56
Fig. 81 — V-Belt Force Label
BELT TENSION METHOD
Requires belt tension gage that measures tension in belt in units of
lbs force.
Fig. 82 — Belt Drive Motor Mounting
Pre-Start and Start-Up
This completes the mechanical installation of the unit. Refer to the
unit’s Service Manual for detailed Pre-Start and Start-Up instruc-
tions.  Download  the  latest  versions  from  HVAC  Partners
(www.hvacpartners.com).
Troubleshooting the Ultra Tech™ Compressor
The Ultra Tech
1
 compressor’s molded plug should be used at all
times. The maximum power is 5A. 
MODULATION CONTROL INPUT SPECIFICATIONS
The compressor will modulate from part load to full load when the
voltage supplied to the molded plug is 18 to 28vdc or 18 to 28 vac
rectified to vdc. The compressor will modulate from full load to
part load when the current in the circuit drops below 0.9 MA. See
Table 24 and Fig. 83 for details.
TORQUE ALL SHEAVE SET SCREWS TO 110-130 in. lbs
SET
SCREW
SET
SCREW
STRAIGHT
EDGE
BELT SPAN
BELT DEFLECTION FORCE - SEE TABLE 1
DEFLECTION = BELT SPAN
       64
Table 1
Table 2
BELT 
CROSS 
SECTION
SMALLEST 
SHEAVE 
DIAMETER
BELT DEFLECTION FORCE (LBS)
UNNOTCHED 
BELTS
NOTCHED BELTS
USED NEW USED NEW
A, AX
3.0-3.6 3.7 5.5 4.1   6.1
3.8-4.8 4.5 6.8 5.0   7.4
5.0-7.0 5.4 8.0 5.7   8.4
B, BX
3.4-4.2 — — 4.9   7.2
4.4-5.6 5.3 7.9 7.1 10.5
5.8-8.6 6.3 9.4 8.5 12.6
BELT CONDITION TENSION FORCE IN BELT (LBS)
New 100
Used 80
1. UltraTech™ is a trademark of Emerson Climate Technologies, Inc.
BLOWER PULLEY
V-BELT
MOTOR 
PULLEY
MOTOR
MOTOR MOUNTING
PLATE 
MOUNTING
BOLTS (4) 
Table 24 — Troubleshooting Ultra Tech Compressor
STAGE CAPACITY METERING
LIQUID LINE
SOLENOID
COMPRESSOR
UNLOADER
FOR ULTRA TECH 
COMPRESSOR 
TROUBLESHOOTING 
(COMPRESSOR CURRENT)
FOR LIQUID LINE SOLENOID 
VALVE TROUBLESHOOTING 
(TOP EVAPORATOR COIL 
TEMPERATURE)
Y1
Part Load 
(66%)
TXV
Closed (De-
energized)
De-energized Approx. 80% or less
Top section of the evaporator coil 
will not be cold (U-bend tubes)
Y1+Y2
Full Load 
(100%)
TXV+Fixed Open (Energized) Energized 100%
Top section of the evaporator coil 
will be cold (U-bend tubes)