Boiler
112
Error code 112 on a Potterton boiler indicates an overheat condition — the boiler has detected that its internal temperature has exceeded safe limits and has shut itself down as a safety precaution. This is not a fault to ignore; left unresolved, it can cause lasting damage to heat exchanger components.
What does this error mean?
The boiler’s safety thermostat or thermistor has registered a temperature above the designed maximum threshold — typically around 95–100°C on Potterton models. The boiler locks out automatically to prevent damage to internal components and to eliminate any risk of a dangerous pressure or temperature event. The fault will not clear on its own; the root cause must be identified before normal operation can resume.
Est. repair cost
£80–£250 for professional repair (pump, sensor, or flush); heat exchanger replacement £300–£600; new boiler £1,800–£3,500 installed
🔍 Likely causes
🛠️ Step-by-step fix
Check the boiler pressure gauge: it should read between 1.0 and 1.5 bar when cold. If it’s below 1 bar, top up via the filling loop (consult your manual for the exact procedure) and attempt a reset.
Attempt a boiler reset: press and hold the reset button (usually marked with a flame and cross symbol) for 3–5 seconds. If the boiler fires and runs normally, monitor it closely for 30 minutes.
Check all radiator valves and system isolation valves are fully open — a closed valve anywhere in the system can restrict flow and cause overheating at the boiler.
Bleed your radiators to release any trapped air: use a radiator key, open the bleed valve until water (not air) flows steadily, then re-check boiler pressure and top up if needed.
If the boiler locks out again after a successful reset, stop here — do not keep resetting repeatedly. Repeated resets without fixing the root cause can damage the heat exchanger and may be a gas safety risk.
Call a Gas Safe registered engineer for all further diagnosis and repair. This is a legal requirement in the UK — it is illegal for an unqualified person to work on gas appliances beyond the steps above.
📞 When to call a professional
If the boiler locks out again within a short time of resetting, or if you cannot identify an obvious cause such as low pressure or a closed valve, call a Gas Safe registered engineer immediately. Tell them: ‘My Potterton boiler is showing error code 112, it’s locking out on overheat, and a reset only fixes it temporarily.’ Do not attempt to open or modify any gas components — this is illegal without Gas Safe registration and extremely dangerous.
⚖️ Repair or replace?
A professional repair for a 112 fault typically costs £80–£250 depending on the cause — a pump replacement sits at the lower end, while a heat exchanger descale or replacement is more expensive. If your Potterton boiler is over 10–12 years old and requires a heat exchanger or pump, a new boiler installation (£1,800–£3,500 fully fitted) is likely better value long-term. For boilers under 8 years old in otherwise good condition, repair is almost always the right call.