Greenheck Fan Centrifugal Roof Downblast Exhaust Fans GB - Manual (Page 50)

50
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 3.25 in. wg
(809 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 first 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.