If you have an iComfort thermostat, check the fault log before opening the furnace: Menu > Diagnostics > Fault Log. Timestamps on E223 tell you what you are dealing with. E223 appearing only at 4-8 AM in cold weather is a frozen condensate drain routed through an unconditioned space.
Look, E223 is basically your furnace saying it can't verify safe exhaust before it lights. Most of the time when I show up to one of these calls it's the condensate trap. Not the drain line itself, the trap. That little check valve inside gets gummed up and the whole system locks out. Ignore this and you're running space heaters until a tech comes out, and in February that's not a great situation.
Your furnace can't confirm safe exhaust flow before firing the burner, so it won't try. The board watches the pressure switch, and if it doesn't close within a few seconds of the inducer spinning up, the whole thing locks out. On the EL296V especially, I see this constantly on units past 7 years old. Usually a $20 fix, though if the pressure switch itself is dead you're looking at $35-55 in parts plus your time.
Most Likely Causes
Based on aggregated repair data, here is the probability breakdown for this error code:
Condensate trap clogged with algae or mineral deposits40%
Flue vent blocked reducing exhaust flow and draft12%
Inducer motor running slowly and not generating sufficient draft10%
Symptoms You May Notice
E223 sitting on the control board or iComfort display while the furnace just cycles the inducer over and over without ever lighting
You can hear the inducer motor spin up and then everything goes quiet, no igniter glow, no click from the gas valve, just silence and cold air
Condensate water dripping inside the cabinet or a small puddle forming under the trap housing
Furnace keeps restarting every few minutes but never actually heats, house just gets colder while you wait
Fault log on the iComfort S30 shows E223 firing consistently between 4-8 AM on the coldest nights of the week
Can you reset a Lennox furnace to clear the E223 code?
Flip the thermostat to off and wait a full 60 seconds, then switch it back to heat. You can also kill power at the furnace power switch on the side of the cabinet or flip the breaker. Either way, wait at least 60 seconds before restarting. Here's the thing though: if you haven't fixed whatever caused E223, it'll come right back the second the inducer tries to start. Don't reset and hope. Fix the trap, hose, or switch first.
Tools Required for Diagnosis
Phillips #2 screwdriverFlathead screwdriverMultimeter with continuity modeWet/dry shop vacuumFlashlight or headlampPipe cleaner or small bottle brushWhite vinegar (for trap flush)Bucket or old towel for condensate spill
Diagnostic Checklist
Follow these steps in order. We start with the easiest external fixes before opening up the machine.
Replacement Parts
If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.
Part Name
OEM Number
Estimated Price
Lennox Pressure Switch101290-01 · $25–$45
101290-01
$25 – $45
Condensate Trap Kit606096-01 · $15–$30
606096-01
$15 – $30
Frequently Asked Questions
What's the Lennox pressure switch part number for the SL280V and EL296V?
For most SL280V and EL296V units it's 101290-01, but honestly don't just order that without double-checking first. The exact trip pressure value changes with BTU rating and model suffix, so a 60k BTU unit might use a different switch than an 80k. Punch your full model and serial number into the Lennox parts lookup at lennox.com or call an authorized distributor. Putting in a switch with the wrong trip pressure setting means E223 again, possibly forever, and you won't know why.
How do I clean the condensate trap on a Lennox SL280V?
Pull the trap off, disconnect both tubes, and flush it with 50/50 white vinegar and water. A pipe cleaner or small bottle brush through each port gets the gunk out. The thing most people miss is the internal check valve, that little flap inside. It's got to move freely. If it's stiff or stuck, cleaning probably won't fully fix it and you need part 606096-01. Before you reinstall, pour a little clean water back into the trap to restore the water seal, because without that seal you're basically letting flue gas bypass the trap on every cycle.
Why does my Lennox furnace show E223 every fall but works fine after a few days?
Classic algae situation. The trap sits dry all summer, algae and mineral scale build up on the internal walls and check valve, and then the first time you fire up in fall it partially blocks and triggers E223. Once the furnace runs for a bit and condensate flushes through, it clears on its own. But it'll happen every single fall until you clean it. Just clean the trap every September before you need the heat and you'll stop seeing this code at the worst possible time, like a Sunday night in January.
Can low gas pressure cause E223 on a Lennox furnace?
Nope. E223 is strictly a draft-side fault in the induced draft circuit. Nothing to do with gas pressure. If it was gas pressure, you'd see a different code related to ignition failure or gas valve operation. E223 means the pressure switch didn't close, and that's always about airflow: condensate drain, sensing hose, pressure switch diaphragm, inducer motor speed, or the flue vent. Gas pressure lives upstream of all that stuff.
How do I know if the condensate trap needs replacement vs just cleaning?
Two things. First, look at the housing itself for cracks, especially around those barbed fitting ports where the tubes connect. A crack lets air leak into the sensing circuit and E223 keeps coming back even after you clean everything perfectly. Second, test the internal check valve by blowing through it in both directions. It should flow one way and block the other. If it's stuck open both ways or cemented completely shut, cleaning won't fix it. Replace with part 606096-01, about $18-25, and it actually takes less time than cleaning a really gunked-up trap anyway.
Is it safe to keep resetting E223 and running the furnace?
No. The pressure switch is there to confirm your furnace can safely exhaust combustion gases before the gas valve opens. When E223 fires, the furnace is correctly refusing to light. Some people bypass the switch or short the wires to force ignition, and that's genuinely dangerous. You could end up with a furnace running without confirmed exhaust flow, which is how carbon monoxide ends up inside a house. So E223 itself isn't a dangerous running condition, it's a lockout that's working correctly. The right move is diagnosing and fixing the actual cause, not jumping the switch.