Lennox Furnace Error Code E225

E225 indicates the low pressure switch was detected in the open position during the trial for ignition or during run mode. This switch monitors the negative pressure created by the inducer motor to confirm proper draft through the furnace and venting system. When the switch does not close as expected, the furnace locks out to prevent unsafe operation. The root cause is typically a venting restriction, an inducer issue, or a faulty pressure switch.

No. The E225 fault code exists specifically because the furnace could not confirm adequate airflow through the heat exchanger and venting system. Running the furnace in this condition risks incomplete combustion or improper venting of combustion gases. Leave the furnace off until the fault is diagnosed and repaired.

Resetting the furnace may allow it to attempt another ignition cycle, but the E225 fault will return if the underlying cause has not been corrected. The pressure switch must close during every heat call, so any condition preventing that from happening will trigger the error again. Repeated reset attempts without fixing the root cause will not resolve the problem and may indicate additional wear on the inducer or ignition components.

Some of the underlying causes can be addressed by a knowledgeable homeowner, such as clearing a visible blockage at the vent termination or replacing a cracked pressure switch hose. However, diagnosing the fault accurately requires a manometer to measure inches of water column pressure at the switch port and a working understanding of the inducer and venting system. If the inducer motor or pressure switch needs replacement, most homeowners will want to hire a licensed HVAC technician to complete the repair safely.

Repair costs vary depending on the cause. Clearing a vent obstruction or replacing a pressure switch hose is typically a low-cost fix, often in the range of $75 to $200 for a service call and minor parts. Replacing a failed pressure switch generally runs $150 to $350 including labor. Inducer motor replacement is more involved and typically costs $400 to $900 or more depending on the specific model and local labor rates.