Remeha H.01.15 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha H.01.15 fault code mean?
The H.01.15 code appears on Remeha Ace-series boilers (including the Quinta Ace and Tzerra Ace ranges) and translates on-screen as 'Max Tflue Gas'. It means the temperature of the exhaust gases leaving the boiler through the flue system has risen above the safe operating threshold. The 'H' prefix tells you this is a blocking fault rather than a permanent lockout — the boiler shuts down temporarily as a precaution, and may attempt to restart automatically once the underlying condition clears. If the fault keeps returning, or the boiler does not recover on its own, investigation by a Gas Safe registered engineer is required.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Blocked or restricted flue terminal Common
The most frequent trigger. Bird nests, wind-blown debris, ice build-up, or physical damage to the external flue terminal can restrict the escape of hot exhaust gases. With nowhere to go efficiently, heat accumulates and trips the sensor. A quick visual check of the terminal from outside the property is a sensible first step.
- Fouled heat exchanger (flue-gas side) Common
Over time, soot, limescale, and combustion residues can coat the flue-gas passages inside the heat exchanger. This insulating layer traps heat within the boiler rather than transferring it to the heating water, causing flue-gas temperatures to climb. This is more likely on older boilers or those that have missed annual services.
- Faulty flue gas NTC temperature sensor Sometimes
The NTC sensor that monitors flue-gas temperature can drift out of calibration or develop an open/short-circuit fault, causing it to report falsely elevated readings and trigger the H.01.15 code even when actual temperatures are within normal range. An engineer can test the sensor's resistance with a multimeter to confirm whether it has failed.
- Exhaust fan fault or poor flue ventilation Sometimes
If the flue fan is running below speed, has a worn bearing, or the flue route is poorly designed with excessive bends, exhaust gases are not expelled quickly enough and heat builds up. A fan that sounds laboured or intermittent is a tell-tale sign.
How to fix it
- Inspect the external flue terminal for obvious blockages DIY safe
Go outside and look at the flue outlet — typically a white plastic terminal on an outside wall or roof. Check for bird nests, leaves, ice, or any physical damage. Do not probe inside the terminal or dismantle anything; simply note what you can see and photograph it to show an engineer. Clear any loose, surface-level debris only if it is safely accessible from ground level.
- Check your boiler's system pressure DIY safe
Look at the pressure gauge on the boiler — it should read between 1.0 and 1.5 bar when cold. If it is below 1.0 bar, top it up via the filling loop. If you are unsure how to do this, refer to your boiler's user manual or contact an engineer.
- Reset the boiler (up to two or three times) DIY safe
Once you have checked the flue terminal and pressure, press the reset button on the boiler. Because H.01.15 is a blocking (H-type) fault, the boiler may restart automatically, but a manual reset can help confirm whether the fault clears. If it returns within a short time, do not keep resetting — repeated resets without fixing the underlying cause can mask a developing problem.
- Have a Gas Safe engineer inspect and clean the flue system Gas Safe engineer
An engineer will check the full length of the flue run for restrictions, measure back-pressure, and inspect the flue fan for correct operation. Cleaning or re-routing a flue must only be carried out by a competent professional, as incorrect flue installation is a serious safety hazard.
- Have a Gas Safe engineer inspect and clean the heat exchanger Gas Safe engineer
The engineer will access the flue-gas side of the heat exchanger, check for soot or scale build-up, and clean it using appropriate brushes or chemical descalers. In some cases the heat exchanger must be partially dismantled for a thorough clean. If it is heavily scaled or corroded, replacement may be recommended.
- Have the flue gas NTC sensor tested and replaced if faulty Gas Safe engineer
Using a multimeter, the engineer will check the sensor's resistance against the manufacturer's specification at a known temperature. Wiring and connectors will also be checked for corrosion or damage. If the sensor is out of specification, a like-for-like replacement should resolve the fault if the flue and heat exchanger are otherwise clear.
- Call a Gas Safe registered engineer if the fault persists or keeps returning Gas Safe engineer
If none of the above steps have resolved the H.01.15 code, or the boiler continues to block out repeatedly, contact a Gas Safe registered engineer. For Remeha-specific technical support you can also call Remeha by Baxi on 0330 678 0140. Do not continue to run the boiler if it is producing this fault regularly — persistent overtemperature can cause long-term damage to the heat exchanger and flue components.
Parts you may need
- Flue gas NTC temperature sensor · from £45
- Flue exhaust fan assembly · from £275
- Primary heat exchanger · from £425
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £120–£400, depending on the underlying cause.
Frequently asked questions
Will the Remeha H.01.15 fault clear itself, or do I need to reset the boiler?
Because H-type codes on Remeha Ace boilers are blocking faults rather than permanent lockouts, the boiler may attempt to restart on its own once temperatures drop back to normal. However, if the root cause is still present the fault will simply return. You can try a manual reset once or twice, but if the code comes back you should arrange for a Gas Safe engineer to investigate rather than continuing to reset.
How much will it cost to fix the H.01.15 fault on my Remeha boiler?
For the most common causes — a blocked flue terminal or a dirty heat exchanger — most homeowners pay somewhere between £120 and £400 including parts and labour. Replacing the flue gas NTC sensor typically sits at the lower end of that range (around £100–£200 all-in). A more involved heat exchanger clean or fan replacement will push towards the higher end. In rare cases where the heat exchanger itself needs replacing, costs can rise to £500–£900 or more; if your boiler is over ten years old, it may be worth comparing that against the cost of a new boiler.
Can I fix the Remeha H.01.15 fault myself?
There is one safe DIY check: take a look at the external flue terminal for any obvious blockage such as a bird nest or ice, and clear anything that is safely accessible from ground level. Beyond that, work on the flue, heat exchanger, sensors, or fan must be done by a Gas Safe registered engineer. Flue systems carry combustion gases and must be left in a safe and correctly sealed condition — improper interference is a legal and safety risk.
What is the difference between an H code and an E code on a Remeha Ace boiler?
Remeha uses the letter prefix to indicate how serious a fault is. An H code (like H.01.15) is a temporary blocking fault — the boiler shuts down as a precaution but may recover automatically once the fault condition passes. An E code is a permanent lockout, meaning the boiler will not restart until a manual reset is performed (and ideally until the fault is investigated). Both types should be taken seriously; a recurring H code that keeps coming back needs the same professional attention as a lockout.