AAON LL-540 - Manual (Page 54)

54
will change the speed of the VFD to
maintain 195 psig.
The unit controller will monitor the sump
temperature and if it exceeds 105°F, it will
reduce the number of compressors that are
running. The unit controller monitors the
condenser pump pressure switch. If this
switch opens, it will not allow the
compressors to operate. The unit controller
also monitors the VFD fault status. If it
receives a VFD fault, it will activate the
alarm contacts on the unit controller. The
VFD will no longer run, but the compressors
will run until the pressures or temperatures
get too high. The controller will reduce the
number of compressors to try to keep as
much of the unit running as possible. The
VFD bypass switch can be set to “line” to
operate the condenser fans at full speed.
Units with diagnostics can operate below
35°F down to 0°F. This is possible because
of the finned de-superheat coil. When the
ambient temperature is below 32°F, the
condenser pump will not operate. As the
ambient
temperature increases, the
condenser pump will activate at 35°F. As
the ambient temperature decreases, the
condenser pump will deactivate at 32°F.
This dead band prevents the condenser
pump from cycling too much. Below 32°F,
the unit operates as an air-cooled condenser.
An optional sump heater operates when the
ambient temperature is below 40°F to
prevent the sump from freezing and offers
freeze protection to 0°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 make-up 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. Adjust float
as required.
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