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Dampers are an essential component to regulate air flow in a duct system. More
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Duct Dampers Provide Control in an HVAC System

The use of duct dampers to control the flow of air is an integral part of any HVAC (Heating, Ventilation, and Air Conditioning) system. There are several different functions of these units within the duct work, and they can be automatic or operated manually.

Duct dampers are valves or plates that regulate air flow inside of the duct work. HVAC dampers can be used to control the temperature in different areas of a building, or to shut off the flow of air to an unoccupied zone. More specifically, fire dampers shut off the air flow to prevent the spread of smoke or fire between the floors or rooms of an environment.

If a system includes long ducts in some areas and shorter ducts in other areas, the rooms with longer ducts would be farther away from the blower fan. This would make it more difficult and energy consuming to heat or cool those rooms. The use of dampers in the ducts are essential in balancing the air flow to allow for efficient heating and cooling to all rooms in the building.

Manual duct dampers are mechanical doors that are operated by hand to control the amount of heated or cooled air entering an area. The doors can be partially or completely closed by the operator via a control lever to balance the air flow to different rooms. Unoccupied rooms can be cut off from air flow, directing the conditioned air to the rooms in use.

In older homes, the operator may have difficultly locating these air duct dampers. Once located, the dampers are easy to adjust. When the handle is in a position across the duct, it is closed and the air flow is shut off. When the control handle is parallel to the direction of the duct, it is on the open position.

A more sophisticated HVAC system might use automatic, or motorized duct dampers. These are mechanical doors that open and shut by means of a thermostat as control. They provide individual zones with heated or cooled air when a central air conditioning unit or a single warm air heater serves the system. Automatic dampers open in response to the zone's thermostats and have an external motor mounted on the ducts in certain locations.

Some automatic duct dampers, known as fire dampers, serve an important purpose in the prevention of the spread of smoke throughout an environment. They work in a similar way to other motorized duct dampers but are linked to a fire sensing mechanism rather than a thermostat. When a fire becomes detected, air flow is shut off to prevent the smoke from spreading. These dampers may also act as fire doors, sealing off the spread of fire between the floors and sections of the building.

Duct dampers are an essential part of the balance of operation within an HVAC system. Efficiency of the system is improved, and more specialized dampers can provide life-saving functions within a building.