HVACopediaLennox · Furnace
E274 Soft lockout - limit opened
What the control is telling you
Last recycle failed because the limit opened or stayed open more than 3 minutes. 1-hour soft lockout.
Applies to: EL296UHV(X) series furnaces (integrated control 103130-XX and 107045-XX)
Likely causes
- Low airflow
- Overfiring
- Blockage
Test and repair steps
- Inspect the filter (should be checked monthly) and replace if dirty; oversized pressure drop from high-efficiency filters can trip the limit.
- Measure external static pressure heating speed must not exceed 0.8 in. w.c.
- Measure temperature rise (supply minus return) and confirm it is within the rating-plate range, adjusting blower heat speed (DIP 11-13) if needed.
- Check gas pressures with a manometer supply natural gas 4.5-13.0 in. w.c. (LP 11.0-13.0); manifold natural 1.7 low fire / 3.5 high fire (LP 4.5 / 10.0) at 0-4500 ft. Clock the gas meter to confirm input; if manifold pressure is right but rate is wrong, check orifices.
- Check the blower wheel for debris and verify blower operation.
- Check for blockage in the heat exchanger.
- The limit must reclose within 3 minutes or the control enters Watchguard for 1 hour; do not substitute a limit with a different set point.
Settings for these units
Recommended filter size by cabinet width · EL296UHV
| Cabinet width | Side return | Bottom return |
|---|---|---|
| 17-1/2 in. | 16 x 25 x 1 in. (1) | 16 x 25 x 1 in. (1) |
| 21 in. | 16 x 25 x 1 in. (1) | 20 x 25 x 1 in. (1) |
| 24-1/2 in. | 16 x 25 x 1 in. (2) | 24 x 25 x 1 in. (1) |
Number in brackets is the quantity of filters.
Filters are field supplied and installed outside the furnace; inspect monthly.
Recommended filter size by cabinet width · Lennox SL280UHV
| Cabinet width | Side return | Bottom return |
|---|---|---|
| 14-1/2 in. | 16 x 25 x 1 in. (1) | 14 x 25 x 1 in. (1) |
| 17-1/2 in. | 16 x 25 x 1 in. (1) | 16 x 25 x 1 in. (1) |
| 21 in. | 16 x 25 x 1 in. (1) | 20 x 25 x 1 in. (1) |
| 24-1/2 in. | 16 x 25 x 1 in. (2) | 24 x 25 x 1 in. (1) |
Number in brackets is filter quantity; filters are field supplied.
Never run the unit without a filter installed.
- Filter sizes by cabinet width · Lennox ML180UHE
- Filter sizes by cabinet width · Lennox SL297NV
Models that show this code
34 models in EL296UHV, Lennox SL280UHV, Lennox ML180UHE, Lennox SL297NV
Other codes on the same units
- E270 Soft lockout - no flame after max retries
- E271 Soft lockout - retries exceeded, pressure switch opened
- E272 Soft lockout - recycles exceeded, pressure switch opened
- E273 Soft lockout - recycles exceeded, flame failure
- E275 Soft lockout - flame out of sequence, now gone
- E276 Watchguard calibration failure
- E290 Ignitor circuit fault
- E291 Heat airflow below minimum
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Source: Lennox EL296UHV(X) Unit Information / Service Literature, Table 5 Ignition Control 103130-XX Diagnostic Codes, p.36; Ignition Control 107045-XX Diagnostic Codes table, p.43, Troubleshooting: Heating Sequence of Operation flowchart, p.110-112, Typical Operating Characteristics p.86, Maintenance p.86-87, Heating System Service Checks p.82-85. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.