Remeha H.00.16 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha H.00.16 fault code mean?
H.00.16 is a temporary blocking fault on Remeha e-Smart boilers (Tzerra Ace, Quinta Ace, Gas 320/620 Ace and similar ranges). The 'H' prefix means the boiler has halted operation as a precaution but has not permanently locked out — it may self-recover or can be manually reset. Group '00' covers core control and sensing parameters, and sub-code '16' points specifically to a flame detection or ionisation signal anomaly: the control board has either detected an unexpected ionisation signal when the burner should be off (sometimes called a 'ghost flame'), or it has registered an ionisation signal inconsistency during or immediately after a burner firing cycle. Because any unintended flame condition is a safety concern, the boiler shuts down until the issue is resolved. Note that the permanent lockout equivalent of this fault is E.00.16 — if your display shows that code instead, the boiler requires a manual reset after the underlying problem is fixed.
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
- Worn or contaminated ionisation/ignition electrode Common
The combined ignition and ionisation probe is the most common culprit. Over time the electrode tip erodes, accumulates carbon deposits, or the ceramic insulator cracks, causing it to produce weak or erratic ionisation readings. On Remeha e-Smart systems the ionisation current should typically sit between 3 µA and 9 µA; a fouled electrode can read as low as 0.2 µA even when a visible flame is present, which is enough to trigger H.00.16.
- Loose or damaged electrode wiring Common
Boiler vibration gradually works connectors loose between the electrode and the PCB. A poor connection generates a noisy or intermittent signal that the control board interprets as a spurious flame event. An engineer will check the full wiring loom with a multimeter and reseat or replace any damaged connectors.
- Faulty PCB (printed circuit board) Sometimes
If the PCB's ionisation measurement circuitry malfunctions, it can report a flame signal when none exists. This is more likely on older boards or those that have been exposed to moisture. The PCB can be tested electronically before any decision is made to replace it.
- Gas valve leaking by Sometimes
A gas valve that fails to close fully can allow a small residual flow of gas past the seat, which may partially ignite and create a low-level flame signal when the boiler should be fully off. Gas valve faults must only be investigated and rectified by a Gas Safe registered engineer.
- Flue gas recirculation Rare
A blocked, damaged, or poorly routed flue can allow combustion products to be drawn back into the air intake. This alters the air-to-gas ratio and can interfere with the ionisation signal, causing the control board to register signal inconsistencies during and after burner operation.
How to fix it
- Attempt a single boiler reset DIY safe
Locate the reset button on the boiler's front panel (refer to your user guide if unsure). Press and hold as directed, then wait about 60 seconds to see if the boiler fires successfully. If it returns the H.00.16 code immediately or after one or two firing attempts, do not keep resetting — repeated resets without identifying the cause can mask a developing problem.
- Check the system pressure DIY safe
Look at the pressure gauge on the boiler fascia. It should read between 1.0 and 1.5 bar when the system is cold. If it has dropped below 1 bar, top up via the filling loop following your boiler's user guide, then attempt one further reset. Low pressure alone is unlikely to cause this specific code, but it is worth ruling out before calling an engineer.
- Inspect the external flue terminal DIY safe
Go outside and visually check the flue outlet and air intake terminal for obvious obstructions — debris, bird nesting material, or ice in cold weather. Do not attempt to dismantle any flue components; simply clear any external blockage you can reach safely from ground level. If the terminal looks clear, the issue is internal and requires an engineer.
- Engineer: inspect and test the ionisation/ignition electrode Gas Safe engineer
A Gas Safe registered engineer should remove the electrode assembly, check the ceramic insulator for cracks, measure the electrode gap, and test the ionisation current under live firing conditions. A reading outside the 3–9 µA range indicates the electrode needs cleaning or replacement. The electrode itself is a relatively low-cost part (typically £15–£30), making this the first physical component to address.
- Engineer: check CO₂ combustion settings and gas valve operation Gas Safe engineer
Incorrect CO₂ levels at the gas valve affect combustion quality and can destabilise the flame enough to produce erratic ionisation readings. The engineer should verify combustion analysis figures, check the gas valve actuator and seating for signs of leaking-by, and confirm adequate gas pressure and flow rate at full load. Any gas valve work is strictly Gas Safe only.
- Engineer: test the wiring loom and PCB Gas Safe engineer
Using a multimeter, the engineer should check continuity and signal integrity on the wiring between the electrode and the PCB. If wiring checks out, the PCB's ionisation detection circuit should be tested. Depending on the findings, the PCB may be repairable by a specialist, which is generally more cost-effective than a straight replacement.
- Engineer: inspect the flue system for recirculation Gas Safe engineer
If no component fault is found, the engineer should carry out a full flue integrity check — looking for incorrect terminal positioning, gaps in the flue run, or signs that combustion gases are being recirculated into the air supply. Flue modifications must comply with current Gas Safe and Building Regulations requirements.
- Call a Gas Safe registered engineer if the fault persists Gas Safe engineer
If the boiler continues to display H.00.16 after a reset and your basic checks reveal nothing obvious, contact a Gas Safe registered engineer. Provide them with the full code, your boiler model, and any pattern you have noticed (e.g. only faults on ignition, or only after the boiler has been running a while). You can verify any engineer's registration at gassaferegister.co.uk.
Parts you may need
- Ionisation / ignition electrode · from £22
- Electrode lead / ignition cable · from £18
- Gas valve · from £130
- PCB (control board) · from £320
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–£380, depending on the underlying cause.
Frequently asked questions
Can I just keep resetting the boiler to clear H.00.16?
You can try one or two resets — the 'H' blocking code may clear itself if the fault was a momentary signal glitch. However, if the code returns each time the boiler attempts to fire, repeated resets will not fix the underlying problem and could mask a developing fault. Stop resetting after two or three attempts and arrange for a Gas Safe engineer to diagnose the root cause.
What is the difference between H.00.16 and E.00.16?
Both codes point to the same ionisation or flame signal fault, but the prefix tells you how serious it is. An 'H' code is a temporary blocking fault — the boiler has paused and may recover on its own or after a reset. An 'E' code is a permanent lockout, meaning the boiler will not restart at all until a Gas Safe engineer investigates and manually resets the unit. If your display has changed from H.00.16 to E.00.16, the fault has escalated and engineer attendance is now urgent.
My Remeha boiler is still under warranty — will this repair be covered?
Remeha (now marketed as Remeha by Baxi) offers a standard 2-year warranty on commissioned products and a 5-year warranty on the heat exchanger. If your boiler is within its warranty period, contact Remeha's customer support or your installing engineer before arranging an independent repair, as unauthorised work may affect your warranty. A warranty claim could mean the repair costs you nothing.
Could a PCB replacement be the answer, and how much does it cost?
A faulty PCB is a possible but less common cause of H.00.16 — engineers will typically test and replace the electrode and check the gas valve first, as these are cheaper and more frequently at fault. If the PCB does need replacing, the part alone typically costs £280–£380 for Remeha Ace-series boards, plus £100–£150 in labour. Some independent PCB repair specialists can refurbish the board for considerably less. If the PCB replacement cost approaches the value of an older boiler, it may be worth obtaining a new boiler quote for comparison.