Vacuum pumps are part of one of the final processes in the Ac Vacuum Pump repair procedure. After you’ve diagnosed and repaired any leaks or other issues in the machine it is time to recharge. Before recharging you really want to make sure the system is free of any undesirable gasses, air, or water. If we were holding to remain in the machine, it could turn the oil it runs on into sludge and keep 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 requirements, look at the tonnage of the systems you work on. Take the square root of that amount and you’ll get the approximate CFM you must have to work with that system. Typical residential systems need 4-5 CFM, while industrial and rooftop systems generally need 
as much as 6-8 CFM.