HVACopediaLennox · Furnace
E224 Low pressure switch failed closed
What the control is telling you
Low-fire pressure switch stays closed on a heat call for longer than 150 seconds.
Applies to: EL296UHV(X) series furnaces (integrated control 103130-XX and 107045-XX)
Likely causes
- Switch contacts stuck closed
- Jumpered switch
- Wiring short
Test and repair steps
- Check whether the low pressure switch is stuck closed at the start of a heat call (more than 150 seconds).
- The control checks that the pressure switches are open before the inducer starts; a switch closed at that point blocks ignition.
- Warning: Remove any jumper across the pressure switch; it must never be bypassed.
- Check the switch wiring for a short.
- Measure operating pressure with a manometer and compare to set-point tables.
- 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.
- Inspect vent and inducer operation.
- Replace the switch if contacts are stuck.
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
- E205 Gas valve relay contact shorted
- E206 Gas valve second-stage relay failure
- E207 Hot surface ignitor open
- E223 Low pressure switch failed open
- E225 High pressure switch failed open
- E226 High pressure switch failed closed
- E227 Low pressure switch opened during ignition or run
- E228 Inducer calibration failure
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Source: Lennox EL296UHV(X) Unit Information / Service Literature, Table 5 Ignition Control 103130-XX Diagnostic Codes, p.35; Ignition Control 107045-XX Diagnostic Codes table, p.42, Troubleshooting: Heating Sequence of Operation flowchart, p.110-112. Summarized in our own words; check the original manual for your model.
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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.