Using a Vacuum Pump With a Recovery Machine
Many contractors pull the refrigerant out and think the work is done. In reality, once you get to 15 inches of vacuum, you are only half finished. Once the recovery machine has done its work, it’s time to finish off the job with a vacuum pump.
Why a Vacuum Pump?
Many manufacturers recommend evacuation to well below 1000 microns. Some even call for evacuation to 400 microns. At 15 inches of vacuum, you could still have an incredible amount of water vapor in the system. When you have water vapor in your system, the risk of icing up capillary tubing and expansion valves becomes much higher.
A high quality vacuum pump will be able to take you down to 200-500 microns. With the system almost completely free from water vapor, you are ready to put the refrigerant back in the system.
A thorough approach to recovery ensures longer equipment life and reduced risk of problems. Finish what you start. Use a vacuum pump after refrigerant recovery.
Use a Vacuum Gauge to Read Vacuum Down to 15 Microns
The only tool that can measure vacuum at evacuation levels below 1000 microns is a digital vacuum gauge. The best place to measure vacuum is at the system, not at the pump.
With a combination vacuum/charging valve, you can attach the digital vacuum gauge directly to the system and isolate it from the pump, hoses and manifold for a true indication of the vacuum in the system. With a digital vacuum gauge, the technician can see the last evidence of moisture being removed and witness that the system has been dehydrated.