Carrier 50LC 07, Service And Maintenance Instructions, Page: 83 / 100

83
Internal Wiring
Check all electrical connections in unit control boxes.
Tighten as required.
Refrigerant Service Ports
Each unit system has two 1/4” SAE flare (with check
valves) service ports: one on the suction line, and one on
the compressor discharge line. Be sure that caps on the
ports are tight.
Compressor Rotation
On 3--phase units with 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 gauges to suction and discharge
pressure fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge
pressure 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
position and fan switch at AUTO. position. Adjust
thermostat to a setting approximately 5
_
F (3
_
C) below
room temperature. Both compressors start on closure of
contactors.
Check unit charge. Refer to Refrigerant Charge section.
Reset thermostat at a position above room temperature.
Both compressors will shut off. Evaporator fan will shut
off after a 30--second delay. The supply fan and both
compressors will shut off.
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 thermostat setting.
Heating
To start unit, turn on main power supply.
Set system selector switch at HEAT position and set
thermostat at a setting above room temperature. Set fan at
AUTO position.
First stage of thermostat energizes the first--stage electric
heater elements; second stage energizes second--stage
electric heater elements, if installed. Check heating effects
at air supply grille(s).
If electric heaters do not energize, reset limit switch
(located on evaporator--fan scroll) by pressing button
located between terminals on the switch.
To Shut Off Unit
Set system selector switch at 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
See Table 27 for torque values.
Table 27 – Torque Values
Supply fan motor mounting
120
¦
12 in---lbs 13.5
¦
1.4 Nm
Supply fan motor adjustment plate
120
¦
12 in---lbs 13.5
¦
1.4 Nm
Motor pulley setscrew
72
¦
5 in---lbs 8.1
¦
0.6 Nm
Fan pulley setscrew
72
¦
5 in---lbs 8.1
¦
0.6 Nm
Blower wheel hub setscrew
72
¦
5 in---lbs 8.1
¦
0.6 Nm
Bearing locking collar setscrew 65 to 70 in---lbs 7.3 to 7.9 Nm
Compressor mounting bolts 65 to 75 in---lbs 7.3 to 7.9 Nm
Condenser fan motor mounting bolts
20
¦
2 in---lbs 2.3
¦
0.2 Nm
Condenser fan hub setscrew
84
¦
12 in---lbs 9.5
¦
1.4 Nm