Lennox SLP98UHV Error Code E 276: Soft Lockout - Calibration Retries Exceeded
What Does Code E 276 Mean?
Before each heat cycle, the SureLight Variable Capacity Integrated Control on the SLP98UHV runs a pressure-switch calibration routine that learns the draft references it needs to prove venting at the furnace's different firing rates. When a single calibration attempt fails, the control sets E 228 and retries after about five minutes. E276 is what happens next when those retries keep failing: the control has exceeded its maximum number of calibration retries and has entered a soft lockout to stop trying.
In short, E 228 is the recurring calibration failure and E276 is the lockout it escalates to. The manual routes E276 troubleshooting straight back to E 228, because they share a root cause — the control cannot capture a stable, trustworthy pressure reference. This is a calibration fault, so it is distinct from E 223 (the low-fire pressure switch failing to close) and E 225 (the high-fire pressure switch failing to close), which report a specific switch that would not close rather than a calibration that could not settle.
The usual reasons calibration keeps failing are a pressure-sensing hose that is disconnected, cracked, or holding condensate, a loose or corroded pressure-switch wiring connection, or a vent condition that makes draft pressure fluctuate too much for a baseline to be established. Because the furnace is now in a soft lockout, it will not keep retrying on its own until the underlying condition is corrected and it is allowed to recalibrate.
What You'll Notice
- The furnace will not start and the 7-segment display shows E 276
- You may see E 228 in the code history leading up to the lockout
- The furnace made several attempts, each separated by a pause, before giving up
- No heat, with the furnace sitting idle after the lockout
- Cycling power may allow a few more attempts, but the furnace returns to E 276
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Persistent pressure switch or venting issue preventing calibration | Most common | ✗ Call a pro → |
How This Is Diagnosed
Because E276 is the lockout end of the E 228 calibration problem, a technician diagnoses it the same way — by finding what prevents the control from establishing a stable pressure reference. As a homeowner-safe first check, you can inspect the outdoor exhaust and intake terminations for blockages such as ice, snow, debris, or nests, since an unstable vent is a common reason calibration cannot complete.
The rest is technician work. They inspect the pressure-switch hose between the inducer housing and the switch for cracks, a loose fit, or trapped water, check the pressure-switch wiring for looseness or corrosion, confirm the combustion-air inducer spins up strongly, and measure the operating draft in inches of water column against the switch specification. The goal is to eliminate every source of an unstable reading so the calibration routine can succeed.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace is locked out on E 276 and will not restart on its own
- E 228 also appears in the error history
- The code returns after you clear the outdoor vent and cycle power
- You find a disconnected, cracked, or water-filled pressure-switch hose
Frequently Asked Questions
What is the difference between E 228 and E 276?
E 228 is the individual pressure-switch calibration failure, which the furnace retries after about five minutes. E 276 is the soft lockout the furnace enters after those calibration retries have been exceeded. They share the same root causes; E 276 just means the furnace has stopped retrying on its own.
Can I clear E 276 myself?
Cycling power at the breaker will reset the lockout, but if the calibration still cannot succeed the furnace will fail again and return to E 276. Because the fault is tied to safe venting verification on a gas furnace, the hose, wiring, and vent condition should be diagnosed rather than repeatedly reset.
Does E 276 mean the pressure switch is bad?
Not necessarily. The calibration depends on the switch, its sensing hose, the wiring, and a stable draft. A cracked hose, a loose connector, or an unstable vent can defeat calibration while the switch itself is fine. A technician isolates which part is actually at fault.
✓ Verified against manufacturer service manual — March 2026