Alpha Boiler Fault Codes: Complete List, Meanings and Safe Checks

Alpha boiler fault codes help identify why your boiler has stopped working, locked out or displayed an error message. Common Alpha error codes can relate to ignition failure, low system pressure, overheating, fan faults, flame detection problems, circulation issues or flue-related faults.

The fault code is only a starting point. It does not always confirm the failed part. Alpha fault-code meanings can also vary by boiler model, so always check the manual for your exact Alpha boiler before ordering parts or attempting a reset.

Quick Answer

If your Alpha boiler is showing a fault code, check the display code, boiler model and pressure gauge first. Some simple checks, such as confirming the gas supply, checking system pressure or looking for visible leaks, may be safe for homeowners. However, faults involving gas, combustion, fans, flues, PCBs, sensors or internal components must be investigated by a Gas Safe registered engineer.

Alpha’s E-Tec 28 and 33 manual advises checking that gas, electrical and water supplies are available, checking that the boiler pressure is in the green area when cold, and confirming that controls are switched on before using the fault table. It also says that if a fault persists, Alpha Heating Innovation Technical Helpline should be contacted.

Important Note Before Using This Guide

Alpha has produced several boiler ranges, including E-Tec, E-Tec Plus, E-Tec NX, Evoke, InTec, CD, CB, Eco2, InTec2 and others. Not every code has the same meaning on every model.

Use this guide as a practical overview, then confirm the fault against:

Your exact Alpha boiler model
The boiler data plate
The manufacturer manual
The fault history, where available
A qualified engineer’s diagnosis

Do not remove the boiler case or work on gas, flue, combustion, fan, PCB or internal wiring components. Gas Safe Register states that people who are not Gas Safe registered must not fit a gas appliance or carry out gas work and then ask a registered engineer to check it afterwards.

Alpha Boiler Fault Codes Table

Alpha E01 Fault Code

The Alpha E01 fault code usually points towards ignition failure or the boiler failing to detect a stable flame. On common Alpha E-Tec fault tables, code 01 is listed as ignition failure, with possible causes including gas supply, ignition/sensing electrode, ignition lead, gas valve operation, PCB or wiring connections.

Safe homeowner checks are limited. You can check whether other gas appliances in the property are working and whether a prepayment gas meter has credit. Do not open the boiler or attempt to adjust ignition, gas valve or electrode components.

Read the full guide: Alpha E01 fault code

Alpha E02 Fault Code

The Alpha E02 fault code usually relates to an overheat boiler lockout on common Alpha E-Tec and InTec fault tables. This can happen when the boiler detects that it has overheated or that heat is not being moved away from the heat exchanger correctly.

Possible causes can include:

Pump or flow problem
Blocked heat exchanger
Air in the heat exchanger
Restricted primary flow
Closed or restricted heating valves

The E-Tec manual lists overheat activation and related flow or heat-exchanger issues in the fault-code section, while the Alpha E-Tec Regular fault-code table also describes code 2 as overheat boiler lockout caused by pump/flow problems, blocked heat exchanger or air in the heat exchanger.

Homeowners should not keep resetting an overheat fault. Turn the boiler off, allow it to cool and call a heating engineer or Gas Safe engineer if the code returns.

Alpha E8 / E08 Fault Code

The Alpha E8 fault code is commonly linked with the maximum number of resets being reached. In simple terms, the boiler has already been reset several times and is now preventing further reset attempts until the original issue is dealt with.

This matters because E8 is often not the first fault. It may appear after repeated attempts to clear another problem, such as ignition failure, flame loss, low pressure or another lockout condition.

Read the full guide: Alpha E8 fault code

Alpha E10 Fault Code

The Alpha E10 fault code usually means low primary system pressure. If the boiler pressure drops too low, the boiler may stop operating to protect itself.

Safe checks include:

Check the pressure gauge when the boiler is cold.
Look for visible leaks around radiators, pipework and beneath the boiler.
Think about whether radiators have recently been bled.
Repressurise only if you understand your filling loop and there is no visible leak.

Alpha fault tables list code 10 as primary system pressure low. Related checks can include the expansion vessel pressure, system leaks, expansion relief valve operation and primary pressure switch.

Read the full guide: Alpha E10 fault code

Alpha E16 Fault Code

The Alpha E16 fault code usually points towards a fan fault. The fan is an important safety-related component because it helps move combustion air and flue gases correctly.

Possible causes include:

Fan wiring connection issue
Fan fault
PCB fault

The Alpha E-Tec fault table lists fan wiring connections, fan fault and PCB fault as possible causes for fan-related fault code 16.

This is not a DIY fault. Fan, PCB and combustion-related checks must be handled by a Gas Safe registered engineer.

Alpha E20 Fault Code

The Alpha E20 fault code commonly relates to flame sensing. This means the boiler may be having trouble confirming the flame signal correctly.

Possible causes can include:

Flame sensing electrode issue
Flame sensing electrode lead issue
PCB fault
Wiring or connection problem

The Alpha E-Tec Regular fault table lists code 20 as a flame sensing fault and points towards the flame sensing electrode, lead and PCB checks.

Read the full guide: Alpha E20 fault code

Alpha E27 Fault Code

The Alpha E27 fault code usually relates to primary flow or circulation. On common Alpha fault-code tables, code 27 is described as insufficient primary flow. On the E-Tec 28 and 33 table, code 27 is associated with primary circuit overheat caused by insufficient circulation.

Possible causes include:

Blocked or restricted primary flow
Air in the heat exchanger
Boiler or heating circuit valve closed
Pump fault
Primary flow sensor fault

Homeowners can check whether the boiler pressure looks normal and whether radiator valves are open. However, pump, sensor and internal circulation checks should be carried out by a heating engineer or Gas Safe engineer.

Alpha E37 Fault Code

The Alpha E37 fault code is commonly linked with low supply voltage. If the voltage reaching the boiler is too low or unstable, the boiler may stop operating correctly.

Safe checks include:

Check whether there has been a local power cut.
Check whether other electrical appliances are affected.
Check the consumer unit has not tripped.
Do not open the boiler casing or test internal wiring.

The E-Tec fault table describes code 37 as low supply voltage and notes insufficient supply voltage to operate the boiler.

Read the full guide: Alpha E37 fault code

Alpha E43 Fault Code

The Alpha E43 fault code commonly relates to loss of flame rectification. In plain English, the boiler has detected a flame problem during operation.

Possible causes may include:

Gas supply or working-pressure issue
Flame sensing electrode or lead fault
Flue gas recirculation
Gas valve setting issue
Fan speed setting issue

Common Alpha fault-code tables describe code 43 as loss of flame rectification and list gas supply, flame sensing electrode, flue gas recirculation, gas valve settings and fan speed settings among the checks.

Read the full guide: Alpha E43 fault code

Alpha E45 Fault Code

The Alpha E45 fault code usually means the boiler has detected a high temperature difference between the flow and return sensors.

This can suggest that water is not circulating through the boiler and heating system as expected. The boiler may limit output to protect itself and may resume normal operation once conditions return to normal.

Common fault-code tables describe code 45 as a high-temperature difference where the boiler detects an unexpected increase between the system flow and return sensors.

Possible causes may include:

Restricted circulation
Air in the system
Blocked filter or heat exchanger restriction
Pump issue
Flow or return sensor issue
Closed or partially closed valves

A homeowner can check pressure and visible radiator valves, but repeated E45 faults should be diagnosed by an engineer.

Alpha E78 Fault Code

The Alpha E78 fault code should be treated carefully because it is not clearly listed across the common Alpha E-Tec 28/33 and InTec C/X fault tables checked for this guide.

E78 appears to be model-specific. Do not assume its meaning without checking the manual for the exact Alpha boiler model.

If an Alpha boiler displays E78, note the full boiler model from the data plate and check the correct manual or contact Alpha technical support through a qualified engineer.

Alpha E96 Fault Code

The Alpha E96 fault code is commonly discussed as a blocked or restricted flue, airflow or flue-sensing related issue on some Alpha models, including some InTec/Eco2-style discussions. However, this should always be checked against the exact boiler manual.

Because E96 can involve the flue, airflow, combustion circuit, fan pressure or flue sensor, it should not be treated as a homeowner repair. A homeowner may visually check from outside that the external flue terminal is not obviously blocked by leaves, snow or debris, but internal flue, fan and combustion checks are Gas Safe engineer work.

Read the full guide: Alpha E96 fault code

Safe Checks for Homeowners

You can carry out a few simple checks before calling an engineer, as long as you do not remove the boiler cover or touch internal parts.

Safe checks include:

Check the fault code shown on the display.
Check the boiler pressure gauge when the system is cold.
Check whether other gas appliances are working.
Check whether there has been a power cut.
Check the thermostat is calling for heat.
Check radiator valves are open.
Look for visible leaks around radiators and pipework.
Visually check the outside flue terminal if it is safely accessible from ground level.
Reset the boiler once only if the manual says it is safe to do so.

For reset guidance, read: How to reset an Alpha boiler

When to Call a Gas Safe Engineer

Call a Gas Safe registered engineer if:

The same fault code returns after one reset.
The boiler keeps losing pressure.
You can smell gas.
The fault involves ignition, flame sensing or gas supply.
The fault involves a fan, flue, PCB, gas valve or internal wiring.
The boiler has overheated.
The boiler case needs removing.
The fault code is not listed in your manual.
The boiler displays E16, E20, E43, E96 or repeated E01.

Do not keep resetting a boiler to force it to run. Repeated resets can hide the original fault and may make diagnosis harder.

FAQs