Remeha H.02.36 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha H.02.36 fault code mean?
H.02.36 is a Blocking (H-type) code on Remeha boilers using the e-Smart control system. Blocking codes temporarily suspend normal boiler operation as a safety measure — the boiler pauses rather than entering a full lock-out, and in some cases will attempt to restart automatically after a short interval (typically around ten minutes). The .36 sub-number within the H.02 group points to a problem with the secondary (second) return temperature sensor — the sensor is either reading a temperature outside its expected range, or the control system has lost a valid signal from it altogether. This can stem from a failed sensor, a wiring or connector fault, or unusual return-circuit conditions such as poor circulation or very low system pressure. The H.02 group can also be triggered by an external blocking input being active (for example, a frost-protection signal) or by incorrect parameter settings, so context matters. Always allow the boiler a full ten-minute wait before attempting a manual reset, as forcing a reset too early may mask the underlying fault.
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
- Faulty or disconnected secondary return temperature sensor Common
The second return temperature sensor may have developed an open circuit, drifted out of its calibrated resistance range, or become physically dislodged from its pocket. This is the most direct cause implied by the .36 sub-code, which mirrors the H.00.36 'T 2nd Return Open' description found in Remeha service documentation.
- Loose, corroded or damaged sensor wiring Common
Even if the sensor itself is sound, a loose plug, corroded pin or chafed cable between the sensor and the PCB can break the signal and trigger the same blocking condition. Connector corrosion is particularly common in plant-room installations where condensation is present.
- Low system pressure or poor circulation Sometimes
If system pressure has dropped below roughly 0.8 bar, or if the circulating pump is struggling (air-locked, worn, or partially closed valve), return temperatures can behave erratically and cause the control system to flag a sensor-related blocking fault as a precaution.
- External blocking input or frost-protection signal active Sometimes
Remeha's H.02 group of blocking codes can be triggered by an active external blocking input — for example, a building management system (BMS) sending a blocking signal, a frost-stat tripping, or a low-water-pressure switch. In this scenario the sensor itself may be perfectly healthy.
- Incorrect parameter settings on the control board Rare
If the boiler has recently been serviced or the PCB replaced, an incorrectly configured sensor type or circuit parameter can cause the control system to reject valid sensor readings and raise a blocking fault.
How to fix it
- Check system pressure at the boiler gauge DIY safe
The pressure gauge should read between 1.0 and 1.5 bar when the boiler is cold. If it has dropped below 1.0 bar, top up via the filling loop until it reaches about 1.2 bar, then close the filling loop valves fully. A boiler manual will show the filling loop location. Do not overfill beyond 2.0 bar.
- Wait the full ten-minute interval before resetting DIY safe
H-type blocking faults on Remeha's e-Smart system sometimes clear automatically after their internal check interval. Wait at least ten minutes, then press the reset button once. If the fault clears and the boiler fires normally, monitor it over the next hour for a recurrence.
- Attempt up to two further resets if the fault returns immediately DIY safe
A manual reset is acceptable two or three times in total. If the code reappears within minutes each time, do not continue resetting — repeated resets without an underlying fix will not resolve the fault and may complicate diagnosis for the engineer.
- Check that the gas supply is on and other gas appliances work DIY safe
Confirm that other gas appliances in the property (hob, gas fire) are working normally. If no gas is available anywhere, contact your gas supplier — this is not a boiler fault and no further boiler investigation is needed until supply is restored.
- Inspect sensor wiring and connectors (engineer task) Gas Safe engineer
A Gas Safe registered engineer will visually inspect the secondary return sensor and its wiring loom, check for corroded or loose connectors at both the sensor end and the PCB, and test sensor resistance with a multimeter against Remeha's published resistance-temperature table to confirm whether the sensor is within spec.
- Test and replace the secondary return temperature sensor if faulty (engineer task) Gas Safe engineer
If resistance readings are out of range or the sensor shows an open circuit, the engineer will replace it with the correct Remeha-approved part, verify the new sensor reads correctly on the live system, and clear the fault from the control panel.
- Investigate circulation, pump and system pipework (engineer task) Gas Safe engineer
If the sensor tests good, the engineer will check pump operation, flow and return pipework, and whether any motorised valves are stuck or partially closed. They will also verify that no external blocking signal is being sent from a BMS, frost-stat, or external controller.
- Check and correct PCB parameters or replace PCB if required (engineer task) Gas Safe engineer
If wiring, sensor, and circulation all check out, the engineer will review control board parameter settings — particularly sensor-type configuration — and update them if incorrect. A PCB replacement is only considered once all other causes have been ruled out.
- Call a Gas Safe registered engineer Gas Safe engineer
If the steps above have not resolved the fault, or if you are unsure at any point, book a Gas Safe registered engineer with Remeha experience. Provide them with the full code (H.02.36) and note how often it appears and whether it clears on its own, as this will help them diagnose the fault more efficiently.
Parts you may need
- Remeha secondary return temperature sensor (NTC) · from £45
- Sensor wiring loom / connector harness · from £30
- Remeha e-Smart PCB (control board) · from £280
- Circulating pump (Grundfos or equivalent OEM fit) · from £95
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–£320, depending on the underlying cause.
Frequently asked questions
Can I reset a Remeha H.02.36 fault myself?
Yes, a manual reset is a reasonable first step for a homeowner. Wait at least ten minutes after the code appears (some Remeha blocking faults have a built-in ten-minute check interval before they will clear), then press the reset button. If the boiler restarts and runs normally, keep an eye on it over the next hour. If the code comes back within a few minutes, or returns repeatedly over the following days, stop resetting and arrange for a Gas Safe registered engineer to investigate — repeated resets without a fix will not resolve the underlying fault.
What does the 'H' mean in Remeha fault codes, and is H.02.36 dangerous?
On Remeha's e-Smart control system, the letter prefix tells you the fault category: A is an advisory warning, H is a Blocking fault (boiler pauses operation temporarily as a precaution), and E is a full Lock-out (boiler shuts down and requires a manual reset to restart). H.02.36 is a Blocking fault, so the boiler has stopped as a safety measure rather than failing catastrophically. It is not immediately dangerous, but you should not ignore it — a faulty temperature sensor or circulation problem left unchecked can lead to more serious damage over time.
How much does it cost to fix a Remeha H.02.36 fault in the UK?
Most people with this fault pay somewhere between £120 and £320. A straightforward wiring or connector repair at the lower end, and a sensor replacement including labour at the higher end, both fall comfortably within that range. If the fault turns out to involve the PCB (control board), costs can rise to £400–£550 or more, but PCB replacement is an uncommon outcome for this specific code — it is worth ruling out the sensor and wiring first. Always ask for a written quote before authorising parts.
Which Remeha boiler models display the H.02.36 code?
H.02.36 appears on Remeha boilers that use the e-Smart control platform, which includes the Quinta Ace, Quinta Pro, Avanta, Calora Tower, Gas 210 Eco, and Tzerra ranges, among others. If you are unsure whether your specific model uses this code system, check the fault-code section of your boiler's installation or service manual, or contact Remeha UK directly. The code structure (letter + two-digit group + two-digit sub-code) is consistent across the e-Smart range.