Belt Adjustment - York ZF076 Installation Manual

5725848-XIM-A-0319
Belt drive blower systems MUST be adjusted to the
specific static and CFM requirements for the application.
The belt drive blowers are NOT set at the factory for any
specific static or CFM. Adjustments of the blower speed
and belt tension are REQUIRED. Tighten blower pulley
and motor sheave set screws after these adjustments.
Re-checking set screws after 10-12 hrs. run time is
recommended.
(A)
Figure 20: Belt adjustment
Procedure for adjusting belt tension:
1. Loosen six nuts (top and bottom) A.
2. Adjust by turning (B).
3. Never loosen nuts (C).
4. Use belt tension checker to apply a perpendicular
force to one belt at the midpoint of the span as shown.
Deflection distance of 4mm (5/32") is obtained.
To determine the deflection distance from normal position,
use a straight edge from sheave to sheave as reference
line. The recommended deflection force is as follows:
Tension new belts at the max. deflection force
recommended for the belt section. Check the belt
tension at least two times during the first 24 hours of
operation. Any retensioning should fall between the min.
and max. deflection force values.
5. After adjusting re-tighten nuts (A).
36
Defl Force
(B)
*Never Loosen
(C)*
Note the following:
1. Pulleys can be adjusted in half turn increments.
2. The tension on the belt should be adjusted as shown in the
Belt Adjustment Figure 20.
3. Tighten blower pulley and motor sheave set screws after
any adjustments. Re-check set screws after 10-12 hrs. run
time is recommended.
Start the supply air blower motor. Adjust the resistances in both
the supply and the return air duct systems to balance the air
distribution throughout the conditioned space. The job
specifications may require that this balancing be done by
someone other than the equipment installer.
To check the supply air volumetric flow rate after the ini-
tial balancing has been completed:
1. Remove the two 8 mm (5/16") dot plugs from the blower
motor and the filter access panels shown in Figure 19.
2. Insert at least 200 mm (8") of 6 mm (1/4") tubing into each
of these holes for sufficient penetration into the air flow on
both sides of the indoor coil.
NOTE: The tubes must be inserted and held in a position
perpendicular to the air flow so that velocity pressure
will not affect the static pressure readings.
3. Using an inclined manometer, determine the pressure drop
across a dry evaporator coil. Since the moisture on an
evaporator coil may vary greatly, measuring the pressure
drop across a wet coil under field conditions would be
inaccurate. To assure a dry coil, the compressors should
be deactivated while the test is being run.
4. Knowing the pressure drop across a dry coil, the actual
volumetric flow rate through the unit can be determined
from the curve in Pressure Drop vs. Supply Air flow rate
(Figure 21).
Failure to properly adjust the total system air
quantity can result in extensive blower damage.
After readings have been obtained, remove the tubes and
reinstall the two 8 mm (5/16") dot plugs that were removed in
Step 1.
NOTE: De-energize the compressors before taking any test
measurements to assure a dry indoor coil.
Johnson Controls Ducted Systems