The old 400 CFM/Ton rule (for A/C) comes from an era when evaporator coils were smaller and SEER was much lower. It no longer applies and is causing mold problems in humid areas. A better rule is needed.

At the techmethod website, we have been crunching the numbers in search of a better way. We have considered typical to heavy latent loads, with typical bypass factors from .05 to .20. This assumes a system which has no humidity controls, with a target RH of 50% at the thermostat.

The bottom line is:

Near the end of the run cycle, the airflow should be adjusted to achieve supply air DB temperature that is 20-25F below the thermostat setpoint.

Comments?