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Table 4. Alert Codes and
Troubleshooting
Critical alerts are displayed on Home (user) screen, in the Homeowner alert tab, and in
the Installer alert tab. Minor and Moderate alerts are found only in the Installer alert tab.
Alert ID
Message Name
Priority
Action required to Clear/Recover
10
(Stat) Unknown Device Detected
− [any unit]
Critical
An unknown device is seen on the subnet in or outside of configuration
mode.
Clear by reconfiguring the system. Press and hold Lennox Logo,
press setup tab, press start, and press confirm. If problem persists, then
check all DEVICE connections to make sure they are icomfort−compatible.
11
(Stat) Missing − [any unit]
Critical
Check all connections and cycle system power. If problem persists, then
reconfigure the system using procedure mentioned above.
12
(Stat) Incomplete System
Critical
Thermostat did not find an Indoor Unit. Check R, i+, i− and C connections,
ohm wires and cycle power. Replace indoor board if no response.
14
(Stat) Too Many Devices of the
Same Type
Critical
Thermostat found more than one outdoor unit, or more than one indoor
unit, or more than one thermostat connected to the system. Check wiring
and remove duplicate equipment. Reconfigure system.
18
(Stat) Low Ambient HP Heat
Lockout
Minor
Minor alarm. Notification only − Outdoor Temp is below the Low Balance
Point. HP will not be used to service a heating demand.
19
(Stat) High Ambient Auxiliary
Heat Lockout
Minor
Minor alarm. Notification only − Outdoor Temp is above the High Balance
Point. Indoor Unit (Furnace or Electric Heat) will not be used to service a
heating demand.
29
(Stat) Over Temperature Protec-
tion
Critical
Indoor Temp rose above 99ºF during a heating or cooling demand. Heat-
ing operation is not allowed. Check to ensure that Heating Equipment is
not stuck ON (reversing valve, etc.). Check accuracy of thermostat tem-
perature sensor. Select cooling system mode to cool the indoor space.
30
(Stat) Low Temperature Protec-
tion
Moder-
ate
Indoor Temp fell below 40ºF. Cooling operation is not allowed. Check to
ensure that cooling equipment is not stuck ON. Check accuracy of the
thermostat temperature sensor. Try to heat the space to above 40ºF.
31
(Stat) Lost Communication with −
[any unit]
Critical
[Indicated unit] has not communicated with thermostat for more than 3
minutes. Check connections. Ohm wires. If fault persists, then cycle pow-
er. Fault clears after communication is restored.
32
(Stat) Asynchronous Reset − [any
unit]
Moder-
ate
[Indicated unit] is resetting itself. Check power connections and check
24VAC voltage at DEVICE. The alarm is only cleared by pressing the
clear button on the Installer Alerts Tab. If fault persists after checking con-
nections, replace board.
34
(Stat) Must Program Unit Capac-
ity −−
[any unit]
Critical
[Indicated unit] is missing the programmed unit capacity. Go to [indicated
unit] and program unit capacity manually. See unit IOM for programming
instructions. Remove power to thermostat before programming control
board. Once programming is complete, reconnect thermostat wires and
reconfigure system.
35
(Stat) Incorrect Operation of −
[any unit]
Critical
[Indicated unit] did not follow thermostat command. Message sent by
T’STAT when a device fails to heat/cool when asked to do so for 15 min-
utes, or when device is still in heating or cooling mode when it was told to
stop for more than 15 minutes. Unit will shut down. Check wiring connec-
tions and cycle power.
105
(Stat / Furnace / Air Handler /
Outdoor Unit) Communication
Problem
Critical
Equipment is unable to communicate. Indicates numerous message er-
rors. In most cases errors are related to electrical noise. Make sure high
voltage power is separated from RSBus. Check for mis−wired and/or loose
connections between the stat, indoor unit and outdoor unit. Check for a
high voltage source of noise close to the system. Fault clears after com-
munication is restored.
110
(Furnace) Low AC Line Voltage
Critical
Line Voltage Low (Voltage lower than nameplate rating).
Check power line
voltage and correct. Alarm clears 5 seconds after fault recovered
111
(Furnace) Line Voltage Polarity
Reversed
Critical
Reverse line power voltage wiring. System resumes normal operation 5
seconds after fault recovered.
112
(Furnace) Earth Ground Not De-
tected
Criti-
cal
System shuts down. Provide proper earth ground. System resumes nor-
mal operation 5 seconds after fault recovered.
113
(Furnace) High AC Line Voltage
Criti-
cal
Line Voltage High (Voltage higher than nameplate rating). Provide power
voltage within proper range. System resumes normal operation 5 seconds
after fault recovered.
114
(Furnace / Air Handler)
AC Line Frequency/Distortion
Problem
Criti-
cal
No 60 Hertz Power.
Check voltage and line power frequency. Correct volt-
age and frequency problems. System resumes normal operation 5 sec-
onds after fault recovered.
table continued on next page
