SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: (F/G)9MAE
Specifications subject to change without notice.
4
440 04 4700 00
START
−
UP, ADJUSTMENT, AND SAFETY
CHECK
General
1. Furnace must have a 115-v power supply properly
connected and grounded.
NOTE
: Proper polarity must be maintained for 115-v wiring.
Control status indicator light flashes code 10 and furnace does
not operate if polarity is incorrect or if the furnace is not
grounded.
2. Thermostat wire connections at terminals R, W/W1, G,
Y/Y2, etc. must be made at 24-v terminal block on
furnace control. See communicating wall control
instructions for proper wiring of communicating controls.
3. Natural gas service pressure must not exceed 0.5 psig
(14- in. w.c., 350 Pa), but must be no less than 0.16 psig
(4.5-in. w.c., 1125 Pa).
4. Blower door must be in place to complete 115-v
electrical circuit and supply power to furnace.
UNIT OPERATION HAZARD
Failure to follow this caution may result in intermittent unit
operation or performance dissatisfaction.
These furnaces are equipped with a manual reset limit
switch in burner assembly. This switch opens and shuts off
power to the gas valve if an overheat condition (flame
rollout) occurs in the burner assembly/enclosure. Correct
inadequate combustion-air supply, improper gas pressure
setting, improper burner or gas orifice positioning, or
improper venting condition before resetting switch. DO
NOT jumper this switch.
CAUTION
!
Before operating furnace, check flame rollout manual reset
switch for continuity. If necessary, press button to reset switch.
EAC-1 terminal is energized whenever blower operates. HUM
terminal is only energized when blower is energized in heating.
Select Setup Switch Positions
There are four sets of setup switches on the furnace control
board. These switches configure the furnace for correct
application requirement. They also select the airflow settings for
Air Conditioning and Continuous Fan airflows.
The Setup Switch locations are shown and described on
Figure 3
,
Figure 4
,
Table 3
and
Table 6
. The set up switches
are also shown on the unit wiring label.
Setup Switches (SW1)
The furnace control has eight setup switches that may be set to
meet the application requirements. Refer to
Figure 4
and
Adjustments section for set up switch configurations.
To set these setup switches for the appropriate requirement:
1. Remove blower door.
2. Locate setup switches on furnace control.
3. Configure the set-up switches as necessary for the
application.
4. Replace blower door.
NOTE
: If a bypass humidifier is used, setup switch SW1-3
(Min/Int Rise Adjust) should be in ON position. This
compensates for the increased temperature in return air
resulting from bypass.
NOTE
: If modulating dampers are used, blower motor
automatically compensates for modulating dampers.
Air Conditioning (A/C) Setup Switches (SW2)
The air conditioning setup switches are used to match furnace
airflow to required cooling airflow or high stage cooling airflow
when a two
−
stage outdoor unit is used. Refer to
Figure 4
and
the Adjustments section for set up switch configurations.
To set the desired cooling airflow:
1. Remove blower door.
2. Locate A/C setup switches on furnace control.
3. Determine air conditioning tonnage used.
4. Configure the switches for the required cooling airflow.
NOTE
: Incorrect airflow caused by improper A/C switch setup
may cause condensate blow
−
off or a frozen indoor coil in the
cooling mode.
5. Replace blower door.
Continuous Fan (CF) Setup Switches (SW3)
The CF setup switches are used to select desired airflow when
thermostat is in continuous fan mode or to select low-cooling
airflow for two-speed cooling units. Refer to
Figure 4
and the
Adjustments section for set up switch configurations.
1. Remove blower door.
2. Locate CF setup switches on furnace control.
3. Determine desired continuous fan airflow or low-cooling
airflow.
4. Configure the switches for the required continuous fan or
low
−
cooling airflow.
5. Replace blower door.
Additional Setup Switches (SW4)
The furnace control has three additional setup switches labeled
SW4.
Setup switch SW4-2 can be used to lock the furnace into
intermediate heat. When setup switch SW4-2 is ON it will over
ride setup switch SW1-2 if it is ON. SW4
−
3 is used to adjust
airflow. Refer to
Figure 4
and the Adjustments section for set
up switch configurations.
1. Remove blower door.
2. Locate setup switch SW4 on furnace control.
3. Configure the switches for the required heat stages air
flow if necessary.
4. Replace blower door.
Prime Condensate Trap with Water
!
WARNING
FIRE OR EXPLOSION HAZARD
Failure to follow these warnings could result in personal injury
or death.
Failure to use a properly configured trap or NOT
water-priming trap before operating furnace may allow
positive pressure vent gases to enter the structure through
drain tube. Vent gases contain carbon monoxide which is
tasteless and odorless.
UNIT OPERATION HAZARD
Failure to follow this caution may result in intermittent unit
operation or performance satisfaction.
Condensate trap must be PRIMED or proper draining may
not occur. The condensate trap has two internal
chambers which can ONLY be primed by pouring water
into the inducer drain side of condensate trap.
CAUTION
!
1. Remove upper and middle collector box drain plugs
opposite of the condensate trap. (See
Figure 1
)
2. Connect field-supplied 5/8-in. (16 mm) ID tube with
attached funnel (see
Figure 1
) to upper collector box
drain connection.
