Vacuum method for air-conditioner

When install new air-conditioner or replaced new compressor or change new expansion valve,we need to evacuation or vacuum process.This is important to ensure no air inside the piping system.For easy understanding,this process is to vacuum the system to take out the air and moisture.

If air remain in the air-conditioner and refrigerant piping,it will affect the compressor performance,reduce the cooling capacity,clogged the cycle of refrigerant and could lead a malfunction.

This procedure very important to make sure air-conditioner running properly and can use for long period without breakdown.All maintenance person or electrical technician must know how to perform evacuation procedure.

 Evacuation or vacuum procedures for Air-Condition


1) Firstly we need to ensure the unit already switch off before we start evacuation procedure.Connect manifold gauge to the system.The low pressure hose ( blue hose ) connect to service port 3 way valve and service hose ( yellow hose ) connect to vacuum pump.

2) Switch on the vacuum pump and open the valve for low side of manifold gauge.We can see the needle at pressure gauge move from 0 psi ( 0 cmHg ) to -14.5 psi ( -76 cmHg ).This process continue around 10 until 20 minute.

3) After that,Close the low side valve of manifold gauge first the switch off the vacuum pump.Now the system in the vacuum pressure.

4) Make sure the needle of low pressure gauge not move after approximately 10 minute.This procedure is to check refrigerant system from leaking.

5) After completed the leak tested,disconnected the manifold gauge hoses from vacuum pump.

6) Charges or refill the system with refrigerant ( refer name plate for types of refrigerant,e.g : R22,R134a,R407c ) until 43 psi.This process is to fill the system with 50% of refrigerant before we charge with full capacity.

I hope this post a can get you some idea how to perform vacuum method for air-conditioner.For more detail how to refill refrigerant for air-conditioner,please watch my video


  1. Thank u so much. for Knowlege Air condition.Email:

  2. shrikant vallal says

    Thanks for HVAC n related electrical information.

  3. what is the “3 way valve”?

  4. Hi how can save the refrigerant while doing a vacuum on the system

  5. Sir
    Please how many system indoor & outdoor ,

  6. Hey, great share……
    We are about to install a new new air-conditioner. Thanks for sharing this vacuum method for air-conditioner. It is definitely going to help me out. Keep sharing more…

    Nice post!!

  7. hey!!!!

    indeed a very nice share…

    After reading this I must say this is the best guide for the beginners..who really don’t have idea about the maintainance of the air compressors.
    Keeping it lubed with compressor oil, and having a stock of compressor parts on hand will ensure that your compressor runs smoothly and works when you need it to.
    The best part about the blog is .. each and every point you have explained is really good.

    thanks for the share.

  8. Hey Lemau !!

    Great share,Pulling a vacuum on a system is important to make the system operate properly and efficiently, and to help ensure a long service life. Yet many technicians are never fully schooled on how to pull a proper vacuum.Replacement of a compressor requires the use of a vacuum pump. Solar powered vaccine refrigerators are generally located away from the utility grid. Most vacuum pumps are powered by AC grid power making compressor replacement difficult.

    Keep posting !!
    Have a great day

  9. Hi,
    An awesome post on air condition evacuation method. Thanks for sharing the post. Keep posting some more articles like this. Will be waiting for the next post.
    Once again thanks for the informative post.

  10. Nice article! Air Conditioning systems are really important and so is maintaining them. So if you ever need that service come and visit us for more info. Thanks!

  11. Amazing information on Air condition evacuation method. Thanks for sharing.

  12. Divakaran says

    Hi Lemau – great articles on vaccum. I have few query on this and can you clarify.

    1. while doing vacuum in AC, on the 3 way valve, do i need to open the service port by screw in (valve front seat) the valve shaft so that the compressor and service port have access together or keep it closed so that the compressor and system line have access together and not the service port Please clarify. thanks and appreciate your great article

Speak Your Mind


This site uses Akismet to reduce spam. Learn how your comment data is processed.