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The recommended procedure for removing and cleaning the expansion valve screen involves performing a low-side pumpdown and then adjusting the low-side pressure to one pound positive. This process is crucial for ensuring that the system is in a safe state for maintenance.

By conducting a low-side pumpdown, you remove refrigerant from the evaporator and drain liquid refrigerant from the expansion valve, reducing the chances of refrigerant escaping when the valve is opened. This operation minimizes the risk of flooding and potential injury caused by pressurized refrigerants.

Adjusting the low-side pressure to one pound positive following the pumpdown maintains a slight positive pressure in the system, thereby preventing air and moisture from entering the refrigerant circuit when the expansion valve is opened. It also helps to avoid damaging the valve itself during maintenance since the low-side pressure ensures that no significant pressure differential allows refrigerant to escape rapidly.

Therefore, this procedure safely prepares the system for cleaning the expansion valve screen, helping maintain the efficiency and reliability of the cooling system.