Lennox EL296UHV Error Code Ignition on High Fire - Information Only: Ignition on High Fire - Information Only

What Does Code Ignition on High Fire - Information Only Mean?

Error code E229 on the Lennox IFC control board indicates that the furnace ignition sequence has been switched to high fire because the control board detected abnormal conditions during the normal low-fire startup. On two-stage and modulating Lennox furnaces, the system typically starts at low fire and ramps up as needed. When the board detects that the inducer or pressure switch readings are outside expected parameters for low-fire operation, it may switch to high fire to attempt successful ignition.

This code often appears alongside or shortly before pressure switch codes (E223, E225, E227). The board is essentially trying to compensate for a venting issue by running the inducer harder. While this may allow the furnace to light, it indicates that something is interfering with normal low-fire venting — a partial blockage in the exhaust or intake, a condensate drain restriction, or pressure switch hose issues.

E229 is not a lockout by itself, but it signals an underlying problem that should be investigated. If the furnace continues operating only at high fire due to venting issues, it may eventually encounter a hard failure and lock out with a more severe code. The vent system should be checked and cleared to allow normal multi-stage operation.

How to Fix It: Check Exhaust Vent and Combustion Air Intake

What You'll Need

• Flashlight
• Step ladder (if vent terminations are above ground level)
• Mirror or phone camera (to look inside vent pipes)

Steps

1. Turn off power AND shut off gas supply Switch the furnace power off at the disconnect switch near the unit AND at the circuit breaker. Locate the gas shutoff valve on the gas line leading to the furnace and turn it to the OFF position (perpendicular to the pipe). If you smell gas at any point, leave the area immediately and call your gas company from outside.
2. Inspect the exhaust vent and intake pipe terminations Find where the exhaust vent and combustion air intake pipes exit your home. Check both openings for partial blockages — nests, ice/snow buildup, leaves, debris, or clogged screens. Even a partial blockage that allows some airflow can trigger E229, since the furnace can still run at high fire but not at low fire. Remove any obstructions.
3. Check the vent pipe runs Trace the vent pipes from the furnace to the exterior. Look for partially disconnected joints, sagging sections, or areas of buildup. A partial restriction anywhere in the vent run can prevent normal low-fire operation while still allowing high fire.
4. Check the condensate drain (high-efficiency models) On high-efficiency Lennox furnaces (90%+ AFUE), inspect the condensate drain and trap. A slow-draining trap can cause intermittent vacuum issues that affect low-fire operation. Ensure the drain flows freely.
5. Check the pressure switch hose(s) Inside the furnace, inspect the rubber hose(s) connecting the inducer to the pressure switch(es). Look for cracks, kinks, water accumulation, or loose connections. On two-stage models, check both the low-fire and high-fire pressure switch hoses.
6. Restore power and test Replace the access panel. Turn the gas supply back on (valve handle parallel to the pipe). Restore power at the disconnect switch and breaker. Set your thermostat to call for heat and observe the startup sequence. On a properly functioning system, the furnace should start at low fire.

When to Call a Professional

Contact a licensed HVAC technician if:

• The vents are clear but the furnace still switches to high fire for ignition
• E229 appears alongside E223, E225, or E228
• The inducer motor sounds louder than normal or runs at inconsistent speeds
• The furnace only operates at high fire and never runs at low fire
• You notice a gas smell at any point during the process