Ariston SP1, SP2 and SP3 Fault Codes: Ignition Sequence Explained
Estimated reading time: 7 minutes
Ariston SP1, SP2 and SP3 fault codes indicate that the boiler has experienced a problem while trying to ignite or maintain a flame.
These codes are officially written as 5P1, 5P2 and 5P3. However, the number 5 can look like the letter S on some boiler displays, which is why homeowners often search for SP1, SP2 and SP3.
SP1 means the first ignition attempt was unsuccessful, SP2 means the second attempt failed, and SP3 means the flame was lost after ignition. If one of these codes keeps returning, reset the boiler once and contact a Gas Safe registered engineer.
Quick Answer
The three Ariston codes describe different points in the ignition process:
| Displayed Code | Format | Meaning |
| SP1 | 5P1 | First ignition attempt unsuccessful |
| SP2 | 5P2 | Second ignition attempt unsuccessful |
| SP3 | 5P3 | Flame cut-off or flame lost after ignition |
SP3 does not simply mean that a third ignition attempt failed. It means the boiler detected a flame and then lost it. Ariston’s Clas ONE installation manual lists these codes within the ignition and flame-detection fault group.
Why Does the Display Show SP Instead of 5P?
The first character is the number 5, not the letter S.
Ariston uses the first digit to identify the section of the boiler involved. Group 5 relates to ignition and flame detection. The letter P identifies a warning within that operating group.
Because of the shape of the digital display, 5P1 may appear to read as SP1. Both versions usually refer to the same code.
How the Ariston Ignition Sequence Works
When the boiler receives a request for heating or hot water, it begins an automatic ignition sequence.
In simple terms, the boiler must:
Confirm that operating conditions are safe.
Start the fan where required.
Open the gas valve.
Generate a spark at the ignition electrode.
Light the burner.
Confirm the flame through the flame-detection electrode.
Maintain a stable flame while heat is required.
SP1, SP2 and SP3 help identify the stage at which this process was unsuccessful.
They do not identify the exact faulty component. A Gas Safe engineer must diagnose why ignition failed or why the flame was lost.
What Does Ariston SP1 Mean?
Ariston SP1, officially 5P1, means the first ignition attempt was unsuccessful.
The boiler requested a flame but did not confirm successful ignition during its first attempt. Depending on the model and operating conditions, the boiler may automatically try again. If it moves to another attempt, SP2 may then appear.
A single SP1 warning may occasionally be temporary. However, repeated appearances indicate that the boiler is struggling to ignite reliably.
What Does Ariston SP2 Mean?
Ariston SP2, officially 5P2, means the second ignition attempt was unsuccessful.
This means the boiler has already attempted ignition once and has tried again without successfully confirming a flame. SP2 therefore suggests that the ignition problem is continuing rather than being limited to one unsuccessful start.
The boiler may eventually enter a lockout or display another ignition-related error if a flame cannot be established.
What Does Ariston SP3 Mean?
Ariston SP3, officially 5P3, means flame cut-off.
Unlike SP1 and SP2, SP3 indicates that a flame may have been established but was then lost or could no longer be confirmed.
Possible reasons include an unstable gas supply, poor flame detection, combustion instability or a problem with the components controlling the burner. Ariston also describes 5P3 as flame detachment or flame loss, while 5P1 and 5P2 indicate unsuccessful ignition attempts.
Possible Causes of SP1, SP2 and SP3
| Possible Cause | Why it may trigger the code | Who Should Investigate |
| Interrupted or inadequate gas supply | The burner may not receive enough gas to ignite or maintain a flame. | Gas Safe engineer |
| Ignition electrode fault | A weak or missing spark may prevent successful ignition. | Gas Safe engineer |
| Flame-detection electrode fault | The boiler may not recognise that the burner has lit. | Gas Safe engineer |
| Damaged electrode lead or wiring | The ignition spark or flame signal may not reach the PCB correctly. | Gas Safe engineer |
| Gas valve fault | The valve may not open or regulate gas correctly. | Gas Safe engineer |
| Burner contamination or damage | The burner may not light evenly or maintain a stable flame. | Gas Safe engineer |
| Fan or air-supply problem | The boiler may not establish the correct conditions for combustion. | Gas Safe engineer |
| Flue or combustion issue | Poor air intake or combustion-gas removal may affect flame stability. | Gas Safe engineer |
| Incorrect combustion settings | The gas-and-air mixture may not ignite or remain stable. | Gas Safe engineer |
| PCB fault | The PCB may not control ignition or interpret the flame signal correctly. | Gas Safe engineer |
These codes should not be used alone to decide which replacement part is needed.
Can You Reset Ariston SP1, SP2 or SP3?
You can try one reset using the reset control shown in the user manual for your exact Ariston boiler.
After resetting:
Allow the boiler to complete its start-up sequence.
Check whether the code disappears.
Do not continue resetting if the code returns.
Repeated resets do not repair the underlying ignition problem. Ariston documentation advises contacting technical assistance when shutdowns occur frequently and notes that some models limit the number of resets allowed within a short period.
If SP1, SP2 or SP3 appears again after one reset, arrange an inspection by a Gas Safe registered engineer.
What Should a Gas Safe Engineer Check?
The correct diagnostic process depends on the exact Ariston model, but an engineer may check:
The complete ignition sequence
Inlet and working gas pressure
Ignition spark quality
Ignition-electrode condition and position
Flame-detection or ionisation signal
Electrode leads and wiring
Electrical earth continuity
Gas-valve operation
Burner condition
Fan operation
Air intake and flue condition
Combustion readings
PCB inputs and outputs
Stored error history
The engineer should follow the installation and servicing instructions for the exact boiler rather than relying only on the displayed warning.
Boiler gas repairs must be completed by an appropriately qualified Gas Safe registered engineer.
Are SP1, SP2 and SP3 the Same as Ariston 501?
No, although they are closely related. SP1 and SP2 describe unsuccessful ignition attempts. SP3 describes flame loss after ignition.
Error 501 means that no flame has been detected and may appear if the boiler cannot complete the ignition process successfully.
This article focuses only on SP1, SP2 and SP3, but the codes may appear as part of the sequence leading to a full ignition lockout.
Parts That May Be Related
Depending on the diagnosis, an engineer may find a problem involving:
Ignition electrodes
Flame-sensing electrodes
Combined ignition and detection electrodes
Electrode leads
Gas valves
Fans
Burners
Wiring harnesses
Printed circuit boards
Do not order a replacement part based only on SP1, SP2 or SP3. Different Ariston boiler models and production versions can use different components.
Find Ariston Spare Parts
Frequently Asked Questions
SP1 is generally an ignition warning showing that the first attempt was unsuccessful. The boiler may try again or later enter a lockout if ignition cannot be completed.
SP1 relates to the first failed ignition attempt. SP2 means the boiler’s second ignition attempt was also unsuccessful.
No. SP3 means flame cut-off or flame loss. A flame may have formed but was not maintained or detected reliably.
Yes. Insufficient or unstable gas pressure can prevent ignition or cause an established flame to become unstable. This requires investigation by a Gas Safe engineer.
Potentially. An ignition electrode may prevent the burner from lighting, while a flame-detection electrode may fail to confirm or maintain the flame signal. Testing is needed before replacing either part.
No. Try one reset. If the warning returns, stop resetting and arrange professional diagnosis.
Key Takeaways
- Ariston SP1, SP2, and SP3 codes indicate issues with ignition attempts or flame loss during the ignition process.
- SP1 (5P1) means the first ignition attempt failed, SP2 (5P2) indicates the second attempt failed, and SP3 (5P3) signifies a flame loss after ignition.
- Repeated appearances of these codes suggest ongoing ignition problems, requiring a Gas Safe engineer for diagnosis.
- You can reset the boiler once; however, continuous resetting won’t fix the underlying issues and may lead to lockout conditions.
- Troubleshooting may involve checking gas supply, ignition components, and ensuring compliance with safety standards.
