Exhaust Fan On/Off Control - Daikin RoofPak RPS Series Installation And Maintenance Manual

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 to
adjust the belt.
It is very important that the drive pulleys remain in proper
alignment after adjustments are made (see
Misalignment of pulleys results in premature belt wear noise,
vibration, and power loss.
Fasteners and Setscrews
Any fan vibration has a tendency to loosen mechanical
fasteners. A periodic inspection should include checking all
fasteners and set screws for tightness. Particular attention
should be paid to setscrews attaching the propeller to the shaft
and the shaft to the bearings. Loose bearing set screws will
lead to premature failure of the fan shaft.
Figure 110: Drive Pulley Alignment
M u s t b e
p a r a l l e l
B e a r i n g
M o t o r
M u s t b e
p a r a l l e l
Table 22: Propeller Exhaust Fan Troubleshooting
Problem Cause
System resistance is too high
Unit running backwards
Reduced Airflow
Fan speed too low
Excessive dirt on propeller
Bearings
V-Belt drive
Excessive Noise
Excessive vibration
Defective motor
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Exhaust Fan ON/OFF Control

The exhaust fans are turned on and off based on building
static pressure, outdoor air damper position, and discharge
fan capacity. Exhaust fans do not have to always run while the
supply fan is on, as does a return fan. They are turned on and
off through output MCB-B02 on the Main Control Board. For
detailed information on Propeller Exhaust Fan Control, refer to
the operation manual supplied with the unit
Figure 110).
Exhaust Fan Troubleshooting
Table 22
the propeller exhaust fan options. A list of parts is provided in
Figure
Figure 111: Propeller Exhaust Fan Replacement Parts List
C e n t e r l i n e s
m u s t c o i n c i d e
A d j u s t a b l e
S h e a v e
Corrective Action
Check backdraft dampers for proper operation. Remove obstructions in ductwork. Clean dirty filters. Check for
adequate supply for air exhaust fans or exhaust air for supply fans
See "Prestarting Checks" on page 94
Increase fan speed
Clean propeller
Tighten bearing collars and setscrews. Lubricate bearings. Replace defective bearings
Tighten pulleys on motor shaft and fan shaft. Adjust belt tension. Align pulleys. Replace worn belts or pulleys
Clean dirt build-up from propeller. Check all setscrews and fasteners for tightness. Check for worn bearing.
Correct propeller imbalance. Check for loose dampers, guards or ductwork
Replace motor
93
provides guidelines for troubleshooting problems with
111.
IM 926-3 • ROOFPAK APPLIED SYSTEMS
Unit Options
(OM 920).