127878-YIM-C-1208
Johnson Controls Unitary Products 31
PHASING
Predator
MagnaDRY™ DR units are properly phased from
the factory. If the unit does not start up, the electrical connec-
tion to the unit may be misphased. If unit is equipped with a
Phase Monitor check the phase monitor for a Red LED, indi-
cating a misphase. Change the phasing of the Field line
connection at the Factory or Field Supplied Disconnect
to obtain a Green LED on the Phase Monitor. (Scroll com-
pressors operate in only one direction. If the scroll is drawing
low amperage, has similar suction and discharge pressures,
or producing a high noise level, the scroll is misphased.)
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’).
BELT TENSION
The tension on the belt should be adjusted as shown in Fig-
ure 30.
Scroll compressors require proper rotation to oper-
ate correctly. Units are properly phased at the fac-
tory. Do not change the internal wiring to make the
blower condenser fans, or compressor rotate cor-
rectly.
TABLE 18: SUPPLY AIR LIMITATIONS
Unit Minimum Maximum
090
2250 3750
120
3000 5000
150
3750 6250
FIGURE 30 - 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 rec-
ommended for the belt section. Check the belt ten-
sion 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 retighten nuts (A).
A
A
A
B
SPAN LENGTH
DEFL. FORCE
C*
* NEVER LOOSEN
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