Lennox iComfort SL18XC-01 Installer Setup Manual page 26

Table 1. Alert Codes and Troubleshooting
Alert
Priority Alert Text
Code
(Furnace) The furnace is in Watchguard
271 Critical mode. The furnace low pressure switch is
open.
(Furnace) The furnace is in Watchguard
272 Critical mode. The furnace low pressure switch is
open during run mode.
(Furnace) The furnace is in Watchguard
273 Critical mode. The furnace flame is going off during
a heating cycle.
(Furnace) The furnace limit switch has been
274 Critical
open for more than 3 minutes.
(Furnace) The furnace flame is out of se­
275 Critical
quence.
(Furnace) The furnace is not able to calib­
276 Critical rate or the high pressure switch opened or
failed to close in run mode.
(Furnace) There is a problem with the fur­
290 Critical
nace ignition circuit.
(Furnace) The heating airflow is below the
291 Critical
minimum required level.
(Furnace / Air Handler) The (furnace or
292 Critical air­handler) indoor blower motor will not
start.
(Furnace) There is over current in the fur­
294 Critical
nace inducer motor.
(Furnace) The indoor blower motor is over
295 Minor
heating.
507341-02
Critical alerts are displayed on Home (user) screen, in the Homeowner alert button, and in
the Installer alert button. Minor and Moderate alerts are found only in the Installer alert
button.
Steps to clear
This is a five strike condition during a single demand. Check pressure (inches w.c.) of low
pressure switch closing during a heat call. Measure operating pressure (inches w.c.).
Inspect vent and combustion air inducer for correct operation and restriction. The alarm/
fault will clear on successful ignition.
Check operation of low pressure switch to see if it is stuck open during a heat call. Meas­
ure operating pressure (inches w.c.). Inspect vent and combustion air inducer for correct
operation and restriction. The alarm/fault will clear when a heat call ends successfully.
Check micro­amperes of flame sensor using thermostat diagnostics. Clean or replace
sensor. Measure voltage of neutral to ground to ensure good unit ground. The alarm/fault
will clear when a heat call ends successfully.
The system will go into Watchguard mode. Check firing rate and air flow. Check for block­
age. The alarm/fault will clear when a heat call ends successfully.
The system will go into Watchguard mode. Shut off gas. Check for gas valve leak. The
alarm/fault will clear on next successful ignition.
The system will go into Watchguard mode. Check vent system and pressure
switch wiring connections. The fault/alarm will clear when the furnace calibrates itself
successfully.
The system will go into Watchguard mode. Measure resistance of hot surface igniter.
Replace the hot surface ignitor it is not within specifications. The alarm/fault will clear on
next successful ignition.
The system will go into Watchguard mode. Check for dirty filters and other air flow restric­
tions. Check blower performance. The alarm/fault will clear when a heat call ends suc­
cessfully.
The system will go into Watchguard mode. Indoor blower motor unable to start. This could
be due to seized bearing, stuck wheel, obstruction etc. Replace motor or wheel if as­
sembly does not operate or meet performance standards. The alarm/fault clears after the
indoor blower motor starts successfully.
The system will go into Watchguard mode. Check combustion blower bearings, wiring and
amps. Replace if does not operate or does not meet performance standards. The alarm/
fault clears after inducer current is sensed to be in­range after the ignition following the
Watchguard mode or reset.
Indoor blower motor over temperature (motor tripped on internal protector). Check motor
bearings and amps. Replace if necessary. The alarm/fault clears after blower demand is
satisfied.
26