Error E55

Safety precautions:

- If you smell gas, leave the property immediately and call the emergency gas number — do not attempt any checks.

- Before doing anything on the boiler, switch it off at the boiler control, then isolate power at the fused spur or wall switch. Allow at least 2–3 minutes for the electronics to fully power down.

- Do not remove the boiler cover or probe internal wiring unless you are a Gas Safe registered engineer. PCB work and calibration must only be done by qualified personnel.

Initial checks a homeowner can do:

1. Note the exact error code, any other displayed codes, and when it started (after a power cut, storm, etc.).

2. Check the external mains switch/fused spur to confirm the boiler has a stable power supply and check the fuse in the spur or consumer unit for a blown fuse.

3. Check that the gas supply to the property is on and any external controls (room thermostat, programmer, smart heating hub) are calling for heat and communicating correctly. If you use a wireless thermostat, confirm it is paired and batteries are okay.

4. Check boiler water pressure is in the normal range (typically around 1–1.5 bar when cold). Low pressure can cause unrelated lockouts but is worth confirming.

Controlled reset (safe first step):

1. Turn the boiler off at the control panel.

2. Isolate the boiler at the fused spur or wall switch and wait 2–3 minutes.

3. Restore power at the fused spur/wall switch and switch the boiler on.

4. Use the boiler’s reset function: either press and hold the reset button (often a flame symbol) for about 3–5 seconds, or turn the selector to R (Reset) and hold for 5 seconds, depending on your fascia. Wait for the boiler to attempt a restart and observe whether E55 clears and the boiler returns to normal operation.

5. If the code clears and the boiler runs normally, monitor for recurrence. If E55 returns intermittently, record when it occurs and any preceding events (power cuts, storms, flue blockage, noisy pump) — this information helps the engineer diagnose.

If the E55 code persists after reset or returns immediately:

- Do not keep repeatedly resetting the boiler. Repeated resets can mask a developing fault and may stress components.

- The likely causes that need professional assessment are: a PCB that needs service/calibration, a faulty or corroded communication cable or connector, failed temperature sensors (NTC), a faulty pump/valve affecting feedback to the PCB, or mains voltage issues.

Information and checks to prepare for the engineer:

- Boiler make and model (Baxi GA range), serial number, and age if known.

- Exact error code and whether any other codes appeared.

- What you have already tried (power cycle, reset, checks of gas supply and pressure) and when the fault started.

- Any recent events (power cut, work to the heating system, water leaks).

What a Gas Safe registered engineer will do (diagnostic steps they will perform):

- Safely isolate and open the boiler to inspect the PCB, wiring looms and connectors for corrosion, loose pins or water ingress.

- Measure mains supply voltage and check for voltage drops or irregular supply that can cause communication/calibration errors.

- Use the service menu to read fault history, run diagnostics and attempt the official calibration/auto‑set procedure for combustion and sensors.

- Test and if required replace or re‑secure sensors (flow and return NTCs, hot water sensor), check flame sensing electrodes and the gas valve wiring, and test communication cables to external controls.

- If the PCB fails internal tests or cannot be calibrated, the engineer may recommend replacement of the PCB or its reprogramming by an authorised service agent.

Final note:

- E55 frequently starts as a temporary communication glitch and can be fixed with a safe reset, but if it persists it indicates an electrical or control fault that requires a Gas Safe registered engineer. Do not attempt internal repairs, calibration or PCB replacement yourself.