To verify proper defrost system operation during commissioning, several steps can be taken. First, review the system design and specifications to ensure the defrost system is properly sized and configured. Next, observe the defrost cycle in operation, checking for proper sequencing, timing, and temperature changes. Additionally, monitor system performance data, such as pressure, temperature, and flow rates, to ensure the system is operating within design parameters. Finally, perform functional tests to verify the defrost system’s ability to effectively melt frost and restore optimal system performance.