What is essential to check through the contactors before starting the cooling system?

Checking the interlock circuit before starting the cooling system is crucial because it ensures that all safety mechanisms are functioning properly. The interlock circuit is designed to prevent the system from operating under unsafe conditions. It typically includes checks for various system components, such as pressure levels, temperature thresholds, and operational states of other parts of the system. If the interlock circuit isn't closed or functioning correctly, it could indicate that there are potential hazards present, which could lead to system damage or dangerous operating conditions. This safety measure helps to ensure that the system only operates when all conditions are appropriate, thereby protecting both the equipment and personnel involved.

While the other options are important for the overall operation of the cooling system, the interlock circuit specifically addresses immediate operational safety before startup, making it a critical step in readiness checks. Checking refrigerant levels, cooling water supply, and electrical connections are also important; however, they can be addressed after confirming that the system is safe to run.