
Type REBC Recirculating (exhaust/recirculation) Roof Ventilator
APPLICATIONS: Type REBC recirculators are multi-purpose power roof ventilators, used for exhaust or recirculation. They are suggested for use in commercial and industrial applications where there is sufficient ceiling height to create a temperature differential between the floor and ceiling. These applications include factories, warehouses, and large commercial buildings. Type REBC recirculators function as normal power roof ventilators in warmer weather and as an energy-saving recirculation system in cold weather. Each unit is equipped with a reversible fan that redistributes warm ceiling air throughout the plant and reduces the building’s heating requirement. With the flip of a switch, it can function as a conventional roof ventilator.
CONSTRUCTION: Type REBC PRVs can exhaust to the outside,
or recirculate inside building air. With the addition of an optional
modulating damper motor, various amounts of outside air may be mixed
with recirculated inside building air. The fan/damper plenum is
suspended from a roof opening, and a hood and base are mounted to a
curb above the opening on the roof. The
hood and base are made of galvanized steel. An exterior finish coat of
epoxy
can be specified. Motor operated, center pivoted dampers are located in
the
sides of the plenum and at the top of the plenum in the throat of the
roof
curb. Dampers are linked together so that as the throat damper closes,
the
plenum dampers open and vice versa. All dampers are shipped installed
in
the plenum. When the direction of airflow is up, the dampers in the
sides of the plenum are closed and the damper at the top of the plenum
is opened creating an exhaust PRV. When the direction of airflow is
reversed and the damper arrangement is not changed, the unit acts as a
supply PRV. With the direction of airflow down and the damper positions
reversed, a recirculating unit is created. For directing airflow from
the plenum into the plant area aThree-Way Diffuser is used. It is
shipped mounted to the plenum. The 14 gauge
frame and 20 gauge blades are constructed of galvanized steel.
MODULATING DAMPER MOTOR is desirable to maintain a predetermined inside
temperature by
mixing varying amounts of recirculated plant air and cool outside air.
The
modulating motor, complete with linkage, electronic temperature
controller and transformer are mounted within the plenum. A remote
temperature sensor with set point is also provided for mounting and
wiring in teh field.
A simple roof
ventilator is essentially an opening in the roof with a cover to keep
out rain and to prevent winds from interfering with its functioning.
Natural convection is an appreciable aid to ventilation in a large
building only if it contains sources of large amounts of heat. A
further useful adjunct is a fan fan, device for agitating air or gases
or moving them from one location to another. Mechanical fans with
revolving blades are used for ventilation, in manufacturing, in
winnowing grain, to remove dust, cuttings, or other waste, or to
provide draft for a fire. The addition of distribution ducts to the fan
and a system for forcing air into the building provides greater
efficiency. Outlets are designed to attain maximum mixing of air and to
move large amounts of air at low velocity so that temperature layers
are eliminated. Factories have special suction hoods and enclosures to
draw away localized dust, fumes, and heat. Incoming air may be cleaned
of dust by filters or electrostatic precipitators. Natural ventilation
depends on winds outside and convection currents inside a building.
Winds raise air pressure slightly on the windward side of a building
and lower it slightly on the lee side. The pressure difference promotes
circulation into the building on the windward side and out of it on the
lee side. Convection currents are caused by the sinking of colder and
therefore heavier air, which displaces the warmer air. A building may
have a roof ventilator to allow the rising warm air to escape. If there
is an opening to the outside at the bottom of the building, fresh, cool
air will be drawn in.