Can you mix r22 and nu22?

Mixing R-22 and R-422B (commonly referred to as Nu-22) is not recommended, as it can lead to system inefficiencies, increased pressure, and potential damage to the HVAC system. R-422B is a replacement for R-22, but they have different properties and pressure characteristics. If you need to switch refrigerants, it's best to completely evacuate the system of the old refrigerant and charge it with the new one. Always consult with a qualified HVAC technician for proper handling and replacement procedures.