How To Vacuum Down a Mini Split and Release Refrigerant
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.
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
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
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.
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.
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.
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.)
