Static pressure is an important HVAC measurement; think of it in similar terms to your own blood pressure. Anything too high or too low is problematic. Specifically, static pressure refers to the amount of air pressure inside a system’s air ducts. Pressure that’s too high can result in damaged HVAC equipment (such as blower motors) and other duct work problems. Static pressure that measures too low, on the other hand, may result in poor air flow—which can make it difficult for an HVAC system to maintain a comfortable temperature.
How Static Pressure is Measured and Calculated
All HVAC technicians should know how to properly measure and calculate static pressure, as it’s one of the most common troubleshooting steps they can perform. The entire process should take no more than five minutes. It is relatively simple, but there are some special tools required and specific steps that need to be taken for the most accurate measurement.
The basic tools needed to measure static pressure include:
- A quality manometer and carrying case
- Rubber/neoprene tubing
- Static pressure tip
- A 3/8-inch drill bit with bullet tip
- 3/8-inch hole plugs
Begin by identifying the spots in the ductwork where you plan to test using your pressure tips and test ports. Use the drill bit to drill holes before inserting the ports, which should be connected to your manometer. Once the ports are in place, take the necessary readings using your manometer. Be sure to take both a supply and return measurement.
Once you have these two measurements, calculate total static pressure by adding the supply static pressure and return static pressure figures to find your final number.
Troubleshooting High and Low Static Pressure
Once you have your total external static pressure reading measurements from your manometer, refer to the Product Data for the equipment you are servicing to determine your system CFMs. Anything significantly higher or lower than that should be addressed, especially if obvious system problems are present.
There are many potential causes of high static pressure, including poor airflow and blockages in the system. In some cases, a clogged air filter could even lead to a high static pressure reading, so this is a good place to start.
For low static pressure, leaky ductwork is often the cause, though a weak HVAC blower fan can also be to blame. Improperly sized ductwork can also cause a low static pressure reading.
The Bottom Line
Being able to measure and calculate static pressure is a basic, yet important, skill for any HVAC professional. Investing in the right quality tools and manometers from CE will make taking accurate measurements that much easier. Have questions about HVAC tools? Contact our CE team today!