However, the same underlying principle holds for all tables and curves. Figure 1 is an example of a superheat-charging curve instead of a table. The curve is based on 400-cfm/ton airflow at 50% relative humidity across the evaporator coil. The steps to charge a system according to this curve are listed below.
1. Measure indoor drybulb temperature (DBT). This is the return air at the air handler. Note: Use wetbulb temperature (WBT) if the percentage of relative humidity is above 70% or below 20%.