Temperature split is the difference between return air temperature and supply air temperature as it exits the system, typically measured in degrees Fahrenheit. For cooling systems, normal temperature split ranges from 15-22 degrees Fahrenheit. This measurement indicates evaporator coil efficiency and proper refrigerant circulation without requiring system evacuation or charge adjustment.
Measurement and Interpretation
Technicians measure return air temperature at the filter or return duct and supply air temperature 6-12 inches downstream of the supply register. A split below 15 degrees suggests insufficient airflow, restricted coil, or low refrigerant charge. A split exceeding 22 degrees may indicate excessive airflow or overcharge. For heating systems, normal temperature split ranges from 40-60 degrees Fahrenheit.
Diagnostic Value
Temperature split provides quick assessment of evaporator performance without invasive testing. Combined with pressure and humidity measurements, it helps diagnose restricted filters, dirty coils, blower problems, and refrigerant issues. This non-destructive test is especially useful for initial system assessment and can guide technicians toward the most likely problem areas for further investigation.