BoilerFaultCodesAlpha 0E99 Fault Code
The Alpha 0E99 fault code means: your boiler is struggling to talk to another heating unit connected to it, which is preventing the system from operating correctly.. It appears on 3 Alpha models in our database.
Technical description: Simple cascade communication error.
What causes the Alpha 0E99 fault?
This fault occurs when the communication link between multiple boilers in a shared system is broken or interrupted. The most common reason is a loose connection in the wiring that links the units together, or a failure in the electronic control board that manages how the boilers talk to each other.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Alpha models that show the 0E99 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Alpha 0E99 fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026