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Dampers operate safely within a temperature range, known as the temperature limit. Too hot, or too cold, and the damper may not open. Learn more with this quick Condenser article.
Dampers and Their Limits
All dampers have their limits. It’s important to understand these limitations when selecting dampers for your HVAC system. Otherwise, you risk damaging the damper.
Things like air velocity and air pressure are key factors to consider when choosing a damper, but even ambient temperature can be a limitation. By understanding the needs of each application, you can choose dampers that will work in that environment.
All control dampers will have a temperature limit. Keep these limits in mind when choosing a damper for your duct.
A temperature limit can be either a maximum temperature or a range. Dampers will safely operate within this range. In the US, manufacturers will use Fahrenheit to express temperature limits.
The temperature in the duct should not exceed the maximum or fall below the minimum. Dampers may refuse to open or close when the surrounding temperature is outside of these limits. For example, a damper rated for -30 degrees Fahrenheit may seize if the surrounding air falls to -35 degrees. Or worse, the damper will fail when trying to rotate its blades. A failed damper will damage your HVAC system.
Note the damper's maximum limit. This damper will operate safely at 160 degrees.
Determining Temperature Limits
How are these limits determined? Manufacturers keep track of important data for each component used to build the damper, including the component's minimum and maximum temperature. Tolerances are based on a few factors, including the metal used in the component. Components with the weakest temperature limits will typically determine the damper's overall temperature limit. If the component fails, the damper is expected to fail with it. Therefore, this lowest tolerance becomes the damper’s overall temperature limit.
Standard HVAC dampers will typically have a temperature limit of 200 degrees Fahrenheit and a minimum temperature of -40 degrees. Industrial dampers are designed with reinforced components and can tolerate much higher temperatures, sometimes over 1000 degrees Fahrenheit.
The temperature has fallen below the damper's minimum limit. This damper cannot safely operate in these conditions.
Life safety dampers, fire dampers and combination fire-smoke dampers, are designed to close when temperatures exceed a given threshold. These dampers must stay closed and intact throughout a fire event. Life safety dampers will have specific requirements that should be met.
Temperatures will fluctuate inside the duct as your system heats and cools the building. Air will be hotter in certain parts of the system and colder in others. External factors may also affect the temperatures in the duct. Engineers can help determine the minimum and maximum temperatures in a length of ductwork during standard operation. Use these numbers to determine the damper’s limitations. If a duct is expected to reach 150 degrees, then a standard control damper will work. Understand the needs of the application and choose dampers that can meet those needs.
For more on HVAC dampers, check out these Newsstand articles:
- Five Specialty Dampers for HVAC Design
- The Condenser - Product Spotlight: The 517-518 Series
- Five Things to Know When Selecting Dampers
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