One common customer complaint about their central HVAC systems is that the a/c system is running but not providing any cool air to the controlled space. One of the most common reasons for this situation is that the a/c condenser or evaporator coil has frozen over. This term or phrase literally means that ice has formed on the heat exchanger, preventing the transfer of heat since the ice is acting as an insulator.

While many of those R-22 systems have been replaced with R-410A units, a large installed base still remains, meaning that technicians will have to know how to troubleshoot and service both types of equipment for many years to come.

Bob and Tim have had a big day at work — it’s 3:30 in the afternoon, and they are done for the day. They’re having coffee at a local restaurant, talking about their careers when Tim asked a question, “What is a ton of refrigeration, and why is it called a ton?”