AAON M1-011 - Manual (Page 27)

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− Clean the drain line, “P” trap, and condensate pan.
− Check refrigerant pressures, and temperatures
every Spring, and correct unusual operation.
− Check heating section every Fall. Check all
electrical connections for tightness, and check
heater elements for indications of overheating.
Determine cause and replace elements if
necessary.
Blower Assembly
AAON air handlers use backward inclined airfoil
blower wheels that are non-overloading, very efficient,
and very easy to clean. Clean blower wheels are
necessary to reduce electrical use, maintain capacity
and reduce stress on the unit. The blower wheel, and
blower section need to be inspected periodically, and
cleaned of dust, or debris.
To inspect and clean the blower; set thermostat to the
“OFF” position; turn the electrical power to the unit to
the “OFF” position at the disconnect switch. Clean the
assembly, check the bearings for looseness, inspect
the belt condition and tightness, check screws for
tightness, rotate blower wheel while listening close to
each bearing to check for noise or roughness in the
bearing, which indicates a failing bearing.
Bearings
AAON uses pre-lubricated bearings, and bearings that
have been sized for an average failure rate of 50%
after 200,000 hours, or 22.8 years, of operation (see
heading “Lubrication” in this section for more
information). The bearing sizing tables below are
based on rotational speeds, and radial loading.
However, the alignment of the bearing to the shaft,
and the security of the bearing inner race to the shaft
will greatly affect bearing life. Even though the
manufacturer is responsible for bearing tolerances,
and mounting design, the installer is advised to
check the security of the bearing locking system
before start-up.
Table 7.1, Bearing Setscrew Torque Recommendations
Setscrew Locking Skewzloc Locking Shaft
Size
(In.)
Thread Torque (In-Lbs) Thread Torque (In-Lbs)
1 1/4 - 28 66 - 85 8 - 32 63 - 70
1 3/16 1/4 - 28 66 - 85 8 - 32 63 - 70
1 7/16 5/16 - 24 126 - 164 10 - 24 81 - 90
1 7/8 3/8 - 24 228 - 296 1/4 - 20 162 - 180
Belts
Belt drive misalignment is one of the most common
causes of premature belt failure. A belt can be
destroyed in a matter of days if the drives have been
aligned incorrectly.
The most common tool for measuring misalignment is
a straightedge. Hold the straightedge flush across one
pulley to gauge the degree of misalignment of the two
sheaves. The maximum allowed misalignment is one
half degree of angular misalignment, and 1/10
th of an
inch per foot between sheave centers for parallel
misalignment.
Figure 7.1, Angular Misalignment
Corrected by moving the position of the motor.
Figure 7.2, Parallel Misalignment
Corrected by adjusting sheaves on one, or both shafts.
Frequent belt tensioning is highly recommended. Most
belt manufacturers would suggest a retensioning after
as little as 8 hours of operation. A simplified method of
adjusting tension is to gauge the amount of force
required to deflect the belt by 1/64
th of an inch per inch
of distance between sheave centers. For example, if
the sheaves are 20 inches apart, then the amount of
deflection with the forces listed below is 20/64
th (5/16 th )
of an inch.
Straightedge
Pulley
Pulley
Belt
Straightedge
Pulley Pulley
Belt
Deflections required for:
“A” belts: 4 to 6 lbs.
“B” belts: 6 to 10 lbs.
“C” belts: 10 to 18 lbs.