Carrier 48NLT - Manual (Page 10)

SPECIAL PROCEDURES FOR 208-V OPERATION
Á WARNING
Make sure that the power supply to the unit is switched
OFF before making any wiring changes. Electrical shock
can cause personal injury or death.
1. Disconnect the orange transformer-primary lead from the
contactor. See unit wiring label.
2. Remove the tape and cover from the terminal on the end
of the red transformer-primary lead.
3. Save the cover.
4. Connect the red lead to the contactor terminal from which
the orange lead was disconnected.
5. Using the cover removed from the red lead, insulate the
loose terminal on the orange lead.
6. Wrap the cover with electrical tape so that the metal ter­
minal cannot be seen.
Indoor blower motor speeds should be changed for 208-v
operation. In the unit control box, change motor leads on
the printed circuit board so that high speed is used for cool­
ing and medium speed is used for heating. Do not change
blower speed setting for 460-v rated units. Refer to Start-
Up, Indoor Airflow and Airflow Adjustments section.
CONTROL VOLTAGE CONNECTIONS - Locate the room
thermostat on an inside wall in the space to be conditioned,
where it will not be subjected to either a cooling or heating
source or direct exposure to sunlight. Mount the thermostat
4 to 5 ft above the floor.
Use no. 18 American Wire Gage (AWG) color-coded,
insulated (35 C minimum) wires to make the control volt­
age connections between the thermostat and the unit. If the
thermostat is located more than 100 ft from the unit (as
measured along the control voltage wires), use no. 16 AWG
color-coded, insulated (35 C minimum) wires.
A grommeted, control voltage inlet hole is located in the
panel adjacent to the control access panel. Run the low-
voltage leads from the thermostat, through the inlet hole,
and to the control voltage terminals through a hole in the
bottom of the unit control box. Pass control voltage leads
through wire ties located under unit control box. Connect
the thermostat leads to the terminals as shown in Fig. 10.
HEAT ANTICIPATOR SETTING - The room thermostat
heat anticipator must be adjusted properly to ensure proper
heating performance. Set the heat anticipator, using an
THERMOSTAT (TYPICAL)
-TERMINAL BOARD
I I I -CONTACTOR TERMINALS
(SEE UNIT WIRING LABEL)
¿)( y )¿(¿
(U);j~
(L2)i^
(Q)- —
V-*cnKr-—
CONTROL BOX
POWER
SUPPLY
rh
GND
FIELD SUPPLIED
FUSED DISCONNECT
3-PHASE
UNITS ONLY
FIELD CONTROL-VOLTAGE WIRING
FIELD HIGH-VOLTAGE WIRING
ammeter between the W and R terminals to determine the
exact required setting.
NOTE: For thermostat selection purposes, use 0.6 amp for
the approximate required setting.
Failure to make a proper heat anticipator adjustment will
result in improper operation, discomfort to the occupants
of the conditioned space and inefficient energy utilization;
however, the required setting may be changed slightly
to provide a greater degree of comfort for a particular
installation.
TRANSFORMER CIRCUIT PROTECTION - The unit
transformer contains an auto, reset overcurrent protector for
control circuit protection. If this device trips, it may reset
without warning, starting the heating or cooling section of
this product. Use caution when servicing; if overcurrent
protector continues to trip, there is a problem in the low-
voltage electrical circuit, such as an electrical short, ground
or transformer overload. Disconnect power, correct the con­
dition, and check for normal unit operation.
PRE-START-UP
A WARNING
Failure to observe the following warnings could result
in serious personal injury:
1. Follow recognized safety practices and wear protec­
tive goggles when checking or servicing refrigerant
system.
2. Do not operate compressor or provide any electric
power to unit unless compressor terminal cover is
in place and secured.
3. Do not remove compressor terminal cover until all
electrical sources are disconnected.
4. Relieve all pressure from system before touching or
disturbing anything inside terminal box if refriger­
ant leak is suspected around compressor terminals.
5. Never attempt to repair soldered connection while
refrigerant system is under pressure.
6. Do not use torch to remove any component. System
contains oil and refrigerant under pressure. To re­
move a component, wear protective goggles and pro­
ceed as follows:
a. Shut off gas supply and then electrical power to
unit.
b. Relieve all pressure from system using both high-
and low-pressure ports.
c. Cut component connecting tubing with tubing cut­
ter and remove component from unit.
d. Carefully unsweat remaining tubing stubs when
necessary. Oil can ignite when exposed to torch
flame.
Fig. 10 — High- and Control-Voltage Connections
Proceed as follows to inspect and prepare the unit for ini­
tial start-up:
1. Remove alt access panels.
2. Read and follow instructions on all WARNING, CAU­
TION and INFORMATION labels attached to, or shipped
with, unit.
Make the following inspections:
a. Inspect for shipping and handling damages such as
broken lines, loose parts, disconnected wires, etc.
b. Inspect for oil at all refrigerant tubing connections
and on unit base. Detecting oil generally indicates
10