Lennox E227 Error Code

What does Lennox E227 mean?

E227 means the low-pressure switch opened during the trial for ignition or during the run period when it should have remained closed. Unlike E223 (switch never closed), E227 indicates the switch closed initially but then dropped open — signaling a draft interruption mid-cycle. Common causes include a partially blocked vent that allows the inducer to make initial draft but loses it as the heat exchanger warms and thermal resistance increases.

Symptoms

• Furnace lights briefly or begins the ignition trial, then shuts down mid-cycle.
• E227 alert displayed; inducer may cycle off and on repeatedly.
• Alert occurs more frequently in cold weather when condensate freezing can partially block vent terminations.
• Condensate trap shows water backing up into the inducer housing.

Common causes

• Partially blocked vent pipe where initial draft is sufficient but drops during the heating cycle.
• Frozen vent termination reducing exhaust flow after several minutes of operation.
• Clogged or slow-draining condensate trap backing water into the inducer housing during run.
• Inducer motor losing speed during run due to a failing motor capacitor.
• Kinked pressure switch hose that collapses under positive pressure during operation.

Ask the AskWhiz AI about Lennox E227

AskWhiz

online

Hi — I'm the HVAC demo. Ask me anything in this domain.

What causes Lennox E227?Step-by-step fix for Lennox E227?Is Lennox E227 safe to ignore?

MessageHelp me troubleshoot Lennox E227

Diagnostic steps

1. Check vent termination for ice or debris

   Inspect the PVC exhaust and intake terminations outside the building for ice buildup, debris, or animal intrusion. Clear any blockage and verify termination clearances per the IOM.

2. Clear the condensate trap

   Remove and flush the condensate trap. Verify the drain flows freely so water does not back up into the inducer housing during a heating cycle.

3. Check the pressure switch hose during operation

   With the furnace running, gently feel the pressure switch hose for collapse or kinking under draft pressure. Replace any hose that deforms during operation.

4. Measure inducer draft during the heating cycle

   Connect a manometer to the inducer housing tap and monitor draft pressure throughout the heating cycle — not just at startup. A draft that starts adequate then falls indicates a thermal restriction or weakening motor.

5. Test the inducer motor capacitor

   Check the run capacitor on the inducer motor with a capacitance meter. A weak capacitor causes the motor to run below rated speed once heat buildup raises motor winding temperature. Replace if out of spec.

When to call a professional

Intermittent E227 that occurs only during extended heating cycles often points to a failing inducer motor or capacitor that only manifests under thermal load. A licensed technician can measure motor RPM and current draw under load, assess heat exchanger restriction through combustion analysis, and confirm whether inducer motor replacement is required.