Lennox E224

What does Lennox E224 mean?

E224 means the low-pressure switch is stuck in the closed position when it should be open. During pre-ignition, the IFC checks that the low-pressure switch is open before starting the inducer — a switch that is already closed (for more than 150 seconds during a heat call) indicates a stuck contact or a pressure switch hose that is blocked with water, holding residual pressure against the diaphragm. The board logs E224 and aborts ignition.

Symptoms

• Furnace fails to start the inducer — heat call initiated but sequence stops immediately.
• E224 alert on the thermostat or control board at the start of a heating cycle.
• Low-pressure switch contact reads closed with an ohmmeter when inducer is off.
• Alert clears temporarily after the system dries out or is power cycled.

Common causes

• Pressure switch diaphragm stuck closed due to condensate water held in the pressure switch hose.
• Failed low-pressure switch with a welded or stuck closed contact.
• Pressure switch hose partially blocked by water, maintaining pressure on the diaphragm after the inducer stops.
• Inducer housing pressure tap plugged with condensate residue causing residual pressure.

Diagnostic steps

1. 01

   Check low-pressure switch contact state with inducer off

   Power down the furnace. Disconnect the pressure switch leads and measure continuity — a healthy switch should read open (no continuity) when no pressure is applied and the inducer is off.

2. 02

   Inspect and drain the pressure switch hose

   Remove the hose from the pressure switch port. Drain any trapped condensate. Blow through the hose to verify it is clear. Reinstall and test whether the switch now reads open.

3. 03

   Clear the inducer housing pressure tap

   Remove the hose at the inducer housing tap and probe the port with a small wire or compressed air to clear any condensate deposits blocking the tap.

4. 04

   Replace the low-pressure switch if contact remains closed

   If the switch contact still reads closed after clearing the hose and tap, the diaphragm or contact is mechanically failed. Install the Lennox-specified replacement switch.

5. 05

   Restore power and verify alert clears

   Power up the furnace, initiate a heat call, and confirm the inducer starts normally and E224 does not reappear. Run three consecutive heat cycles to verify resolution.

When to call a professional

Recurring E224 on a furnace with a recently replaced pressure switch points to an underlying drainage or condensate management issue. A technician can measure static pressure at the inducer housing to confirm the tap is clear, evaluate condensate trap design, and identify why water is consistently reaching the pressure switch — conditions that, if left unaddressed, will repeatedly fail new switches.