Supply Air Limitations; Belt Adjustment - York ZR Series Installation Manual

Phasing
ZR078-150 units are properly phased at the factory. Check for
proper compressor rotation. If the blower or compressors rotate
in the wrong direction at start-up, the electrical connection to
the unit is misphased. Change the phasing of the field line
connection at the factory or field supplied disconnect to obtain
proper rotation. Scroll compressors operate in only one
direction. The scroll is misphased if it is drawing low amperage,
has similar suction and discharge pressures, or it produces a
high noise level.
Scroll compressors require proper rotation to operate
correctly. Units are properly phased at the factory. Do
not change the internal wiring to make the blower
condenser fans, or compressor rotate correctly.
Blower rotation
Check for proper supply air blower rotation. If the blower is
rotating backwards, the line voltage at the unit point of power
connection is misphased. See Phasing on page 45.
Table 16: Supply air limitations
Unit size (ton)
078 (6.5)
090 (7.5)
102 (8.5)
120 (10)
150 (12.5)
Adjusting the belt tension
To adjust the belt tension complete the following steps.
1. Loosen the six belts nuts at the top and bottom. See Figure
28
Note: Never loosen the static nut at the top of the adjustment
bolt.
2. Turn the adjustment bolt.
3. Use a belt tension checker to apply a perpendicular force
to one belt at the midpoint of the span shown in Figure 28.
A deflection distance of 4 mm (5/32 in.) is obtained.
4. To determine the deflection distance from normal position,
use a straight edge from sheave to sheave as a reference
line.
The recommended deflection force is as follows:
Tension new belts at the max. deflection force
recommended for the belt section.
Johnson Controls Ducted Systems
Minimum Maximum
1950 3250
2250 3750
2550 4250
3000 5000
3750 6250
5. Re-tighten the belt nuts.
A
C*
* NEVER LOOSEN
A
B
Item
A
B
C
Figure 28: Belt adjustment
Check the belt tension at least two times during the first
24 hours of operation. Any retensioning must fall
between the min. and max. deflection force values.
CFM static pressure and power-altitude and temperature
corrections
Use the information below to assist in the application of the
product at altitudes at or exceeding 1000 feet above sea level.
The air flow rates listed in the standard blower performance
tables are based on standard air at sea level. As the altitude or
temperature increases, the density of air decreases. In order to
use the indoor blower tables for high altitude applications,
certain corrections are necessary.
A centrifugal fan is a constant volume device. This means that,
if the RPM remains constant, the CFM delivered is the same
regardless of the density of the air. However, since the air at
high altitude is less dense, less static pressure is generated and
less power is required than a similar application at sea level. Air
density correction factors are shown in Table 17 and Figure 29.
5167531-YIM-J-1019
A
SPAN LENGTH
DEFL. FORCE
Component
Belt nuts
Adjustment bolt
Static nut
39