Supply Air Drive Adjustment - York International ZQ Series Installation Manual

Supply Air Drive Adjustment

CAUTION
Before making any blower speed changes review
the installation for any installation errors, leaks or
undesirable systems effects that can result in loss of
airflow.
Even small changes in blower speed can result in
substantial changes in static pressure and BHP. BHP
and AMP draw of the blower motor will increase
by the cube of the blower speed. Static pressure
will increase by the square of the blower speed.
Only qualified personnel should make blower speed
changes, strictly adhering to the fan laws.
At unit start-up, the measured CFM may be higher
or lower than the required CFM. To achieve the
required CFM, the speed of the drive may have
adjusted by changing the datum diameter (DD) of
the variable pitch motor sheave as described below:
Use the following tables and the DD calculated per
the above equation to adjust the motor variable
pitch sheave.
EXAMPLE NEW DATUM DIAMETER
A 4 ton unit was selected to deliver 1,600 CFM with a
1VL34 motor sheave, but the unit is delivering 1,350
CFM. The variable pitch motor sheave is set at 4
turns open.
Use the equation to determine the required DD for
the new motor sheave,
52 INSTALLATION MANUAL ZQ SERIES 3 - 5 ton 60 Hertz R-410A
Use Table 37 to locate the DD nearest to 2.48 in.
Close the sheave to 2 turn open.
EXAMPLE NEW BHP
= (Speed increase)
= (Speed increase)
EXAMPLE NEW MOTOR AMPS
= (Speed increase)
= (Speed increase)
Table 37: Motor Sheave Datum Diameters
Turns Open
0
1/2
1
1-1/2
2
2-1/2
3
3-1/2
4
4-1/2
5
5-1/2
6
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.
Verify proper sheave alignment; tighten blower pulley
and motor sheave set screws after these adjustments.
Re-checking set screws and belt tension after 10-12
hrs. run time is recommended.
Johnson Controls Ducted Systems
• Original BHP = New BHP
3
3 • BHP at 1,350 CFM
• Original Amps = New Amps
3
• Amps at 1,350 CFM
3
1VL34
Datum Diameter Turns Open
2.9 0
2.8 1/2
2.7 1
2.6 1-1/2
2.5 2
2.4 2-1/2
2.3 3
2.2 3-1/2
2.1 4
2.0 4-1/2
1.9 5
- 5-1/2
- 6
CAUTION
1VL44
Datum Diameter
3.8
3.7
3.6
3.5
3.4
3.3
3.2
3.1
3.0
2.9
2.8
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