Viessmann FF fault codewhat it means and how to fix it
On the two-character units FF is the same burner control unit fault as Fd. On a Vitotronic 200-W it means an internal fault or a disabled reset key, and Viessmann say restart the appliance.
Take care
Which display does your Viessmann have?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
Which display does your Viessmann have?
Burner control unit fault, identical to Fd: check the ignition electrodes and cables and any source of interference, reset, and replace the control unit if it persists.
One reset on your unit's control; then a Gas Safe engineer if FF returns.
Which display does your Viessmann have?
Internal fault or reset button R disabled. Viessmann: restart the appliance; replace the control unit if it will not restart.
Switch the boiler off and on once at its ON/OFF switch. If FF is still shown, call your heating contractor.
What FF means
FF has two homes. On the WB1B, WB1C, B1HA/B1KA and B1HC/B1KC, the 111-W B1LA to B1LD and the 050-W BPJD it is word for word the Fd row: "Burner blocked — Burner control unit fault — Check ignition electrodes and connecting cables. Check whether a strong interference (EMC) field exists near the appliance. Press Reset. Replace control unit if fault persists." The WB1A table has no FF. Two codes for one row is a quirk of the burner control unit reporting two different internal supervision paths, and Viessmann do not distinguish them in the measures, so nor do we; the Fd page explains why the electrodes come first.
On the Vitotronic-controlled 200-W B2HA and B2HB, 222-F B2TA and 242-F B2UA the row is "Burner blocked or in a fault state — Internal fault or reset button R disabled — Restart the appliance. Replace the control unit if the appliance will not restart." That is one of very few places where a Viessmann table tells anyone to power-cycle the boiler, and it is aimed at the contractor, but the operating instructions for those units do describe the ON/OFF switch, so a householder switching the boiler off and on once is within what Viessmann publish; if FF is still there afterwards, the control unit is the finding and the contractor is the next call. The "reset button R disabled" half of the cause is worth knowing: if the R key appears to do nothing, that is the fault, not the user. The 2020-on numeric-table units fold both into F.70 and F.458 (faulty reset sequence).
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Ignition electrodes, cables or interference (two-character units) | The same first measures as Fd: a high-voltage lead arcing where it should not, or a strong external field, upsets the control unit's supervision. | Common |
| Burner control unit internal fault | On both families the final measure is to replace the control unit if the fault persists after a reset or a restart. | Occasional |
| Reset key R disabled (Vitotronic units) | The Vitotronic cause column names a disabled reset button. Restarting the appliance is the published remedy; if R still does nothing, the unit is at fault. | Occasional |
What to try yourself
Only on a Vitotronic-controlled 200-W, 222-F or 242-F: switch the boiler off at its ON/OFF switch, wait a few seconds, and switch it back on. This is Viessmann's own measure for FF on these units — "Restart the appliance".
On a two-character 100-W, 111-W or 050-W, FF is a Fd-type control unit fault and a power cycle is not in the table; use the single reset for your unit instead.If FF is still displayed after the restart, or if the reset key R does nothing, stop. Viessmann's next line is "Replace the control unit if the appliance will not restart", which is a contractor's job.
Get a Gas Safe registered engineer to look at your Viessmann FF
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What it costs to fix
Typical repair cost
£70–£500
Time on site
1h 30m
A restart that clears it costs nothing. Electrodes within a visit are the low figure; a control unit the high one.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Viessmann ignition electrode set
£25–£65Authorised Viessmann parts distributor
Price checked 28 September 2026
Viessmann burner control unit (control unit PCB / HBMU heat management unit)
£250–£500Authorised Viessmann parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Viessmann fault codes
- F0Get it checkedInternal fault in the burner control unit. Viessmann's only measure on the two-character units is "Replace control unit"; the Vitotronic B2HB allows one reset first. Not a householder repair.Related: electronics and power
- F.59Get it checkedMains undervoltage on a 2020-on Vitodens: the burner locks out and the pump stops until the supply recovers. If the voltage is good and it recurs, Viessmann replace the fan unit.Related: electronics and power
- F.70Get it checkedAn internal fault in the HBMU heat management unit of a 2020-on Vitodens. Nearly twenty numbers say the same: reset once, and if it returns the unit is replaced. Engineer only.Related: electronics and power
- FdGet it checkedBurner control unit fault, which Viessmann first blame on the ignition electrodes, their cables or electrical interference, and only then on the unit. FF is the same row. Engineer job.Related: electronics and power
- 0CGet it checkedMains voltage too low. The burner is blocked while the supply is out of range and restarts on its own when it recovers. Viessmann's measure on the WB1A is to contact the electricity supplier.Related: electronics and power
- b7Get it checkedOn the B1HC-generation 100-W and 111-W, b7 is emergency mode after a control unit fault and Viessmann say to switch the boiler off and on. On a Vitotronic unit it is a coding card fault.Related: electronics and power
Own a Viessmann boiler? Save it and its codes come first next time.
Related guides
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.