During what condition should the chiller be leak tested to ensure safety?

The correct choice emphasizes the importance of conducting leak tests under specific conditions to ensure operational safety and prevent refrigerant loss. When the chiller is fully charged, it contains the right amount of refrigerant that could potentially escape if there are leaks. Testing for leaks in this state is crucial because it allows technicians to identify any leaks that might pose a risk to the system's efficiency and the environment.

A fully charged system will reflect the normal operating conditions; therefore, any detectable leaks can be accurately measured, which helps in maintaining compliance with environmental regulations. Additionally, this practice protects the chiller from unanticipated failures and prolongs its lifespan.

The other options do not ideally align with best practices for testing. For instance, a leak test during or after a repair ensures the new components are sealed correctly, but it may not account for pre-existing issues or provide a full assessment of the chiller's overall integrity, which is why testing when the system is fully charged is typically recommended.