Carrier 48NHT024 - Preparing Unit for Startup

4. Insulate low-voltage wires for highest voltage con¬
tained within conduit when low-voltage control wires
are run in same conduit as high-voltage wires.
5. Do not damage internal components when drilling thru
any panel to mount electrical hardware, conduit, etc.
A. High-Voltage Connections
The unit must have a separate electrical service with a field-
supplied, waterproof, fused disconnect switch mounted at,
or within sight from the unit. Refer to the unit rating plate
for maximum fuse size and minimum circuit amps (ampac¬
ity) for wire sizing. Tables 2 thru 7 show recommended wire
sizes based on rating plate data.
The field-supplied disconnect switch box may be mounted
on the unit over the high-voltage inlet hole in the control
corner panel. See Figs. 2 and 3.
Proceed as follows to complete the high-voltage connections
to the unit:
1. Connect ground lead to chassis ground connection
when using separate ground wire.
2. Run high-voltage leads into unit control box and con¬
nect to contactor. See unit wiring label, and Fig. 8.
B. Special Procedures for 208-V Operation
A 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.
For operation on 208 volts, disconnect the orange
transformer-primary lead from the contactor. See the unit
wiring label. Remove the tape and cover from the terminal
on the end of the red transformer-primary lead. Save the
cover. Connect the red lead to the contactor terminal from
which the orange lead was disconnected.
Using the cover removed from the red lead, insulate the
loose terminal on the orange lead. Wrap the cover with elec¬
trical tape so that the metal terminal can not be seen.
Indoor blower motor speed taps should be changed for 208V
operation on 208/230v rated units. Interchange motor leads
at printed circuit board (PCI) in unit control box. High
speed for cooling and medium speed for heating operation.
See Step 9-C and unit wiring label. Do not change blower
speed setting for 460V rated units.
C. 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 AWG color-coded, insulated (35 C minimum)
wires to make the control voltage 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. See Figs. 2 and 3.
Run the low-voltage leads from the thermostat, thru the
inlet hole, and to the control voltage terminals through a
hole in the bottom of the unit control box. Pass control volt¬
age leads through wire ties located under unit control box.
Connect the thermostat leads to the terminals as shown in
Fig. 8.
D. Heat Anticipator Setting
The room thermostat heat anticipator must be properly
adjusted to ensure proper heating performance. Set the heat
anticipator, using an ammeter to determine the exact
required setting.
NOTE: For thermostat selection purposes, use 1.0 amp for
the approximate required setting.
THERMOSTAT (TYPICAL)
(w)(y)(g)(r)@
! I I I
I ! I I
—TERMINAL BOARD
<2^
r
CONTROL BOX
Jr
GND
r CONTACTOR TERMINALS
1 (SEE UNIT WIRING LABEL)
FIELD SUPPLIED
FUSED DISCONNECT
- 3-PHASE
UNITS ONLY
■ FIELD CONTROL-VOLTAGE WIRING
' FIELD HIGH-VOLTAGE WIRING
A87380
Fig. 8—High and Control Voltage Connections
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.
E. C i r cuit Breaker
Unit has manual reset circuit breaker which is located in the
low voltage wiring box adjacent to low voltage terminal
board. If unit fails to operate, first check breaker for tripped
position. If breaker is tripped, re-set and try to start unit. If
breaker continues to trip there is a problem in the low volt¬
age electrical circuit. (Electrical short, ground, or trans¬
former overload) Correct the condition and check for normal
unit operation.
Step 7—Preparing Unit for Startup
A WARNING
DANGER: 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 have been 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
remove a component, wear protective goggles and
proceed as follows:
a. Shut off gas supply and then electrical power to
unit.
b. Relieve all pressure from system.
c. Cut component connecting tubing with tubing
cutter and remove component from unit.
d. Carefully unsweat remaining tubing stubs when
necessary. Oil can ignite when exposed to torch
flame.
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