Lennox SLP98UHV Error Code E 227: Low Pressure Switch Open During Run
What Does Code E 227 Mean?
Error code E227 on the Lennox SLP98UHV indicates that the low-fire pressure switch opened during trial for ignition or during active run mode. This means the furnace initially had adequate draft to close the pressure switch, but something caused the draft to weaken or fluctuate enough for the switch to open during operation.
When the pressure switch opens mid-cycle, the control board immediately shuts off the gas valve and stops ignition attempts. This is a critical safety function — without proper draft, combustion gases could spill into your home instead of being vented outside.
Common causes include intermittent vent blockages (such as wind gusts pushing exhaust back into the vent), condensate buildup in the vent pipe or pressure tubing, or a weakening inducer motor that cannot maintain consistent draft. In cold climates, ice formation in the vent pipe is a frequent culprit. A technician should measure the draft pressure during operation, inspect the entire vent run for restrictions, and check the inducer motor performance.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Intermittent vent blockage or wind-related draft disruption | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace starts but shuts down during the heating cycle with E227
- The code appears primarily during windy or very cold weather
- You notice water or ice in or around the exhaust vent termination outside
✓ Verified against manufacturer service manual — March 2026