Fan Drive Adjustments; Vm And Vp Variable Pitch Key Type Sheaves - Daikin Destiny VFD Series Installation And Maintenance Manual

Fan Drive Adjustments

ROTATING FAN can use severe injury or death. Before
servicing fans, lockout and tag out power.
Do not open the hinged access door and access panels while the unit
is operating. Moving parts and strong suction forces can cause severe
personal injury or death.
Before entering any fan section, make sure the electrical power source to
the fan motor is disconnected, locked out and tagged out.
Upon completion of the air balance, replace the variable
pitched motor sheave with a properly sized, fixed sheave. A
matching fixed sheave provides longer belt and bearing life and
vibration-free operation. Initially, it is best to have a variable
pitched motor sheave for the purpose of air balancing. Once
the balance is achieved, fixed sheaves maintain balancing and
alignment more effectively. Replace the adjustable sheaves
with fixed sheaves.
With the electrical power disconnected, locked and tagged
out, measure the diameter of the V-belt outer surface where
it passes around the sheave (pitch diameter). Calculate fan
speed from the motor nameplate rpm.
Measured diameter at motor sheave
Fan rpm = Motor rpm ×
Measured diameter at fan sheave
Figure 49: VP Type Sheave Adjustment
Single groove
A
B
E
D
C
Key E projects
to provide a grip
for removal.
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WARNING
Two groove
B
A
C
Note: Do not operate sheave with flange
projecting beyond the hub end.
VM and VP Variable Pitch Key Type
Sheaves
Mounting:
1. Mount all sheaves on the motor or driving shaft with the
setscrews A toward the motor. See
2. Verify that both driving and driven sheaves are in
alignment and that shafts are parallel.
3. Fit internal key D between sheave and shaft and lock
setscrew A securely in place.
Adjusting:
1. Loosen setscrews B and C in moving parts of sheave
and pull out external key E. (This key projects a small
amount to provide a grip for removing.)
2. Adjust sheave pitch diameter for desired speed by
opening moving parts by half or full turns from closed
position.
Do not open more than five full turns for A belts or
six full turns for B belts.
3. Replace external key E and securely tighten setscrews
B over key and setscrews C into keyway in fixed half of
the sheave.
4. Put on belts and adjust belt tension. Do not force belts
over grooves . See
50.
5. Make future adjustments by loosening the belt tension
and increasing or decreasing the pitch diameter of the
B
sheave by half or full turns as required. Readjust belt
tension before starting drive.
6. Adjust both halves of two-groove sheaves the same
E
number of turns from closed position to provide the same
pitch diameter.
D
7. Verify that all keys are in place and that all setscrews
are tight before starting drive. Check setscrews and belt
C
tension after 24 hours service.
47
Service and Maintenance
Figure 49.
Fan Drive Belt Adjustment on page
IM 782-12 • DESTINY AIR HANDLERS