Alpha Boiler Fault Codes
Gas Safe registered fault diagnosis for Alpha E-Tec Plus, Evoke, and InTec models. E10, E50, E20, E28, E30 — all explained with repair costs and repair vs. replace guidance.
Understanding Alpha boiler fault codes
Alpha is a budget boiler brand with a lower upfront cost — common in South London buy-to-let properties. Parts availability varies and some specialist components can take longer to source than Vaillant or Worcester Bosch equivalents. Reion carries out Alpha repairs and will give an honest repair-vs-replace assessment on boilers over 8 years old.
This guide covers the five most commonly searched Alpha fault codes, with technical explanations of what each fault means, what causes it, and what a Gas Safe engineer will do to fix it. Reion Miller (Gas Safe 919881) handles Alpha boiler repairs across South London.
Alpha fault codes explained
Low water pressure
System pressure has dropped below the operating threshold. Alpha boilers display E10 when pressure falls below 0.5 bar — typically the safest fault for a homeowner to address.
Ignition lockout
The boiler attempted ignition but could not establish a stable flame. The most common Alpha fault requiring a Gas Safe engineer.
Overtemperature lockout
The high limit thermostat has tripped because flow temperature exceeded a safe threshold. In South London's hard water, limescale on the heat exchanger is the leading cause.
Fan / APS fault
The PCB cannot confirm the fan is running correctly or the air pressure switch has not triggered. Prevents ignition as a flue safety measure.
NTC temperature sensor fault
The flow or return NTC thermistor is reading outside its expected range. The boiler cannot safely monitor water temperature and shuts down.
Alpha boiler fault code table
Extended fault code reference for common Alpha E-Tec Plus, Evoke, and InTec models.
| Code | Meaning | Common cause | Action |
|---|---|---|---|
| E10 | Low water pressure | System pressure below 0.5 bar | Repressurise to 1.2–1.5 bar (homeowner safe if no leak) |
| E50 | Ignition lockout | No flame detected after multiple attempts | Gas Safe engineer required |
| E20 | Overtemperature lockout | Flow temperature exceeded safe threshold, limescale | Gas Safe engineer — allow to cool first |
| E28 | Fan / APS fault | Fan motor failure, blocked flue, APS failure | Gas Safe engineer required |
| E30 | NTC temperature sensor fault | Flow or return thermistor out of range | Gas Safe engineer required |
| E40 | Flue sensor fault | Flue gas thermostat reading out of range | Gas Safe engineer required |
| E60 | Fan speed fault | Fan running at incorrect speed, tachometer failure | Gas Safe engineer required |
| E70 | PCB fault | PCB internal failure or corrupted programme | Gas Safe engineer — PCB replacement likely |
| E80 | Gas valve fault | Gas valve not responding or operating out of spec | Gas Safe engineer — do not reset repeatedly |
| E15 | DHW sensor fault | Domestic hot water thermistor failure | Gas Safe engineer required |
Why Alpha boilers fault more often in London
Hard water accelerates heat exchanger degradation on Alpha boilers — E20 overtemperature is particularly common in Wandsworth, Merton, and Lewisham on Alpha units that have missed annual servicing. The calcium deposits from Thames Water create an insulating layer on the heat exchanger, causing flow temperatures to spike and the high-limit thermostat to trip.
Parts sourcing is an additional consideration with Alpha boilers. Some Alpha specialist components can take 3–5 days to arrive, compared to next-day availability for Vaillant and Worcester Bosch. Reion factors this into repair-vs-replace advice — on an older Alpha with a major component fault, the wait time and parts cost may make new boiler installation the more practical route.
Reion recommends fitting a Fernox TF1 or Adey MagnaClean magnetic filter on every Alpha boiler in South London and running an annual service to remove calcium build-up before it causes heat exchanger damage or sensor failures.
Alpha boiler fault code questions
How do I reset an Alpha boiler after a fault code?
Why does my Alpha boiler keep showing fault codes in London?
Can I fix an Alpha boiler fault code myself?
Should I repair or replace my Alpha boiler?
How much does an Alpha boiler repair cost in London?
Alpha boiler fault code showing?
Reion is Gas Safe registered (919881), carries common Alpha parts, and serves all of South London. Fixed price after the £80 diagnostic — no obligation to proceed.
