Blowers are typically installed in a blow-through or draw-through setup. All residential and commercial heating, ventilation and cooling (HVAC) systems have a motorized fan. Known as a blower, it’s connected to the air ducts. The blower will move air over the evaporator coil to condition it, after which the conditioned air will enter the ductwork. There are different setups available for blowers, however, including blow-through or draw-through.

What Is a Blow-Through Setup?

A blow-through setup is a design in which the blower is placed before the evaporator coil. Air conditioning systems, as well as heat pumps, have an evaporator coil. Consisting of a series of metal, hollow tubes, it acts as a heat exchanger. Hot refrigerant will travel through the inner passages of the evaporator coil. As air moves over the evaporator coil, the refrigerant will become cooler.

The blower is designed to move air over the evaporator coil and into the ductwork. In a blow-through setup, the blower is installed directly before the evaporator coil. It’s known as a “blow-through” setup because it blows air forward.

What Is a Draw-Through Setup?

A draw-through setup is a design in which the blower is placed after the evaporator coil. The blower still serves the same purpose of moving air over the evaporator coil; it simply uses a different method of operation.

In a draw-through setup, the blower will pull or draw air over the evaporator coil and into the ductwork. You can find the blower after the evaporator coil. When running your air conditioning system, the blower will pull or draw air from the surrounding space. The air will pass over the evaporator coil where it helps to release heat from the coil’s refrigerant.

Differences Between Blow-Through and Draw-Through

The placement of the blower in relation to the air conditioning system’s evaporator coil will determine whether it uses a blow-through or draw-through setup. Blow-through setups involve the blower being placed before the evaporator coil. Draw-through setups, in comparison, involve the blower being placed after the evaporator coil.

Draw-through setups are oftentimes more efficient than blow-through setups. They can move air over the evaporator coil in a more uniform pattern, resulting in a higher level of efficiency. In addition to being more energy efficient, draw-through setups may provide better dehumidification. They can remove more moisture vapor from the air than their blow-through counterparts. With that said, the differences between blow-through and draw-through setups are minimal at best for residential HVAC systems.