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The Continuous Fan airflow selection via Setup switches SW3 is
also the switch setting for low-speed cooling when the furnace is
used with a 2-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 9 and Fig. 65.
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 Fig. 38 and Fig. 65.
NOTE
: The cooling airflow settings for SW2 and SW3 selections
are the same, EXCEPT for the default values. See Table 9.
For a complete explanation of cooling airflow, refer to the section
titled “Sequence of Operation.”
Adjust Continuous Fan Airflow (and Low-Speed
Cooling Airflow)
Adjust continuous fan and low--stage cooling airflow using SW3
and refer to Fig. 65 and Table 9. The continuous fan speed can be
further adjusted at a conventional thermostat using the continuous
fan speed select function. Changing the continuous fan speed at a
conventional thermostat DOES NOT change the low--speed
cooling airflow selected via SW3 at the control board. Refer to the
section titled “continuous Blower Speed selection for Thermostat.”
Adjust Thermostat Heat Anticipator.
a. Mechanical thermostat. Set thermostat heat anticipator to
match the amp. draw of the electrical components in the
R--W/W1 circuit. Accurate amp. draw readings can be ob-
tained at the wires normally connected to thermostat sub-
base terminals, R and W. The thermostat anticipator should
NOT be in the circuit while measuring current.
(1.) Set SW1--2 switch on furnace control board to ON.
(2.) Remove thermostat from subbase or from wall.
(3.) Connect an amp. meter as shown in Fig. 62 across
the R and W subbase terminals or R and W wires
at wall.
(4.) Record amp. draw across terminals when furnace is
in low heat and after blower starts.
(5.) Set heat anticipator on thermostat per thermostat
instructions and install on subbase or wall.
(6.) Turn SW1--2 switch OFF.
(7.) Install blower door.
b. Electronic thermostat: Set cycle rate for 3 cycles per hr.
Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked
in the Start--up procedure section as part of normal operation.
1. Check Main Limit Switch
This control shuts off combustion system and energizes air--cir-
culating blower motor, if furnace overheats. By using this
method to check limit control, it can be established that limit is
functioning properly and will operate if there is a restricted re-
turn--air supply or motor failure. If limit control does not func-
tion during this test, cause must be determined and corrected.
a. Run furnace for at least 5 minutes.
b. Gradually block off return air with a piece of cardboard or
sheet metal until the limit trips.
c. Unblock return air to permit normal circulation.
d. Burners will re--light when furnace cools down.
2. Check Pressure Switch(es)
This control proves operation of the draft inducer blower.
a. Turn off 115--v power to furnace.
b. Disconnect inducer motor lead wires from wire harness.
c. Turn on 115--v power to furnace.
d. Set thermostat to “call for heat” and wait 1 minute. When pres-
sure switch is functioning properly, hot surface igniter should
NOT
glow and control diagnostic light flashes a status code
32 If hot surface igniter glows when inducer motor is discon-
nected, shut down furnace immediately.
e. Determine reason pressure switch did not function properly
and correct condition.
f. Turn off 115--v power to furnace.
g. Reconnect inducer motor wires, replace door, and turn on
115--v power.
h. Blower will run for 90 sec before beginning the call for heat
again.
i. Furnace should ignite normally.
Checklist
1. Put away tools and instruments. Clean up debris.
2. Verify that switches SW1--1 and SW1--6 are
OFF
and other
setup switches are set as desired. Verify that switches
SW1--7 and SW1--8 for the blower
OFF DELAY
are set as
desired per Table 19.
3. Verify that blower and control doors are properly installed.
4. Verify that there are no unsealed openings in the blower
shelf or casing.
5. Cycle test furnace with room thermostat.
6. Check operation of accessories per manufacturer’s instruc-
tions.
7. Review Owner’s Manual with owner.
8. Attach literature packet to furnace.
Содержание 986TC
Страница 72: ...72 A190157 Fig 64 Service Label Information ...
Страница 74: ...74 A190155 Fig 65 Furnace Setup Switches and Description Continued ...
Страница 91: ...91 A190153 Fig 72 Wiring Diagram ...