Quick answer
Lennox furnace error code E223 means the low pressure switch failed open: the switch that proves draft through the vent did not close. The furnace will not fire, and it resumes normal operation once the fault clears. Clear snow and ice from the intake and exhaust terminations, check that the condensate drain is not frozen, and never bypass the switch. Call if E223 persists.
Lennox furnace error code E223 is a draft-proving fault: the low pressure switch failed open. The control started the combustion air inducer, waited for the switch that confirms air is moving through the vent, and the switch never closed. Lennox lists it that way in the ignition control diagnostic code table for the EL296DFV. Other Lennox models can number things differently, so the code legend on the label inside your furnace panel takes priority.
Is it safe to keep running a furnace that shows E223?
Yes, in the sense that the furnace protects itself: it will not fire with the low pressure switch open, and it resumes normal operation on its own once the fault clears. The risk comes from one specific shortcut, which is bypassing the switch with a jumper. That switch is the part confirming exhaust is leaving the house, so a bypassed furnace can burn gas into a blocked vent. Do not do it, and do not let anyone else do it as a temporary fix.
Clear the intake and exhaust, then check the drain for ice
The one useful homeowner step is outdoors. A high-efficiency Lennox like the EL296 vents through plastic pipes that usually leave through a side wall, and a drift or a cap of ice at either pipe is enough to hold the switch open.
- Find the two plastic pipes where they leave the house, normally through a side wall and sometimes through the roof.
- Clear snow an arm's length back from both, and break ice off the pipe ends by hand. Do not chip inside the pipe with a tool.
- Look into each opening for frost, leaves or a nest sitting behind the screen.
- Follow the condensate drain from the furnace to the floor drain or pump. Where the tube crosses a cold garage, crawlspace or exterior wall, feel for a frozen section.
- Leave the furnace powered. If the blockage was the cause, it restarts by itself.
Step-by-step versions of both checks are in what to do when a furnace vent is blocked by snow and what to do if the condensate line is frozen.
In the 2000s-and-newer subdivisions of Milton, north Oakville and Brampton, furnace terminations can sit low on a side wall in the narrow gap between two houses, where snow drifts against the wall. After a heavy overnight snowfall, that is the first place to look.
What causes E223, most likely first
- A restricted vent or combustion-air pipe: snow, ice, a nest, or a section that has sagged and filled with water.
- A blocked condensate trap or drain. Water backs up inside the furnace and the switch cannot sense the inducer's draft.
- A weak combustion air inducer that spins but no longer moves enough air to close the switch.
- A cracked or wet pressure-switch hose. The small tube between the switch and the furnace splits with age or holds a slug of condensate.
- A failed switch. It is last on the list for a reason: the switch is usually reporting a real draft problem.
What a technician measures on an E223 call
A technician does not guess between those five. A manometer is teed into the switch hose, and the draft the inducer produces is compared with the switch's closing pressure, a figure given in inches of water column. If the draft is there and the switch stays open, the switch is replaced; if the draft is short, the vent, the drain and the inducer are inspected in turn.
E223 means the switch never closed at all. A switch that closes and then drops out is a different code, E227, with a different set of likely causes.
- Diagnostic visit: $90–$150, credited to the repair if you proceed
- Condensate drain cleaning or trap replacement: $150–$350
- Pressure switch: $250–$500
- Draft inducer motor: $400–$900
If E223 is still on the display after the pipes and drain are clear, the fault is inside the furnace and it is time for furnace repair. ZK Mechanical services Lennox furnaces across Burlington, Oakville, Milton, Hamilton and Mississauga, with TSSA-licensed technicians and a written price before work begins. Tell us the code and what you found outside, and see the Lennox furnace error code guide for the neighbouring codes.