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.
- 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.
Most mini split units will also need an adapter to connect to the low-pressure port.
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.
A clockwise turn shuts a valve off. Counter-clockwise turns a valve open.
It is usually best to shut the blue valve off before turning the vacuum pump off.
Steps To Vacuum Down a Mini Split
- Be sure both High (Red) and Low (Blue) valves are shut Off at the gauges.
- Hook the HVAC Gauges Blue hose to Low-Pressure Port on the outside condensing unit. (Usually the only port on the unit.)
- Hook Center Yellow Hose to the Vacuum Pump.
- Turn On the vacuum pump and open the valve on the HVAC Gauges Low Pressure Side (Blue).
- Let the pump run until it goes into a Vacuum, negative pressure.
- Let the pump run for at least 15-20 minutes or more and then turn the vacuum pump off.
- Let the unit sit for some time 20-30 minutes or more and be sure the vacuum holds.
- 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.
- 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.
- 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.
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.