excessive airflow, effecting heat exchange

[Abby Normal]

I did a telephone switch job once, blow through saved 9 tons off of the load

When it gets on the dry side, there is sort of less enthalpy per pound going into the coil. When the airflow is not exactly high, it tends to drive the suction pressure down, makes the coil run colder

Blow through adds some heat to the entering air

Easier for the coil to get the fan heat this way, than it is for the coil to over cool, and usually over dehumidify air, to compensate for the fan reheat of draw through