32
Compressor Rotation
On 3-phase units with scroll compressors, it is important to be cer-
tain 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 approximately 5°F (3°C) below room temperature.
Both compressors start on closure of contactors.
Check unit charge. Allow system to operate a minimum of
15 minutes prior to checking refrigerant charge. Refer to Re-
frigerant 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 ther-
mostat 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 ter-
minals on the switch. Ensure indoor fan is operational upon a
call for heating.
TO SHUT OFF UNIT
Set system selector switch at OFF position. Resetting thermo-
stat 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.
FIELD CONTROL WIRING
The 50LC size 14-26 units require an external temperature
control device such as a thermostat (field-supplied).
THERMOSTAT
Install a Carrier-approved accessory thermostat according to
installation instructions included with the accessory. For com-
plete economizer function and 3-stage compressor operation
select a three-stage cooling thermostat. If a 3-stage cooling
thermostat is not available, use a 2-stage cooling thermostat in-
stead, but note that this will limit cooling to just 2 stages. When
electric heat is installed in the 50LC size 14-26 units, the ther-
mostat must be capable of energizing the G terminal (to ener-
gize the Indoor Fan Contactor) whenever there is a space call
for heat (energizing the W1 terminal). The accessory thermo-
stats listed on the unit price pages can provide this signal but
they are not configured to enable this signal as shipped.
Locate the thermostat accessory on a solid wall in the condi-
tioned space to sense average temperature in accordance with
the thermostat installation instructions.
If the thermostat contains a logic circuit requiring 24-v power,
use a thermostat cable or equivalent single leads of different col-
ors with minimum of eight leads. If the thermostat does not re-
quire a 24-v source (no “C” connection required), use a thermo-
stat cable or equivalent with minimum of seven leads. Check the
thermostat installation instructions for additional features which
might require additional conductors in the cable.
For wire runs up to 50 ft (15 m), use no. 18 AWG (American
Wire Gage) insulated wire (35°C [95°F] minimum). For 50 to
75 ft (15 to 23 m), use no. 16 AWG insulated wire (35°C
[95°F] minimum). For over 75 ft (23 m), use no. 14 AWG insu-
lated wire (35°C [95°F] minimum). All wire sizes larger than
no. 18 AWG cannot be directly connected to the thermostat and
will require a junction box and splice at the thermostat.
Fig. 39 — Typical Low-Voltage Control Connections
UNIT WITHOUT THRU-BASE CONNECTION KIT
Correctly rated low voltage wire can be routed through the rub-
ber grommet located on the corner post adjacent to the control
box access panel. Route wire through the grommet and then
route the wire behind the corner post utilizing the factory provid-
ed wire ties secured to the control box. This will ensure separa-
tion of the field low voltage wire and the high voltage circuit.
C
G
C
G
O/B/Y2
Y2
R
R
Y1
Y1
Y3
Y3
(Note 1)
(Notes 2 & 3)
(Note 3)
W1
W1
W2
W2
T
H
E
R
M
O
S
T
A
T
Note 1: Typical multi-function marking. Follow manufacturer’s configuration
Instructions to select Y2.
Note 2: Y2 to Y3 connection required for 2 stage cooling operation and
when integrated economizer function is desired.
Note 3: To Connect a 2-Stage Thermostat:
Y2 to Y3 connection required for 2 stage cooling operation which
provides low and high cooling states.
Field
Wiring
Integrated
Staging Control
(ISC) Board
Typical
Thermostat
Connections
Summary of Contents for 50LC 14
Page 26: ...26 Fig 34 50LC 14 26 Control Wiring Diagram...
Page 27: ...27 Fig 35 50LC 14 26 RTU Open Control Wiring Diagram...
Page 28: ...28 Fig 36 50LC 14 20 208 230V 3 Phase Power Wiring Diagram...
Page 29: ...29 Fig 37 50LC 24 26 208 230V 3 Phase Power Wiring Diagram...
Page 30: ...30 Fig 38 50LC 14 26 460V 575V 3 Phase Power Wiring Diagram...