SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: (F/G)9MAC
Specifications subject to change without notice.
4
440 04 4201 01
START
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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.
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.), but must be no less than 0.16 psig (4.5-in.
w.c.).
4. Blower door must be in place to complete 115-v
electrical circuit to furnace.
UNIT OPERATION HAZARD
Failure to follow this caution may result in intermittent
unit operation or performance satisfaction.
These furnaces are equipped with a manual reset
limit switch in burner assembly. This switch opens
and shuts off power to the gas valve is an overheat
condition (flame rollout) occurs in burner assembly.
Correct inadequate combustion
−
air supply 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 (4) 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 CFM.
The Setup Switch locations are shown and described on
Figure 4
. The set up switches are also shown on the unit wiring
label.
Setup Switches (SW1)
The furnace control has 8 setup switches that may be set to
meet the application requirements. To set these setup switches
for the appropriate requirement:
S
Remove blower door.
S
Locate setup switches on furnace control.
S
Configure the set-up switches as necessary for the
application.
S
Replace blower door.
NOTE
: If a bypass humidifier is used, setup switch SW1-3
(Minimum Heat 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 cooling unit used.
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
: Excessive airflow caused by improper A/C switch setup
may cause condensate blow-off in 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. This setup feature allows
continuous fan airflow or low-cooling airflow to be adjusted. To
set desired continuous fan airflow or low-cooling airflow:
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 3 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. See communicating control instructions for use of
SW4
−
1. To activate setup switch SW4-2 and SW4
−
3:
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
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 inducer housing drain plugs
opposite of the condensate trap. (See
Figure 1
)
2. Connect field-supplied 1/2-in. (13 mm) OD tube to upper
inducer housing drain connection.
3. Insert field-supplied funnel into tube.
4. Pour one quart of water into funnel/tube. Water should
run through inducer housing, overfill condensate trap,
and flow into open field drain.
5. Remove funnel; replace inducer drain plug.
6. Connect field-supplied 1/2-in. (13 mm) OD tube to middle
inducer housing drain port.
7. Pour one quart of water into funnel/tube. Water should
run through inducer housing, overfill condensate trap,
and flow into open field drain.
8. Remove funnel and tube from inducer housing and
replace inducer drain plug.
