisture; if they have been in use for any period, especially in a system that has had refrigerant replaced or components serviced, they may already be saturated.

The other options do not capture the importance of preventive measures. Replacing the filter drier before any system operation does not consider the actual need based on the system's condition. Waiting for it to become clogged can lead to insufficient performance and possible damage in the meantime. Additionally, relying on system pressure drops as an indication for replacement is not a reliable method, as pressure variations can occur for various reasons unrelated to the condition of the filter drier.