Lennox EL296UHV Error Code E 225: High Pressure Switch Failed Open

What Does Code E 225 Mean?

Error code E225 on the Lennox EL296UHV means the high pressure switch failed to close during a call for heat. Because the EL296UHV is a two-stage furnace, the combustion-air inducer changes speed between firing rates, and a separate high pressure switch proves that draft is adequate at the higher inducer speed used for high fire. When the inducer spins up to the high-fire rate but the high switch never senses enough negative pressure to close, the SureLight control posts E225.

The high pressure switch is set to a stronger draft threshold than the low switch because high-fire combustion moves more air and needs more venting capacity. That makes E225 sensitive to even a partial restriction: a small amount of ice at the vent termination, debris in a screen, a sagging pipe, or an inducer that has lost some speed can leave draft high enough for low fire but short of the high-fire threshold.

E225 is the high-fire counterpart to E223 (the LOW pressure switch failing to close) and the opposite condition to E226, where the high pressure switch is stuck CLOSED when it should be open. Because the low switch may still close, the furnace can sometimes run on low fire while failing to reach full output. Repeated pressure-switch failures can escalate the board into soft-lockout codes such as E271. The furnace resumes normal operation once the fault is cleared.

What You'll Notice

• The furnace runs but only ever puts out low heat and never steps up to full output
• The seven-segment display shows E225
• The home struggles to reach the thermostat setpoint on the coldest days
• Failures are more likely in freezing or windy weather when the vent can partly restrict
• Longer, less effective heating cycles than the furnace used to run

How This Is Diagnosed

A technician drives the inducer to its high-fire speed and measures the draft (in inches of water column) with a manometer, comparing it against the high pressure switch's rated closing pressure. If the draft reaches spec but the switch will not close, the switch or its wiring is suspect; if the draft falls short at high speed, the problem is a restriction or a weakening inducer.

They inspect the full vent and intake path for partial blockages that only matter at the higher airflow — outdoor terminations, screens, sagging or undersized pipe, and condensate traps — and check the high-switch hose for cracks, moisture, or a loose port. A noisy or slow inducer wheel confirmed by low high-speed draft points to the inducer. This is diagnostic information only; the corrective work is on the sealed venting and combustion system and is not a homeowner task.

When to Call a Professional

This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:

• The furnace runs on low heat but never steps up, and the display shows E225
• The home cannot reach setpoint on the coldest days
• The outdoor vent terminations look clear but E225 keeps returning
• E225 appears alongside E226 (high pressure switch stuck closed) or E271 soft lockout
• The inducer sounds weak or changes pitch when the furnace tries to reach high fire

✓ Verified against manufacturer service manual — March 2026