71
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 thermostatanticipator 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 Contr ols
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 shut s off combustion s ystem and energizes air--c ir-
culating bl ower motor, if furnace overheats. By usi ng t his
method to check limit control, it can be established that limit is
functioning properly and will operate if the re is a restricted re-
turn--a i r supply or motor fa ilure. If li m i t c ontrol does not func-
tion during this test, cause must be determined and corrected.
a. Run furnace for at least 5 minutes.
b. Gr adually block off return air with a pi ece of c ardboard or
sheet metal until the limit trips.
c. Unblock re turn a i r to pe r m it nor mal circulati on.
d. Burners wi ll re--light when f urnace c ools down.
2. Check Pressure Switch(es)
This cont rol pr oves ope ration of t he dra ft induc e r 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 funct ioning properly, hot sur face ignit er 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 f urnace imm edia tely.
e. Determine r eason pre ssure swi tch did not func tion pr operl y
and c orrect condi tion.
f. Turn off 115--v power to furnace.
g. Re connect inducer motor wires, repl ace door, and tur n on
115--v power.
h. Bl ower wil l run f or 90 se c befor e beginning t he c all for hea t
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.
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