Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual page 170

for electrical connections included in the furnace section. A
Control Instruction Sheet with the Sequence of Operation for
the system under the supervision of the stage controller is also
available in the information packet. See Fig. 145 for a typical
wiring diagram.
HEAT ENABLE ANALOG INPUT
T2
T1
Fig. 145 — Gas-Fired Rack System Furnace
Typical Wiring Diagram
VERIFICATION — Verify the following before placing the
equipment into service:
• Electrical supply matches the heater voltage marked on
the furnace Rating Plate.
• Gas supply provided matches the Gas Type marked on
the furnace Rating Plate.
• Furnace is installed in orientation marked on vestibule.
Orientation is specific to airflow direction through the
heating section of the unit.
• There is an adequate supply of fresh air for the combus-
tion and ventilation process. Combustion air openings in
the cabinet should be sized to provide 1 sq in. of free area
per 4000 Btuh of input.
CAUTION
The presence of chlorine vapors in the combustion air
supplied to gas-fired heaters presents a substantial cor-
rosion hazard.
(0-10 vdc)
–
+
GROUND
• A properly designed vent system is connected to the
heating unit to convey the products of combustion (flue
gases) outside the building. For outdoor applications be
sure the flue gases are directed away from any combus-
tion air inlets.
• Rack furnace assembly is installed in a non-combustible
duct or cabinet on the positive pressure side of the circu-
lating air blower.
• An airflow proving switch is installed and wired to prove
operation of the system circulating air blower.
• An auxiliary manual reset limit switch is installed to shut
off furnace in the event of low airflow conditions due to
filter blockage, coil blockage and or damper failure.
• A drain tube is installed for disposal of condensate, if the
heating unit is equipped with modulating controls or is
located downstream of cooling system.
• Equipment access panels and doors are sized and located
to provide easy access for servicing, adjustment and
maintenance of the heating units installed.
CONDENSATE DRAINS — A CPVC condensate drain line
is provided and connected to the individual heaters. In applica-
tions operating with modulating controls some condensation
may occur in the heating cycle. In these applications connec-
tion of a condensate drain line is required to avoid condensate
build-up and possible heat exchanger damage. Flue gas con-
densate is acidic. Refer to local codes and ordinances for
proper disposal.
If heating section is located downstream of a refrigeration
system or cooling coil, condensation can occur during opera-
tion of the air conditioning, resulting in condensation from
warm, moist air in the heat exchanger tubes and flue collector.
This condensate is not harmful to the heat exchanger provided
it is drained continuously.
FURNACE COMPONENT IDENTIFICATION — See
Fig. 146 for rack system gas furnace components.
OPERATING AND SAFETY CONTROLS — The follow-
ing controls are provided for the gas furnace rack system:
System/Ignition Control Module — Ignition controls are
available having a number of different operating functions.
IMPORTANT: Refer to Sequence of Operation Sheet, pro-
vided with heater documentation, for a detailed description
of the control features for the model control installed. This
documentation is located in the heater section, or contact
your Carrier service representative.
170