Before releasing refrigerant into the HVAC system it is necessary to remove all air and moisture from the lines.  This is done by drawing a 500-micron vacuum on the lines via a service port on the external unit. It was less expensive and more convenient to purchase a vacuum pump, digital micron gauge (the rectangular blue object), and the necessary fittings and hoses than to schedule a service call with an HVAC technician. Once the lines were evacuated, I charged them with refrigerant and proceeded to test the system. I only had time to test the cooling operation which worked perfectly and will verify the heating mode tomorrow. I am amazed at how quiet both the internal and external units are.  Whisper quiet is not an exaggeration.