Lennox EL296UHV Error Code E 224: Low Pressure Switch Failed Closed
What Does Code E 224 Mean?
Error code E224 on the Lennox EL296UHV means the low pressure switch failed closed. At rest the SureLight control expects the low pressure switch to be OPEN, and it should close only after the combustion-air inducer builds draft. With E224 the switch is already closed when it should be open and stays that way beyond the control's timing window — longer than roughly 150 seconds on a heat call — so the board treats it as stuck.
Because the EL296UHV is a two-stage furnace, the low pressure switch is the one that proves adequate draft at the low firing rate. The control relies on seeing that switch make a clean open-then-close transition to trust that it is genuinely sensing draft. A switch that never opens cannot prove venting, so instead of trusting it the control reports the fault. In effect, a switch stuck closed defeats the very safety check it exists to perform.
Common causes are a mechanically stuck or failed switch, condensate holding pressure on the diaphragm, or a wiring short across the switch terminals. E224 is the mirror image of E223, where this same low pressure switch fails to CLOSE on demand. E224 is rated lower severity than E223 because the fault usually lies in the switch itself rather than a blocked flue, but it still needs a technician because it disables a safety interlock.
What You'll Notice
- The furnace will not begin a normal heating cycle, and the display shows E224
- The seven-segment display shows E224 after a call for heat
- Heating is intermittent, working on some cycles and faulting on others
- A noticeable pause at the start of a cycle before the furnace faults
- The code recurs even though the outdoor vent terminations are clearly open
How This Is Diagnosed
A technician checks the state of the low pressure switch with the inducer off, expecting it to read open at rest. If the contacts are closed with no draft present, the switch is the prime suspect. They inspect the pressure-switch hose for trapped condensate or a pinch that could hold pressure on the diaphragm, and check the wiring for a short across the switch terminals that would make the board read a permanently closed switch.
With a manometer they confirm the actual draft (in inches of water column) during a cycle so a genuinely faulty switch can be told apart from a system that is holding residual pressure. Because the switch is a sealed safety device, its replacement and any tubing correction are technician tasks rather than homeowner repairs.
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 display shows E224 and the furnace will not run a normal cycle
- Heating is intermittent and the code comes and goes
- The outdoor vent terminations are open but the switch still reads closed at rest
- The pressure-switch hose shows condensate, kinks, or a loose connection
- The code returns after the furnace has run normally for a while
Frequently Asked Questions
How is E224 different from E223?
They are opposite failures of the same low pressure switch. E223 means the switch would not close when the inducer ran; E224 means the switch is stuck closed when it should be open at rest. Both leave the switch unable to prove draft.
Why is E224 marked lower severity if it still stops the furnace?
The usual cause is the switch or its tubing rather than a blocked flue, so it points to a component fault instead of an active venting hazard. It still needs a technician because a stuck-closed switch defeats a safety interlock.
Can I clear E224 by resetting the furnace?
A stuck switch keeps re-tripping the fault until the switch or tubing is corrected. The control resumes normal operation only after the underlying condition is resolved, which a technician should handle.
✓ Verified against manufacturer service manual — March 2026