Lennox gas furnace error codes

Lennox gas furnace code E105

Device communication problem: no other devices on the RS BUS. The equipment is unable to communicate and there are numerous message errors.

Check for loose or miswired connections between the thermostat, indoor unit and outdoor unit, and for a high-voltage source of noise near the low-voltage wiring.

Lennox says errors like this are mostly electrical noise: keep high-voltage power separate from the RSBus, and check for miswired or loose connections. The fault clears after communication is restored.

Lennox gas furnace code E110

Low line voltage: the voltage is lower than the nameplate rating. The alarm clears 5 seconds after the fault recovers.

Check whether other large loads or a tripped or weak breaker are affecting the furnace circuit.

Lennox says to check the power line voltage and correct it. Line-voltage measurement is for a licensed electrician or HVAC technician.

Lennox gas furnace code E111

Lennox's table lists E111 with the status 'Low line voltage' and the action 'Reverse line power voltage wiring', which is a line-power polarity problem. The system resumes normal operation 5 seconds after the fault recovers.

Note whether the furnace worked before recent electrical work or a control replacement.

Lennox's action is to reverse the line power voltage wiring so the hot and neutral connections are correct. This is electrical work for a licensed technician.

Lennox gas furnace code E112

Ground not detected. The system shuts down and resumes normal operation 5 seconds after the fault recovers.

Confirm the furnace has not lost its grounding after recent electrical or duct work.

Lennox says to provide a proper earth ground. Grounding is electrical work for a licensed technician.

Lennox gas furnace code E113

High line voltage: the voltage is higher than the nameplate rating. The system resumes normal operation 5 seconds after the fault recovers.

Note whether the code appears at particular times of day or after utility work.

Lennox says to provide power within the proper voltage range. Correcting supply voltage is for the electrician or the utility.

Lennox gas furnace code E114

The line-voltage frequency is wrong: Lennox lists it as no 60 Hertz power. The system resumes normal operation 5 seconds after the fault recovers.

Note whether the furnace is running from a generator or inverter.

Lennox says to check the voltage and line-power frequency and correct any voltage and frequency problems. Correcting supply power is an electrician's or the utility's job.

Lennox gas furnace code E115

Low 24V: the 24-volt control power is below the 18 to 30 volt range. The control restarts if the error recovers.

Note any recently added accessories (smart thermostat, humidifier, zone controls) that draw from the same transformer.

Lennox says to check and correct the voltage, look for power-robbing equipment connected to the system, and that a larger VA transformer may be needed in the furnace or air handler.

Lennox gas furnace code E116

High 24V: the 24-volt control power is above the 18 to 30 volt range. It clears when the control senses a proper voltage.

Note whether the furnace was recently rewired or the transformer replaced.

Lennox says to check and correct the voltage and to check for the proper line voltage (120V, 240V, etc.) to the equipment.

Lennox gas furnace code E120

Unresponsive device, communication only. Lennox says this is usually caused by a delay in the outdoor unit responding to the indoor unit's polling. It clears after the device responds to any inquiry.

Cycle power to the system once at the breaker and wait a few minutes.

Lennox says to recycle power and check all wiring connections.

Lennox gas furnace code E124

The active communicating-thermostat signal has been missing for more than 3 minutes. The furnace lost communication with the thermostat, stops all services and waits for a message from it.

Check that the thermostat display is on and that its wires are seated at the thermostat.

Lennox says to check the four wiring connections, ohm the wires and cycle power at the thermostat. The alert clears after a valid thermostat message is received.

Lennox gas furnace code E126

Control internal communication problem: a hardware problem on the control. It clears 300 seconds after the fault recovers.

Turn power off at the furnace switch, wait a minute and restore it once.

Lennox says to cycle power on the control and replace it if the problem prevents service and is persistent.

Lennox gas furnace code E131

Corrupted control parameters, in communicating mode only. The control will still operate on default parameter settings.

Note whether the system was recently commissioned or a board replaced.

Lennox says to reconfigure the system, execute 'Set Factory Default' after exiting commissioning, and replace the control if heating or cooling is not available. It applies only in communicating mode, not during startup.

Lennox gas furnace code E200

Hard lockout: the flame rollout circuit is open or was previously open. Flame rollout means flame or hot gas came out of the burner area, which is a safety trip.

Do not reset the furnace repeatedly; leave it off and do not look for the rollout switch yourself.

Lennox says to correct the cause of the rollout trip, or replace the flame rollout switch, and then test furnace operation. A rollout trip is a combustion or venting fault, so this needs a technician.

Lennox gas furnace code E201

Indoor blower communication failure: the control is unable to communicate with the blower motor, including a power outage to it.

Confirm the furnace has power and the blower door is seated.

Lennox lists possible causes as the motor not powered or loose wiring, with the problem on the control side or the motor side. It clears after the fault recovers. Inspection of motor wiring is technician work.

Lennox gas furnace code E202

Indoor blower motor mismatch: the motor horsepower does not match the unit capacity. Lennox says an incorrect appliance capacity code was selected.

Note whether the control or the blower motor was recently replaced.

Lennox says to check the configuration against the Unit Size Codes for the furnace or air handler in the configuration guide or installation instructions. It clears after the correct match is detected following a reset, with the thermostat removed from the system while power is applied and the unit reprogrammed.

Lennox gas furnace code E203

Appliance capacity or size is not programmed: no appliance capacity code is selected. This is a critical alert.

Note whether the control board was recently replaced.

Lennox says to set the appliance capacity code using the Unit Size Codes on the configuration guide or in the installation instructions. It clears after a valid unit code is read following a reset. Setting this is technician work.

Lennox gas furnace code E204

Gas valve mis-wired. The alert clears when the wiring is repaired.

Note whether the gas valve or control was recently replaced.

Lennox says to check gas valve operation and wiring. Gas-valve wiring is technician work.

Lennox gas furnace code E205

The gas valve control relay contact is shorted.

Leave the furnace off if it will not shut off.

Lennox says to check the wiring on the control and the gas valve and, if the wiring is correct, replace the control. That is a gas-valve control fault for a technician.

Lennox gas furnace code E206

Gas valve second-stage relay failure. The furnace operates on first stage for the rest of the heating demand.

Note whether the house heats more slowly than usual.

Lennox says the alert clears after the fault recovers, and that if the control is unable to operate second stage it should be replaced.

Lennox gas furnace code E207

Hot surface ignitor sensed open, meaning the ignitor has failed open or its circuit is broken. Normal operation resumes after the fault is cleared.

Note whether the furnace clicks or hums but never lights.

Lennox says to measure the hot surface ignitor's resistance and replace it if it is open or outside the range printed in the installation and operation manual.

Lennox gas furnace code E223

Low pressure switch failed open: it did not close on the call for heat. Normal operation resumes after the fault is cleared.

Lennox says to check the pressure at which the low-pressure switch closes on a heat call, measure operating pressure in inches of water column, and inspect the vent and combustion air inducer for correct operation and restriction.

Lennox gas furnace code E224

Low pressure switch failed closed: it was still closed on the heat call for longer than 150 seconds. Normal operation resumes after the fault is cleared.

Note whether the inducer runs before a heat call.

Lennox says to check whether the low-pressure switch is stuck closed on a heat call, measure operating pressure, and inspect the vent and combustion air inducer for correct operation and restriction.

Lennox gas furnace code E225

High pressure switch failed open: it did not close on the call for heat. Normal operation resumes after the fault is cleared.

Lennox says to check the pressure at which the high-pressure switch closes on a heat call, measure operating pressure, and inspect the vent and combustion air inducer for correct operation and restriction.

Lennox gas furnace code E226

High pressure switch failed closed. Normal operation resumes after the fault is cleared.

Note whether the inducer runs before a heat call.

Lennox says to check the operation of the high-pressure switch closing on a heat call, measure operating pressure, and inspect the vent and combustion air inducer for correct operation and restriction.

Lennox gas furnace code E227

Low pressure switch open during the trial for ignition or during run mode. Normal operation resumes after the fault is cleared.

Lennox says to check the pressure at which the low-pressure switch closes on a heat call, measure operating pressure, and inspect the vent and combustion air inducer for correct operation and restriction.

Lennox gas furnace code E228

Combustion air inducer calibration failure: the control was unable to perform pressure-switch calibration. Normal operation resumes after the fault is cleared.

Lennox says to check the vent system and the pressure-switch wiring connections.

Lennox gas furnace code E229

Ignition on high fire. The control switched to high-fire ignition because the low-fire pressure switch did not close in the allowed time. Lennox says no action is needed.

Note whether the code shows only briefly at the start of a heating cycle.

Lennox's action is none: no action is needed. If it repeats with pressure-switch codes, the vent or inducer is the thing to look at.

Lennox gas furnace code E240

Low flame current in run mode. The alert clears after the current heat call has been completed.

Note whether the furnace starts, runs a short time and shuts off.

Lennox says to check the flame sensor's microamperes using the control diagnostics, clean or replace the sensor, and measure neutral-to-ground voltage to confirm a good unit ground.

Lennox gas furnace code E241

Flame sensed out of sequence: flame is still present when it should not be. The alert clears when the fault is recovered.

Turn the thermostat down and, if flame is visible in the sight glass with no heat call, turn off the gas.

Lennox says to shut off the gas, check for a gas-valve leak and replace the valve if necessary. Flame with no call for heat is a safety condition.

Lennox gas furnace code E250

Limit switch circuit open. If the limit does not close within 3 minutes, the unit goes into a 1-hour soft lockout. Normal operation resumes after the fault is cleared.

Turn the thermostat down, let the furnace cool, replace a dirty filter and open all registers.

Lennox says to check for the proper firing rate on the furnace, ensure there is no blockage in the heater, and check for proper airflow. Restricted airflow is the usual cause, so start with the filter and registers.

Lennox gas furnace code E252

Discharge air temperature too high, on gas heat only. It clears when the heat call is finished.

Replace a dirty filter and check that supply registers are open.

Lennox says to check temperature rise, airflow and input rate.

Lennox gas furnace code E270

Soft lockout: the maximum number of retries was exceeded and no flame current was sensed. It clears when a heat call finishes successfully.

Note whether the burners never light or light and go out.

Lennox says to check for proper gas flow, make sure the ignitor is lighting the burner, and check the flame sensor current.

Lennox gas furnace code E271

Soft lockout: the maximum number of retries was exceeded and the last retry failed because the pressure switch opened. It clears when a heat call finishes successfully.

Lennox says to check the pressure at which the low-pressure switch closes on a heat call, measure operating pressure, and inspect the vent and combustion air inducer for correct operation and restriction.

Lennox gas furnace code E273

Soft lockout: the maximum number of recycles was exceeded and the last recycle was due to flame failure. It clears when a heat call finishes successfully.

Note whether the burners light and then go out after a few seconds.

Lennox says to check the flame sensor's microamperes using the control diagnostics, clean or replace the sensor, and measure neutral-to-ground voltage to ensure a good unit ground.

Lennox gas furnace code E274

Soft lockout: the maximum number of recycles was exceeded and the last recycle failed because the limit circuit opened, or the limit stayed open longer than 3 minutes. This is a 1-hour soft lockout.

Turn the thermostat down, let the furnace cool, replace a dirty filter and open all registers.

Lennox says to shut down the system and check the firing rate, airflow and for blockage. It clears when a heat call finishes successfully.

Lennox gas furnace code E275

Soft lockout: flame was sensed out of sequence and the flame signal is gone. This is a 1-hour soft lockout that clears when flame has been proven stable.

If flame is visible with no heat call, turn off the gas.

Lennox says to shut off the gas and check for a gas-valve leak.

Lennox gas furnace code E276

Watchguard calibration failure: the control was unable to perform pressure-switch calibration. This is a 1-hour soft lockout that clears when calibration has finished successfully.

Lennox says to check the vent system and the pressure-switch wiring connections.

Lennox gas furnace code E290

Ignitor circuit fault: a failed ignitor or triggering circuitry. This is a 1-hour soft lockout that clears when flame has been proven stable.

Note whether the furnace clicks or hums but never lights.

Lennox says to measure the hot surface ignitor's resistance and replace it if it is open or not within specifications.

Lennox gas furnace code E291

Heat airflow is restricted below the minimum. This is a 1-hour soft lockout that clears when a heat call finishes successfully.

Replace a dirty filter and open every supply and return register.

Lennox says to check for a dirty filter and an airflow restriction, and to check blower performance.

Lennox gas furnace code E292

The indoor blower motor is unable to start because of an obstructed wheel or seized bearings. This is a 1-hour soft lockout that clears after the circulator successfully starts.

Confirm the furnace has power and listen for a humming motor that does not turn.

Lennox says to replace the motor or wheel if the assembly does not operate or meet performance standards. Opening the blower compartment is technician work.

Lennox gas furnace code E294

Combustion air inducer over current. It clears after inducer current is sensed to be in range at ignition following the soft lockout or a reset.

Listen for an unusually loud, grinding or struggling inducer at the start of a cycle.

Lennox says to check the combustion blower's bearings, wiring and amps, and replace it if it does not operate or does not meet performance standards.

Lennox gas furnace code E295

Indoor blower motor temperature is too high: the motor tripped on its internal protector. It clears after blower demand is satisfied.

Replace a dirty filter, open registers and let the motor cool.

Lennox says to check the motor bearings and amps and replace the motor if necessary.

Lennox gas furnace code E311

Heat rate reduced to match indoor blower airflow. This is a warning only: the furnace blower is in cutback mode because of restricted airflow, and the control reduces the firing rate every 60 seconds to match the available airflow. Two-stage controls reduce the firing rate to first stage.

Replace a dirty filter and open all registers.

Lennox says to check the filter and duct system and clear the warning by replacing the filter if needed or repairing or adding duct. It clears when the heat call finishes successfully.

Lennox gas furnace code E312

Restricted airflow in cooling or continuous-fan mode: the indoor blower is running at a reduced airflow below the setting. This is a warning only. The variable-speed motor has speed and torque limiters that protect it outside its design range of 0 to 0.8 inches of water column total external static pressure.

Replace a dirty filter and open all registers.

Lennox says to check the filter and duct system and clear the warning by replacing the filter if needed or repairing or adding duct. It clears after the current service demand is satisfied.

Lennox gas furnace code E370

The interlock switch sensed open for 2 minutes: the control has lost 24 volts AC for 2 minutes. It terminates all services and waits for the interlock switch to close.

Check that the blower door is fully seated so its interlock switch closes.

Lennox says the alarm clears when 24 volts AC is continuously sensed on the DS terminal for at least 10 seconds, or on a power reset.