Liebert CHALLENGER 3000 - Manual (Page 53)

Component Operation and Maintenance
45
6.3 Blower Package
Periodic checks of the blower package include: belt, motor mounts, fan bearings, and impellers.
6.3.1 Fan Impellers and Bearings
Fan impellers should be periodically inspected and any debris removed. Check to see if they are
tightly mounted on the fan shaft. Rotate the impellers and make sure they do not rub against the fan
housing.
Bearings used on the units are permanently sealed and self-lubricating. They should be inspected for
signs of wear when the belt is adjusted. Shake the pulley and look for movement in the fan shaft. If
any excessive movement is noticed, bearings should be replaced. However, the cause of the wear must
be determined and corrected before returning the unit to operation.
6.3.2 Belt
The drive belt should be checked monthly for signs of wear and proper tension. Pressing in on belts
midway between the sheave and pulley should produce from 1/2" to 1" (12 to 25 mm) of movement.
Belts that are too tight can cause excessive bearing wear.
Belt tension can be adjusted by raising or lowering the fan motor base. Loosen nut above motor
mounting plate to remove belt. Turn nut below motor mounting plate to adjust belt tension. If belt
appears cracked or worn, it should be replaced with a matched belt (identically sized). With proper
care, a belt should last several years.
6.3.3 Air Distribution
All unit models are designed for constant volume air delivery. Therefore any unusual restrictions
within the air circuit must be avoided. Refer to the following table for recommended free area for
proper air flow.
Grilles used in raised floors vary in size, the largest being 18" x 6" (46 cm x 15 cm). This type of grille
has approximately 56 in 2 (361 cm 2 ) of free area. Perforated Panels are usually 2' x 2' (61 cm x 61 cm)
and have a nominal free area of approximately 108 to 144 in 2 (697 to 929 cm 2 ).
NOTE
After adjusting or changing the belt, always be certain that motor base nuts are tightened.
The bottom adjustment nut should be finger tight. The top locking nut should be tightened
with a wrench.
Table 17 Recommended free area ft
2
(m
2
) for grilles or perforated panels at output velocities of
550 and 600 fpm (2.8 and 3.1 m/s)
Model
550 FPM
(2.8 m/s)
600 FPM
(3.1 m/s)
60 Hz Units
3 Ton 2.5 (0.22) 2.3 (0.21)
5 Ton 3.8 (0.34) 3.5 (0.33)
50 Hz Units
3 Ton 2.9 (0.27) 2.6 (0.24)
5 Ton 3.5 (0.33) 3.3 (0.31)
NOTE
Absolutely avoid any under-floor restrictions such as clusters of cables or piping. Whenever
possible, cables and pipes should be run parallel to the air flow. Never stack cables or piping.