37
Compressor Rotation
50JC units use scroll compressors; it is important to be certain
compressor is rotating in the proper direction. To determine
whether or not compressor is rotating in the proper direction:
1. Connect service gages to suction and discharge pressure
fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge pres
-
sure should rise, as is normal on any start-up.
If the suction pressure does not drop and the discharge pressure
does not rise to normal levels:
1. Note that the evaporator fan is probably also rotating in
the wrong direction.
2. Turn off power to the unit and install lockout tag.
3. Reverse any two of the unit power leads.
4. Re-energize to the compressor. Check pressures.
The suction and discharge pressure levels should now move to
their normal start-up levels.
NOTE: When the compressor is rotating in the wrong direction,
the unit will make an elevated level of noise and will not provide
cooling.
Cooling
Set space thermostat to OFF position. To start unit, turn on
main power supply. Set system selector switch at COOL posi
-
tion and fan switch at AUTO. position. Adjust thermostat to a
setting below room temperature. Compressor starts on closure
of contactor.
Check unit charge. Refer to Refrigerant Charge section on
Reset thermostat at a position above room temperature. Com
-
pressor will shut off. Evaporator fan will shut off after a
30
-
second delay.
To shut off unit, set system selector switch at OFF position.
Resetting thermostat at a position above room temperature
shuts unit off temporarily until space temperature exceeds ther
-
mostat setting.
Heating
To start unit, turn on main power supply. Set system selector
switch to the HEAT position and set thermostat at a setting
above room temperature. Set fan to AUTO position.
First stage of thermostat energizes the first stage of the electric
heaters. Second stage of thermostat energizes the second stage
of electric heaters (if installed). Check heating effects at air
supply grille(s).
If electric heaters do not energize, reset limit switch (located on
supply-fan scroll) by pressing button located between termi
-
nals on the switch.
To shut unit off, set system selector switch to the OFF position.
Resetting thermostat at a position below room temperature
temporarily shuts unit off until space temperature falls below
thermostat setting.
Ventilation (Continuous Fan)
Set fan and system selector switches at ON and OFF positions,
respectively. Evaporator fan operates continuously to provide
constant air circulation.
FASTENER TORQUE VALUES
Table 12 —
Torque Values
START-UP, SYSTEMVU CONTROLS
CAUTION
EQUIPMENT DAMAGE HAZARD
Failure to follow this caution can result in premature wear and
damage to equipment.
Scroll compressors can only compress refrigerant if
rotating in the right direction. Reverse rotation for
extended times can result in internal damage to the
compressor. Scroll compressors are sealed units and
cannot be repaired on site location.
Heat shield screws
30 in.-lb (3.4 Nm) ±2 in.-lb (0.2 Nm)
Stator motor mounting
screws
23 in.-lb (2.6 Nm) ±2 in.-lb (0.2 Nm)
Fan rotor mounting screws
23 in.-lb (2.6 Nm) ±2 in.-lb (0.2 Nm)
Limit switch screws
50 in.-lb (5.7 Nm) ±5 in.-lb (0.6 Nm)
Fan deck bracket screws
50 in.-lb (5.7 Nm) ±5 in.-lb (0.6 Nm)
Condenser fan motor
mounting screws
30 in.-lb (3.4 Nm) ±3 in.-lb (0.3 Nm)
Condenser fan hub set screw
60 in.-lb (6.8 Nm) ±5 in.-lb (0.6 Nm)
Compressor mounting bolts
65 in.-lb (7.3 Nm) +10 in.-lb (1.2Nm)
IMPORTANT: SET-UP INSTRUCTIONS
Installation, wiring and troubleshooting information for
the SystemVu™ Controller can be found in the following
manual: 48/50JC 04-06 Ultra High Efficiency Single
Package Rooftop Units with SystemVu™ Controls
Version X.X Controls, Start-up, Operation and
Troubleshooting Instructions. Have a copy of this manual
available at unit start-up.
