AAON RL-240 - Manual (Page 61)

61
If a fault occurs in the evaporative
condenser fan motor VFD, normally closed
fault terminals on the VFD will interrupt the
safety circuit, thereby shutting down the
system.
If the VFD does fault and cannot be reset,
there is a VFD bypass switch mounted near
the VFD. This switch has four positions—
line, off, drive, and test. The “line” position
will bypass the VFD, sending power to the
motor. In this position, the condenser fans
will run at full speed. The “off” position will
not allow power to pass through the switch.
This functions as a disconnect switch. The
“drive” position runs power through the
VFD. This is the normal operation for the
switch. The “test” position routes power to
the VFD but not to the motor. This is useful
for running tests on the VFD without
sending power to the motor.
A Johnson Controls A350P controls the
VFD speed. This device sends a 0-10 VDC
signal to the VFD. This controller is set to
maintain a sump temperature of 70°F. On a
rise in sump temperature, the controller
increases the voltage to the VFD, increasing
the speed of the condenser fans. Conversely,
on a drop in sump temperature, the
controller will decrease the voltage to the
VFD, decreasing the speed of the condenser
fans.
An outside air thermostat does not allow the
condenser to operate when the ambient
temperature is below 35°F.
Pump Maintenance
Cleaning - Remove oil, dust, water, and
chemicals from exterior of motor and pump.
Keep motor air inlet and outlet open. Blow
out interior of open motors with clean
compressed air at low pressure.
Labeled Motors - It is imperative for repair
of a motor with Underwriters’ Laboratories
label that original clearances be held; that all
plugs, screws, other hardware be fastened
securely, and that parts replacements be
exact duplicates or approved equals.
Violation of any of the above invalidates
Underwriters’ Label.
Fan Motor Maintenance
Same as pump maintenance
Access Doors
If scale deposits or water is found around the
access doors, adjust door for tightness.
Adjust as necessary until leaking stops when
door is closed.
Bearings - Lubrication
Every 6 months or after a prolonged shut
down. Use waterproof, lithium based grease.
Below 32°F - Esso Exxon or Beacon 325.
Above 32°F – Mobil Mobilox EP2, Shell
Alvania EP2 or Texaco RB2.
Recommended Monthly Inspection
1. Clean sump section interior. Dirt and
other impurities which have accumulated in
the sump should be removed from the sump
area. Shut off makeup water ball valve and
open the drain connection for flushing of the
sump.
2. Clean dirt out of sump using a water hose
(not a pressure washer).
3. Clean sump suction strainer.
4. Check water operating level.
5. Inspect fan motor(s) and water circulation
pump(s) and lubricate per the lubrication
nameplate
or manufacture’s
recommendations.
6. Inspect axial fans and eliminators
removing any debris which may have
accumulated during operation.
7. Inspect the water distribution system to
insure that nozzles and spray orifices are
functioning correctly. The inspection should