HVACR416 - Design Grills, Registers, and Diffusers

Diffusers, Grilles, and Registers Room openings to ducts serve two purposes: o Control airflow. o Keep large objects out of the duct. Several different openings: o Registers. o Grilles. o Diffusers.

Diffusers, Grilles, and Registers The drawing shows a typical warm air grille; the photos are of two variations.

Diffusers, Grilles, and Registers Diffusers deliver widespread, fan-shaped airflow into the room.

Dampers Dampers help obtain an even distribution of airflow in a forced air system. o Used to balance airflow. o May open and close certain ducts for zone control. Three commonly used dampers: o Multiple blade. o Butterfly. o Split damper.

Dampers

Dampers Multiple-blade dampers are used primarily in square or rectangular ducts to restrict or completely shut off airflow to the room or zone. Butterfly dampers are used in round ducts to control airflow. Split dampers are used when the air path is split into two directions (branch or duct line); permit restriction of airflow to one or other branches of the duct.

Dampers When installing a damper, draw a line on the end of the damper shaft that extends out of the duct to show the damper position.

Dampers Dampers should be tight fitting with minimal leakage. Many dampers are controlled automatically for either zone heating or cooling. Automatic controls are used for: o Humidity control. o Temperature control. o To mix two airflows for either fresh air or recirculated air.

Dampers These diagrams show typical damper installations.

Fire Dampers Automatic fire dampers should be installed in all vertical ducts in commercial and industrial buildings. Ducts going into or through a firewall must have fire dampers. These dampers are rated as follows: o Class A: Opening will hold back a fire indefinitely. o Class B: Fire dampers may be used when a two- to four-hour hold is required. This class approved for most general installations. o Class C: Fire dampers are used where a one-hour hold is required. Dampers should be inspected and tested at least once a year to ensure they are in good operating condition.

Fire Dampers The following are fail-safe damper units: o Spring-loaded to close. o Weight-loaded to close. Vertical shafts serving two or more floors must be closed in a fire partition. Fire dampers must be used. Ducts of less than 20 in 2 (129 cm 2 ) area do not require a fire damper.

Fire Dampers Fire dampers are usually held open by a fusible link. Heat will melt the link and the damper will closed.

Fire Dampers Some fire dampers have electronic sensors that operate the closing mechanism. Damper blade latches may use power to close the damper. Electric power devices may be used to close damper. Smoke dampers use a photoelectric device to detect smoke and then trip the holding device. The damper will the close. Prior to installing ducts, local smoke and fire damper regulations must be checked.