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vacuuming ac system

How To Vacuum Down a Mini-Split and Release Refrigerant

Vacuuming down, a mini-split process is essential before releasing the refrigerant.

Also, it is the most important way a unit is tested for leaks.

The procedure is not hard and simple enough for a DIYer with the ideal tools.

Tools Needed:

  • Allen Keys
  • Mini Split Adapter 5/16 into 1/4 Coupler
  • HVAC Gauges
  • Vacuum Pump
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HVAC gauges and a vacuum pump are required to decide on a mini-split into a vacuum.

Alternatively, a micron gauge may be utilized in HVAC gauges and do the same thing.

A vacuum pump just removes all of the air from the system by putting it in a vacuum.

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

Many low-cost devices work well enough for anybody who only uses them sometimes.

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

Basic Working Of HVAC Gauges 

Manifold gauges are an essential tool in HVAC and simple to use once they're understood.

Here are the fundamentals of how gauges go when pumping a mini-split device.

Manifold Gauge Hose Connections and Color Codes.

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  • The blue hose attaches to the low-pressure line on an HVAC system like a mini-split.
  • The red hose attaches to the high-pressure line and won't be used during a mini-split install.
  • The center yellow center hose connects to a vacuum pump when pumping a miniature split down.
how to vacuum a mini split system

The pressure gauges will note any pressures once joined.

The two side valves turn off or on, which will steer the flow into the center hose.

A clockwise turn closes a valve. Counter-clockwise turns a valve available.

The two side valves should typically be off unless in use.

The red valve will always be shut while pumping down a mini-split, and the blue valve only opens when the vacuum pump starts working.

It is usually best to close the blue flap before turning off the vacuum pump.

The hose ports on the back go to nothing and keep dirt out of the hoses when not in use.

Steps To Vacuum a Mini Split

vacuuming ac system
  1. 1
    Ensure both Low (Blue) and High (Red) valves are shut Off in the gauges.
  2. 2
    Connect the Blue hose of HVAC gauges to the low-pressure port on the outside condensing unit. (Normally the only port on the device.)
  3. 3
    Hook Center Yellow Hose into the Vacuum Pump.
  4. 4
    .Switch on the vacuum pump and open the HVAC Gauges Low-Pressure Side (Blue) valve.
  5. 5
    Allow the pump to run till it goes to a vacuum, negative pressure.
  6. 6
    Allow the pump run for at least 15-20 minutes or longer and then turn off the vacuum pump.
  7. 7
    Allow the unit to sit for 20-30 minutes or longer, and be sure the vacuum holds.
  8. 8
    If it contains the vacuum, there are no leakages, turn the Blue valve on the gauges closed, and refrigerant can be released to the system.
  9. 9
    Using an Allen Key, allow the refrigerant into the system. Open both the low and high-pressure valves on the external condenser. Open them out that will take several turns.
  10. 10
    Eliminate the low-pressure hose from the device as soon as attainable. A little bit of refrigerant will come out that will be minimum. This is necessary as not to break the vacuum.
vacuuming ac lines


Vacuuming down a miniature split and releasing the refrigerant isn't so tricky and falls to the DIY category.

Naturally, if in doubt, make sure to call a specialist.

Some mini-split systems come set in a vacuum and don't need to use indicators.

Most units will require the machine is pumped into a vacuum.

About the Author Tom Hanson

I’ve worked as an HVAC tech in Phoenix, AZ for the past 10 years. I created to help home owners select the right portable air conditioner, cooler or air purifier for their needs & budget in just a few minutes.

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