66389-BIM-C-1208
26
Johnson Controls Unitary Products
PHASING
DW units are properly phased and protected by a Phase
Monitor from the factory. If the unit does not start up, the elec-
trical connection to the unit may be misphased. Check the
Phase Monitor for a Red LED, indicating a misphase.
Change the phasing of the
Field line connection at the Fac-
tory or Field Supplied Disconnect
to obtain a Green LED
on the Phase Monitor. (Scroll compressors operate in only
one direction. If the scroll is drawing low amperage, has simi-
lar 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
Figure 24.
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 14: SUPPLY AIR LIMITATIONS
Unit
Minimum
Maximum
DW-12
3750
6250
FIGURE 24 - 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
