What does “spring closed” mean? In this Condenser, we will explore the various closure types for air control and life safety dampers. Learn more on the Newsstand.
The phrase “power open, spring closed” seems self-explanatory. This refers to the actuator’s method of opening and closing the damper. As the phrase implies, the damper will open and hold when the actuator has power.
The blades will stay in full-open position until the actuator loses power. The actuator will be part of a circuit that removes power when necessary. Actuator manufacturers will explain the specifics in their installation instructions.
For most actuators, the “spring” refers to an internal spring inside the actuator. This spring drives the rotating arm back to the closed position. For life safety dampers, the return spring is often an external component tied directly to the blade. When the actuator loses power, the spring will drive the damper’s blades to the fully closed position.
You can also choose to configure electric actuators for “spring open, power closed” action, where the actuator holds the damper closed until it loses power.
In this scenario, the damper is set to open when the building loses power. This configuration is good for smoke control dampers. Any smoke in the duct can flow through the damper to a containment zone or exhaust point.
“Power open, spring closed” is the default closure type. For control dampers, the actuator will only need power to open the damper and keep it opened. Control dampers remain closed until their specific HVAC zone needs airflow. This closure type also assumes that system fans will stop during a power outage.
“Spring open” is better suited for HVAC systems with built-in smoke control, where system fans can help direct smoke to unoccupied parts of the building.
Your actuators will be “power open, spring closed” by default, unless you know you need a damper that opens during power loss. The closure type will depend on the application. Are you using the actuator on a smoke damper or a control damper? What does your project need?
Always review your project’s requirements before selecting dampers and actuators.
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