5567611-BIM-B-1218
48
Johnson Controls Ducted Systems
Phasing
ZV 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.
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
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
26
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 26.
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.
5.
Re-tighten the belt nuts.
Figure 26: Belt adjustment
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 18 and Figure 27.
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.
Table 17: Supply air limitations
Unit Size (Ton)
Minimum
Maximum
-06 (6.50)
1950
3250
-07 (7.5)
2250
3750
-08 (8.5)
2550
4250
-10 (10.0)
3000
5000
-12 (12.5)
3750
6250
Item
Component
A
Belt nuts
B
Adjustment bolt
C
Static nut
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.
A
A
A
B
SPAN LENGTH
DEFL. FORCE
C*
* NEVER LOOSEN
