How To Vacuum Down a Mini Split and Release Refrigerant

By | June 8, 2020

How To Vacuum Down a Mini Split
A video is at the bottom of the page for a visual walk-through if needed.

Vacuuming down a mini split system is necessary before releasing the refrigerant.

It also is the main way a unit is tested for leaks.

The process is not difficult and easy enough for a DIYer with the right tools.

Tools Needed

  • Vacuum Pump
  • HVAC Gauges
  • Mini Split Adapter 5/16 to 1/4 Coupler
  • Allen Keys

HVAC gauges and a vacuum pump are needed to set a mini split into a vacuum.

Alternatively, a micron gauge can be used in place of HVAC gauges and do the same thing.

A vacuum pump simply evacuates all the air from the system placing it in a vacuum.

The gauge will show the pressure, which will go negative as the air is pumped out.

There are many low-cost units that work well enough for anyone who only uses them occasionally.

Most mini split units will also need an adapter to connect to the low-pressure port.

Budget Vacuum Pump on Amazon
ZENY 3.5CFM Single-Stage 5 Pa Rotary Vane Economy Vacuum Pump 3.5 CFM 1/4HP Air Conditioner Refrigerant HVAC Air Tool R410a 1/4″ Flare Inlet Port, Blue

Budget 410a Manifold Gauges on Amazon
ZENY Diagnostic A/C Manifold Gauge Set R134a Refrigeration Kit Brass Auto Serivice Kit 4FT w/Case, 1/4″ SAE Fittings

Mini Split Adapter 5/16 to 1/4 Coupler On Amazon
Wadoy R410a Adapter for Mini Split HVAC System 5/16″ Female Quick Couplers x 1/4″ Male Flare

Basic Overview of How HVAC Gauges Work
Manifold gauges are a necessary tool in HVAC and easy to use once they are understood.

Here is the basics of how gauges work when pumping down a mini split system.

Manifold Gauge Hose Color Codes and Connections.

  • The Blue hose connects to the low-pressure line on an HVAC system such as a mini split.
  • The Red hose connects to the high-pressure line and will not be used during a mini split install.
  • The center Yellow hose connects to a vacuum pump when pumping a mini split down.

The pressure gauges will read any pressures once connected.
How To Vacuum Down a Mini Split and Release Refrigerant 2020
The two side valves turn open or off which will direct the flow to the center hose.

A clockwise turn shuts a valve off. Counter-clockwise turns a valve open.

The two side valves should usually be off unless in use.
How To Vacuum Down a Mini Split and Release Refrigerant Gagues
When pumping down a mini split the red valve will be always shut and the blue valve only open once the vacuum pump starts working.

It is usually best to shut the blue valve off before turning the vacuum pump off.

The hose ports on the back go to nothing and are to keep dirt out of the hoses when not in use.
How To Vacuum Down a Mini Split and Release Refrigerant Gagues Back

Steps To Vacuum Down a Mini Split

  1. Be sure both High (Red) and Low (Blue) valves are shut Off at the gauges.
  2.  

  3. Hook the HVAC Gauges Blue hose to Low-Pressure Port on the outside condensing unit. (Usually the only port on the unit.)
  4. Hook Center Yellow Hose to the Vacuum Pump.
  5. How To Vacuum Down a Mini Split Step 2

  6. Turn On the vacuum pump and open the valve on the HVAC Gauges Low Pressure Side (Blue).
  7.  

  8. Let the pump run until it goes into a Vacuum, negative pressure.
  9. Let the pump run for at least 15-20 minutes or more and then turn the vacuum pump off.
  10.  

  11. Let the unit sit for some time 20-30 minutes or more and be sure the vacuum holds.
  12.  

  13. If it holds the vacuum there are no leaks, turn the Blue valve on the gauges shut, and refrigerant can be released into the system.
  14.  

  15. Using an Allen Key let the refrigerant into the system. Open both the high and low pressure valves on the outside condenser. Open them all the way out which will take several turns.
  16. How To Vacuum Down a Mini Split Step 8

  17. Remove the Low Pressure Blue Hose from the unit as quickly as possible. A small amount of refrigerant will come out which will be minimal. This is necessary as to not break the vacuum.
  18. How To Vacuum Down a Mini Split Step 9

Summary
Vacuuming down a mini split and releasing the refrigerant is not difficult and falls into the DIY category.

Of course, if in-doubt be sure to call a professional.

There are some mini split systems that come set in a vacuum and do not require using gauges such as Mr Cool Mini Split Kit.

Most units will require the system be pumped down into a vacuum.

Here is a video I made installing a Senville mini split unit.

The vacuum process starts at roughly minute 10:50 in the video.


 




 

15 thoughts on “How To Vacuum Down a Mini Split and Release Refrigerant

  1. Michael D Clark

    I vacuumed it down for 20 minuets it held perfectly. so I shut the low side valve off and turned pump off . It lost pressure. Do I have a leak because it holds pressure until I shut the valve off. It don’t make since ,Why would hold pressure with and valve on?

    Reply
    1. Don

      The vacuum needs to hold when the pump is turned off or there is a leak.

      Reply
  2. Mazen Akkam

    Excellent instructions, based on your experience would the Zeny pump, recommended in this article, be adequate to vacuum a split system central AC with 30 feet line set down to 500 Micron?
    Thanks,

    Reply
  3. Ed

    Hi there, I’m wondering about the vacuum procedure for a 2 zone mini split.

    I think each of the zones has separate coolant systems that don’t interact with each other?

    So you would vacuum each of them separately but when do you release the refrigerant?

    Do you 1) vacuum one line and release the refrigerant for that line and then vacuum the second line and release the refrigerant for the second line; or, 2) vacuum both lines first and then release refrigerant for both zones at the same time?

    Reply
  4. Chris Curtis

    I can not get my system to take a vacuum. What is the best way to find the leak?

    Reply
  5. Derek Walter

    How would I go vacuuming a 17kw add on cooler. Would I need to do anything different. Do I need to put nitrogen in. Or add refrigerant if it’s only 12m?
    Please reply to my email as well if possible
    Much appreciated.

    Reply
  6. James w Mcknight

    I’m using a 4 way manifold what’s the instructions for it concerning the mini split units

    Reply
    1. Anthony

      The instructions are the same only use the left 2 hoses and low pressure gauge. One hose goes to the vacuum pump and the other hose the low pressure port. The right gauge and hoses are not used.

      Reply
  7. Abhishek Anand

    While vacuuming a new system: does the low side (thicker pipe) valve need to be closed before vacuuming. I know the high side need to be closed.

    Reply
    1. spoddy

      It needs to be open on the side connected which is usually the low-side (the other side closed). Connect the hoses, start the pump, open the valve, let it pump down 10-20 minutes, close the valve, turn off the pump.

      Reply
  8. Roy Benoit

    Would be nice to have more info re the gauges. Which ones are closed/open and when do you open/close them. What is the purpose of the red hose? Is the red valve closed or open? And what is the purpose of the yellow hose and is the yellow gauge open or closed. Very, very confusing to a beginner.

    Reply
    1. Aaron Benetti Post author

      There is a leak somewhere that needs to be fixed. Often there is a bad Flare that has a leak and the first place to look.

      Reply
  9. vcnt008

    1.Can you make a show on how to install ceiling or cassette type ac? Does it comes with a pump to expell water to the outside. Show us in detail also on how to make a vacuum on the system…
    2.The 2 zone mini split wall type ,does it have 2 highs and 2 lows pipe connectors outside the system? To make a vacuum check, is that the same steps as a single zone split ac.
    Thank you.

    Reply

Leave a Reply to Chris Curtis Cancel reply

Your email address will not be published. Required fields are marked *

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