Lennox iComfort SL18XC-01 Installer Setup Manual page 25

Table 1. Alert Codes and Troubleshooting
Alert
Priority Alert Text
Code
(Furnace) The furnace low pressure switch
224 Critical
is stuck closed.
(Furnace) The furnace high pressure switch
225 Critical
is failing to close.
(Furnace) The furnace high pressure switch
226 Critical
is stuck closed.
(Furnace) The furnace low pressure switch
227 Moderate
is open in run mode.
(Furnace) The furnace control is not able to
228 Moderate
calibrate the pressure switch.
(Furnace) The furnace control has switched
229 Minor to high fire ignition because the low fire pres­
sure switch did not close in the allowed time.
240 Moderate (Furnace) The furnace flame current is low.
(Furnace) The furnace flame is going out
241 Critical
while the furnace is heating.
(Furnace) The furnace primary limit switch is
250 Moderate
open.
(Furnace) The furnace discharge air­temper­
252 Moderate
ature is high.
(Furnace) The furnace is in Watchguard
270 Critical mode. The furnace igniter cannot turn on the
flame.
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
Check operation of low pressure switch to see if it is stuck closed for longer than 150
seconds during a heat call . Measure operating pressure (inches w.c.). Inspect vent and
combustion air inducer for correct operation and restriction. The alarm/fault clears after the
issue is corrected.
Check pressure (inches w.c.) of high 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 clears after the issue is corrected.
Check operation of high 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 clears after the issue is corrected.
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 clears after the issue is corrected.
Unable to perform pressure switch calibration. Check vent system and pressure
switch wiring connections. Check the drain trap for blockage. The alarm/fault clears after a
successful calibration.
IFC switched to high fire ignition because low fire pressure switch did not close in allowed
time. No action is needed.
Check micro­amperes of the flame sensor using thermostat diagnostics. Clean or replace
the flame sensor. Measure voltage of neutral to ground to ensure good unit ground. The
alarm clears after a proper micro­amp reading has been sensed.
Shut off gas. Check for a gas valve leak. Replace the gas valve if needed. The alarm/fault
will clear when a heat call ends successfully.
Check for proper firing rate on furnace. Ensure there is no blockage in the furnace and the
duct work. Check for proper air flow. If limit switch is not closed within 3 minutes, the unit
will go into 1­hour Watchguard mode. The alarm/fault will clear when a heat call ends
successfully.
Check temperature rise, air flow and input rate. Check for dirty filters. The alarm/fault will
clear when a heat call ends successfully.
This is a five strike condition during a single demand. Check for proper gas flow. Ensure
that igniter is lighting burner. Check flame sensor current. Check for dirty filters. The alarm/
fault will clear on successful ignition.
25 iComfort Wi‐Fi
®
7-Day Programmable Communicating Thermostat