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Belt Drive Specifications
Model GB
Spun aluminum downblast exhaust fans shall be
belt drive type. These fans are specifically designed
for roof mounted applications exhausting relatively
clean air. Performance capabilities range up to
44,700 cfm (75,946 m
3
/hr) and 2.5 in. wg (623 Pa)
of static pressure. The maximum continuous
operating temperature shall be 180°F (82°C).
Model GB fans are available in twenty sizes with
nominal wheel diameters ranging from 11 to
54 inches (279 to 1372 mm) (071-540 unit sizes).
Each fan shall bear a permanently affixed
manufacturer’s engraved metal nameplate containing
the model number and individual serial number.
All fans shall bear the AMCA Sound and Air
Performance seal.
The fan wheel shall be centrifugal non-overloading
backward-inclined, constructed of aluminum and
shall include a wheel cone carefully matched to the
inlet cone for precise running tolerances. Wheels
shall be statically and dynamically balanced in
accordance to AMCA Standard 204-05.
Motors shall be heavy-duty ball bearing type,
carefully matched to the fan load and furnished at
the specified voltage, phase and enclosure. Drives
shall be sized for a minimum of 150% of driven
horsepower. Motors and drives shall be mounted
on true vibration isolators, out of the airstream.
Fresh air for motor cooling shall be drawn into the
motor compartment from an area free of discharge
contaminants. Motors shall be readily accessible
for maintenance. True vibration isolators shall be
double-studded or pedestal mount with no metal-to-
metal contact. Each vibration isolator shall be sized
to match the weight of each fan.
Fan shafts shall be precision ground and polished
solid steel with an anti-corrosive coating. Fan
shafts shall be mounted in permanently sealed,
lubricated pillow block ball bearings. The rst critical
speed on a fan shaft shall be at least 25 percent
over maximum operating speed. Bearings shall be
selected for a minimum L
10
life in excess of 100,000
hours (L
50
life of 500,000 hours) at maximum
cataloged operating speed. All bearings are 100
percent factory tested.
The fan housing shall consist of the motor cover,
shroud, curb cap and lower windband, and shall be
constructed of heavy-gauge aluminum. Housing shall
have a rigid internal support structure and leakproof
design. The fan shroud shall be one piece with a
rolled bead for extra strength which directs exhaust
air downward. The lower windband shall be one
piece with formed edges for added strength and the
curb cap shall include prepunched mounting holes to
ensure correct attachment.
Drive frame assemblies shall be constructed of
heavy-gauge steel and mounted on true vibration
isolators. Pulleys shall be of the fully machined cast
iron-type, keyed and securely attached to the wheel
and motor shafts. Motor pulleys shall be adjustable
for final system balancing.
A disconnect switch is a positive electrical shutoff
and shall be wired from the fan motor to a junction
box installed within the motor compartment. Factory
standard shall be a NEMA-1 disconnect switch
with other NEMA rated options also available.
Disconnect switches shall be factory mounted and/
or shipped loose for field mounting.
Options and accessories shall include: auto belt
tensioner, curb extension, curb seal, dampers,
coatings, hinge kit, hinge base, pressure probe, roof
curbs, and tie-down points.
Fans shall be model GB as manufactured by
Greenheck Fan Corporation of Schofield,
Wisconsin, USA.