Error E50

Safety first

1) If you smell gas, leave the property immediately, do not operate electrical switches, and call the gas emergency number. 2) Before touching the boiler, switch off the electrical supply at the isolator and the mains. If you are not confident working around electrical equipment or plumbing, stop and call a professional. 3) Do not attempt any gas or combustion component repairs yourself — these must be done by a Gas Safe registered engineer.

Initial quick checks a homeowner can do

1) Record the error exactly (E50) and take a photo of the display. This helps the engineer. 2) Try a boiler reset following the instructions in your user manual (typically hold the reset button or use the selector to R for several seconds). Note whether the boiler restarts and whether E50 returns immediately or after some time. 3) Check system water pressure on the pressure gauge; very low pressure can cause circulation issues. Top up if you know how and it is safe to do so. 4) Check that hot water taps are open and there is normal flow — if there is no circulation to the DHW heat exchanger this can cause high temperatures and sensor trips. 5) Inspect the flue terminal and condensate pipe for obvious blockages or freezing (relevant if other related faults are present) and clear obvious external obstructions.

Basic visual diagnostic steps (only if comfortable and with power isolated)

1) Isolate electrical supply to the boiler. Remove the boiler casing only if you are competent; many warranties and safety rules mean owners should not open sealed covers. 2) Locate the hot water temperature sensor/NTC (consult the manual or wiring diagram). Check the wiring connector for corrosion, loose wires or damaged insulation. Reseat any loose connectors. 3) If you have a multimeter and know how to use it safely, you can check continuity of the sensor wiring and the sensor resistance. Do not rely on a single measurement; manufacturer resistance vs temperature charts are required to interpret readings. If you are unsure what the readings should be, stop and call an engineer.

What to try and what to avoid

1) Try reset after any visible connector reseating. If E50 clears and stays cleared during normal operation, monitor the boiler — intermittent faults usually point to a loose wire or connector. 2) If the error returns immediately or the sensor wiring looks damaged, do not attempt to bypass safety devices. 3) Do not spray cleaners or water into the boiler or sensors. Do not apply power to the boiler with covers off unless you are qualified.

When a professional should be called

1) Call a Gas Safe registered engineer if: the fault persists after a reset; wiring looks damaged; sensor replacement is required; there are additional fault codes (overheat, circulation fault, gas supply or fan errors); or you are not confident performing the visual checks above. 2) Tell the engineer the exact model, the E50 code, any other codes, and what checks you have already performed (reset, pressure, photos). This saves time and helps diagnosis.

Likely professional fixes the engineer may perform

1) Confirm sensor fault using diagnostic tools, replace the hot water NTC sensor and its seal if faulty, and test the system. 2) Check and repair wiring/connectors or the PCB if required. 3) Check primary circulation (pump, valves, heat exchanger) to ensure adequate flow and that overheating did not cause a secondary trip. 4) Check flue/condensate and air-pressure components only if they are implicated. 5) Complete a full safety and performance test and clear any lockouts.

Final notes

1) Do not attempt gas, combustion or sealed-component repairs yourself. 2) Keep a record of resets and recurring errors; this information is useful to the engineer. 3) Regular servicing reduces the chance of sensor and circulation faults causing lockouts.