Lennox furnace Alert code 229: Ignition on high fire — information only
Alert 229 is classed Information only and needs no action. The furnace lit on high fire because the low fire pressure switch did not close in the allowed time.
Applies to: Lennox communicating gas furnaces on systems using the S30, S40 or comparable communicating thermostats, as documented in the Lennox Residential Communicating Systems Alert Code Guide.
What it means
Lennox classifies this as Information rather than a fault, and states plainly that no action is required. The furnace attempted to light on low fire, the low fire pressure switch did not close within its window, and the control switched to high fire ignition instead — which produces more draft and therefore closes the switch. That is adaptive behaviour rather than a failure. Lennox adds a note about early models: if the fan is already running when a first-stage heat call arrives, the unit fires on high for 60 seconds before dropping to low. Both behaviours are by design.
Most common causes
- The low fire pressure switch not closing within the allowed time, so the control fires on high instead.
- On early models, the blower already running when a first stage heat call arrives, producing 60 seconds of high fire by design.
- Marginal draft at low fire, which high fire overcomes.
- Normal adaptive operation in certain venting configurations.
How to diagnose it
- Note that Lennox classes this Information only and says no action is required.
- Note whether it appears occasionally or on nearly every cycle. Occasional is normal adaptive behaviour; constant may indicate marginal low-fire draft worth mentioning at the next service.
- Note whether other pressure switch alerts appear alongside it, since a persistent pattern of this alert plus 223 or 227 points at a real restriction.
- Note the furnace's age, since Lennox flags different behaviour on early models.
How to fix it
- Nothing needs doing. Lennox states no action is required.
- If it happens on nearly every cycle, mention it at the next routine service — persistent low-fire draft marginality is worth a look even though it is not a fault.
- Do not have parts replaced on the strength of this alert alone.
- Do not disable or reconfigure anything to stop it appearing. It is the control adapting correctly.
Notes
Manufacturers rarely publish informational codes with an explicit no-action-required classification. Lennox doing so is genuinely helpful, because a homeowner seeing any code at all naturally assumes something is wrong.
Related
All codes for this manufacturer
Lennox furnace alert codes — every code, with what differs between models.