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The 24 Hour Boiler Repairs call centre is open right around the clock. Our team of friendly operators are on hand to take your call and dispatch a highly trained engineer to your door. Our commitment to dealing quickly with all boiler emergencies, regardless of when or where they happen, means we have one of the best response times around. So, rest assured, when you get in contact with 24 Hour Boiler Repairs, your problem will be dealt with at speed by a team of highly skilled professionals. If you have an issue with your heating system, get in touch straight away.

Address
24 Hour Boiler Repairs
86-90 Paul Street
London
EC2A 4NE

Phone
0203 868 6251

Email
info@24hourboilerrepairs.co.uk

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Need a Gas Safe engineer in London ASAP? Call us 24 Hours a day!

Viessmann

Viessmann Boiler Repairs London

Gas Safe registered engineers · 24/7 call handling · London wide

Tell us the fault code and model. We will advise the safest next step.

  • Experienced Viessmann Boiler Repairs specialists
  • Available 24 hours a day, 7 days a week
  • Insurance approved
  • All parts guaranteed for a year
  • Fully Gas Safe trained engineers

Lines open now

0203 868 6251

Have your Viessmann model and fault code ready.

★★★★★4.6/5 on Google

Common Viessmann models we repair include Vitodens 050-W, Vitodens 100-W, Vitodens 111-W, and Vitodens 200-W, with frequent calls for EE, F2, 0B, and F9.

We fix Viessmann boiler fault codes, no heating, no hot water, lockout, leaking, and low pressure across London.

We also offer boiler servicing and boiler installation across London.

Safety First

Smell gas? Turn off the gas supply at the meter if it is safe to do so. Open windows. Leave the property. Call the National Gas Emergency Service on 0800 111 999. Do not use switches, and do not use naked flames.

CO alarm sounding? Stop using the boiler. Open doors and windows. Leave the property. Call the National Gas Emergency Service on 0800 111 999. If anyone is drowsy, breathless or has a headache, call 999 as well. Do not re-enter until you are told it is safe.

Boiler leaking heavily? Turn off the boiler at the controls. If safe, turn off the water supply. Call an engineer.

★★★★★Perfect service and professional engineer!Halil Atarkan · Google review★★★★★Resourceful and helpful with the issue we had with our boilerKatarina Jezovnik · Google review★★★★★The engineer was punctual, honest about costs and carried out the work to a very high standard.Siva Yelakarajula · Google review

Quick Checks Before You Call

Before calling an engineer, these safe checks may resolve simple issues with your Viessmann boiler.

Check the gas supply

Is gas working at other appliances in your home? If not, check your meter and any prepayment credit.

Check the pressure gauge

Pressure should read around 1.0 to 1.5 bar when cold. If below 1 bar, you may need to repressurise using the filling loop.

Check the thermostat

Is the room thermostat set above current room temperature? Are the batteries working?

Check the timer or programmer

Is the heating scheduled to be on? Check the clock is set correctly.

Try a single reset

Locate the reset button marked R on your Viessmann boiler. Press once and wait. If the fault returns, do not keep resetting. Call an engineer.

Check the condensate pipe

In cold weather, the external condensate pipe can freeze. Look for a white plastic pipe exiting through an outside wall. If frozen, pour warm water over it gently.

Gas Safe registered boiler engineers

Fully Gas Safe trained engineers

Every gas repair is carried out by a Gas Safe registered engineer. You are told what needs doing and what it costs before anything starts.

★★★★★4.6/5 on Google

Viessmann Fault Codes

Taken from Viessmann's own published fault tables for the Vitodens range. Viessmann splits faults into two states, and the difference matters: burner blocked clears by itself once the cause is gone, while burner in fault mode stays locked out until the reset button marked R is pressed. If a fault mode code comes straight back after one reset, the cause is still there.

Code/What It Means/What To Do

Flame and ignition

EE No flame signal at burner start, or the signal is too weak

The boiler tried to light and never proved a flame. This is the Vitodens equivalent of an ignition lockout and the most common reason a Viessmann stops. Check gas is on at other appliances, and in freezing weather check the external condensate pipe. Press R once. If EE returns, call an engineer.

EF Flame lost immediately after lighting

The burner lit but the flame failed within the safety time. Often the ionisation electrode, the gas supply pressure, or flue gas being drawn back into the air intake. Press R once, then call an engineer.

F3 Flame signal already present at burner start

The boiler sees a flame before it has asked for one. This is a gas safety fault, not a nuisance code. Switch the boiler off at the controls and call an engineer.

E5 Flame amplifier fault

The circuit that reads the flame signal has failed, so the boiler cannot prove combustion. Viessmann's remedy is to replace the control unit. Call an engineer.

Overheating and flue gas temperature

F2 Fixed high limit switch has opened

The safety limiter has cut the boiler out because it reached an unsafe temperature. Almost always poor circulation: a failing pump, sludge, closed radiator valves, or a blocked heat exchanger. Do not keep resetting a limiter lockout. Call an engineer.

F1 Maximum flue gas temperature exceeded

Flue gas has passed the 110°C limit. It usually points at a scaled or sooted heat exchanger, or poor heat transfer. Call an engineer.

E3 Heat transfer too low, limiter shut the boiler down

The boiler cannot get its heat away into the system, so the limiter stopped it. Check radiator valves are open. If it repeats, the system needs looking at properly. Call an engineer.

E2 Heating water flow rate too low

Not enough water is moving through the boiler. Viessmann's own remedy is to check pump flow and remove scaling or blockage. Call an engineer.

Combustion and calibration

E8 Ionisation current outside the permitted range

The flame sensing current is wrong. Viessmann lists gas supply pressure, the gas type setting, and a dirty or badly positioned ionisation electrode as causes. Call an engineer.

E7 Ionisation current too low during calibration

Usually a worn, sooted or misaligned ionisation electrode, or flue gas recirculating into the air intake. Call an engineer.

E1 Ionisation current too high during calibration

The opposite of E7, and checked the same way: the gap between the ionisation electrode and the burner gauze. Call an engineer.

EB Repeated flame loss during calibration

The flame keeps dropping out while the boiler tries to calibrate itself. Gas type setting and flue system are the usual causes. Call an engineer.

EA Ionisation current outside range during calibration

The reading has drifted too far from the previous one. Viessmann notes that after several failed resets the boiler coding card may need replacing. Call an engineer.

EC Parameter fault during calibration

A settings or parameter error stopped the calibration completing. Call an engineer.

Fan and gas valve

F9 Fan speed too low during burner start

The fan is not reaching the speed the boiler needs before it will light. Call an engineer. Never remove the casing or work on a flue yourself.

FA Fan not at standstill

The fan is still turning when the boiler expects it to have stopped, so it will not start a new cycle. Call an engineer.

FC Gas valve fault, or the flue is blocked

Viessmann lists a faulty gas valve, faulty modulation valve control, or a blocked vent system. All three are engineer-only. Call an engineer.

F8 Gas valve closes too late

The gas valve is not shutting within its permitted time. Switch the boiler off at the controls and call an engineer.

Sensors

30 Boiler water temperature sensor shorted

Burner blocked until the sensor is replaced. The boiler will restart on its own once the fault is cleared. Call an engineer.

38 Boiler water temperature sensor lead broken

The same sensor, but an open circuit rather than a short. Call an engineer.

B0 and B8 Flue gas temperature sensor fault

B0 is a short circuit, B8 a broken lead. Either blocks the burner until the sensor is checked. Call an engineer.

52 Flow sensor shorted, CombiPLUS models

Specific to CombiPLUS units. You may lose hot water while heating still works. Call an engineer.

Water flow, power and controls

0B Insufficient water flow

On the Vitodens 100-W. Insufficient flow, flow in the wrong direction, or a defective flow switch. Check the pressure gauge reads 1.0 to 1.5 bar cold and top up if it does not. If 0B stays, call an engineer.

0C Insufficient power supply

The boiler is not getting a stable supply. Check the fused spur and that nothing has tripped at the consumer unit. If the supply is sound, call an engineer.

FD and FE Boiler coding card missing or wrong

The card that tells the control which boiler it is fitted to is absent, damaged or incorrect. FE can also point at the main PCB. Call an engineer.

FF Internal fault, or the reset button is stuck

Sometimes literally a jammed R button. More often an internal control fault. Call an engineer.

ED Internal fault

An internal control fault. Press R once. If ED returns, call an engineer.

No code, no heating

If the display is blank or the boiler simply is not firing with no code shown, check the room thermostat, the programmer and its batteries, and the fused spur. If those are all right, call us.

Note: Viessmann uses different code sets across the Vitodens ranges and across control generations, and the same characters do not always mean the same thing on a 100-W as on a 200-W. The codes above are the published ones for the current Vitodens ranges. If your display shows something not listed here, F4 being a common example on older units, do not assume it matches a code you have read elsewhere. Call us with the exact code and the model from the data badge and we will tell you what it means before anyone attends.

Not sure which fault you have?

Call with your model and the code on the display. We will tell you what is likely involved before anyone attends.

0203 868 6251

Most Searched Viessmann Problems

If you are seeing a lockout, loss of hot water, or your Viessmann boiler keeps resetting, tell us the fault code and model and we will confirm the safest next step.

EE – ignition lockout

EE is the code you are most likely to see on a Vitodens. The boiler attempted to light and no flame signal was proved. Common causes are a gas supply problem, a worn or sooted ionisation electrode, or a frozen condensate pipe in winter. Check gas is on elsewhere in the home. Press R once. If the lockout returns, stop and call an engineer.

Low pressure

If your Viessmann shows a low pressure warning, system pressure has dropped below the minimum threshold. Top up via the filling loop to around 1.0 to 1.5 bar when cold. If pressure drops again within days, there may be a leak in the system or a failing expansion vessel. Call an engineer to find the cause.

F2 – overheat protection

If your Viessmann shows F2, the fixed high limit switch has opened and the boiler has locked out for safety. This usually indicates a circulation problem, pump failure, or a blocked heat exchanger. Do not keep resetting. Call an engineer to check the system.

No hot water but heating works

On Viessmann combi boilers, you may get heating but no hot water, or the reverse. This often points to a diverter valve issue. The diverter valve directs hot water between taps and radiators. When it wears or sticks, hot water delivery becomes unreliable. Call an engineer for diagnosis.

Why Viessmann Boilers Develop Faults

Viessmann is a German manufacturer known for high-quality engineering. Here is what we commonly see.

Ionisation electrode wear

Viessmann leans heavily on the ionisation electrode to prove and measure the flame, which is why so many of its codes point at it. When the electrode wears, sooths over, or drifts out of position, you get EE, EF, E7 or E8. Condensate blockages in winter contribute to repeated lockouts too.

Low pressure and expansion vessel faults

Low pressure faults often point to a failing expansion vessel or a weeping pressure relief valve. The expansion vessel absorbs pressure changes as water heats and cools. If the diaphragm fails or the air charge is lost, pressure drops can occur.

Circulation and flow issues

Restricted flow can indicate poor circulation through the system, and on a Vitodens it shows up as E2, E3 or F2. This may be caused by a failing pump, sludge buildup, or closed radiator valves. A powerflush may help restore flow.

Fan and airflow faults

Fan faults prevent safe combustion and flue gas extraction. The boiler will lock out for safety with F9 or FA. Causes include fan motor failure, wiring faults, or flue blockages.

Diverter valve on combi boilers

The diverter valve directs hot water between your taps and radiators. When it wears or sticks, you may get heating but no hot water, or the reverse.

Viessmann Models We Repair

We repair Viessmann combi, system, and regular boilers in London, including:

Viessmann boiler repairs London We repair every Viessmann model Combi, system and regular boilers, current ranges and older units
Vitodens 050-W Entry-level combi and system boilers
Vitodens 100-W 100-W B1GA, 100-W B1HA, 100-W B1KA
Vitodens 111-W Storage combi with integrated cylinder
Vitodens 200-W Premium range with higher efficiency
Vitodens 222-F Floor-standing combi with cylinder
Vitodens 300-W Top-of-range condensing boiler

Viessmann parts are available through their UK network. We check availability before attending and advise honestly if repair is not viable or cost effective.

Repair or Replace Your Viessmann Boiler?

We help you decide based on age, reliability, and parts availability.

Repair makes sense when

  • Boiler is under 10 years old
  • This is the first major fault
  • Parts are readily available
  • Boiler has been regularly serviced

Replacement may be better when

  • Boiler is 12 to 15 years old or more
  • You have had multiple breakdowns recently
  • Parts are obsolete or hard to source
  • The boiler is undersized for the property
  • Energy bills are higher than expected for the property size

Our engineers give honest assessments. We focus on safety and reliability, not pushing unnecessary replacements.

Viessmann Boiler Servicing

Annual servicing reduces breakdown risk and keeps your Viessmann boiler running efficiently. See Boiler servicing London.

Landlords and Letting Agents

We provide boiler repairs and gas safety certification for landlords across London. See Landlord gas safety certificate (CP12).

London based boiler repair engineers

Viessmann Repairs Across London

London wide coverage for Viessmann boiler repairs. Book an engineer or view our London areas we cover.

Have your postcode and fault code ready and we will confirm the quickest appointment slot.

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Worcester • Vaillant • Ideal • Baxi • Glow-worm • Main • Potterton • Vokera • Alpha • Ferroli
View all brands ›

Viessmann Boiler Repair FAQs

How quickly can you attend for a Viessmann breakdown?

We offer same day attendance where slots are available. For no heating or hot water, we prioritise urgent breakdowns. Call our 24/7 line and we will advise availability.

Do you carry Viessmann parts?

We stock common Viessmann parts including diverter valves, ionisation electrodes, pressure sensors, and PCBs. For less common parts, we can usually source within 24 to 48 hours.

Is it safe to reset my Viessmann boiler?

Press the button marked R once. If the fault returns after resetting, stop and call an engineer. Do not keep resetting, especially for F2 where the safety limiter has tripped, or for F3 and F8 where the fault involves the flame or the gas valve.

What is the difference between burner blocked and burner in fault mode?

Viessmann uses both terms. Burner blocked means the boiler has stopped but will start itself again once the cause clears, so a sensor fault may come and go. Burner in fault mode means it stays locked out until the R button is pressed. A fault mode code that returns immediately after one reset means the cause has not gone away.

Related Services

Emergency boiler repairs Breakdowns, lockouts and leaks Boiler servicing London Annual service and safety checks Boiler installation London Replacements and new fitting Power flush London Cold radiators and system sludge Landlord gas safety certificate (CP12) Certification across London London areas we cover Book an engineer in your borough

What customers say

Verified Google reviews. 4.6 out of 5.

★★★★★

Great guy on time true professional resolve the issue same day

David BrazierGoogle review
★★★★★

Good value for money & was able to sort out my boiler quickly by ordering next day delivery for broken parts. Friendly, punctual service and laid out all the costs beforehand which was helpful. Would recommend.

Emma CourtneyGoogle review
★★★★★

Used this company after being recommended and I am glad I did. The engineer was punctual, honest about costs and carried out the work to a very high standard. Felt like a trustworthy service.

Siva YelakarajulaGoogle review

Speak to Our Team

For safe next steps, call now.

Call 0203 868 6251

Book an Engineer ›

Gas Safe registered · 24/7 call handling · Quote before work
24 Hour Boiler Repairs, 86-90 Paul Street, London EC2A 4NE
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Google reviews

★★★★★4.6/5 on Google
★★★★★

Really impressed with the boiler repair service. Clear communication from the start and no surprises with pricing. The engineer was friendly, knowledgeable and got everything sorted efficiently.

Nishanth ThachemaGoogle review
★★★★★

Good value for money & was able to sort out my boiler quickly by ordering next day delivery for broken parts. Friendly, punctual service and laid out all the costs beforehand which was helpful. Would recommend.

Emma CourtneyGoogle review
★★★★★

Booked them in for a power flush after ongoing heating issues. The engineer was very thorough and explained what was being done at each stage. We noticed a huge difference in how quickly the radiators now heat up.

S ThanuGoogle review

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