Understanding Pressure Classifications for Ductwork Systems

When it comes to duct systems, there are three main pressure ratings to consider. Low-pressure systems are usually chosen when the ducts have limited space, when noise levels need to be taken into account, and when the transport of particles such as wood chips or grains is not necessary. Over the years, the terms “low pressure” and “high pressure” have been used interchangeably in the HVAC industry, as these two factors are interdependent. To maintain a steady flow despite greater duct friction, higher pressures in the air source are necessary. The dividing line between high and low pressure can vary depending on the application, with some sources defining it as 1500 ft/min and others as 2500 ft/min.

Generally speaking, it is accepted that a speed of 2000 ft/min with a 1” (wg) water pressure gauge is suitable for most applications. Low pressure ratings should be used for secondary ducts such as diversions and bypasses from the main ducts to the end terminals. As an expert in the HVAC industry, I understand that it is important to be aware of the different pressure classifications for ductwork systems. Pressure ratings are essential for ensuring that your system is running efficiently and safely. Low-pressure systems are ideal for applications where noise levels need to be kept low and where particles such as wood chips or grains are not necessary.

High-pressure systems are best suited for applications where greater duct friction needs to be overcome in order to maintain a steady flow. The dividing line between high and low pressure can vary depending on the application, but it is generally accepted that a speed of 2000 ft/min with a 1” (wg) water pressure gauge is suitable for most applications. It is also important to note that low-pressure ratings should be used for secondary ducts such as diversions and bypasses from the main ducts to the end terminals. This will help ensure that your system is running safely and efficiently. Understanding these pressure classifications can help you make informed decisions about your ductwork system.