Vacuum Leak Test System For Air Conditioner generally welds the pipe first before connecting to the external machine, flushes nitrogen to 3.5-4 MPa, external pressure gauge, and records the pressure after the pressure is balanced. The pressure drop is within 0.2 within 24 hours. After this check is completed, connect the internal and external machines, evacuate through the vacuum port, and select a suitable vacuum pump according to the size of the system. Generally, small machines are pumped for half an hour, large machines are connected for more than two hours, and then refrigerant is added. The high and low pressure are measured by a pressure gauge. The low pressure is generally around 0.5 and the high pressure is around 2.8. The difference in ambient temperature has a certain effect on the pressure value. The pressure mentioned above is based on R410A refrigerant. I hope it will help you.