Propeller Exhaust Fan Option - Daikin RDT-135c Installation And Maintenance Manual

Unit Options: Propeller Exhaust Fan Option

Propeller Exhaust Fan Option

Economizer units may include propeller exhaust or centrifugal
return fan options. This section covers maintenance and
operating instructions for the propeller exhaust option.
Centrifugal return fan construction, maintenance and operation
is similar to that for supply fans and covered in other sections
of this manual.
Figure 99. Two fans with back return shown
Fans and motors
VFD
Starters
Prestarting Checks
Check all fasteners and set screws for tightness. This is
especially important for bearing set screws.
The propeller should rotate freely and not rub on the fan panel
venturi. Rotation direction of the propeller should be checked
by momentarily turning the unit on. Rotation should be in the
same direction as the rotation decal affixed to the unit or as
shown in Figure 100 on page 96. For three-phase installations,
fan rotation can be reversed by simply interchanging any two
of the three electrical leads. For single phase installations
follow the wiring diagram located on the motor.
The adjustable motor pulley is preset at the factory for the
specified fan RPM. Fan speed can be increased by closing or
decreased by opening the adjustable pulley. Two or three
groove variable pitch pulleys must be adjusted an equal
number of turns open. Any increase in fan speed represents a
substantial increase in horsepower required from the motor.
Always check motor load amperage and compare to name
plate rating when changing fan speed.
96
Figure 100. Fan rotation
Once the fan is put into operation, set up a periodic
maintenance program to preserve the reliability and
performance of the fan. Items to include in this program are:
• Belts
• Bearings
• Fasteners
• Setscrews
• Lubrication
• Removal of Dust/Dirt
Belts
Premature belt failures are frequently caused by improper belt
tension (either too tight or too loose) or misaligned pulleys.
The proper tension for operating a V-belt is the lowest tension
at which the belts will not slip peak load conditions. For initial
tensioning, the proper belt deflection half way between pulley
centers is 1/64" for each inch of belt span. For example, if the
belt span is 64 inches, the belt deflection should be one inch
using moderate thumb pressure at midpoint of the drive,
See Figure 101.
Check belt tension two times during the first 24 hours of
operation and periodically thereafter. To adjust belt tension,
simply loosen four fasteners (two on each side of the motor
plate) and slide the motor plate away from the fan shaft until
proper belt tension is attained. On some fans, fasteners
attaching the motor to the motor plate must be loosened in
order to adjust the belt.
It is very important that the drive pulleys remain in proper
alignment after adjustments are made. Misalignment of pulleys
results in premature belt wear noise, vibration, and power loss.
See Figure 102.
Rotating parts can cause severe personal injury or death.
Replace all belt/fan guards that are removed temporarily for
service.
WARNING
IM 738-2