Choose a location for the outside condenser unit. The condenser unit contains the compressor and needs to be located on a level surface at least a foot away from the exterior of your home. Install a concrete pad that is level for the best results. Set the condenser unit on the concrete pad according to manufacturer directions.
Follow the manufacturer directions when you choose the interior location. Most manufacturers of ductless air conditioning recommend installing the interior unit near the top of the wall or at the ceiling. This location is chosen because cold air circulates from top to bottom. Measure carefully on the inside and outside of your room before cutting a hole in the wall.
Cut a hole in the wall that is less than 3 inches in diameter. Use a hole saw or reciprocating saw and follow manufacturer directions for your ductless air conditioning system. Run the copper tubing and refrigerant lines from the condenser to the interior wall where the interior unit is to be installed. Don't forget to install a line for the condensate from the interior unit.
Install the mounting plate for the unit on the interior, at the height the manufacturer recommends. Make sure the mounting plate is level and securely attached for a safe and less noisy air conditioning unit.
Connect the mechanicals of your ductless air conditioning unit only if you are an expert. Many locales insist that a licensed plumber or electrician finish the connections. If a licensed tradesman doesn't install the ductless system, your manufacturer may void the warranty, so be sure to check local regulations before you begin.