Blower Maintenance (Belt Drive)
Belts tend to stretch after a period of time. They
should be periodically checked for tension and wear.
When replacing belts, use the same type as supplied
with the unit. Replacement of belts should
be accomplished by loosening the tensioning
“L-Bolts” so the belts may be removed by hand. Do
not force belts on or off as this may cause breakage
of cords and lead to premature belt failure.
Belt tension should be adjusted to allow 1/64 in. of
belt deflection per 1 in. of belt span. For example,
a 16 in. belt span should have 16/64 in. or 1/4 in. of
deflection with moderate thumb pressure at mid-point
between the pulleys. (Fig. 3). Refer to Greenheck’s
Product Application Guide, “Measuring Belt Tension”
for additional information—FA/127-11 found online at
www.greenheck.com under the library section.
Shaft bearings are the most critical moving part of a
fan. Therefore, special attention should be given to
keeping the bearings clean and well lubricated. Proper
lubrication provides for reduction in friction and
wear, transmission and dissipation of heat, extended
bearing life and prevention of rust.
In order for a lubricant to fulfill these tasks, the proper
grease applied at regular intervals is required. See the
recommended bearing lubrication schedule below.
If unusual conditions exist - temperatures below 32°F
or above 200°F, moisture or contaminants - more
frequent lubrication is required.
• Lubrication interval is based on 12 hour per
day operation and maximum 160°F housing
temperature. For 24 hour per day operation, the
interval should be cut in half.
• Lubricant should be added with the shaft rotating
and until clean grease is seen purging from the
bearing. The lubrication interval may be modified
based on the condition of the purged grease. If
bearing is not visible to observe purged grease,
lubricate with number of shots indicated in chart
for bore size.
• For conditions including high temperatures,
moisture, dirt or excessive vibration, consult the
factory for a specific lubrication interval for your
• Lubricant should be a high quality lithium complex
grease conforming to NLGI Grade 2. Factory
recommends Mobilux EP-2.
• The use of synthetic lubricants will increase
lubrication intervals by approximately 3 times.
In addition to lubricating the bearings at specified
intervals, set screws in the bearing collars should be
checked for tightness. A bearing collar which has
loosened will cause premature failure of the fan shaft.
Fasteners attaching the bearings to the drive frame
should also be checked.
Motor Maintenance (Belt & Direct Drive)
Motor maintenance is generally limited to cleaning
and lubrication (where applicable). Cleaning should be
limited to exterior surfaces only. Removing dust and
grease buildup on the motor housing assures proper
motor cooling. Use caution and do not allow water
or solvents to enter the motor or bearings. Under no
circumstances should motors or bearings be sprayed
with steam, water or solvents.
Many fractional horsepower motors are permanently
lubricated for life and require no further lubrication.
Motors supplied with grease fittings should be
greased in accordance with the manufacturer’s
Wheel and Fastener Maintenance
Wheels require very little attention when exhausting
clean air, however, air heavily laden with grease or
dirt will tend to accumulate on the wheel causing
unbalance. Wheels exhausting dirty or grease-laden
air require frequent cleaning to assure smooth and
All fasteners, including set screws in the bearing
collars, should be checked for tightness each time
maintenance checks are performed.
A proper maintenance program will help preserve the
performance and reliability designed into the fan.
Recommended Bearing Lubrication Schedule
Relubrication Schedule in Months
Bearing Bore, inches
To 250 12 12 12 12 12
500 12 12 11 10 8
750 12 9 8 7 6
1000 12 7 6 5 4
1250 12 6 5 4 3
1500 12 5 4 3 2
2000 12 3 3 2 1
2500 12 2 2 1 0.5
3000 12 2 1 0.5 0.25
3500 12 1 0.5 0.25 x
4000 12 0.5 0.25 x x
5000 12 0.25 x x x
4 8 8 10 16
Centrifugal Utility Fans