HVACopediaLennox · Furnace
E276 Watchguard calibration failure
What the control is telling you
Pressure switch calibration failed; 1-hour soft lockout.
Applies to: EL296UHV(X) series furnaces with integrated control 103130-XX only
Likely causes
- Vent system problem
- Pressure switch wiring fault
Test and repair steps
- Inspect vent and intake piping for restrictions.
- After snow, ice or freezing fog, check intake and exhaust terminations and remove any obstruction.
- Check pressure switch wiring and connections.
- Check the condensate trap and the condensate hose screens at the cold end header box for blockage (power off; twist and pull screens, rinse); prime the trap with 10 fl. oz. (300 ml) of water if dry. If furnace and coil drains are combined, the A/C drain must be vented or the pressure switch will not work properly.
- Check hoses and inducer operation.
- Clears when calibration finishes successfully.
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 SL297NV
Models that show this code
22 models in EL296UHV, Lennox SL280UHV, Lennox SL297NV
Other codes on the same units
- E272 Soft lockout - recycles exceeded, pressure switch opened
- E273 Soft lockout - recycles exceeded, flame failure
- E274 Soft lockout - limit opened
- E275 Soft lockout - flame out of sequence, now gone
- E290 Ignitor circuit fault
- E291 Heat airflow below minimum
- E292 Blower motor will not start
- E294 Inducer over current
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Source: Lennox EL296UHV(X) Unit Information / Service Literature, Table 5 Ignition Control 103130-XX Diagnostic Codes, p.36, Maintenance p.87. Summarized in our own words; check the original manual for your model.
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