5. Place the scale end of the tension checker squarely
on one belt at the center of the belt span. Apply
force on the plunger until the bottom of the large O-
ring is even with the top of the next belt or until it is
even with a straight edge laid across the sheaves.
6. Read the force scale under the small O-ring to deter-
mine the force required to give the needed deflection.
7. Compare the force scale reading in Step 6 with the
correct value for the belt style and cross section. The
force scale reading should be between the minimum
and maximum values shown in Table 3.
8. If the deflection value is below the minimum, tighten
the belts. If the deflection value is above the maxi-
mum, loosen the belts. The tension on new belts
should be checked during the first day of operation,
at the end of the first week and monthly thereafter.
Optional Plenum Supply Fan and Motor
To remove optional supply plenum fan and motor, discon-
nect the four-wire service connector between the motor
and the VFD (#1, Figure 7). Remove the four bolts (#2,
Figure 7) and slide the motor and plenum fan past the inlet
cone, then lift out of the unit. A 1¾” socket is required to
remove the fan from the motor shaft.
Both motor shaft and fan bore must be completely free of
paint, grease, oil and dirt. If necessary, clean the surfaces
with non-petroleum based solvent, such as isopropyl
alcohol. Insert the bushing into the fan, making sure the
mating hub is flush against the shoulder at the flats. Posi-
tion the assembly at the desired location on the motor
shaft and hand tighten nut (clockwise) until the assembly
becomes snug on the shaft.
Using a torque wrench and a 1¾” socket, tighten the nut
to the proper installation torque. See Table 4 for torque
value.
Fan should overlap inlet cone by 3/8” [9 mm] and have a
clearance of 1/16” [2 mm]. Motor/fan assembly position
is adjustable by loosening the four bolts (#3, Figure 7) and
sliding shelf forwards and back.
WARNING
No lubrication is necessary during servicing.
Plunger with deflection
force scale (lbs)
Body with deflection
distance scale (inches)
Small O-ring
Large O-ring
Force
Belt span
deflection
Figure 6: Belt tension adjustment
Table 3: Recommended Deflection Force
V-belt
Cross
Section
Small
Sheave
Diameter
Range
Recommended Deflection Force
(lbs)
Initial
Installation
Re-tensioned
Maximum
Minimum
A
3.0” to 3.4”
3.3
2.9
2.2
3.6” to 4.2”
3.5
3.1
2.4
4.6” to 6.0”
3.7
3.3
2.5
B
4.6” to 5.4”
6.0
5.1
4.0
5.6” to 7.4”
6.3
5.5
4.2
8.6” to 9.4”
6.6
5.7
4.4
WARNING
Disconnect the main power switch to the unit before per-
forming service and maintenance procedures.
WARNING
Do not hammer or use any type of impact to force the
bushing along the shaft.
WARNING
The shaft must fully engage the shaft gripping area of the
bushing.
Table 4: Torque Value
Shaft Size
ft-lb
5/8” to ¾”
100
13/16” to 1”
125
1-1/16” to 1¼”
167
Figure 7: Plenum fan and motor
VCES-VHC-IOM-1F – VHC-36, -42 & -50
21
