SERVICE AND TECHNICAL SUPPORT MANUAL Gas Furnace: (F/G)9MAC
Specifications subject to change without notice.
440 04 4201 03 9
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of Set up switch SW1−3. When set to
ON, airflow is raised 18% for Minimum Heat and for
Intermediate Heat. Factory default position is OFF.
5. Turn 115 VAC power on.
6. Re−check Minimum Heat Temperature Rise.
To lock the furnace in Intermediate Heat:
1. Turn SW1−2 OFF and SW4−2 ON at the furnace control.
2. Connect a jumper across R and W/W1 at the thermostat
terminals at the furnace control.
3. Allow the burners to ignite and the blower to turn on.
4. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in Intermediate
Heat:
1. Remove jumpers from R and W/W1.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of Set up switch SW1−3. When set to
ON, airflow is raised 18% for Minimum Heat and for
Intermediate Heat. Factory default position is OFF.
5. Turn 115 VAC power on.
6. Re−check Intermediate Heat Temperature Rise .
To lock the furnace in Maximum Heat:
1. Connect a jumper across R and W/W1 and W2 at the
thermostat terminals at the furnace control.
2. Allow the burners to ignite and the blower to turn on.
3. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in Maximum
Heat:
1. Remove jumpers from R and W/W1 and W2.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of Set up switch SW1−4. When set to
OFF, and SW1−3 is set to OFF, airflow is raised 10% for
Minimum Heat, 7.5% for Intermediate Heat and 17.5%
for Maximum Heat. Factory default position is ON. If
SW1−3 is ON and SW1−4 is OFF, airflow is raised 18%
for Minimum and Intermediate heat and 10% for
Maximum Heat.
5. Turn 115 VAC power on.
6. Re−check Maximum Heat Temperature Rise.
After the temperature rise has been verified:
1. Remove jumpers from thermostat terminals.
2. Allow the blower off delay to complete.
3. Turn Set up switches SW1−2 and SW4−2 to the OFF
position unless two−stage thermostat operation is
desired. (See Figure 4)
4. Proceed to “Adjust Blower Off Delay” or install blower
door if complete.
FIRE HAZARD
Failure to follow this warning could result in personal injury,
death, and/or property damage.
Reinstall manifold pressure tap plug in gas valve to
prevent gas leak.
!WARNING
FURNACE OVERHEATING HAZARD
Failure to follow this caution may result in reduced furnace
life.
Recheck temperature rise. It must be within limits specified
on the rating plate. Recommended operation is at the
mid−point of rise range or slightly above.
CAUTION
!
Adjust Blower Off Delay (Heat Mode)
a. Remove blower door if installed.
b. Turn Dip switch SW−7 or SW−8 ON or OFF for
desired blower off delay. (See Table 2, Figure 3 and
Figure 4)
Table 2 Blower Speed Taps
DESIRED HEATING MODE
BLOWER OFF DELAY
(SEC.)
SETUP SWITCH POSITION
SW1-7 SW1-8
90 OFF OFF
120 ON OFF
150 OFF ON
180 ON ON
Adjust Cooling Airflow −High−Speed and
Low−Speed Cooling
The ECM blower can be adjusted for a range of airflows for
low−speed or high−speed cooling. See Table 3 −Airflow
Switch Table, Table 6 −Air Delivery −CFM (with Filter) and
Figure 4. Furnace Setup Switches and Descriptions.
Depending on the model size, the cooling airflow can be
adjusted from 1.5 tons to 6 tons of nominal cooling based on
350 CFM ton.
NOTE: 6 ton airflow will truncate at 2200 CFM on applicable
models.
The high−speed or single−speed cooling airflow is adjusted by
turning setup switches SW2−1, SW2−2 and SW2−3 either ON
or OFF. Select the required airflow from Table 6. Table 6 is
based on 350 CFM per ton. For other CFM per ton setup switch
selections, see Table 3, Figure 4 and Figure 15.
The Continuous Fan airflow selection via setup switches SW3
is also the airflow for low−speed cooling when the furnace is
used with a two−speed cooling or heat pump unit. Adjust the
Continuous Fan CFM setup switches SW3 to match the airflow
required for low−speed cooling. Select the required airflow from
Table 6 and Figure 4.
NOTE: The airflow selected via SW3 (low−speed cooling
airflow) cannot exceed the airflow selected via SW2
(high−speed cooling airflow). For other CFM per ton setup
switch selections, see Table 3 and Figure 4.
NOTE: The airflow settings for SW2 and SW3 selections are
the same, EXCEPT for the default values. (See Table 6)
For a complete explanation of cooling airflow, refer to the
section titled “Sequence of Operation.”
Adjust Continuous Fan Airflow/Low Speed
Cooling Airflow
NOTE: When the furnace is used with a two−speed cooling or
heat pump unit, the airflow selected for Continuous Fan via
setup switch SW3 will also be the airflow used for low−speed
cooling, and vice versa.
NOTE: When the furnace is used with a two−speed cooling or
heat pump unit, adjust the Continuous Fan CFM setup
switches SW3 to match the airflow required for low−speed
cooling.
Select the required Continuous Fan airflow using setup
switches SW3 as shown in Table 3, Figure 4 and Figure 15.
