On the covered Lennox gas furnace, E272 means soft lockout: the maximum number of recycles was exceeded and the last recycle was due to the pressure switch opening. It clears when a heat call finishes successfully. First, check the outdoor intake and exhaust terminations for snow, ice or debris.
Differential
Likely causes of “Lennox gas furnace code E272”, and how to tell them apart
- 1
The maximum recycles exceeded because the pressure switch opened
What separates it E272 appears and the furnace stops
How to confirm Lennox words it as a soft lockout
- 2
A blocked intake or exhaust
What separates it Snow, ice or debris outside
How to confirm Check the terminations
- 3
A low-pressure switch stuck closed
What separates it The switch does not follow
How to confirm Technician testing
- 4
A weak combustion air inducer
What separates it The inducer is slow
How to confirm Technician testing
- 5
A high-pressure switch that does not close
What separates it The switch closes late
How to confirm Technician measurement
Before you touch a setting
Record this first — changing settings destroys the evidence
- That the code reads E272
- Whether it clears after a heat call
- Whether the terminations are clear
- The weather
Try in this order
0 of 8 completedWhat to do first
ReversibleCheck the outdoor intake and exhaust terminations for snow, ice or debris.
Correct only the documented fault domain
ReversibleLennox says to check whether the low-pressure switch is stuck closed on a heat call, check the pressure at which the high-pressure switch closes, measure operating pressure, and inspect the vent and combustion air inducer.
Look outside
ReversibleAt intake and exhaust.
Clear snow or debris
ReversibleCarefully.
Let it restart
ReversibleA soft lockout clears after a good call.
Watch one cycle
ReversibleTime it.
Note whether it repeats
ReversibleAnd when.
Call a technician
ReversibleFor pressure tests.
Model-specific
What is true of this model and not of its siblings
- A soft lockout
- The control stops after too many recycles but can try again.
- Lennox's checks
- Whether the low-pressure switch is stuck closed on a heat call, the pressure at which the high-pressure switch closes, the operating pressure, the vent and the combustion air inducer.
- Outside
- A blocked termination is the first look.
- Inducer
- A slow inducer lets pressure drop.
- Records
- Note when it appears.
- Safety
- Never bypass.
- Soft and hard lockouts
- A soft lockout stops the furnace but lets the control try again, often after a delay or when a call completes. A hard lockout needs a reset. Lennox words E272 as soft, so the furnace may recover without help, then trip again.
- Reading Lennox's checks
- Lennox points a technician to the low-pressure switch, which should not be stuck closed, the pressure at which the high-pressure switch closes, the operating pressure, and the vent and combustion air inducer. They are all about airflow.
- Outside work for you
- Keep the intake and exhaust clear of snow, ice and leaves, and trim shrubs back from the terminations. If the unit has a condensate line, check that it is not frozen or blocked.
- Telling Lennox's causes apart
- A switch that is stuck closed on a heat call is a switch fault. A high-pressure switch that closes at the wrong pressure suggests the inducer or the vent. Operating pressure that is low points to an airflow restriction. The technician measures all three, usually with a manometer and a meter.
- What clears the lockout
- A soft lockout clears itself once a heat call finishes successfully, so the furnace may heat normally for days between events. Keep a note of the dates, because a code that returns during cold or windy weather suggests a vent or termination issue.
Stop boundary
When this stops being a self-service repair
- !Never bypass, jumper or tape over a safety switch
- !Stop for a carbon monoxide alarm, soot, scorch marks or flame outside the burner compartment
- !Call a qualified technician for anything behind the furnace's panels
- !If you smell gas, leave the building and call the gas utility from outside; do not use switches or phones inside
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does E272 mean on a Lennox gas furnace?+
Soft lockout: the maximum number of recycles was exceeded and the last recycle was due to the pressure switch opening. It clears when a heat call finishes successfully.
Does it clear?+
When a heat call finishes successfully.
What can I check?+
The outside terminations.
Who tests pressures?+
A technician.