Viessmann F2 fault code: the temperature limiter has responded

What does the Viessmann F2 fault code mean?

The Viessmann F2 fault code means the temperature limiter, the boiler's high-limit overheat safety switch, has responded and shut the burner down. Viessmann's installation and service instructions for the Vitodens 200-W record it as 'Burner in a fault state', cause 'Temperature limiter has responded'. In plain English, the water in the boiler got hotter than the safety switch allows, almost always because heat could not get away fast enough, so the boiler locked out rather than carry on firing.

You will see the code written both ways. The display shows two characters, so it reads F2 with no leading zero, but plenty of people search for F02 after padding it out of habit. F2 and F02 are the same fault.

Two-character codes are easy to mix up, and the published lists do not all agree, so it is worth being clear about what F2 is not. F2 is an overheat lockout on the water side of the boiler. It is not a flame-loss code, and Viessmann gives flame problems their own separate codes. If a list you are reading gives F2 a different meaning, check the code against the manual for your own boiler, or ask a Viessmann trained installer, because code sets differ between models and generations.

Viessmann does not publish F2 for homeowners

Worth saying plainly, because it explains why the answers online disagree. Viessmann UK runs a public fault code checker on its own website, and it does publish plenty of codes. Checked in August 2026, it listed 5C, 5D, 5E, 5F, 10, 18, 58, A4, 0C, D1, D4, F6, F9, F-E1, F-E2 and F-F6, with no plain F2 entry at all. The checker also warns that the diagnosis behind a code can differ depending on the boiler.

The authoritative wording sits in installation and service instructions written for contractors, such as Viessmann's installation and service instructions for the Vitodens 200-W, published in Viessmann's own technical documentation library. Those documents are written for installers rather than homeowners. No Viessmann page aimed at homeowners answers what F2 means, which is why third-party sites have filled the gap with answers that do not agree with each other.

Key facts

• Meaning: the temperature limiter, the high-limit overheat switch, has responded and the burner has locked out. Viessmann's own wording.
• Also written F02. Same code, same fault, shown as two characters.
• Not flame loss. F2 is an overheat lockout on the water side, and flame faults carry their own separate codes.
• Not published for homeowners: Viessmann UK's public fault code checker carried no F2 row when we checked it in August 2026.
• Safe to check yourself: let the boiler cool right down first, then pressure, radiator valves, trapped air, then one reset.
• Reset once only. F2 is a safety lockout, so clearing it repeatedly to keep the boiler running is not safe.
• Code sets differ between Viessmann models and generations, so check the code against the manual for your own boiler.
• Smart Plan boiler and central heating cover: parts and labour up to £500 in any 12-month period if the boiler is under 7 years old, or up to £200 if it is over 7, shared across every fault in that period.
• Cover is for future breakdowns, not a fault the boiler already has. Using a module starts a 12-month agreement period the first time you use a service, and there is a 14-day cooling-off period which ends the moment a service is carried out.

Why does the F2 code appear?

Every cause of F2 comes back to one problem: the burner is putting heat in faster than the system carries it away. Viessmann's own measures tell you where to look, because each implies its cause. Check the heating system fill level. Check the circulation pump. Vent the system. Check the temperature limiter and its connecting cables. Then, last of all, press reset button R. That is low pressure, a pump not moving water properly, trapped air, and a failed limiter or damaged cable.

In real houses the same overheat condition also comes from sludge and scale narrowing the heat exchanger and pipework, and from zone valves or thermostatic radiator valves stuck shut, so the hot water has nowhere to go. Viessmann does not name those in the F2 row, but they produce exactly the condition it describes.

One cause you can probably cross off. Several sites blame a frozen condensate pipe for F2. A frozen condensate is a real fault on a condensing boiler, but it is not among the measures Viessmann lists against F2, which all point at heat failing to get away from the boiler.

F2 causes and what to do about each one

What you can safely check yourself

Only one of Viessmann's own F2 measures is a homeowner job, and that is the heating system fill level. You can also bleed radiators and check that valves are open, then reset once. The circulation pump and the temperature limiter sit behind the case, and venting the boiler itself is engineer work. Before any of it, deal with the heat.

1. Turn the boiler off at the programmer and let the system cool right down before you touch anything. F2 means the water got hotter than the safety switch allows, and water from a bleed valve or a filling loop can scald.

2. Read the pressure gauge with the system cold and compare it against the figure printed in your own user manual. Low fill level is the first measure Viessmann lists. Topping up through the filling loop is a normal user task on most Viessmann combis, if your manual covers that.

3. Check the radiators, still cold. Cold at the top usually means trapped air, and bleeding a radiator is routine. Make sure radiator valves and TRVs are open, so the boiler has somewhere to send its heat.

4. Look and listen. Check the pipework and the area around the boiler for leaks or damp patches, and listen for kettling or banging, a sign of poor circulation.

5. Press the reset button once. Viessmann's last measure is to press reset button R, and it comes after the checks above, not before them.

Then stop. If F2 comes back, do not reset it again. It is an overheat safety lockout, and clearing it repeatedly so the boiler keeps firing is what that switch exists to prevent. Anything past this point means taking the case off a gas appliance, which is Gas Safe registered work.

When to call a Gas Safe registered engineer

Call one as soon as F2 returns after a single reset, and straight away if the boiler is kettling or banging, if radiators stay cold while the boiler pipework is scalding, or if you have topped the pressure up twice in a few weeks, which usually means a leak.

The engineer's side is everything behind the case: testing or replacing the circulation pump and the temperature limiter and its cables, checking the boiler water temperature sensor and the zone valves, power flushing the system, and clearing a blocked plate or primary heat exchanger.

For the F2 in front of you now, book a one-off repair with us, or call 0333 772 6247. One-off repair appointments run Monday to Friday, 09:00 to 17:00, carry a £95 call-out fee paid in advance, and do not come with a workmanship guarantee. We work with a national network of thousands of Gas Safe registered engineers.

If you would rather the next boiler breakdown was handled for you, a Smart Plan boiler and central heating module covers parts and labour up to £500 in any 12-month period if your boiler is under 7 years old, or up to £200 if it is over 7. That limit is shared across every fault in the same 12-month period, and anything above it you would pay yourself. Cover is for future breakdowns, so an F2 showing on your boiler today counts as a pre-existing fault and is not covered. Book a one-off repair for that. Smart Plan is a service plan, not insurance, so it arranges and funds covered repairs up to your limit rather than paying you a sum of money.

The parts worth reading before you sign up: a £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, if the engineer cannot get access, and for early annual-service requests. Cover still applies in those first 30 days. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00, unless it is a genuine emergency breakdown, so a Friday evening or weekend fault can wait until Monday. Within those hours we aim to get an engineer out to you within two working days, which is a target rather than a promise. Using a module starts a 12-month agreement period the first time you use a service. There is a 14-day cooling-off period, but it ends the moment a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance.

One note above all of this. F2 is a heat fault, not a gas escape, but if you ever smell gas or suspect carbon monoxide, do not wait for an engineer. Call the National Gas Emergency Service on 0800 111 999 straight away and open the windows.

Viessmann F2 fault code FAQs

F2 back after a reset? Get an engineer to it.

Book a one-off repair and a Gas Safe registered engineer can test the pump, the temperature limiter and the water side of the boiler. One-off repair appointments run Monday to Friday, 09:00 to 17:00, carry a £95 call-out fee paid in advance, and do not come with a workmanship guarantee. Thinking further ahead instead? A Smart Plan boiler and central heating module covers parts and labour up to £500 in any 12-month period if the boiler is under 7 years old, or up to £200 if it is over 7, shared across every fault in that period. It covers future breakdowns, not the F2 already on your display, so book the repair for that one. A £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, no-access visits and early annual-service requests, and cover still applies in those first 30 days. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00, unless it is a genuine emergency breakdown, and within those hours we aim to get an engineer out to you within two working days, which is a target rather than a promise. Using a module starts a 12-month agreement period the first time you use a service, there is a 14-day cooling-off period which ends the moment a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance. Smart Plan is a service plan, not insurance. Call 0333 772 6247, Monday to Friday, 08:00 to 18:00.

Helpful links

• All Viessmann fault codes
• Boiler repair
• No heating
• Boiler & central heating cover
• Smart Plan blog
• Viessmann's own fault code checker (no F2 entry)
• Check an engineer on the Gas Safe Register