Greenheck G/GB (471558) - Manual (Page 8)

Downblast Centrifugal Roof Exhaust 8
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10. Belt tension can be adjusted by loosening four
fasteners on the drive frame, see Figure 11. The
motor plate slides on the slotted adjusting arms
and drive frame angles in the same manner.
11. Sizes 071-161: Belts should be tensioned just
enough to prevent slippage at full load.
Note: Belts should have a slight bow on the slack
side while running at full load, see Figure 12a.
Slack
Side
Belt
Span
Deflection =
Belt Span
64
Figure 12a Figure 12b
Sizes 180-540: Belt tension should be adjusted
to allow 1/64 in. (0.397 mm) of deflection per inch
of belt span. For example, a 15 in. (381 mm) belt
span should have 15/64 in. (0.234 mm) (or about
1/4 in. (6 mm)) of deflection with moderate thumb
pressure at mid-point between pulleys, see
Figure 12b.
12. The adjustable motor pulley is factory set for
the RPM specified. Speed can be increased by
closing or decreased by opening the adjustable
motor pulley.
13. Any increase in speed represents a substantial
increase in the horsepower required by the unit.
14. Motor amperage should always be checked to
avoid serious damage to the motor when speed
is varied.
IMPORTANT
Adjust (tighten) belt tension after the first
24-48 hours of operation.
Operation
1. Before starting up or operating fan, check all
fasteners for tightness. In particular, check the
setscrews in wheel hub.
2. While in the OFF position or before connecting the
fan to power, turn the fan wheel by hand to be sure
it is not striking the venturi or any obstacle.
3. Start the fan and shut it off immediately to check
rotation of the wheel with directional arrow in the
motor compartment.
4. When the fan is started, observe the operation and
check for any unusual noises.
5. With the system in full operation and all ductwork
attached, measure current input to the motor and
compare with the nameplate rating to determine if
the motor is operating under safe load conditions.
6. Keep inlets and approaches to fan clean and free
from obstruction.
Inspection
Inspection of the fan should be conducted at the
first 30 minute and 24 hour intervals of satisfactory
operation.
30 Minute Interval
Inspect bolts, setscrews and motor mounting bolts.
Adjust and tighten as necessary.
24 Hour Interval
Check all internal components. On GB unit only,
inspect belt alignment and tension. Adjust and tighten
as necessary.