Air Handling Units
Buffalo Fan Co.
offers two major gas fired Air-Handling Unites (AHU) types: direct gas-fired
and indirect gas-fired.
DIRECT GAS-FIRED AHU
Direct gas-fired AHUs have a gas burner installed directly in
the outside makeup-air stream. The products of combustion (carbon dioxide
[CO2], carbon monoxide [CO], nitrogen dioxide [NO2])
are discharged directly into the makeup air stream and supplied to the building
INDIRECT GAS-FIRED AHU
An indirect gas-fired AHU has a sealed combustion chamber where
all products of combustion are discharged through a flue to the outside environment
and no products of combustion are discharged within the make-up air supplied
to the building. Such equipment also frequently is utilized for recirculating-air
Though simple in principle of operation, direct gas-fired AHUs
have sophisticated burner-control systems. Unit sizes range from 1,000 cfm
with a heating capacity of 80,000 Btuh to 100,000 cfm with a heating capacity
of 15 million Btuh. Direct-gas-fired-AHU components usually include housings,
supply fans, outside air intake hoods, intake dampers, filters and burners.
AIR HANDLING UNIT HOUSINGS
AHU housings are made of galvanized or aluminized steel. Access
panels are provided to access dampers, filters, burners, and fans / motors.
AHUs located outside are provided with a sloped roof and standing seam joints.
AHU SUPPLY FANS
Fans typically are double-width double-inlet (DWDI) with forward-curved
or backward-inclined blades. Fans can come with open drip-proof (ODP) or totally
enclosed fan cooled (TEFC) motors. The most typical external static pressure
in the 2- to 3-in.-wg range. Because most outside istalled air handling units
can operate below 0°F, fan motors and bearings are rated to handle
lower temperatures. For applications that require supply-air temperatures
higher than 110°F, the motors and fan bearings are rated for maximum design
operating temperatures when placed in draw-through configurations.
AIR INTAKE DAMPERS AND HOODS
Outside air intake hoods or weather hoods are designed for an
installation specific location and usually provided with bird screens. Outside-air
intake isolation dampers are furnished to prevent cold air from dropping
through a unit into a warm building and warm air from escaping through a
unit during winter months, when it is not in operation. Low-leakage parallel
blade isolation dampers are most standard. The fan discharge is located at
the opposite to isolation-damper position.
A filter cabinet normally has 30 / 30 filters in a V-bank configuration
to increase filter area and reduce static-pressure drop across the filters.
Higher-efficiency filters are used on application.
A burner consists of a cast-iron or aluminum pipe assembly with
drilled gas orifices. The fuel-air mixing is controlled by perforated stainless-steel
baffles attached to the pipe assembly. The burner can be placed in the outside
airstream or in the outside / return mixed-air stream. But to prevent potentially
hazardous combustion byproducts of indoor-air contaminants, the burner is
placed in the outside airstream only. The required airflow across the burner
must be within a specific velocity range (typically 2,500 to 3,500 fpm) for
proper combustion. For variable airflow units, a modulating bypass damper
or profile plate maintains the airflow velocity within the specified velocity
range. Otherwise, the burner can experience inefficient operation, generate
odors in the occupied spaces served, and create an un-safe increase in certain
products of combustion.
Buffalo Fan Co.
Air Handling Units are well-known for:
LONG SERVICE LIFE: We use premium quality industrial-grade materials
and additional protective coatings for external surfaces and internal components
of our Air Handling Units - to withstand the specific gases flow and the installation
conditions of each application, industrial and commercial / institutional.
CAPACITIES: Up to 100,000 CFM for standard
construction and larger, custom made on special request.
FLEXIBILITY: Every unit is designed for
the specific installation and connections conditions. The unit floor area
and its cross section dimensions are adjusted for precise room available at
EASY INSTALLATION: Packaged compact or
sectional design provided with lifting arrangement and protections for easy
transportation and handling / installation at site.
LOW MAINTENANCE: Service friendly
design which provide large room inside cabinet, access doors, light and rigid
floor ensuring accessibility to all components.
HIGH EFFICIENCY: Fans, coils, motors, humidifiers,
filters, external insulation material, silencers, enclosure tightness, and
other components are carefully selected and engineered for lowest energy consumption.
OPERATIONALLY SAFE: Safety devices and
guards are provided in accordance to the international regulations and the
customer specific requirements.
PRECISE PERFORMANCE: To match the customer
capacities requirement utilizing
the computerized selection for each component.
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