The short answer
On a Lennox furnace in Northern Virginia, E229 is a note, not a problem: the furnace lit on high fire because the low-fire pressure switch didn’t close in time, and Lennox says no action is needed. E228 means the inducer couldn’t calibrate the pressure switch; Lennox says to check the vent and the switch wiring. E227 means the low pressure switch opened while the furnace was lighting or running. Repeat E227 or E228 codes point at the vent, the condensate drain or the inducer.
If you smell gas, skip all of it. Leave the house and call the gas company and 911 from outside. If a carbon monoxide alarm is going off, get everyone out first (what to do when the CO alarm sounds).
The three codes side by side
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| Code | What Lennox says | What it usually is |
|---|---|---|
| E227 | Low pressure switch open during trial for ignition or run mode | The vent or drain choked partway through a cycle |
| E228 | Combustion air inducer calibration failure. Unable to calibrate pressure switch; check vent and switch wiring. | A blocked vent, water in the switch tubing, or a wiring problem |
| E229 | Ignition on high fire. No action is needed. | Informational. Worth a look only if it shows on every start. |
| E276 | Watchguard calibration failure | Calibration kept failing. A one-hour soft lockout. |
These codes live on the Lennox furnaces with the small number display, like the SL280, EL296 and SLP99. For E223, E224 and E271, see Lennox pressure switch codes.
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We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
What the pressure switch is doing
Before the gas opens, the small inducer fan pulls air through the burners and out the vent. The pressure switch is a small round switch with a rubber hose on it. It closes only when the inducer is pulling hard enough, which proves the exhaust has a clear way out. A two-stage furnace has two: one for low fire, one for high fire.
E229 means the low-fire switch was slow, so the control skipped ahead and lit on high fire. The furnace runs. Once is nothing. On every start, it’s an early sign of the same trouble that causes E227.
E228 comes from furnaces that set their inducer speed by finding where the pressure switch closes. The test failed: the switch didn’t close the way the control expected. If it keeps failing, you’ll see E276 and a one-hour lockout.
E227 means the switch closed, the furnace started, and then the switch opened. Something changed mid-cycle: water backing up in the drain, wind or snow at the vent, or an inducer that slowed down as it warmed up.
What to check before you call
- The vent pipes outside. High-efficiency furnaces vent through two white plastic pipes. Snow, leaves, a nest or frost at the end blocks them. Clear what you can reach safely by hand.
- Water near the furnace, or gurgling. A clogged condensate trap backs water into the system and the switch opens. Condensate drain clogs covers it.
- Photo the code, then reset once. Take a photo of the code before you reset anything. A reset can clear what’s showing, and that number saves the tech time and you money. How to reset a Lennox furnace has the safe way.
- Leave the switch alone. Don’t pull its hose or jumper its wires. It’s the part that keeps the furnace from burning gas when the exhaust can’t get out.
What it usually turns out to be
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| The cause | How a tech confirms it | Our price |
|---|---|---|
| Clogged condensate trap or drain | Water backed up in the trap or the switch tubing | $175 to $420 |
| Water or a crack in the switch tubing | Tubing checked and blown clear | Priced in writing |
| Blocked or sagging vent pipe | Pressure measured at the switch, vent checked end to end | Priced in writing |
| Weak inducer motor | Pressure it makes against what the switch needs | Priced in writing |
| Failed pressure switch | Holds open with good pressure on it | Priced in writing |
| Control board | Wiring and switch good, calibration still fails | $550 to $1,180 |
Switch, inducer and vent work gets priced after the diagnostic, because the part and the labor change by model. The diagnostic is a flat $99, and the number comes in writing before we start.
Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. On a furnace, for $229 (regularly $467) we also pull the blower wheel and clean it blade by blade. A yearly check is where a slow drain gets spotted before it trips the switch.
If the repair is a big one on an older furnace, get a second look before you spend it. Our free second opinion costs you nothing, and the estimator shows what a new system costs with $1,500 off already in the price. Thinking about brands? Lennox vs Trane lays out the difference.
Every Lennox code in one place: Lennox error codes. Other brands too: furnace and AC error codes.
The system we put in first
Built to take a beating. Put in by our crew.
Heat lamps, snow and rain on one outdoor unit: that’s Trane’s own film. We’re a Trane Comfort Specialist, on Trane’s own dealer locator, and when you pick a Trane, our crew puts it in.
Films: Trane’s own.
Call or book a Lennox repair
Call (703) 997-9757. We answer day or night. Or book online and pick a time. The diagnostic is a flat $99, and you see the repair price in writing before we touch anything. Furnace running fine and you want to keep it that way? Book the $67 heating check from goswiftpro.com/cookiesoffer (book by November 30) and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276. More on Lennox repair in Northern Virginia.
Questions people ask
What does E229 mean on a Lennox furnace?
Ignition on high fire. The low-fire pressure switch didn’t close in time, so the furnace lit on high fire instead. Lennox says no action is needed.
What does E228 mean on a Lennox furnace?
Combustion air inducer calibration failure. The furnace couldn’t calibrate the pressure switch. Lennox says to check the vent and the switch wiring.
What does E227 mean on a Lennox furnace?
The low pressure switch opened while the furnace was lighting or running. A blocked vent, a clogged condensate drain or a weak inducer are the usual causes.
Is it safe to run my Lennox furnace with an E227 or E228 code?
The furnace protects itself: it won’t run the burners unless the pressure switch proves the vent is clear. Don’t bypass the switch. If the code keeps coming back, have the vent and the drain checked.
