Static Pressure

Static pressure and pressure drop is the most important and overlooked variable in air conditioning ductwork design or any device that moves air for that matter. Improper understanding of static pressure when designing a air conditioning or heating system is a recipe for disaster.

Static pressure is the amount of resistance measured in inches of water, produced when air is moves through an object like duct work. The higher the static pressure or resistance, the more energy it takes to move air through the object. In an air conditioning system as the static pressure or resistance increases the horsepower of the fan motor is depleted. Eventually the static pressure will be higher than the airflow and it will stop.

Most central heating and cooling systems are designed for a static pressure of approximately .5" to 1.0" including the ducts and the filter. If you install a filter with a high resistance like a electrostatic filter and the system is not designed for it you will slow down the air movement and reduce the efficiency of the system, possibly causing system freeze up or serious damage.