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Heating engineer · Brussels and Wallonia
Viessmann error codes
The most common codes for Viessmann Vitodens 100-W (current generation, numeric codes), with what they mean and what to do.
Older Vitodens models show different codes (letters and numbers, e.g. F2): they're not listed here. Just give us the code over the phone.
System pressure too low: burner and pump stopped.
PressureCheck the pressure gauge. If it's too low, top up the water (if you know how) and bleed the radiators. If the pressure drops again, there's probably a leak: call us.
No water flow in the system.
PressureCheck the pressure gauge. If it's too low, top up the water (if you know how) and bleed the radiators. If the pressure drops again, there's probably a leak: call us.
No flame (or too weak a flame) when the burner starts.
IgnitionCheck that the gas tap is open, then reset the boiler once. If the code comes back, don't keep trying: repeated resets can lock the appliance. Call us.
Insufficient gas supply.
IgnitionCheck that the gas tap is open, then reset the boiler once. If the code comes back, don't keep trying: repeated resets can lock the appliance. Call us.
Flame lost during operation: the burner restarts.
TemporaryThe boiler restarts on its own once the cause is gone. If the code keeps coming back, call us for a check.
The temperature limiter has tripped: automatic restart after cooling down.
TemporaryThe boiler restarts on its own once the cause is gone. If the code keeps coming back, call us for a check.
The high limit safety cut-out has tripped.
CirculationCheck the pressure and that the radiator valves are open. If everything looks fine and the code comes back, the water circulation needs checking (pump, bleeding, sensors): call us.
The flue gas temperature limiter has tripped.
Flue · safetySwitch the boiler off and air the room. This code concerns the flue: call us. If a CO alarm goes off, or anyone has a headache or nausea, get everyone outside and call 112.
Combustion CO limit exceeded.
Flue · safetySwitch the boiler off and air the room. This code concerns the flue: call us. If a CO alarm goes off, or anyone has a headache or nausea, get everyone outside and call 112.
System pressure too high.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
Internal circulation pump blocked.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
Fan speed too low.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
Condensate backed up in the heat cell.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
This code isn't in the list: call us and give it to us, we'll tell you straight away what's going on.
Source: Viessmann, Vitodens 100-W installation instructions (viessmann.co.uk). Codes and how they're shown can differ between models: if in doubt, your appliance's manual applies.
First steps
- Write down the code shown: it saves us time.
- Check the pressure gauge.
- Check that the gas tap is open.
- Reset once. If the code comes back, call us.
Practical guides: Top up the pressure · Bleed a radiator · Reset the boiler
A breakdown, a question? Get in touch.
Call us or message us on WhatsApp. Or leave your number, with a photo of the boiler if you like: we'll call you back.
