Gas-Fired Rack System Furnaces; Operating And Safety Controls; Unit Location And Clearances; • Gas Supply, Piping And Connections - Carrier AERO 39MN Installation, Start-Up And Service Instructions Manual

Gas-Fired Rack System Furnaces

WARNING
Gas-fired furnaces are not designed for use in hazardous
atmospheres containing flammable vapors or combustible
dust, in atmospheres containing chlorinated or halogenated
hydrocarbons, or in applications with airborne substances
containing silicone.
IMPORTANT: This furnace assembly is not listed or suit-
able for drying or process applications. Use in such appli-
cations voids any warranty and manufacturer disclaims any
responsibility for the duct furnace and/or application.
INSTALLATION REQUIREMENTS — Gas furnaces are fac-
tory installed. If circumstances require field installation of a gas
furnace, it can only be installed in a factory-supplied gas heater
section. All unit installations must be in accordance with the
National Fuel Gas Code ANSI Z223.1 (NFPA 54) in the United
States and Can/CGA-B149 Installation Code in Canada, and all
other applicable local codes and ordinances. These require-
ments include but are not limited to:
• Combustion air supply to the heating equipment
• Venting of the products of combustion (flue gases)
• Gas supply, piping and connections

• Unit location and clearances

All electrical equipment must be grounded and wired in accor-
dance with the National Electric Code (ANSI/NFPA 70) in the
United States, and the Canadian Electric Code (CSA C22.1), in
Canada.
VERIFICATION — Verify the following before placing the
equipment into service:
• Electrical supply matches the heater voltage marked on the
duct furnace Rating Plate.
• Gas supply provided matches the Gas Type marked on the
duct furnace Rating Plate.
• Furnace is installed in orientation marked on vestibule. Ori-
entation is specific to airflow direction through the heating
section of the unit.
• There is an adequate supply of fresh air for the combustion
and ventilation process. Combustion air openings in the cabi-
net 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 sup-
plied to gas-fired heaters presents a substantial corrosion
hazard.
• A properly designed vent system is connected to the heating
unit to convey the products of combustion (flue gases) out-
side the building. For outdoor applications be sure the flue
gases are directed away from any combustion air inlets.
• Duct furnace assembly is installed in a non-combustible duct
or cabinet on the positive pressure side of the circulating 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 mainte-
nance of the heating units installed.
CONDENSATE DRAINS — A CPVC condensate drain line is
provided and connected to the individual heaters. In applications
operating with modulating controls some condensation may
occur in the heating cycle. In these applications connection of a
condensate drain line is required to avoid condensate build-up
and possible heat exchanger damage. Flue gas condensate 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 operation
of the air conditioning, resulting in condensation from warm,
moist air in the heat exchanger tubes and flue collector. This con-
densate is not harmful to the heat exchanger provided it is
drained continuously.
FURNACE COMPONENT IDENTIFICATION — See Fig.
103 for rack system gas furnace components.
OPERATING AND SAFETY CONTROLS — The
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. Refer
to Sequence of Operation Sheet provided with heater documen-
tation 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.
Rollout Switch (Manual Reset) — The furnace module is
equipped with manual reset rollout switch(es) in the event of
burner flame rollout. The switch will open on temperature rise
and shut off gas supply through the ignition control module.
Flame rollout can be caused by insufficient airflow for the
burner firing rate (high gas pressure), blockage of the vent sys-
tem or in the heat exchanger. The furnace module should not be
placed back in operation until the cause of rollout condition is
identified. The rollout switch can be reset by pressing the button
on the top of the switch.
118
follow-