Carrier 39L - Manual (Page 3)

Mount the remote control box as follows:
1. Loosen and remove the 4 nuts securing the control panel
in the control box.
2. Remove the control panel from the box; set the panel and
nuts aside for reassembly later.
3. Mount the control box to the Unistrut
௡ support using field-
supplied fasteners.
4. Locate, mark, and drill pilot holes on the top of the box
for each of the following:
•
Motor starter wiring
• Actuator and sensor wires to fan section junction box
• Supply power wires (ac)
• Valve wiring or tubing (water valves, field-supplied
sensors, or other devices)
5. Expand the pilot holes as required. Recommended sizes
are as follows:
•
Motor starter wiring — 3 ⁄
4
in. (5 wires)
• Actuator and sensor wires to fan section junction
box —
3 ⁄
4
in. to 1 in. (number of wires and hole di-
ameter determined by application)
• Supply power wires (ac) — 1 ⁄
2
in. or 3 ⁄
4
in.
• Valve wiring or tubing — size as required
Fan section panels are provided with pilot holes that can
be drilled or punched to accomodate an electrical conduit
for the remote control box wiring. Where possible, install
the conduit in a panel that will not be removed, such as the
discharge panel. See Fig. 4.
REMOTE CONTROL BOX CONDENSATE PREVEN-
TION — When the remote control box is installed, precau-
tions must be taken to prevent condensation from forming
inside the junction box mounted in the unit’s supply fan sec-
tion. Standard installation practice is to mount the remote
control box adjacent to the air handling unit and then to en-
close the Class II wiring in flexible conduit between the con-
trol box and the junction box in the fan section.
The sheet metal housing of the control box is not airtight,
therefore warm, moist air can migrate through the flexible
conduit to the junction box in the fan section. Condensate
can form inside the junction box and possibly on the termi-
nal lugs.
To prevent moist air from migrating through the conduit,
seal the control wires inside the conduit at the remote con-
trol box enclosure. See Fig. 4. Use a nonconductive, non-
hardening sealant. Permagum (manufactured by Schnee
Morehead) or sealing compound, thumb grade (manufac-
tured by Calgon), are acceptable materials.
Make Electrical Connections — 39L and 39NX units
have internal control wiring for the operation of the PIC sec-
tion and its control devices. The control system requires a
dedicated 120 vac or 230 vac (50 or 60 Hz) power circuit
capable of providing a minimum of 10 amps (but not greater
than 20 amps) to the control box. The actual number of con-
trols on one power source depends on the installation and
power circuit requirements. Do not run PIC power wiring in
the same conduit as sensor wiring or control wiring of field-
installed devices.
IMPORTANT: To ease installation, control wiring is
located on the service side of the unit with electrical
connectors provided at all unit separation points. If a
unit is separated into pieces for installation, rejoin all
connectors in their original alpha-numeric sequence upon
reassembly. Connectors for vertical fan sections that
are shipped out of the normal operating position must
also be joined at final assembly.
For units with an integral PIC section, all unit factory con-
trol wiring is internal. Only a small number of wires must be
field-installed. All internal wiring consists of plenum wires
which enter the rear of the control box through sealed fit-
tings. Control wiring is 18 to 20 gage, 2-conductor twisted
pair.
The electrical power disconnect and fan motor starter are
field-supplied and installed. Connections are provided in the
control box to wire a field-supplied HOA (HANDS/OFF/
AUTOMATIC) switch. If an HOA switch is used, it must be
field-installed in the supply and return fan motor starter cir-
cuit. The factory-wired high-pressure switch (variable air vol-
ume only) and low-temperature thermostat options are en-
ergized when the supply fan circuit is powered.
See Fig. 5-7 for control box component arrangements and
Fig. 8 for fan motor wiring. PIC input and output points are
listed in Table 1. Consult the wiring diagram located in the
control box or Fig. 9-12 for further details.
Power is present in the PIC control box in the motor
starter circuit even when the dedicated power to the PIC
control box is off.
The supply and return fan starter circuits are independent
from each other. Either circuit and its related control box
interface can have 24 vac, 120 vac, or 240 vac power.
All options that require a factory-installed transformer
are fused with 3.2 amp fuses on the secondary of each
transformer.
When the control box is shipped separately for remote mount-
ing, all unit wiring terminates in a junction box located in
the fan section. Refer to Fig. 12 for the applicable wiring
diagram and Table 2 for junction box connections.
If the unit is provided with a factory-installed smoke con-
trol option, refer to the section titled Field-Wiring Connec-
tions, Smoke Control Option, page 54.
All PIC electrical components are UL (Underwriters’ Labo-
ratories) listed. The electronic modules are approved under
UL HVAC Equipment Standard 873. PIC units are listed and
labeled by ETL (Engineering Testing Laboratory) to comply
with UL Standard 1995 for heating and cooling units, and
comply with NFPA (National Fire Protection Association)
Standard 90A.
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