Lennox EL296UHV Error Code E 225: High Pressure Switch Failed Open
What Does Code E 225 Mean?
Error code E225 on the Lennox EL296UHV indicates that the high pressure switch failed to close during a call for heat. The high pressure switch requires a stronger draft than the low pressure switch because it must confirm safe venting conditions for high-fire operation.
When the combustion air inducer motor runs, it creates a vacuum in the vent system. The high pressure switch monitors this vacuum and closes only when draft is strong enough for safe high-fire combustion. If the switch does not close, the furnace may still be able to light on low fire if the low pressure switch closes, but it will not reach full heating output.
The most common cause is a partial blockage in the exhaust vent or combustion air intake — even a small restriction like ice buildup, debris in the vent termination, or a partially blocked screen can prevent the higher draft threshold from being reached. A failing inducer motor losing speed, cracked pressure switch hoses, or a faulty pressure switch itself are also possible causes.
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace is not heating or only operating on low fire
- You have checked the outdoor vent terminations and found no obvious blockages
- E225 appears alongside E271 or E272 pressure switch lockout codes
- The inducer motor sounds weaker or louder than normal
✓ Verified against manufacturer service manual — March 2026