Today the industry is facing new challenges. The move to higher-efficiency unitary systems has resulted in increased use of thermostatic expansion valves (TXVs) instead of cap tubes, and these metering devices have their own idiosyncrasies (see "So Many TXVs to Troubleshoot" in this issue).
In fact, a study on "Field Measurements of Air Conditioners (and Heat Pumps) With and Without TXVs" (Robert J. Mowris, Anne Blankenship, and Ean Jones, Robert Mowris & Associates) states that, out of 6 million new residential and light commercial split systems, heat pumps, and small packaged air conditioners installed annually, "approximately 50-67 percent ...
are installed with improper refrigerant charge and airflow, causing them to operate 10 to 20 percent less efficiently than if they were properly installed."