Lennox SLP98UHV Error Code E 276: Soft Lockout - Calibration Retries Exceeded
What Does Code E 276 Mean?
Error code E276 on the Lennox SLP98UHV indicates a soft lockout that occurred after the system exceeded the maximum number of pressure switch calibration retries. The control board attempted to calibrate the pressure switch multiple times without success, and has now locked out the furnace.
The SLP98UHV performs a pressure switch calibration before each heating cycle to ensure the venting system can safely exhaust combustion gases. When calibration fails repeatedly (triggering the underlying E228 condition multiple times), the board enters this lockout to prevent further unsuccessful startup attempts.
The root cause is typically a problem with the pressure switch itself, its wiring connections, or the pressure sensing hose. A technician should check that the pressure hose is properly connected and free of cracks or moisture, verify the pressure switch wiring is secure, and inspect the vent system for any conditions that would cause unstable pressure readings.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Persistent pressure switch or venting issue preventing calibration | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace has locked out and will not restart on its own
- The code returns after the lockout clears and the furnace retries
- You also see E228 in the error history
✓ Verified against manufacturer service manual — March 2026