Lennox Furnace Troubleshooting Guide & How to Guide

Furnaces, just like any other household appliances, are prone to problems in the course of offering their services. Fortunately, most of these can be avoided with proper care and maintenance. If you are experiencing some challenges with your Lennox furnace-like failure to start or the heat produced is insufficient, a bit of troubleshooting may be what you need to get it back on track. To help you address some of the issues with the Lennox furnace, here is troubleshooting and how-to guide to some of the commonly reported problems.

How to Troubleshoot a Lennox Furnace

• Check furnace filters and clean them. Dirt and dust accumulating over time can clog the filter and impede airflow. If your unit uses disposable filters, they may need a replacement.
• Check the thermostat and make sure it’s set to “heat” and try setting the temperature 5 degrees higher than the current room temperature.
• Check furnace switch and electrical panel for power and if they are turned off.
• Check gas burners for dirt or clogging due to carbon deposits and clean them carefully.
• Properly secure the front panel by following the instructions manual.
• Ensure all the vents are open and unblocked. Make sure there are no furniture, rugs, or anything else restricting airflow.
• Check the pilot light. If it’s out, you may try re-lighting it. If it doesn’t light, try cleaning the pilot light housing.

How Do You Reset a Lennox Furnace?

• Start by finding your electrical panel and switch off the circuit breaker (labeled “Furnace” or “Heating System” to avoid any risk of electrical injuries.
• Then locate your furnace control panel, lift it up and away from the appliance and set this aside for now. The control panel could be located on the top panel on upflow furnaces or the bottom panel on downflow models.
• Look for a raised button or switch to the right of your furnace ignition control box (or “Limit Control” switch).
• Press and release the limit control switch to reset your Lennox furnace.
• Follow these instructions in reverse to replace the control access panel.
• Flip the furnace switch “ON”.

What Would Cause a Lennox Furnace not to Kick On?

If your Lennox furnace unit fails to operate, it could be because of any or a number of the following reasons:

• Access panels are not securely in place.
• The thermostat is not calling for heat.
• Closed main disconnect switch.
• Dirty or plugged filter. These will cause the limit control to shut off the unit.
• Blown out fuse or tripped circuit breaker.
• Gas is not turned on at the meter.
• Closed manual main shut off valve and/or internal manual shut off valve.
• Ignition system is in lock out.
• Tripped flame roll-out switches.
• Closed pressure switch.

How Do I Reset My Furnace Heater?

• Start by checking to see if your pilot light is out.
• Then turn down your thermostat to the lowest setting possible.
• Turn the power to your furnace off.
• Also turn off the main gas supply to the furnace but leave the pilot gas supply line on.
• Light a match and hold it close to the opening of the pilot flame jet, which is located inside the furnace. This should re-light the pilot flame.
• Turn back on the power, then the main gas supply.
• Raise your thermostat to the desired temperature. Your furnace should ignite.

Lennox Furnace Troubleshooting Codes

Lennox furnaces have different error codes, each with a meaning. The common ones;

1. Error code 270

• It means your furnace ignitor can’t activate the flame.

Required actions to clear and recover;

• Check for gas flow, igniting lighting burner, flame sensor current.

2. Error code 225

• High pressure switch is not closing.

Required actions to clear and recover;

• Check inches of water column pressure of high pressure switch on heat call.
• Measure inches of water column of operating pressure.
• Inspect combustion air inducer and vent for correct restriction and operation.

3. Error code e228

• The furnace control is not able to calibrate the pressure switch.

Required actions to clear and recover;

• Retry after 5 minutes.
• Error counter cleared when exiting lockout.
• Check vent system and pressure switch wiring connections.

4. Error code 276

• Soft lockout- Exceeded maximum number of calibration retries.

Required actions to clear and recover;

• Retry after 5 minutes.
• Error counter cleared when exiting lockout.
• Check vent system and pressure switch wiring connections.

5. Error code 291

• Restricted airflow- Cubic feet per minute is lower than what is needed for minimum firing rate.

Require actions to clear and recover;

• Check for dirty filter.
• Check unit air flow restriction.
• Check for blower performance.

6. Error code 274

• Soft lockout- Exceeded maximum number of cycles.
• Last recycle failed due to the limit control opening or limit remained open for more than 3 minutes.

Require actions to clear and recover;

• Check why limit is tripping.
• Check why it overfired.
• Check why low air flow.

7. Error code 271

• Soft lockout- Exceeded maximum number of retries.
• Last retry failed due to the pressure switch opening.

Required actions to clear and recover;

• Check inches of water column pressure during operation of low pressure switch on heat call.
• Measure operating pressure water column.
• Check vent and combustion air inducer for correct operation and restriction.

8. Error code 290

• Ignitor circuit fault- Failed ignitor or triggering circuitry.

Required actions to clear and recover;

• Measure hot surface ignitor resistance.
• Replace if open or not within specification.

9. Error code 228

• Unable to perform successful pressure switch calibration.

Required actions to clear and recover;

• Retry after 5 minutes.
• Error counter cleared when exiting lockout.
• Check vent system and pressure switch wiring connections.

This guide seeks to provide some assistance to users with Lennox furnace units. For any other issues that we may not have been addressed here, try referring to the instructions manual or contacting the manufacturer.