Lennox Furnace E223 Error Code: Pressure Switch Circuit Fault

Quick Answer

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. E223 appearing at any time of day is an active blockage or switch failure. On the SL280V and EL296V, the condensate trap is a cylindrical housing with an internal check valve, and that check valve is the Lennox-specific failure point: as the diaphragm ages, the valve stays partially open and the trap loses its water seal. Clearing the drain does not fix a failed check valve. If the drain line is clear but E223 persists, replace the full trap assembly with Lennox part 606096-01 ($15-30) before condemning the pressure switch 101290-01.

LennoxFurnaceSeverity: highDifficulty: intermediate84% DIY Success

Time to Fix

20–90 min

Difficulty

intermediate

Parts Cost

$15 – $45

Tools Needed

Multimeter (continuity mode), Wet/dry vacuum

Wrong code?

Not seeing E223 on your display?

Select what your appliance is actually doing and we'll take you to the right guide.

all lennox furnace error codes

HUB

inducer motor failure or stall

E228

fault code reset procedure

RESET

What Does the E223 Code Mean?

Pressure switch not detecting draft on SL280V or EL296V. Check iComfort fault log timestamps first, then inspect the cylindrical condensate trap check valve, then test the pressure switch 101290-01.

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%

Pressure sensing hose disconnected or kinked24%

Pressure switch diaphragm failed (part 101290-01)14%

Flue vent blocked reducing exhaust flow and draft12%

Inducer motor running slowly and not generating sufficient draft10%

Symptoms You May Notice

E223 displayed on Lennox SL280V or EL296V control board
Furnace inducer starts but shuts down before gas valve opens
Condensate water dripping inside cabinet or standing in trap
Furnace restarts repeatedly without reaching ignition
No flame during heating cycle despite inducer running

Can you reset a Lennox furnace to clear the E223 code?

After fixing the root cause of E223, set the thermostat to OFF for 30 seconds then back to HEAT. The code clears automatically when the furnace completes a full startup with the pressure switch confirmed closed. If E223 persists, cycle the circuit breaker off for 30 seconds. Do not attempt more than two consecutive resets without additional diagnosis.

Tools Required for Diagnosis

Multimeter (continuity mode)Wet/dry vacuumFlashlightFlathead screwdriverSmall brush or pipe cleaner for trap cleaning

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

If you have a Lennox iComfort or iComfort S30 thermostat

If you have a Lennox iComfort or iComfort S30 thermostat, navigate to Menu > Diagnostics > Fault Log before opening the furnace cabinet. Note the timestamps on E223 entries: faults clustered between 4-8 AM in cold weather indicate a frozen condensate drain in an unconditioned space (add insulation or heat tape to the drain line). Faults with no time pattern mean an active trap or switch failure - proceed below. No iComfort? Skip directly to Step 2.

Trace the small rubber sensing hose from the inducer motor

With power off

With the furnace powered and inducer running (during startup)

Check the exterior flue vent

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

Verify part fitment for your Lennox model

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs

Labor Approach

Our Verdict

REPAIR

Estimated Cost: $30 (Parts) vs $3400 (New Machine)

Frequently Asked Questions

What is the Lennox pressure switch part number for the SL280V and EL296V?

The primary pressure switch part number for most Lennox SL280V and EL296V furnaces is 101290-01. However, the exact part varies by model suffix and BTU rating. Some BTU variants use a different trip pressure value and require a different part number. Always verify the correct part by entering your full model and serial number at lennox.com or at an authorized Lennox parts distributor.

How do I clean the condensate trap on a Lennox SL280V furnace?

Locate the rectangular condensate trap housing on the lower side of the furnace cabinet. Disconnect the inlet and outlet tubing. Remove the trap and flush it with a 50/50 mixture of white vinegar and water to dissolve algae and mineral deposits. Use a small brush or pipe cleaner to clean the internal passages. Refill the trap with clean water before reinstalling to maintain the water seal that prevents flue gases from backflowing through the trap.

Why does my Lennox furnace show E223 every fall but works fine once the season starts?

Algae and mineral scale build up in the condensate trap during summer when the furnace is idle. The first heavy run of the heating season produces enough condensate to back up at the partially blocked trap, triggering E223. This is a seasonal maintenance issue rather than a part failure. Clean the condensate trap each fall before the heating season to prevent the recurring first-startup E223.

Can low gas pressure cause E223 on a Lennox furnace?

No. E223 is specifically a pressure switch circuit fault in the induced draft circuit. It is not related to gas pressure. Gas pressure issues on Lennox furnaces produce different fault codes related to ignition or gas valve operation. E223 is always a draft-side issue: condensate drain, sensing hose, pressure switch, inducer motor, or flue vent.

How do I know if the Lennox SL280V condensate trap needs replacement versus just cleaning?

The condensate trap housing should be inspected for cracks, especially around the barbed fitting ports where the tubing connects. A cracked housing will allow air leakage that creates a false negative pressure signal and persistent E223 even with a clear drain. Also inspect the internal check valve: it should move freely and not be stuck open or cemented shut with mineral deposits. If the trap cannot be restored to full function by cleaning, replacement with part 606096-01 is the correct fix.

Related Lennox Furnace Error Codes

Code: HUBLennox Furnace Error Codes: Complete SL280V and EL296V Fault Reference Code: E228Lennox Furnace E228 Error Code: Inducer Motor Fault Code: RESETHow to Reset a Lennox Furnace

Models Known to Experience E223 Errors

This repair applies to most Lennox furnaces with this error code. Common model numbers include:

SL280V, EL296V, XC21, SL297NV, EL180UH

Last verified for technical accuracy on March 14, 2026