Fossil Fuel Applications
This furnace can be used in conjunction with a heat pump in a
fossil fuel application. A fossil fuel application refers to a
combined gas furnace and heat pump installation which uses an
outdoor temperature sensor to determine the most cost efficient
means of heating (heat pump or gas furnace).
A heat pump thermostat with 3 stages of heat is required to
properly use a 2-stage furnace in conjunction with a heat pump.
Refer to the fossil fuel kit installation instructions for additional
Strictly follow the wiring guidelines in the fossil fuel kit installation
instructions. All furnace connections must be made to the
furnace 2-stage integrated control module and the FURNACE
terminal strip on the fossil fuel control board.
115-Volt Line Connection of Accessories (Humidifier
and Electronic Air Cleaner)
To avoid personal injury or death due to
electrical shock, disconnect electrical
power before servicing or changing any
The furnace integrated control module is equipped with line
voltage accessory terminals for controlling power to an optional
field-supplied humidifier and/or electronic air cleaner.
The accessory load specifications are as follows:
Electronic Air Cleaner
Turn off power to the furnace before installing any
Follow the humidifier or air cleaner manufacturers'
instructions for locating, mounting, grounding and controlling
Accessory wiring connections are to be made through the ¹⁄₄"
quick connect terminals provided on the furnace integrated
The humidifier and electronic air cleaner hot terminals are
identified as HUM and EAC.
The humidifier and electronic air cleaner neutral terminals are
identified as NEUTRAL.
The furnace rating plate includes the approved furnace gas input
rating and gas types. The furnace must be equipped to operate
on the type of gas applied. This includes any conversion kits
required for alternate fuels and/or high altitude.
To prevent unreliable operation or equipment damage,
the inlet gas supply pressure must be as specified on the
unit rating plate with all other household gas-fired
1.0 Amp maximum at 120 VAC
1.0 Amp maximum at 120 VAC
GAS SUPPLY AND PIPING
All field wiring must conform to applicable codes.
Connections should be made as shown in the "Optional
Accessories Wiring" illustration.
Optional Accessories Wiring
Integrated Control Module
If it is necessary for the installer to supply additional line voltage
wiring to the inside of the furnace, the wiring must conform to all
local codes, and have a minimum temperature rating of 105°C.
All line voltage wire splices must be made inside the furnace
The integrated control module humidifier terminals (HUM) are
energized with 115 volts whenever the induced draft blower is
energized. The integrated control module electronic air cleaner
terminals (EAC) are energized with 115 volts whenever the
circulator blower is energized.
A 5" (12.7 cm) long brown wire in the wire harness at the low-fire
pressure switch provides 24 VAC humidifier control. This wire is
powered any time the pressure switch is closed. To connect
24 VAC HUM, connect the 24 VAC line of the humidifier to the 5"
(12.7 cm) brown wire. The connection can be made by either
stripping the wire and using a wire connector or by using a
field-supplied quick connect terminal. The wiring must conform
to all local and national codes. Connect the COM side of the
humidifier to the C terminal on the furnace control board (or to
the COM side of the 24 VAC transformer).
NOTE: Do not connect 115-Volt humidifier to these terminals.
Inlet gas supply pressures must be maintained within the ranges
specified in the Inlet Gas Supply Pressure chart. The supply
pressure must be constant and available with all other household
gas-fired appliances operating. The minimum gas supply pressure
must be maintained to avoid unreliable ignition. The maximum
must not be exceeded to keep the furnace from overfiring.
Inlet Gas Supply Pressure
5.0" W.C. minimum; 10.0" W.C. maximum
11.0" W.C. minimum; 13.0" W.C. maximum