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a. When furnace control R to W/W1-and-Y/Y2 circuits are
closed, furnace control CPU continues blower motor
BLWM operation at heat pump heating speed until the
end of the prepurge period, then shuts off until the end of
the HSI ignitor-on period (22 sec).
b. When installed with a heat pump, the furnace control-
CPU automatically holds blower off time to 22 sec
during HSI ignitor on period. After 17 sec of HSI
ignitor-on period, a trial for ignition sequence occurs as
described above for gas heating. After flame is proved
and without a blower on delay, the blower motor BLWM
will operate on high-gas-heat speed during defrost. For
both single-speed and 2-speed heat pumps, defrost mode
is in high-gas heat only.
c. When furnace control R-W/W1 circuit is opened, the
furnace control CPU begins the normal inducer post
purge period and the blower motor BLWM remains on
for the blower off delay period. If R-G circuit remains
closed, blower motor BLWM reverts to continuous
operation.
III. START-UP PROCEDURES
A. Purge Gas Lines
After all connections have been made, purge the gas lines and
check for leaks.
WARNING: Never purge a line into a combustion
chamber. Never use matches, candles, flame, or other
sources of ignition for the purpose of checking leakage.
Failure to follow this warning can cause fire, explosion,
personal injury, or death.
B. Component Self-Test
The furnace control allows all components, except the gas valve, to
be run for short periods of time. This helps diagnose a system
problem in the case of a component failure.
NOTE: The component test feature will not operate if the control
is receiving any thermostat signals or until all time delays have
expired. The blower access panel door switch must be manually
closed to perform the component test. Release switch when test is
complete.
WARNING: Blower access panel door switch opens
115-v power to control center. No component operation
can occur. Caution must be taken when manually closing
this switch for service purposes. Failure to follow this
warning could result in electrical shock, personal injury,
or death.
The component test sequence is as follows:
1. Short (jumper) the TWIN/TEST terminal to the COM-24V
terminal on the control for approximately 2 sec. (See Fig.
32.)
2. The inducer will start and run on high speed.
3. After 7 seconds the inducer motor will continue to run while
the hot surface ignitor HSI is energized for 15 sec, then
de-energized.
4. The inducer motor changes to low speed and continues to
run the remainder of the component self-test
5. The blower motor operates on LO GAS-HEAT speed for 7
sec.
6. The blower motor operates on HI GAS-HEAT speed for 7
sec.
7. The blower motor operates on HI COOL speed for 7 sec.
8. The gas valve and humidifier terminal HUM are not
energized for safety reasons.
NOTE: The EAC-1 terminal is energized when the blower is
energized.
C. Prime Condensate Trap With Water
CAUTION: Condensate trap must be PRIMED or
proper draining may not occur. The condensate trap has
internal chambers which can ONLY be primed by pour-
ing water into the inducer drain side of condensate trap.
1. Remove upper inducer housing drain connection cap. (See
Fig. 51.)
2. Connect field-supplied 1/2-in. ID tube to upper inducer
housing drain connection.
3. Insert field-supplied funnel into tube.
4. Pour 1 quart of water into funnel/tube. Water should run
through inducer housing, overfill condensate trap, and flow
into open field drain. (See Fig. 52.)
5. Remove funnel and tube from inducer housing and replace
drain connection cap and clamp.
Fig. 51—Inducer Housing Drain Tube
D. Operate Furnace
Follow procedures on operating instructions label attached to
furnace.
E. Furnace Restart
With furnace operating, set thermostat below room temperature
and observe that furnace goes off. Set thermostat above room
temperature and observe that furnace restarts.
IV. ADJUSTMENTS
A. Set Gas Input Rate
Furnace gas input rate on rating plate is for installations at altitudes
up to 2000 ft.
—36—
A99118
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