- Boilers
- Gas boiler
L6
Ideal L6 on a gas boiler: false flame lockout
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On Ideal boilers, L6 is a false flame lockout: the boiler sensed a flame when there should be none. Ideal says to reset once; if L6 returns, it needs an engineer, so contact Ideal or a Gas Safe registered engineer quoting L6.
Safety first
Stop and check this first
- This code involves the flame or the flue, so check that a working carbon monoxide alarm is fitted, as HSE strongly recommends. If it sounds, switch the boiler off, open windows, get everyone outside and call 0800 111 999.
- If you suspect a gas leak: put out any naked flame, do not operate electrical switches, open windows and doors, leave the home and call the National Gas Emergency Service on 0800 111 999 from outside, as Ideal's guide gives the number.
Safe checks you can perform
- Smell of gas or burning
- One reset
- Power left off until the visit
- Gas valve and flame circuit test
Leave these tasks to a qualified professional
- Do not attempt this professional task: Gas shut off and tightness test
- Do not attempt this professional task: Flame signal measurement
- Do not attempt this professional task: Combustion analysis after repair
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Gas shut off and tightness test
What they doThe engineer checks the gas valve closes fully and carries out a gas tightness test.
They must show youthe tightness test result.
In writingthe result and any valve work done.
Flame signal measurement
What they doThe engineer measures the flame signal with the burner off and on and checks electrode, lead and board.
They must show youthe readings.
In writingthe values and the reference of any part replaced.
Combustion analysis after repair
What they doAfter the repair, the engineer measures combustion with a flue gas analyser.
They must show youthe analyser printout.
In writingthe readings against the manufacturer's figures.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Smell of gas or burning
- Who:
- you.
- How:
- notice, without opening anything, whether there is any smell of gas or burning near the boiler.
- Result that matters:
- whether there are signs of gas.
- If you smell gas:
- follow the gas emergency advice and do not reset.
- If there is no smell:
- carry on with one reset.
- Evidence to keep:
- a note of what you noticed.
Evidence: Ideal Instinct2 user guide
One reset
- Who:
- you.
- How:
- press the restart button once, as Ideal advises for L6.
- Result that matters:
- whether L6 clears.
- If L6 returns:
- leave the boiler off; contact Ideal or a Gas Safe engineer quoting L6.
- If it clears:
- note it; even one repeat needs an engineer.
- Evidence to keep:
- a photo of the display and the time.
Evidence: Ideal Instinct2 user guide · Ideal Heating FAQ: what does my boiler fault code mean?
Power left off until the visit
- Who:
- you.
- How:
- if L6 returns, switch the boiler off at its electrical switch and leave it off.
- Result that matters:
- that the boiler cannot try again.
- If you need heating urgently:
- use other safe heating, not repeated resets.
- If the engineer is coming:
- tell them how often L6 appeared.
- Evidence to keep:
- the dates and times of each L6.
Evidence: Ideal Instinct2 user guide
Gas valve and flame circuit test
- Who:
- Ideal or a Gas Safe registered engineer.
- How:
- checks whether gas shuts off fully and measures the flame signal with the burner off.
- Result that matters:
- whether the flame signal is real or false.
- If gas does not shut off:
- the valve is repaired and gas tightness tested.
- If the signal is false:
- the electrode, lead or board is replaced.
- Evidence to keep:
- a job sheet with the measurements.
Gas valve and flame sensing work is only for a Gas Safe registered engineer.
Evidence: Ideal Instinct2 user guide · HSE gas safety for homeowners
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Ideal Heating
- Product type
- Gas boiler
Known code variants
- Ecodan L6
- Ideal boiler L6
- Ideal boiler L6 false flame
- Ideal L06
- Ideal L6
- Ideal Logic L6
- Mitsubishi Ecodan L6
- Mitsubishi L6 heat pump
What it means
Ideal's FAQ and the Instinct2 user guide list L6 as false flame lockout. The boiler checks that no flame signal exists before it lights and after it shuts the gas off; if it detects one, it locks out because the signal is either a real flame that should not be there or a false reading in the flame sensing circuit. Telling these apart needs measurements on the gas valve and flame sensing circuit, which are engineer work.
Warnings and stop conditions
- Higheditorial warning
This code involves the flame or the flue, so check that a working carbon monoxide alarm is fitted, as HSE strongly recommends. If it sounds, switch the boiler off, open windows, get everyone outside and call 0800 111 999.
Evidence: Ideal Instinct2 user guide · HSE gas safety for homeowners
- Criticaleditorial warning
If you suspect a gas leak: put out any naked flame, do not operate electrical switches, open windows and doors, leave the home and call the National Gas Emergency Service on 0800 111 999 from outside, as Ideal's guide gives the number.
Evidence: Ideal Instinct2 user guide · HSE gas safety for homeowners
Symptoms and causes
Probable causes · in order
- Fault in the flame sensing circuitPossible
Fits if L6 appears with no sign of the burner running; the electrode, lead or board gives a signal that is not a flame.
Evidence: Ideal Instinct2 user guide · Ideal Heating FAQ: what does my boiler fault code mean?
- Gas not shutting off fullyPossible
Fits if a flame signal remains after the boiler stops; the gas valve must be checked by an engineer at once.
Evidence: Ideal Instinct2 user guide · HSE gas safety for homeowners
Virtual technician
Does L6 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Ideal Heating · 2023 · manual
- 2
Health and Safety Executive · official_doc
- 3
Ideal Heating FAQ: what does my boiler fault code mean?
Ideal Heating · official_doc
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