35
TABLE 9 —FURNACE SETUP SWITCH DESCRIPTION
SETUP SWITCH
NO.
SWITCH NAME
NORMAL
POSITION
DESCRIPTION OF USE
S W 1 --- 1 Status Code Recovery OFF
Turn ON to retrieve up to 7 stored status codes for troubleshooting
assistance when R thermostat lead is disconnected.
S W 1 --- 2 Adaptive Heat Mode OFF
Allows 2---stage operation with a single stage thermostat. Turn ON
when using 2 stage thermostat to allow Low Heat operation when
R to W/W1 closes and High Heat operation when R to W/W1 and
W2 close.
S W 1 --- 3 Low Heat Rise Adjust OFF
Turn ON to increase Low Heat airflow by 10 percent. This com-
pensates for increased return air temperature caused with bypass
humidifier.
S W 1 --- 4 Comfort/Efficiency Adjustment ON
Turn ON to decrease Low Heat airflow by 22 percent and High
Heat airflow 15 percent for maximum comfort.
S W 1 --- 5 CFM per ton adjust OFF Turn ON for 400 CFM per ton. Turn OFF for 350 CFM per ton.
S W 1 --- 6 Component Self--- Test OFF
Turn ON to initiate Component Self--- Test for troubleshooting as-
sistance when R thermostat lead is disconnected. Tur n OFF when
Self--- Test is completed.
S W 1 --- 7 Blower OFF delay ON or OFF
Control blower O ff Delay time. Used in conjunction with SW1---8.
See Table 10.
S W 1 --- 8 Blower OFF delay ON or OFF
Control blower O ff Delay time. Used in conjunction with SW1---7.
See Table 10.
A04001
Fig. 40 --- Example of Setup Switch in Off Position
5. Remove funnel and tube from inducer housing and replace
drain connection cap and clamp.
Step 4 —Purge Gas Lines
If not previously done, purge the lines after all connections have
been made and check for leaks.
FIRE AND EXPLOSION HAZARD
Failure to follow this warning could result in a fire,
explosion, personal injury, or death.
Never purge a gas line into a combustion chamber.
Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifically
for the detection of leaks to check all connections.
!
WARNING
Step 5 —Sequence of Operation
Using schematic diagram, follow sequence of operation through
different modes. (See Fig. 23.) Read and follow wiring diagram
carefully.
UNIT MAY NOT OPERATE
Failure to follow this caution may result in intermittent unit
operation.
Furnace control must be grounded for proper operation, or
control will lock out. Control is grounded through
green/yellow wire routed to gas valve and burner box
screw .
CAUTION
!
NOTE: If a power interruption occurs during a call for heat
(W/W1 or W/W1--and-- W2), the control will start a 90--second
blower-- only ON period two seconds after power is restored, if
the thermostat is still calling for gas heating. The amber LED
light will flash code 12 during the 90 -- second period, after which
the LED will be ON continuous, as long as no faults are detected.
After the 90--second period, the furnace will respond to the
thermostat normally.
The blower door must be installed for power to be conducted
through the blower door interlock switch ILK to the furnace
control CPU, transformer TRAN, inducer motor IDM, blower
motor BLWM, hot--surface igniter HSI, and gas valve GV.
SINGLE-- STAGE THERMOSTAT AND TWO--ST
AGE
HEATING (ADAPTIVE
MODE)
See Fig. 19 or 50 for thermostat connections.
NOTE: Low--heat--only switch, SW1--2, selects either the low
heat-- only operation mode when ON, (see item 2. below) or
adaptive heating mode when OFF, in response to a call for heat.
(See Fig. 33.) When the W2 thermostat terminal is energized, it
will always cause high-- heat operation when the R to W circuit is
closed, regardless of the setting of the low--heat only switch.
This furnace can operate as a two--stage furnace with a
single--stage thermostat because furnace control CPU includes a
programmed adaptive sequence of controlled operation, which
selects low--heat or high -- heat operation. This selection is based
upon the stored history of the length of previous gas heating
periods of the single-- stage thermostat.
The furnace will start up in either low-- or high--heat. If the
furnace starts up in low--heat, the furnace control CPU determines
the low--heat on time (from 0 to 16 minutes) which is permitted
before switching to high--heat.
58UVB
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