Boiler
F10
The F10 error code on an Intergas boiler indicates a problem with the central heating flow temperature sensor — the boiler is detecting an abnormal or missing temperature reading and has shut itself down as a safety precaution. It’s one of the more common fault codes on Intergas HRE, Kombi Kompact, and ECO RF models, and while it can sometimes be cleared with a simple reset, it often points to a faulty sensor or underlying circulation issue that needs professional attention. In this guide, you’ll learn exactly what F10 means, the most likely causes, what you can safely check yourself, and when to call a Gas Safe registered engineer.
What does this error mean?
The F10 fault code on an Intergas boiler means the boiler’s control board has detected a fault with the CH (central heating) flow temperature sensor, also known as the NTC flow sensor or flow thermistor. This small sensor monitors how hot the water is as it leaves the heat exchanger and heads out to your radiators. When the sensor reads a temperature that is outside the expected range — either implausibly high, implausibly low, or a completely absent signal — the boiler’s built-in safety system triggers an F10 lockout and shuts the boiler down to prevent overheating or damage. Importantly, the F10 code doesn’t always mean the sensor itself has physically failed; a broken wire, a poor electrical connection, or a genuine overheating event (caused by something like a blocked pump or low system pressure) can all produce the same code. Think of it as the boiler saying: ‘I can’t trust what the temperature sensor is telling me, so I’m not going to fire.’
Est. repair cost
£80–£150 for an NTC sensor replacement (parts and labour); £150–£300 for pump-related repairs; £300–£500 if a PCB replacement is required. Gas Safe engineer call-out fees in the UK typically range from £60–£100 before parts.
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Check your boiler pressure gauge first. Look at the pressure gauge on the front of the boiler (usually found below the display). It should read between 1.0 and 1.5 bar when the system is cold. If it is below 1 bar, repressurise the system using the filling loop (consult your Intergas manual for the exact procedure for your model) until it reads around 1.2 bar, then attempt a reset.
Step 2 — Perform a boiler reset. On most Intergas models, press and hold the reset button (marked with a flame or ‘R’ symbol) for 3–5 seconds until the display changes. Allow the boiler to attempt a restart. If the F10 code clears and the boiler fires successfully, monitor it over the next 24–48 hours to see if the fault returns.
Step 3 — Check all radiator valves are open. Make sure that thermostatic radiator valves (TRVs) throughout the house are not all closed simultaneously — this restricts flow and can cause the flow temperature to spike. Open TRVs in at least two or three rooms to ensure adequate circulation.
Step 4 — Bleed any air-locked radiators. Turn off the boiler, use a radiator bleed key to release any trapped air from the highest and furthest radiators in the system, then repressurise if needed before restarting. Air locks restrict water flow and can contribute to localised overheating.
Step 5 — Check for any visible leaks near the boiler. Inspect the pipework, joints, and the area around the boiler casing for signs of dripping water. A slow leak can gradually reduce system pressure and cause repeated F10 lockouts. Do not attempt to fix any gas or internal pipework yourself.
Step 6 — Do NOT attempt to access the boiler’s internal components. Replacing the NTC flow sensor, checking PCB connections, or inspecting the pump all require removing the boiler casing and working near live gas and electrical components. This is not a safe DIY task — stop here and contact a Gas Safe registered engineer.
Step 7 — Make a note of what you’ve tried. Before calling an engineer, write down: the error code (F10), your boiler model (e.g. Intergas HRE 36 or Kombi Kompact 28), the system pressure when you found the fault, and any steps you have already attempted. This will save the engineer time and may reduce your call-out cost.
📞 When to call a professional
Because the F10 fault code on an Intergas boiler relates to a temperature sensor and its associated wiring or PCB — all of which are located inside the boiler casing alongside live gas components — you should call a Gas Safe registered engineer as soon as your basic checks (pressure, reset, bleeding radiators) have not resolved the fault. Do not attempt to open the boiler casing, touch the sensor, or inspect internal wiring yourself. When you call, tell the engineer: ‘My Intergas boiler is showing an F10 error code, which I understand relates to the CH flow temperature sensor. I’ve checked the system pressure, reset the boiler, and bled the radiators, but the fault keeps returning.’ This gives them a clear starting point and confirms you’ve already ruled out the simple fixes. If you do not already have an engineer, visit the Gas Safe Register website (gassaferegister.co.uk) to find a qualified local engineer — always check their Gas Safe ID card before any work begins.
⚖️ Repair or replace?
For most homeowners, the repair decision for an F10 fault comes down to two things: the age of the boiler and the cost of the failed component. If your Intergas boiler is under 10 years old, repair is almost always the right call. Intergas is a Dutch brand with an excellent reputation for reliability and a strong UK parts network, so NTC sensors and wiring harnesses are readily available and relatively inexpensive. A straightforward sensor replacement by a Gas Safe engineer is a quick job — typically under an hour — and is well worth doing. If your boiler is between 10 and 15 years old, ask the engineer to give you an honest assessment of the heat exchanger and pump condition while they’re there. If those components are also showing wear, a new boiler may be more cost-effective in the long run, particularly given modern boilers’ improved energy efficiency. If the F10 fault is caused by a failed PCB, the calculation changes — PCB replacement can cost £300–£500 in parts and labour, at which point a boiler aged over 10 years is often better replaced. Intergas boilers typically come with a manufacturer’s warranty of 2–5 years depending on the model and registration, so if your boiler is still within warranty, contact Intergas directly before paying for any repairs.