Remeha H.01.13 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha H.01.13 fault code mean?
The H.01.13 fault code (displayed as E13 on Remeha Avanta Plus and similar domestic models) means the thermal fuse built into the main heat exchanger has blown. This fuse is a last-resort safety device that reacts to extreme heat on the outer casing of the heat exchanger — the kind of temperature that could ignite surrounding plastic components. Unlike the overheat stats that protect the primary water circuit, this thermal fuse specifically guards against combustion-side heat escaping into the boiler casing. Once it blows, the boiler locks out permanently and cannot be reset — the heat exchanger itself must be investigated and almost certainly replaced before the boiler will fire again.
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
- Heat exchanger failure (internal damage or bent coils) Common
The heat exchanger itself can fail on the combustion side — for example, if the internal coils have deformed or corroded, hot combustion gases bypass the heat transfer surfaces and leak excessive heat into the surrounding casing. This is the direct trigger for the thermal fuse. Simply fitting a replacement part without identifying why this happened risks the same fault recurring on the new unit.
- No water flow or critically low system pressure Common
If circulation through the boiler stops — whether due to a seized pump, airlocked pipework, or pressure that has dropped too low — the heat exchanger receives no coolant and overheats rapidly. The thermal fuse then blows as the final line of defence. Check your system pressure gauge: it should read between 1 and 1.5 bar when cold.
- Sludge build-up restricting flow Common
Years of corrosion debris accumulating in the system can partially or fully block the boiler circuit, starving the heat exchanger of adequate flow. This is especially likely in systems that have never been power-flushed or chemically treated. Noisy pipework and slow-to-warm radiators are warning signs that often precede this fault.
- Blocked or restricted plate heat exchanger (DHW circuit) Sometimes
On combination boilers, a scaled or blocked plate heat exchanger for the hot water circuit can reduce overall flow through the boiler. If hot water output has been noticeably weak before this fault appeared, a restriction here may be a contributing factor.
- Faulty diverter valve Sometimes
A diverter valve that is stuck or not switching correctly can prevent water from circulating through the correct circuit at the right time, leading to localised overheating in the heat exchanger. If central heating was working normally but hot water was poor, the diverter valve is worth investigating.
- Lack of servicing Sometimes
Remeha service kits are relatively expensive, and boilers that have gone several years without a proper annual service are more vulnerable to component degradation, sludge accumulation, and early heat exchanger failure. Poor maintenance history is a common background factor in this fault appearing prematurely.
How to fix it
- Do not attempt to reset the boiler repeatedly DIY safe
Unlike many fault codes, H.01.13 / E13 will not clear with a reset because the thermal fuse is a one-time device. Pressing reset will not restore operation and repeated attempts will not help. Leave the boiler off and proceed to the next steps.
- Check your system pressure DIY safe
Look at the pressure gauge on the boiler — it should read between 1 and 1.5 bar when the system is cold. If it is below 0.5 bar, the system may have been running low on water, which can contribute to overheating. You can top up pressure via the filling loop (refer to your boiler manual), but be aware this alone will not resolve the underlying fault.
- Check that your gas supply is working DIY safe
Confirm that other gas appliances in your home (hob, gas fire) are working normally. If there is no gas supply to the property, contact your gas supplier. This step is unlikely to be the cause of this particular fault but is a quick sanity check before calling an engineer.
- Check your warranty status before spending anything DIY safe
Remeha (part of the Baxi group) offers a standard 2-year warranty on its products and a separate 5-year warranty on heat exchangers on qualifying models. If your boiler is within either of these periods and has been serviced in line with the manufacturer's requirements, the repair may be covered at no cost to you. Locate your installation paperwork or contact Remeha / your installer before authorising any paid repair.
- Call a Gas Safe registered engineer to diagnose the root cause Gas Safe engineer
A qualified engineer needs to confirm that the thermal fuse has blown and, critically, establish why the heat exchanger overheated in the first place. This is essential — fitting a new heat exchanger without addressing the root cause (pump condition, flow rate, system cleanliness, flue integrity) will result in the same fault occurring again, often within months.
- Engineer to replace the heat exchanger if confirmed faulty Gas Safe engineer
Replacing a Remeha heat exchanger is a major strip-down job. The component connects to the burner, fan assembly, and primary pipework, so a large portion of the boiler must be dismantled to access it. This is time-consuming skilled work and parts are expensive — discuss the repair-versus-replace decision openly with your engineer, particularly if the boiler is over 10 years old.
- Consider a power flush or system clean as part of the repair Gas Safe engineer
If sludge, scale, or debris contributed to the overheating, the engineer should recommend a power flush or chemical system clean before the new heat exchanger is commissioned. Skipping this step leaves the root cause unresolved and risks damaging the replacement part prematurely.
Parts you may need
- Remeha primary heat exchanger · from £520
- Central heating pump · from £85
- Diverter valve assembly · from £65
- Plate heat exchanger (DHW) · from £90
- Annual service kit (Remeha) · from £110
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 £450–£850, depending on the underlying cause.
Frequently asked questions
Can I reset a Remeha E13 / H.01.13 fault myself?
No. The E13 fault is caused by a one-time thermal fuse inside the heat exchanger that blows at extreme temperature — it is not resettable. Unlike a standard overheat lockout, no amount of pressing the reset button will clear this fault. The boiler will remain locked out until a Gas Safe engineer has inspected the heat exchanger and, in most cases, replaced it.
Is the heat exchanger covered under warranty?
Remeha offers a 5-year warranty on heat exchangers on qualifying models, provided the boiler has been installed and serviced according to manufacturer guidelines. Standard product warranty is 2 years. If your boiler falls within these periods, contact Remeha or your original installer before authorising any paid repair — a valid warranty claim could save you several hundred pounds.
Should I repair or replace my Remeha boiler if I have this fault?
This depends largely on the age of the boiler and its service history. If the unit is under 7–8 years old and has been regularly serviced, a heat exchanger replacement (typically £450–£850 including labour) can be worthwhile. However, if the boiler is over 10 years old, the repair cost starts to approach the price of a new boiler — typically £2,000–£2,500 installed for an average UK property — and the remaining components will be similarly aged. Many engineers will recommend replacement in that scenario, and it is worth getting a like-for-like quote to compare.
Could a power flush prevent this fault from happening again?
If restricted circulation or sludge build-up contributed to the heat exchanger overheating, then yes — a power flush that clears debris and restores proper flow is an important part of the repair, not an optional extra. Fitting a new heat exchanger without addressing poor system water quality significantly increases the chance of the fault recurring. A power flush typically costs £300–£500 depending on system size and is usually recommended by the engineer as part of the overall fix.