Boiler
110
Error code 110 on a Potterton boiler indicates an overheat fault — the boiler has detected that its internal temperature has exceeded a safe limit and locked out as a safety measure. It’s a serious fault that requires prompt attention and should not be repeatedly reset without investigating the root cause.
What does this error mean?
The 110 error means the boiler’s overheat thermostat or sensor has triggered because the water temperature inside the heat exchanger climbed too high. Potterton boilers are designed to shut down automatically in this situation to prevent damage to components or, in a worst case, a dangerous failure. This is a safety lockout — not a minor glitch — and resetting it without addressing the underlying problem can cause lasting damage to your boiler.
Est. repair cost
£80–£250 for a Gas Safe engineer repair (depending on cause); pump replacement £150–£300 parts and labour
🔍 Likely causes
🛠️ Step-by-step fix
Check your boiler pressure gauge: It should read between 1 and 1.5 bar when cold. If it’s below 1 bar, repressurise the system using the filling loop (see your Potterton manual for your specific model). Low pressure is the most common and easiest fix.
Check that radiator valves and TRVs are open: Walk around your home and make sure thermostatic radiator valves are not all closed at once. Open them to give the heated water somewhere to circulate.
Bleed your radiators: If you hear gurgling or radiators are cold at the top, trapped air may be disrupting circulation. Use a radiator key to bleed each radiator until water (not air) comes out.
Attempt a single reset: Once you’ve checked pressure and valves, press and hold the reset button on your Potterton boiler for 3–5 seconds. If it fires up and runs normally without locking out again within an hour, monitor it closely over the next 24 hours.
Do NOT attempt a second or third reset if the fault returns: Repeatedly resetting an overheating boiler can damage the heat exchanger or pump. If the 110 code comes back, stop resetting and call a Gas Safe registered engineer.
📞 When to call a professional
If the boiler relocks with error 110 after a single reset, or if pressure and valves are all normal, call a Gas Safe registered engineer immediately — do not keep resetting. Tell them: ‘My Potterton boiler is showing error code 110, an overheat lockout, and basic checks haven’t resolved it.’ A qualified engineer will inspect the pump, heat exchanger, and temperature sensors, and carry out a system flush if limescale is suspected.
⚖️ Repair or replace?
A Gas Safe engineer call-out to diagnose and fix a 110 fault typically costs £80–£250 depending on the cause — a pump replacement sits at the higher end, while a sensor swap or system bleed is cheaper. If your Potterton boiler is over 10–12 years old and the heat exchanger is scaled or damaged, repair costs can quickly rival the price of a new boiler (£1,500–£3,000 installed). For boilers under 8 years old with no history of faults, repair is almost always the right call; beyond 12 years, get a replacement quote at the same time as the repair quote.