38
18-CD25D1-2
Installer’s Guide
CONDITIONS THAT AFFECT SYSTEM OPERATION
1. EXCESSIVE COMBUSTION PRESSURE (WIND IN
EXCESS OF 40 M.P.H.) VENT OR FLUE BLOCKAGE
On a call for heat, the Variable Speed Draft Inducer
must first ramp up to speed and close the Pressure
Switch before the ignition sequence is allowed to be-
gin. If the Pressure Switch does not close, the motor
will ramp up to maximum speed and continue to op-
erate there for about 1 minute.
After one minute, the Integrated Furnace Control
will turn the motor off for about 30 seconds and
then back on in an attempt to reestablish proper op-
eration. This condition is indicative of a highly re-
stricted or blocked inlet or outlet vent pipe or a
failed Pressure Switch.
If pressure against induced draft blower outlet be-
comes excessive, the Pressure Switch will open. If
the Pressure Switch is open for more than 3.5 sec-
onds, the variable speed draft inducer will speed up
and attempt to close the Pressure Switch. If the
Pressure Switch is not closed within 12 seconds or
if the maximum speed of the motor is reached, the
draft inducer sends a Fault signal to the Integrated
Furnace Control. If the unit is operating in Second
Stage, an Inducer Fault will cause the Furnace
Control to transition the system to First Stage and
it will operate there for 10 minutes before attempt-
ing to run again in Second Stage. If the unit is oper-
ating in First Stage, an Inducer Fault will cause the
Furnace Control to shut the system down and wait
30 seconds before attempting to reestablish opera-
tion in First Stage.
2. LOSS OF FLAME
If loss of flame occurs during a heating cycle, or
flame is not present at the sensor, the flame control
module will close the Gas Valve. The Integrated
Furnace Control will then recycle the ignition se-
quence, then if ignition is not achieved, it will shut
off the Gas Valve and lock out the system.
3. POWER FAILURE
If there is a power failure during a heating cycle,
the system will restart the ignition sequence auto-
matically when power is restored, if the Comfort
Control still calls for heat.
4. GAS SUPPLY FAILURE
If loss of flame occurs during a heating cycle, the
system Integrated Control Module will recycle the ig-
nition sequence, then if ignition is not achieved, the
Integrated Control Module will shut off the Gas
Valve and lock out the system.
5. INDUCED DRAFT BLOWER FAILURE
Please refer to the Variable Speed Draft Inducer
troubleshooting manual for diagnostic assistance.
6. CONDENSATE DRAIN BLOCKAGE
If the condensate drain is blocked, either by debris,
improper draining, or by freezing condensate, the
Pressure Switch will sense the accumulation of con-
densate in the Furnace drain trap. The unit will not
operate properly until the condensate drain has
been cleared, and the condensate flows freely.
7. RESET AFTER LOCKOUT
When the Integrated Furnace Control has shut the
system down and gone into lockout, the system
must be manually reset before the unit will restart.
The system can be reset by turning the system
power off for more than 1 second, or by removing
24VAC from the control for more than 1 second, or
by removing the Comfort Control call for heat for
more than 1 second but less than 20 seconds.
8. RESET AFTER BURNER BOX LIMIT SHUTDOWN
If the Furnace shuts down, one thing that can be
checked is the Burner Box temperature Limit
Switch. It is located on the bottom of the Burner
Box. The vent and combustion air inlet termina-
tions should be checked for blockage. If blockage ex-
ists, clear the problem and then the reset button
may be depressed.
If there is no blockage of the ter-
minations, the Limit Switch must be reset by quali-
fied service personnel.
WHOLE HOUSE AIR CLEANER CHECKOUT
▲
CAUTION
!
Before changing the position of the High Voltage se-
lector switch on the High Voltage power supply,
make sure the power has been removed from the fur-
nace and the High Voltage power supply.
Check out the Furnace Whole House Air Cleaner instal-
lation in accordance with this instructions page 40. Ad-
just ozone setting if needed. See figure 38 on page 40.
NOTE: Whole House Air Cleaner is energized when
blower is operating and there is a call for heat or cool.
This can result in brief periods of blower operation
with the whole house air cleaner off. This can occur
during the heat fan off period or if the enhanced
mode of operation is chosen for cooling.
