Before performing leak checking on a unit almost out of refrigerant showing 40 psig, what should be done?

Before performing leak checking on a refrigerant system, it is essential to ensure that the system is adequately pressurized to facilitate the detection of any leaks. Adding the same type of refrigerant to bring the system up to bottle pressure is the correct approach. This step allows for a controlled environment where the pressurization with a refrigerant, which is compatible with the system, can help identify leaks effectively.

Bringing the pressure up to the manufacturer's specified level ensures that the leak detection tools or methods used—such as soap solution or electronic leak detectors—can work properly, as the system will have enough pressure for any escaping refrigerant to be noticeable. This method is critical for ensuring the integrity of the repair process and maintaining safety standards, as it helps avoid potential hazards associated with low refrigerant levels during diagnosis.

This approach is also compliant with regulatory practices, promoting environmentally responsible handling of refrigerants. When refrigerant is added prior to testing, it should always be of the same type to prevent any chemical reactions or harmful mixtures within the system.