Vacuum pumps are component of one of the final procedures in the repair procedure. After you’ve diagnosed and repaired any leaks or other issues in the machine it is time to recharge. Before recharging you need to make sure the system is free of any undesirable gasses, air, or water. If these were to remain in the machine, it would turn the oil it runs on into sludge and leave behind damaging impurities.
The draw on a vacuum pump is usually broken down into its “CFM,” or Cubic Feet each and every minute. To estimate what your CFM needs, consider the tonnage of the systems you focus on. Take the sq . root of that number and you’ll obtain the Ac Vacuum Pump china approximate 
CFM you must have to work with that system. Typical home systems need 4-5 CFM, while industrial and rooftop systems generally need as much as 6-8 CFM.