Boiler
116
Error code 116 on a Potterton boiler indicates a fault with the boiler’s temperature sensor (NTC sensor), meaning the boiler cannot accurately read its own water temperature and has shut down as a safety precaution. It’s a moderately serious fault — your heating and hot water will be off until it’s resolved.
What does this error mean?
The 116 code tells you the boiler’s NTC (Negative Temperature Coefficient) thermistor — a small sensor inside the heat exchanger — is reading a temperature outside the expected range, or has failed entirely. The boiler’s control board uses this sensor to regulate burner output and prevent overheating. When the reading is absent or erratic, the boiler locks out to protect itself and your home.
Est. repair cost
£150–£300 for professional NTC sensor or wiring repair; £15–£40 for the part alone (Gas Safe engineer labour required)
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Reset the boiler: Press and hold the reset button (usually marked with a flame or ‘R’) for 3–5 seconds. Wait 2 minutes. If the boiler fires up and runs normally, the fault may have been a temporary sensor glitch. Monitor it closely.
Step 2 — Check your system pressure: Look at the pressure gauge on the boiler front panel. It should read between 1–1.5 bar when cold. If it’s below 1 bar, top up via the filling loop and try resetting again. Low pressure can cause erratic temperature sensor behaviour.
Step 3 — Bleed your radiators: Trapped air in the system can cause hot spots and false sensor readings. Use a radiator key to bleed each radiator until water flows steadily, then re-check boiler pressure and reset.
Step 4 — Inspect visible wiring (visual check only): If you can safely see the wiring around the boiler (without removing panels), look for any obviously burnt, disconnected, or melted cables. Do not touch internal components or remove the boiler casing — this must be done by a Gas Safe engineer.
Step 5 — If the error returns after reset: Stop here. Do not attempt further DIY. The NTC sensor, wiring, or PCB will need professional diagnosis and replacement. Call a Gas Safe registered engineer and quote error code 116.
📞 When to call a professional
If the boiler locks out again within a few hours of resetting, or if the reset doesn’t clear the code at all, call a Gas Safe registered engineer immediately — do not attempt to open the boiler casing yourself, as this is illegal and dangerous on a gas appliance. Tell the engineer: ‘My Potterton boiler is showing error code 116, which I understand is an NTC temperature sensor fault.’ This will save diagnostic time and potentially reduce your call-out cost.
⚖️ Repair or replace?
An NTC sensor replacement typically costs £150–£300 all-in with a Gas Safe engineer (parts are inexpensive at £15–£40, but labour dominates the cost). If your Potterton boiler is over 10 years old and this is one of several recent faults, a new boiler (typically £1,800–£3,000 installed) is likely more cost-effective than repeated repairs. For a boiler under 8 years old with no prior history of faults, repair is almost always the right call.