Static pressure – what is it and why is it important?


dscrtruckStatic pressure is one of the most important factors in HVAC design. Simply put, static pressure refers to the resistance to airflow in a heating and cooling system’s components and duct work. The push of the air must be greater than the resistance to the flow or no air will circulate through the ducts.

Don’t get too technical

In a more technical sense, static pressure refers to the amount of pressure measured in inches of water when air moves through an object, such as duct work. This concept does not have to be understood by the average homeowner or facility manager. The calculations and planning for any HVAC system will be done by the installation company. It does behoove you to have some general knowledge of the subject when discussing your heating and cooling system though.

An easy way to understand static pressure

If it’s a little hard to grab the concept of static pressure, think of measuring that pressure in your HVAC system in terms of the doctor measuring your blood pressure. A blood pressure reading gives the doctor a good indication of your overall health. The same is true of a static pressure reading. It will give the HVAC technician an idea of our system’s general health.

As a matter of fact there is a quick way to determine if the static pressure reading the HVAC technician takes is good or not. Let’s say the fan in the heating and cooling system is rated at “0.5″ of water column”. This figure can be easily obtained by the technician. The 0.5″ reading would correspond to a 120/80, or perfect, blood pressure reading.

If the reading on the HVAC system comes in at “1.0″ of water column” that means there is too much air flow restriction pressure in the unit by a factor of 2. Multiplying both blood pressure figures by 2 gives a corresponding reading of 240/160. This is much too high for a blood pressure reading and also for any HVAC system. Anyone can easily understand this number!

If the reading is “0.75″ of water column” that’s 1.5 times normal pressure. This would give a corresponding blood pressure reading of 180/120. This figure is still too high.

The figures shown using these examples can give the facility manager an easy way to compare and understand what the static pressure in their HVAC system is. If the static pressure in the HVAC system is too high then the system is not going to operate as well as it should, just like a person’s body.

Air needs to flow through the ducts 

If the resistance to the air circulating through the ducts of any heating and cooling system is too great the unit will have to work harder to push the air through the duct work. This will compromise the efficiency of the unit and leave parts of a home too hot or too cold depending on the season. If the resistance gets too strong no air may flow through the system at all.

Too much static pressure is not good for any HVAC system

Static pressure is just the resistance to air flow through any heating and cooling system. Too much pressure and air flow is restricted, or even stopped. This is not good for the HVAC system and will need to be addressed.

DSCR can help you deal with the issue of static pressure. Contact us today to schedule an appointment!