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Models
Lennoxfurnace

SL280

Elite · two-stage · 80% · metal vent

Elite 80% two-stage (SL280UHV / EL280). Category I metal vent. VS SKUs may show the same SureLight 7-seg E2xx family as EL296V — if you see E223 it is still metal-vent draft, not a PVC trap. Flash SKUs use Merit-like 1–9 flashes. Identify the display and the vent before you cut anything.

Not EL296V (96% PVC collector and trap — same E223 number, opposite wet/dry checks). Not ML180 (Merit flash, single-stage; same 80% vent, different board and staging).

Diagnose this modelInstall notesBoard cross-refField wiring

AFUE

80% two-stage · Category I metal vent

Display

VS SKUs: SureLight 7-seg E2xx. Other SKUs: Merit-like 1–9 flash

Staging

Two-stage valve · two-speed inducer

Sister SKU

SL280UHV · EL280 / EL280UH

This board

SureLight 7-seg or Merit LED — read the door

  • First minute: 7-seg E-prefix or flashing LED? VS 80% SKUs speak E2xx. Flash SKUs speak 1–9 like ML180.
  • E223 / E225 / E229 on this plate are metal-vent draft. Do not prime a 96% trap that is not there.
  • 3-flash on a flash SKU is the same metal-vent story as ML180, with a second stage in play.
  • Confirm any odd extra code on THAT door card.

7-seg: E-menu last 10. Flash: write the count before you pull power.

Universal swap

Read the silk

Read the display. E2xx SureLight 107045 → OEM. Older 10M93/12L69 → ICM2813. Flash → Merit OEM.

Silk: 107045 · 10M9301 · 12L6901

White-Rodgers

  • 21D83M-843

    Same older SureLight / 50A62 / 50A66 kit when the WR sheet names that number.

ICM

  • ICM2813

    10M9301 / 12L6901 / 56L8401 / 69M08 / 83M00 only.

Honeywell

—
  • 50A55-843. EL296V 96% board. iComfort SLP99V.

After you pull the dead card

  1. 1Identify the display first. E223 on this plate is still metal-vent draft, not a PVC trap.
  2. 2Kill power. Photograph the silk-screen part number on the dead board before you pull it.
  3. 3Match staging (1 vs 2 vs modulating), igniter (carbide / nitride / spark), and motor (PSC / ECMx / 9-speed tap / serial VS).
  4. 4Set heat-off delay and any 80+/90+ jumper to the door card. Prove one full try and flame µA before you leave.

Field wiring

Written landings for Lennox SL280. Not a factory schematic.

Furnace · two-stage 24V
R / C / W1 / W2 / Y / GGas furnace

Two-stage conventional furnace. W1 low fire, W2 high fire. Outdoor staging is Y or Y1/Y2 — separate from the gas valve.

Written circuit description only — FieldBench does not redraw maker schematics. Example: R to W closes on a heat call; verify 24V at W1 before you change the IFC.

Open manufacturer PDF

Heat sequence

  1. 1Power. L1 / N → IFC → R120V / 24V
  2. 2Low. W1 → inducer LOW → LPS → HSI → valve LOWFirst fire
  3. 3High. W2 → inducer HIGH → HPS → valve HIGHSecond solenoid
  4. 4Flame. Rod → IFCµA DC both stages
  5. 5Blow. IFC → heat blowerAfter flame

This indoor

Elite 80% two-stage. Metal vent.

24V two-stage heat

Door has W1 and W2. Not Infinity. Not ComfortBridge.

Two-stage thermostat

A single-W stat never proves high fire. That is not a weak inducer.

  • R24V hot24V
  • CCommon24V
  • W1Low-fire heat24V
  • W2High-fire heat24V
  • Y / Y1Cool24V
  • Y2Outdoor high if the condenser is two-stage24V
  • GFan24V

Two-stage IFC

W2 is high fire. Do not tee the pressure-switch hoses because there are two stages.

  • RHot24V
  • CCommon to outdoor24V
  • W1Low fire24V
  • W2High fire24V
  • YCool out24V
  • GBlower / cool tap24V

Landing

  • 24VStat W1IFC W1

    Low fire

  • 24VStat W2IFC W2

    High fire. Missing W2 = stuck on low.

  • 24VStat YIFC Youtdoor Y

    Cool

  • 24VC throughout

    Common

IFC harness — two-stage heat

W1 then W2. Low-fire prove is not high-fire prove.

Transformer + fuse

Same 24V transformer as single-stage. Fuse still kills the whole strip.

  • L1 / N120VLine
  • XFMR24V to R24V
  • FUSEOn the IFC24V

24V safety chain

Door, limit, rollout. A limit trip is not an E9 / 32 pressure-switch story.

  • DOORInterlock24V
  • LIMITMain limit24V
  • ROLLOUTManual reset24V

Two-speed inducer + two pressure switches

W1 = inducer low + LPS. W2 = inducer high + HPS. Separate hoses. Do not tee.

  • IND LO120V low-speed inducerLine
  • IND HI120V high-speed inducerLine
  • LPSLow-fire prove24V
  • HPSHigh-fire prove24V
  • HOSESOne hose per switch. Never tee LPS and HPS24V

HSI + two-stage valve

Igniter 120V. Low solenoid on W1. Second solenoid on W2 after HPS closes.

  • HSI120V igniterLine
  • MV / LO24V low-fire solenoid24V
  • HV / HI24V high-fire solenoid24V
  • FLAMEµA DC on the rod24V

Blower — read the motor

PSC has a cap. 9-speed has F-taps. Serial VS has a harness and no cap. Do not mix those playbooks.

  • PSCCap + 3–5 speed leads24V
  • 9-SPDF01–F09 taps24V
  • VSFat serial plug, no cap24V

Landing

  • LineW1IFCinducer LOWLPS

    120V inducer, 24V prove

  • LineIFCHSIvalve LOW

    120V igniter, 24V low solenoid

  • 24VW2inducer HIGHHPSvalve HIGH

    Missing W2 = stuck on low

  • 24VFlame rodIFC

    µA DC

  • LineIFCheat blower

    After flame. Motor class on this plate.

Prove it

  • W1 then W2 at the IFC under a 2-heat call.
  • If it never stages, W2 is missing at the board — not a bad gas valve until that is proven.

Do not

  • Do not convert this to Infinity by landing W on a random terminal.
  • Do not apply AMVC / ARVT ComfortBridge menus or a memory card.

926T / 59TP6 / AR9T96 / GR9T96 / S9V2 / EL296E class. Same landing on 80% metal-vent cousins — the vent is not the wire.

Sequence

  1. 1

    W1

    Low inducer → low PS (E223 or 3-flash if metal-vent draft will not make) → HSI → low-fire valve → flame.

  2. 2

    W2

    High inducer → high PS (E225). Common-vent / chimney load shows up here first on cold days.

Faults on this IFC

Step 1, then 2, then 3. Expected reading and the fail branch sit under each check.

E223 / 3-flash

Low PS open / draft

lockout

Low-fire prove failed. On this 80% that is chimney, inducer, common vent — not a drowned 96% trap.

  1. 1 Prove inducer and the live code

    Do not pull power — that clears the Lennox SL280 active code. Write E223 / 3-flash. Is the inducer spinning on this call? Silent inducer is not a pressure switch. Metal vent, liner, common-vent sizing, inducer wheel, burner-box intake.

    Expect: 120 VAC at the inducer on a heat call. Wheel turning.

    If fail: 120 VAC missing → IFC / door switch / incoming power. Voltage + dead motor → inducer.

    If pass: Inducer running + this code → trap, hose, switch, vent (step 2).

  2. 2 Trap, collector, and the hose

    A drowned 96% trap will not make collector pressure. Pull the trap, flush it, confirm the collector box and inducer outlet are not full. Hose cracked, off the port, or full of water fakes an open switch. If the display is E223 you are on a SureLight VS SKU. Same number as EL296V, opposite vent physics.

    Expect: Trap flowing, hose dry and downhill, ports not swapped on a two-switch board.

  3. 3 Switch ohms, then vent load

    Ohm the pressure switch: NO, must close when that inducer speed is making the collector setpoint. If the switch is good, walk the PVC — bird screen, ice, long 2" run, wind, shared chase.

    Expect: LPS / HPS: Two-stage = two proves. High fire loads the chimney harder.

    If fail: Replace the open switch only after the vent and trap are proven.

    If pass: Switch closes on draft and the code stays → IFC input.

E225

High PS failed OPEN

lockout

High-fire prove failed. Chimney that passed on low will fail on high.

  1. 1 Prove the high-fire call

    Write the live Lennox SL280 code before you pull power. Confirm this IFC is actually commanded to high — W2 at the board, or the staging timer has expired. Inducer actually high? Common vent / wind / liner. High hose not teed to the low switch.

    Expect: R to W2 ~24 VAC (conventional) or a high-stage request on a communicating stat.

    If fail: No high request → thermostat / staging / menu. Not a high-fire pressure switch.

    If pass: Go to step 2. Do not jump the high-fire switch to ‘see if it runs.’

  2. 2 Prove the inducer actually went high

    Listen and amp the inducer on low vs high. No speed-up → IFC high output or inducer winding. Speed-up and this code still live → high-fire PS path (hose, switch, vent).

    Expect: LPS / HPS: Two-stage = two proves. High fire loads the chimney harder.

    If fail: Measure 120 VAC on the high-speed inducer lead during the high call. 0 V = IFC. Voltage + dead motor = inducer.

  3. 3 Isolate the HIGH hose and switch

    High-fire hose on the high tap only — a tee with the low switch is the common first-install miss on this dual-switch plate. Blow the hose, confirm it is dry and downhill to the collector. Ohm the high-fire switch: it is NO and must close only on high draft.

    Expect: LPS / HPS: Two-stage = two proves. High fire loads the chimney harder.

    If fail: Welded open, cracked hose, or water in the line. Replace the failed part — do not leave a jumper.

    If pass: Switch and hose good → step 4 (vent / condensate / IFC).

  4. 4 Vent, condensate, and the IFC input

    High fire needs more draft than a low-fire code ever saw. Check PVC size on this cabinet, shared chase, wind, ice, bird screen, and condensate backing into the collector only on high. If the switch closes on known draft and the code stays, the Lennox SL280 IFC input is the last call.

    Expect: Clear vent, dry collector, known-good switch, then IFC.

E229

Ignition on high fire

info

Low prove failed; IFC lit on high. OEM: fix low-fire draft, not a separate high-fire repair.

  1. 1 Prove the high-fire call

    Write the live Lennox SL280 code before you pull power. Confirm this IFC is actually commanded to high — W2 at the board, or the staging timer has expired. Same metal-vent path as E223. Do not start on the high-fire manifold screw.

    Expect: R to W2 ~24 VAC (conventional) or a high-stage request on a communicating stat.

    If fail: No high request → thermostat / staging / menu. Not a high-fire pressure switch.

    If pass: Go to step 2. Do not jump the high-fire switch to ‘see if it runs.’

  2. 2 Prove the inducer actually went high

    Listen and amp the inducer on low vs high. No speed-up → IFC high output or inducer winding. Speed-up and this code still live → high-fire PS path (hose, switch, vent).

    Expect: LPS / HPS: Two-stage = two proves. High fire loads the chimney harder.

    If fail: Measure 120 VAC on the high-speed inducer lead during the high call. 0 V = IFC. Voltage + dead motor = inducer.

  3. 3 Isolate the HIGH hose and switch

    High-fire hose on the high tap only — a tee with the low switch is the common first-install miss on this dual-switch plate. Blow the hose, confirm it is dry and downhill to the collector. Ohm the high-fire switch: it is NO and must close only on high draft.

    Expect: LPS / HPS: Two-stage = two proves. High fire loads the chimney harder.

    If fail: Welded open, cracked hose, or water in the line. Replace the failed part — do not leave a jumper.

    If pass: Switch and hose good → step 4 (vent / condensate / IFC).

  4. 4 Vent, condensate, and the IFC input

    High fire needs more draft than a low-fire code ever saw. Check PVC size on this cabinet, shared chase, wind, ice, bird screen, and condensate backing into the collector only on high. If the switch closes on known draft and the code stays, the Lennox SL280 IFC input is the last call.

    Expect: Clear vent, dry collector, known-good switch, then IFC.

E250 / 4-flash

Limit

warn

Airflow / overtemp. 5-flash on a flash SKU is still rollout.

  1. 1 Treat this as flame outside the exchanger

    Do not reset the Lennox SL280 rollout and walk away. Write the code, kill the call, and look for flame at the burners, crossover, and vestibule before you do anything else.

    Expect: No flame outside the exchanger. Burners seated. Crossover lit.

    If pass: Still inspect secondary / flue / condensate before you reset.

  2. 2 Secondary, condensate, and flue

    Blocked secondary, drowned collector, or a plugged flue pushes flame out the front. Pull the inducer/collector look, confirm the trap is flowing, and check PVC/vent. VS heat CFM or heat tap, filter, coil. Rollout: exchanger and metal flue.

    Expect: Dry collector, open flue, trap clear.

  3. 3 Reset only after the cause is fixed

    Manual-reset rollout. Recurring rollout on Lennox SL280 is a CO / fire call — cracked primary, misaligned burners, or a failed secondary. Confirm CO in the space before you leave.

    Expect: One clean cycle after the cause is fixed. No second reset as a repair.

E270 / 7-flash

Ignition lockout

lockout

Max retries, no flame current (7-seg) or ignition lockout (flash).

  1. 1 Measure µA while it is running

    Do not clean first and guess. Series-µA the rod on Lennox SL280 during a call. Falling µA is oxide, ground, or a dying flame. A hard drop is often the pressure switch or limit opening, not the rod. Watch a try. HSI, gas, rod. If E271 / 6-flash stores, draft died — go back to the vent.

    Expect: Typically ≥ 1.0 µA DC on this family — confirm the door card. Rising while running.

  2. 2 Rod, ground, then gas

    Clean the rod with a non-scratch pad — not sandpaper. Chassis ground to burner box and IFC (painted screw and missing star washer are classic). Then manifold on the stage that is dropping and confirm LP conversion leftovers.

    Expect: Manifold on the rating plate. Solid burner-box ground.

  3. 3 Prove it is not a switch opening

    Watch the live Lennox SL280 display when flame drops. A PS or limit code that appears at the drop means the rod was a victim. Inducer, hose, vent wind, or a limit on a wrong heat tap.

    Expect: µA stable and the live code stays a flame code — then rod/valve/IFC. Otherwise chase the new code.

E207 / E290

HSI / ignitor circuit

lockout

Ignitor open or trigger fault (7-seg SKUs).

  1. 1 Ohms at the igniter, then at the IFC

    On Lennox SL280 measure cold ohms at the igniter plug, then at the IFC connector. An open at the plug is the element or local harness. Open only at the IFC is the harness rub-through on the collector. Ohms and 120 VAC during trial.

    Expect: Nitride cold ohms per THIS door sticker — do not use an 80% Norton chart.

  2. 2 120 VAC during warm-up

    Call for heat and measure 120 VAC at the igniter during the warm-up window. 0 V + good ohms = IFC igniter relay. Voltage + no glow = cracked nitride.

    Expect: 120 VAC only during warm-up. Visible glow before the valve opens.

  3. 3 Do not keep cycling a cracked element

    A cracked nitride can ohm ‘good’ cold and open hot. If ohms and voltage are good and there is no glow, replace the igniter. Confirm polarity/ground (this plate’s polarity code) before you condemn a new igniter.

    Expect: One clean light after a known-good igniter and a proven ground.

Workflows

Identify 80% vs 96% before cutting a trap

E223 or 3-flash, first minute on an Elite / Merit Lennox.

  1. 1 Prove the call and the live code

    Plate: SL280 / EL280 / ML180 = 80% metal vent. EL296 / ML196 = 96% PVC.

    Expect: Write whatever SureLight 7-seg or Merit LED — read the door is showing. 7-seg: E-menu last 10. Flash: write the count before you pull power.

    If fail: No call at the IFC → stat / harness. Do not change gas parts.

  2. 2 Isolate the first failed step in the sequence

    E223 on metal vent is chimney / inducer / common vent. E223 on EL296V is trap / PVC / inducer port.

    Expect: W2: High inducer → high PS (E225). Common-vent / chimney load shows up here first on cold days.

  3. 3 Confirm with a number, then the next part

    3-flash on SL280 flash SKUs is the ML180 story, not the ML196 story. Do not install a condensing trap on an 80%. Do not chase a chimney liner on a 96%.

    Expect: Vent: Metal Category I. Draft at the hood / collector. · Display: E-prefix = SureLight VS SKU. Flashes = Merit-like SKU. Same 80% physics either way.

    If fail: Stay on this plate. The out-of-range reading is the part.

    If pass: Reading in range → the next step in this workflow is the repair.

Test points

Vent

Metal Category I. Draft at the hood / collector.

Display

E-prefix = SureLight VS SKU. Flashes = Merit-like SKU. Same 80% physics either way.

LPS / HPS

Two-stage = two proves. High fire loads the chimney harder.

Gotchas

  • EL296V techs see E223 and cut a trap. There is no 96% collector on this furnace.
  • ML180 is the single-stage Merit 80% with flashes only. This Elite can be 7-seg or flash — read the door.
  • EL280 is the same Elite 80% family under the older badge.

Related plates

Install this plate

Install SL280 as Elite 80% two-stage. Metal vent. E223 here is chimney — not EL296 PVC.

Cat I metal vent · two-stage · VS SKUs speak SureLight E2xx · SL280UHV / EL280 cousins

Vent vs display

  • Category I. Same E223 number as EL296V — opposite wet/dry checks.
  • Some SKUs are Merit-like 1–9 flash. Read THIS door card.

First fire

  1. 1Confirm Cat I. W1/W2. Spillage / CO fail = stop.

Do not on Lennox SL280

  • Do not apply EL296V trap / collector steps to E223 on this plate.

Maker literature

FieldBench does not host manufacturer files. Each link opens the maker’s own literature page in a new tab.

  • Lennox residential furnacesLiterature searchEL296V / ML196E / SLP99V / SL280V listing. Wiring and I/O: LennoxPros.Open manufacturer PDF

Warranty and bulletins

Affected models, serial range, symptom, remedy, date. Maker files open on the manufacturer site.

All bulletins

  • Residential limited warranty

    warranty sheet

    Lennox furnace warranty

    Registered EL / ML / SL / SLP furnace warranty · Dealer claims portal

    Open factsOpen manufacturer PDF

  • Dealer portals

    dealer

    Where remaining service letters live

    Current-year service letters not on a public literature page · Maker dealer portal

    Open factsOpen manufacturer PDF