Vacuuming down a mini split system is necessary before releasing the refrigerant.
It also is one way a unit can be tested for leaks.
The process is not difficult and easy enough for a DIYer with the right tools.
Tools Needed to Vacuum Down a Mini Split
- 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.
Example 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
Mini Split Adapter, R410a Adapter 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 are 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 the system goes into a Vacuum, negative pressure.
- Let the pump run for at least 15-20 minutes or more, turn the gauge Blue valve shut, 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, 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 so as not to 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 to be pumped down into a vacuum.
The vacuum process starts at roughly minute 10:50 in this video.