The only answer that is correct here isremove impurities. Pulling a vacuum, for those who don’t know, is a term in mechanics. It simply means that one has removed all the fluids and has created a void that can be easily manipulated. The impurities will be suspended there, and they can be taken out of the vacuum by pulling the vacuum.
The impurities come along with what’s being pulled, because the vacuum creates a lot of suction.
However, if you are unsure of when you should pull a vacuum, the best advice I can give is simply to read the manufacturer’s data that comes with your HVAC system. You should be able to look it up online, especially if you’ve never dealt with a specific brand before.
The only reason to pull a vacuum is to remove condensables, air, debris,to clean the system and IS NOT INTENDED FOR LEAK CHECKING, READ ALL THE MANUFACTURE DATA
