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Dampers are an essential component to regulate air flow in a duct system. More
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Creating Balance in HVAC Systems With a Duct Damper

In HVAC (Heating, Ventilation, and Air Conditioning) systems, the role of the duct damper is essential in regulating air flow. These dampers come in many forms and can perform specific functions within the duct work. The operation can be manual or automatic, depending on the function required of the device.

HVAC dampers are valves or plates the control the flow of air inside the duct work. The function of the duct damper may be to cut off central air conditioning to an unoccupied room, or it might regulate air flow for temperature control in different rooms. Fire dampers are used in ducts to shut off air flow to prevent the spread of smoke or fire through the environment.

A manual duct damper is a mechanical door the can be opened or closed by hand to control the amount of heated or cooled air entering an area. The operator can partially or completely close the damper door, by means of a control lever, to balance the flow of air into particular areas of the building.

Use of a duct damper can be most valuable in balancing the air flow in systems that include long ducts in some areas and shorter ducts in others. If the dampers were not present, the rooms closest to the operating blower fan would receive more air flow then the rooms farther away. Those distant rooms would then require more energy and be more difficult to cool or heat.

Some homeowners find it difficult to find the location of these air duct dampers, especially new owners of an older home. Once they are located, they are easy to adjust. Generally, the handle of the control lever is parallel to the damper itself. If the handle is positioned across the duct, it is closed and has shut off air flow. When the control lever is parallel to the direction of the duct work, the handle position is open.

A motorized duct damper has a mechanical door that opens and shuts by means of thermostatic control to provide individual areas with heating or cooling when served by central air conditioning or a single warm air heater. These dampers can be recognized by the external motor mounted on the ducts. Automatic duct dampers open in response to individual zone thermostats to control the flow of conditioned air into that area when needed.

Fire dampers work in a similar way to automatic duct dampers but with a different purpose. When fire is detected in a system, the damper closes off the air duct to prevent the spread of smoke through the building. Normally, a fire damper would remain in the open position, unless a an event is detected. Fire dampers can act as fire doors, to stop the spread of fire between the floors or sections of the building.

No matter the type of duct damper, or whether it is manual or automatic, they are an essential element of any HVAC system.