- Boilers
- Gas boiler
FD
Junkers FD boiler code: power cut or reset pressed by mistake
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Junkers Cerapur boilers, FD shows up after a power interruption or when reset was pressed for no reason. On the CerapurComfort ZWBE it can hide a fault that was already there before the outage. Reset once and write down any new code.
Safety first
Stop and check this first
- Even though FD is an electrical message, if you smell gas near the boiler do not press reset or touch switches and plugs. Shut the valve at the meter, open windows, leave the home warning neighbours and call the gas emergency line from outside.
- Do not keep resetting FD: if another code shows up after one reset, the boiler is reporting a different fault that needs a technician.
Safe checks you can perform
- Confirm whether the house lost power
- Reset the boiler once only
- Write down the code and its three-digit number
- Locking-fault history review after FD
Leave these tasks to a qualified professional
- Do not attempt this professional task: Check the boiler's power supply
- Do not attempt this professional task: Read the code that comes before FD
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Check the boiler's power supply
What they doThey check the mains connection and, if FD keeps returning without clear outages, the supply voltage, since the same manual has its own message for low or intermittent voltage.
They must show youthe voltage reading at the boiler supply.
In writingthe measured value and whether the house wiring needs checking.
Read the code that comes before FD
What they doThe engineer opens the locking-fault history and looks for the last code before FD, as the CerapurComfort ZWBE table instructs.
They must show youthe history screen with the code logged before FD.
In writingwhich fault was present and how it was fixed.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Confirm whether the house lost power
- Who:
- you, looking around the home, without opening the boiler.
- How:
- see whether oven or microwave clocks are blinking, other appliances switched off, or neighbours had an outage around the time FD appeared.
- Result that matters:
- knowing whether FD matches a real drop in the electricity supply.
- If confirmed:
- FD has a likely explanation; go on to the single reset.
- If not confirmed:
- if nobody noticed a cut, tell the technician FD appeared with no obvious outage.
- Evidence to keep:
- rough time of the outage and a photo of FD on the boiler display.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación · Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575)
Reset the boiler once only
- Who:
- you, with the reset button on the panel, as the user manual describes.
- How:
- on the Excellence Compact press reset until Reset shows briefly; on the CerapurComfort ZWBE press reset once or switch the appliance off and on; on the 2012 ZWBC press the reset key again.
- Result that matters:
- the display going back to the flow temperature instead of FD.
- If confirmed:
- if the boiler restarts normally, FD was only the trace of the outage or the button press.
- If not confirmed:
- if another code appears after the reset, stop there: that second code is what the technician needs to see.
- Evidence to keep:
- photo of the display right after the FD reset.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico · Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación · Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de uso de la caldera mural a gas de condensación (6720847002)
Write down the code and its three-digit number
- Who:
- you, reading the Cerapur display.
- How:
- note FD and the number shown below or beside it (for example 231) plus any different code that follows; the user manual asks for both when you call Bosch.
- Result that matters:
- having the exact sequence of codes, because on the ZWBE the real fault comes before FD.
- If confirmed:
- hand the full list to the service engineer when booking.
- If not confirmed:
- if the display only ever showed FD, say so, so nobody hunts for another fault.
- Evidence to keep:
- written list or photos of FD 231 and of any later codes.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación · Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de instalación y manejo para el técnico (6720847000) · Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de uso de la caldera mural a gas de condensación (6720847002)
Locking-fault history review after FD
- Who:
- gas engineer or Junkers authorised service, from the service menu.
- How:
- open the locking-fault history, which keeps the last eight entries, and find the code logged just before FD; then check the boiler's electrical supply.
- Result that matters:
- identifying the fault that locked the boiler before the voltage dropped.
- If confirmed:
- fix that earlier fault following its own row in the fault table.
- If not confirmed:
- if there is no earlier fault, check whether supply interruptions repeat or the voltage runs low.
- Evidence to keep:
- job sheet with the earlier code found and the electrical check carried out.
The service menu and the boiler's internal supply are technician work; the user manual forbids users from removing the casing.
Evidence: Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575) · Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de instalación y manejo para el técnico (6720847000)
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Junkers
- Product type
- Gas boiler
Known code variants
- caldera Junkers FD
- Cerapur Excellence Compact FD
- Cerapur FD
- CerapurComfort Fd
- Junkers FD
- Junkers FD 231
What it means
Junkers gives FD slightly different meanings by model. On the Cerapur Excellence Compact, FD with cause number 231 is a main power error: the electricity supply was interrupted, and the reset key clears it. On the 2015 CerapurComfort ZWBE, FD 231 means mains voltage dropped while the boiler was already in a locking fault; that earlier fault is always the last code logged before FD. On the 2012 CerapurComfort ZWBC, Fd means the reset key was pressed by mistake.
Warnings and stop conditions
- Criticaleditorial warning
Even though FD is an electrical message, if you smell gas near the boiler do not press reset or touch switches and plugs. Shut the valve at the meter, open windows, leave the home warning neighbours and call the gas emergency line from outside.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico · Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación · Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575) · Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de instalación y manejo para el técnico (6720847000) · Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de uso de la caldera mural a gas de condensación (6720847002)
- Mediumeditorial warning
Do not keep resetting FD: if another code shows up after one reset, the boiler is reporting a different fault that needs a technician.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico · Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación · Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575) · Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de instalación y manejo para el técnico (6720847000) · Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de uso de la caldera mural a gas de condensación (6720847002)
Symptoms and causes
Probable causes · in order
- Electricity supply interruptedCommon
The Cerapur Excellence Compact table links FD 231 to an interruption of the electrical supply. A general outage, a short dip or unplugging the boiler is enough to bring up this message.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación · Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575)
- Power lost on top of an existing faultPossible
On the CerapurComfort ZWBE, FD 231 appears when mains voltage is cut during a locking fault. The real problem is the code the boiler stored just before FD, not the outage itself.
Evidence: Junkers CerapurComfort ZWBE 25-3 C y 30-3 C, instrucciones de instalación y manejo para el técnico (6720847000)
- Reset key pressed by mistakePossible
For the CerapurComfort ZWBC 25-2 C, the manual describes Fd as the reset key pressed in error, and the fix is to press it again. It happens when the button is touched with no fault pending.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico
Virtual technician
Does FD still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico
Junkers (Bosch Termotecnia) · 2012 · manual
- 2
Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación
Junkers (Bosch Termotecnia) · 2019 · manual
- 3
Junkers (Bosch Termotecnia) · 2019 · manual
- 4
Junkers (Bosch Termotecnia) · 2015 · manual
- 5
Junkers (Bosch Termotecnia) · 2015 · manual
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