Overview
Error 127 on a Baxi EcoBlue means the boiler did not reach the programmed legionella (anti‑Legionella or hot water sanitisation) temperature during a scheduled hot water cycle. Many modern boilers run a periodic high‑temperature cycle (often around 60°C or higher) to reduce the risk of Legionella bacteria in the domestic hot water system; the error is a protective alert saying that target temperature was not achieved or the boiler failed to complete that cycle. This can occur for several reasons: the domestic hot water thermostat or sensor may be faulty or out of calibration, there may be poor circulation or flow during the cycle, the boiler controls or programmer may be set incorrectly or disabled, gas supply or ignition problems can prevent the burner reaching the required temperature, or internal components such as the heat exchanger, pump, diverter valve or PCB may be failing. In some cases the fault is temporary (sensor glitch, brief loss of gas or low system pressure) and can be cleared by a reset; in other cases it indicates a persistent fault that needs professional attention. Severity: because this relates to the failure to reach a legionella‑control temperature, it is important to address it rather than ignore it. The immediate risk to health in a single event is low if you use hot water normally, but repeated failure of the sanitisation cycle increases the long‑term risk of Legionella growth in stored or slow‑moving hot water systems. For safety and correct diagnosis, start with homeowner checks and resets. If the error persists, call a Gas Safe registered heating engineer to investigate and repair — do not attempt gas or sealed‑system repairs yourself.
Possible Cause: Legionella (cause of Legionnaires’ disease) protection temperature not reached
Troubleshooting Steps
Safety precautions:
1. If you smell gas, leave the property immediately and call the gas emergency number — do not operate electrical switches or the boiler. Call a Gas Safe engineer.
2. Turn off the boiler at the control panel if instructed by the manual when carrying out simple checks. Isolate electrical supply at the fused spur only if you are confident and it is safe to do so. Do not open or attempt repairs on gas or sealed components unless you are Gas Safe registered.
3. Be careful of scald risk when testing hot water — running water at higher temperatures can cause burns; test with a hand or a thermometer carefully.
Initial checks a homeowner can do:
1. Note when the error appeared and whether hot water or central heating is affected. Try to reproduce the problem by calling for hot water (open a hot tap) and observing whether the boiler tries to run.
2. Check boiler display for any additional messages or linked fault codes. Some Baxi models show an E or additional digits; record everything for the engineer.
3. Check the domestic hot water temperature setting on the boiler or cylinder thermostat and on any separate programmer or thermostatic mixing valve. Ensure the legionella/anti‑legionella feature has not been disabled in the menu.
4. Check system pressure on the boiler gauge (aim for normal operating range, typically 1–1.5 bar for combi/systems when cold). Low pressure can cause circulation failures.
5. Try a basic reset: use the boiler reset procedure for your model (press and hold the reset or selector switch in the R position for about 5–10 seconds). Do not repeatedly reset more than 2–3 times; if the fault returns, stop and get professional help.
Specific diagnostic and possible DIY fixes to try:
1. Run a sustained hot water demand: open a hot tap fully and let it run for several minutes while watching the boiler. If the burner fires and water heats to a high temperature, the error may clear after a completed cycle. If the boiler never reaches the required temperature, continue checks.
2. Check the hot water temperature setpoint: increase the DHW temperature slightly (if user adjustable) and try another hot water draw to see if the boiler reaches the higher setpoint. Remember higher settings increase scald risk.
3. Bleed radiators and vents only if central heating circulation problems are suspected and you know how. Air in the system can interfere with circulation but bleeding applies to central heating circuits rather than domestic hot water in combi boilers.
4. Check for obvious signs of blockage or freezing on external condensate pipe (winter): a blocked condensate can cause faults on some models. Thaw frozen condensate with warm water (not boiling) if safe and accessible.
5. Confirm gas supply and ignition: ensure the gas supply is on and any external meters or isolation valves are open. If the boiler attempts to ignite then locks out, log any ignition or flame loss errors and stop further resets.
6. Check cylinder or stored hot water controls if you have a separate hot water cylinder: the immersion thermostat or programmer may be disabled or set incorrectly; thermostatic mixing valves may be diverting water and preventing full cylinder temperature — check settings and ensure timers are calling for a full heat cycle.
When to call a professional and why:
1. Call a Gas Safe registered heating engineer if the error returns after a reset or if you cannot identify an obvious temporary cause. Do not attempt internal boiler or gas component repairs yourself.
2. A professional will test sensors (DHW NTC), thermostats, the plate heat exchanger, pump operation, diverter valve, and combustion (gas valve/ignition) and will correctly diagnose PCB or parameter faults. They can also confirm legionella protection settings and carry out safe repairs or part replacements.
3. If the engineer advises, ensure the anti‑scald/thermostatic mixing valve, cylinder thermostat or storage setup is inspected and set correctly so that stored water reaches a safe sanitisation temperature while protecting users from scalding.
Final notes:
1. Do not keep resetting the boiler repeatedly — this can mask faults and cause further damage. If Error 127 persists, contact a Gas Safe registered engineer.
2. If you have a hot water storage cylinder, run a manual high‑temperature cycle if safe to do so (consult the cylinder manual or a plumber) to reduce short‑term risk, but only after confirming water will not scald vulnerable users.
3. Keep a record of fault codes, dates and any steps you have taken; this helps the engineer diagnose the issue more quickly.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Baxi EcoBlue.