Error E50

Safety precautions:

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

- Before opening the boiler or touching electrical parts switch the boiler off at the control, isolate the electrical supply at the fuse or RCD, and turn off the gas supply if you will access internal components. Only a Gas Safe engineer should work on gas-carrying parts, the burner, or the PCB.

- If you are not competent with basic electrical checks, do not open the boiler. Incorrect work can be dangerous and will invalidate warranties or insurance.

Initial checks a homeowner can do (no tools required):

1. Note the error code and any other codes or LEDs shown. Take a photo of the display for the engineer. Record the boiler model and serial number.

2. Try a boiler reset following the manufacturer procedure (use the reset button or selector switch as described in your manual). If the fault clears and stays cleared, monitor for recurrence. If it returns immediately or soon after, further action is needed.

3. Check system water pressure on the boiler gauge—very low pressure can cause faults elsewhere. Top up only if you know how and the pressure is low. If pressure repeatedly drops, call an engineer.

4. Check external obvious issues: ensure the flue terminal and condensate pipe are not blocked or frozen, and that there are no visible leaks or water ingress around the boiler or pipework.

Specific diagnostic steps (only if you are competent and have isolated power):

5. Visually inspect the accessible wiring and connectors to the DHW sensor (often near the domestic hot-water coil or immersion area on tank versions). Look for loose plugs, corroded pins, dampness, or damaged insulation. Re-seating a visibly loose connector can sometimes clear a fault, but only do this with power isolated.

6. If you have a multimeter and know how to use it safely, you can check the sensor electrical condition with power isolated: disconnect the sensor connector and measure resistance across the sensor pins. An NTC thermistor will show a resistance in the kilo-ohm range at room temperature and that resistance will change when warmed or cooled. An open circuit (infinite reading) or near-zero ohms (short) indicates a failed sensor. If you are unsure about expected values for your model, do not attempt replacement—record the readings and call an engineer.

7. If wiring and the sensor appear OK but the error persists, the fault may be intermittent wiring, a failing PCB input, or another internal fault. Do not attempt to repair PCB or replace electrical components yourself—this must be done by a Gas Safe engineer or qualified appliance electrician.

Fix and next steps:

8. If your checks show the sensor is faulty (open or short) or the connector is irreparably corroded, arrange for a Gas Safe registered engineer to replace the DHW NTC sensor and any seals/grommets. The engineer will also check wiring, test the PCB input, and verify safe operation.

9. If the fault was cleared by a simple reset but returns, call a professional—intermittent faults often indicate a failing sensor or wiring problem that will worsen.

10. When you contact an engineer, give them the boiler model, serial number, the exact error code (E50), how long the fault has been present, and any steps you have already taken. Provide photos of the display and any suspect wiring or corrosion.

Final note: E50 is primarily an electrical temperature-sensor fault. While simple resets and visual checks are reasonable for a homeowner, replacing sensors, repairing wiring inside the casing, or any work involving gas or combustion components must be carried out by a Gas Safe registered engineer to ensure safety and compliance.