Delta-T: What the Temperature Split Tells You
In this instructional video, the speaker introduces HVAC technicians to the concept of temperature split (Delta T) across an evaporator coil, defining it as the difference between return air temperature and supply air temperature. He explains that a healthy cooling system typically shows a Delta T of about 15–22 °F, though exact values depend on conditions and manufacturer specifications. The core purpose of monitoring Delta T is to assess how effectively air and refrigerant interact. A high Delta T usually signals insufficient airflow caused by issues such as dirty filters, blocked returns, or a fouled coil, while a low Delta T can indicate excessive airflow or a refrigerant problem. The speaker emphasizes that Delta T does not provide a direct solution but points technicians toward the right diagnostic focus, with airflow being the first area to examine. He advises measuring return and supply temperatures after the system has run for a few minutes, recording the values, and using the resulting split to guide troubleshooting. The video concludes with an encouragement to share this knowledge with others in the trade.
