What SP1 means on an Ariston boiler
SP1 tells you the boiler's first attempt to light the burner did not work. Ariston's E-Combi One LPG design, installation and servicing instructions for Great Britain and Ireland list it as "1st Ignition Failed" and use it as their example warning, shown with the message "FIRST IGNITION ATTEMPT UNSUCCESSFUL". The Clas One installation and servicing instructions for the 18 to 35 models give the same wording.
The key point is that SP1 is a warning, not a shutdown. The boiler records the failed attempt and keeps trying. If it lights on the next go, your heating and hot water carry on as normal. If it cannot light at all, it moves on to a lockout code that needs your attention.
SP1 or 5P1: reading the display
Ariston manuals print this code as "5 P1". Owners search for SP1 because the 5 on a segment display looks almost exactly like a capital S. They are the same code. The three characters break down like this:
- 5 is the group. Ariston uses 5 for ignition and flame detection.
- P marks a warning rather than a fault.
- 1 is the warning number, in this case the first failed ignition.
So if you ever see 5 P2 or 5 P3, you know straight away they belong to the same ignition group. Our Ariston fault codes overview explains the other groups.
Where SP1 sits in the ignition sequence
SP1 is the first of several codes the boiler can show when lighting goes wrong. All of these appear in the ignition and detection table of both manuals named above.
| Code | Ariston wording | Type | What it tells you |
|---|---|---|---|
| 5 P1 (SP1) | 1st Ignition Failed | Warning | One attempt failed, the boiler will try again |
| 5 P2 (SP2) | 2nd Ignition Failed | Warning | The retry failed too |
| 5 P3 | Flame cut-off | Warning | The flame lit but was lost |
| 5 01 | No flame detected | Shutdown | The boiler has locked out and needs RESET |
If SP1 is followed by SP2, the second ignition warning, the problem has lasted through two attempts. If the boiler then shows error 501, it has given up and locked out.
When SP1 is harmless and when it is not
A single SP1 that clears by itself and does not come back is rarely worth worrying about. A short run of them on the first starts after a gas meter change or supply work is also common, because air in the pipe has to clear before the gas reaches the burner. Treat it as a sign of trouble when:
- it appears most days rather than once in a while
- it is regularly followed by SP2
- it ends in a 501 lockout, even occasionally
- you hear repeated clicking from the boiler without the burner catching
Checks you can make when SP1 appears
An occasional SP1 that clears without you doing anything is not a cause for worry. If it shows up often, start with the gas supply, because a boiler cannot light without it.
- Try another gas appliance. If the hob lights normally, gas is reaching the house.
- Check the meter. On a prepayment meter, make sure there is credit and that the emergency credit has not run out.
- Check the gas isolation valve under the boiler. The handle should sit in line with the pipe. Do not touch anything else under the boiler.
- On LPG models, check the supply. The E-Combi One LPG runs on bottled or bulk LPG, so check the tank gauge or swap an empty bottle as your supplier advises.
- In freezing weather, check the condensate pipe. A frozen condensate pipe can stop many condensing boilers lighting. Thaw it with warm, not boiling, water or a hot water bottle.
If you smell gas, do not try to relight the boiler or operate switches near it. Turn off the gas at the meter if it is safe, open windows and call the National Gas Emergency Service on 0800 111 999. On LPG, also call your LPG supplier's emergency line.
What an engineer will check for repeated SP1 warnings
Ariston's tables give no cause column for SP1, so the job of finding why lighting fails falls to an engineer. A Gas Safe registered engineer will typically measure the gas pressure at the boiler while it tries to light, inspect the ignition electrode and its lead, check the spark generator, check the condensate trap and pipe for blockages and look at the flue and air intake. Do not remove the casing or touch any of these parts yourself.
Before they arrive, keep a short note of:
- roughly how often SP1 appears, and whether it is mostly on the first start of the day
- whether it is worse in cold or windy weather
- whether you have had any gas meter or pipework changes recently
- any other codes you have seen, especially SP2 or 501
Typical repair costs in the UK
If the gas supply checks out and SP1 keeps returning, the fix is usually in the ignition system. Prices vary by region and by the part needed.
| Job | Typical UK cost |
|---|---|
| Engineer call-out and diagnosis | Typically £60 to £150 |
| Ignition electrode | Typically £90 to £180 |
| Ignition lead or spark generator | Typically £100 to £200 |
| Condensate pipe reroute or insulate | Typically £80 to £200 |
| Gas valve replacement | Typically £180 to £350 |
A yearly service is the best way to catch a worn electrode before it starts causing warnings, and our annual boiler service guide explains what is checked.