Vaillant boilers are known for their reliability and efficiency, but like any complex system, they can occasionally run into issues. When problems arise, the boiler will display specific error codes that help identify the fault. Understanding these codes is crucial for diagnosing and resolving issues quickly, whether you're a homeowner or a professional engineer.
These error codes can indicate a range of issues, from problems with the gas supply, safety switches, or temperature sensors, to more specific faults like defective condensate pumps, ignition failures, or incorrect settings.
This guide covers a comprehensive list of Vaillant boiler error codes across various models, such as the EcoTEC Plus, Turbomax Plus, and Ecomax Pro. Each code points to a particular issue, whether it's related to the gas flow pressure, flue gas temperature, or mass flow sensor.
By familiarising yourself with these error codes, you can better understand the problem, decide on the appropriate fix, and maintain your boiler's performance, ensuring a safe and efficient operation for years to come.
Vaillant boiler error codes by model
Vaillant boilers come in various models, each with its own set of error codes. These codes help identify issues ranging from gas supply problems to faulty temperature sensors.
Let’s break down these codes by model so you can quickly find the information relevant to your boiler.
1. Vaillant Turbomax Plus 824/828E
The Vaillant Turbomax Plus 824/828E is a widely used model known for its reliability. However, like any boiler, it can encounter issues. Below is a table of the most common error codes for this model.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| F.00 | NTC Faults | Flow NTC (Negative Temperature Coefficient Thermostat) cable is either defective or broken and needs to be replaced. |
| F.01 | NTC Faults | Similar to F.00, this involves the feed temperature sensor and indicates a faulty connection or open circuit. |
| F.10 | NTC Faults | This refers to a short circuit in the feed temperature sensor. |
| F.20 | Overheating | Your boiler has exceeded the maximum temperature and needs to cool down. |
| F.22 | Dry Fire, Low Water | There’s either no water in your system, a defective pump, or the pump lead is defective. |
| F.28 | Ignition Problem | This could be due to insufficient gas, a defective electrode, ignition lead, or an electronic ignitor. |
| F.29 | Flame Extinguished | The flame or pilot light has gone out. Check your flue duct or gas supply. |
| F.60 | Gas Valve Control Fault | The cable loom connected to your gas valve might have short-circuited. Alternatively, you could have a defective gas valve assembly or electronic control system. |
| F.63 | EEPROM Error | This indicates an electronic fault within your system. |
2. Vaillant EcoMax Pro 18/28E
The Vaillant EcoMax Pro series is another popular model, especially in larger homes. Here are its common error codes.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| F.1 | Gas Supply Issue | This could be due to a lack of gas, a fault with the ignition or flue, or you may need to adjust the gas valve or replace a defective electrode lead. |
| F.4 | Ignition Fault | The boiler failed to ignite. |
| F.5 | Overheating | The system has overheated. |
| F.6 | NTC Fault | Your flow NTC has developed a fault. |
| F.17 | Polarity Issue | Check the polarity of your system. |
| F.24 | Pump Failure | The pump could have failed, overrun, or there could be an issue with the airlock. |
3. Vaillant Ecomax Pro 828E
For larger properties or commercial applications, the Vaillant EcoTEC 65kW is a powerhouse. Below are some common error codes for this model.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| S.O | Heating Issue | No heat demand. |
| S.1 | Fan Start-Up Error | The fan failed to start up. |
| S.3 | Ignition Problem | The boiler failed to ignite. |
| S.4 | Burner On Error | There was an issue with the burner igniting. |
| S.31 | No Heat Demand | This typically occurs in summer operating mode. |
| S.34 | Frost Protection Error | An error occurred during the frost protection mode. |
| S.22 | Pump Flow Error | The pump is not circulating water as it should. |
4. Vaillant EcoTEC 65kW error codes
The EcoTEC Pro and Plus models are among the most popular Vaillant boilers. They are efficient and reliable but can still encounter issues. Here’s a breakdown of the error codes for these models.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| F.00 / F.0 | Flow Temperature Sensor Interruption | The flow temperature sensor is not functioning correctly. |
| F.10 | Flow NTC Short Circuit | The flow NTC has a short circuit. |
| F.20 | Safety Switch Off | The temperature limiter has been triggered. |
| F.22 | Low Water Pressure | The system has low water pressure. |
| F.23 | Temperature Difference Too Great | The temperature difference between flow and return is too large. |
| F.25 | Flue Gas Temperature Too High | The temperature of the flue gases is too high. |
| F.28 | Ignition Unsuccessful | The boiler failed to ignite. |
| F.29 | Re-Ignition Unsuccessful | The boiler failed to re-ignite after the flame went out. |
| F.61 | Gas Valve Regulation Error | The gas valve is not regulating the gas flow correctly. |
| F.62 | Gas Valve Switch Off Delay | The gas valve is not closing as quickly as it should. |
| F.73 | Water Pressure Sensor Signal Too Low | The signal from the water pressure sensor indicates low pressure. |
| F.75 | No Pressure Change Detection | The system did not detect a change in pressure when the pump started. |
5. Vaillant EcoTEC Pro / EcoTEC Plus boiler fault codes
For those with the EcoTEC Plus Regular Gas Boiler, the following error codes are essential to know.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| S.20 | Warmstart Demand | The boiler is waiting for a heat demand. |
| S.21 | Fan Running | The fan is running as expected. |
| S.22 | Pump Running | The pump is running as expected. |
| S.23 | Ignition Sequence | The boiler is in the ignition sequence. |
| S.28 | Anti-Cycling Mode | The boiler is in anti-cycling mode, which prevents it from repeatedly turning on and off. |
| S.34 | Anti-Frost Mode Active | The boiler is in anti-frost mode. |
| S.53 | Modulation F Block Function | The boiler is in a waiting period due to water shortage. |
| S.96 | Return Sensor Error | There’s an issue with the return temperature sensor. |
6. Vaillant EcoTEC Pro / EcoTEC Plus cont.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| S.00 | Heating mode error – no heat demand | No heat demand detected in heating mode |
| S.01 | Heating mode fan start-up | The fan has started up in heating mode |
| S.02 | Heating mode error – water pump running | Error with the water pump in heating mode |
| S.03 | Heating mode – ignition sequence error | Problem with the ignition sequence in heating mode |
| S.04 | Heating mode – burner ignited | Burner has successfully ignited in heating mode |
| S.06 | Heating mode – fan overrun error | Fan is running longer than expected in heating mode |
| S.07 | Heating mode – pump overrun error | Water pump is running longer than expected in heating mode |
| S.08 | Heating remaining cut off time xx minutes | Time remaining until heating mode shuts off |
| S.10 | Hot water demand via impeller sensor | Hot water demand detected via the impeller sensor |
| S.11 | DHW mode fan start-up error | Error with fan start-up in Domestic Hot Water (DHW) mode |
| S.13 | DHW mode ignition error | Issue with ignition in DHW mode |
| S.14 | Hot water demand via fan sensor error | Hot water demand detected via fan sensor error |
| S.15 | DHW mode pump and fan overrun | Both pump and fan running longer than expected in DHW mode |
| S.16 | DHW mode – fan overrun error | Fan is running longer than expected in DHW mode |
| S.17 | DHW mode – pump overrun error | Pump is running longer than expected in DHW mode |
| S.20 | DHW mode – burner on error | Burner issue detected in DHW mode |
| S.21 | DHW mode – fan start-up error | Error with fan start-up in DHW mode |
| S.22 | DHW demand – error pump running | Pump running error detected during DHW demand |
| S.23 | DHW ignition error | Ignition issue in DHW mode |
| S.24 | DHW mode – burner error | Burner error detected in DHW mode |
| S.25 | DHW mode – pump or fan overrun error | Either pump or fan running longer than expected in DHW mode |
| S.26 | DHW mode – fan overrun | Fan running longer than expected in DHW mode |
| S.27 | DHW mode – pump overrun | Pump running longer than expected in DHW mode |
| S.28 | Hot water burner anti-cycling time | Anti-cycling time for the hot water burner |
| S.30 | Room thermostat is blocking heating mode | Heating mode is blocked by the room thermostat |
| S.31 | No heat demand boiler in summer operating mode | No heat demand as the boiler is in summer mode |
| S.32 | Waiting period because of fan speed deviation | Delay due to fan speed deviation |
| S.34 | Heating mode frost protection error | Error in frost protection during heating mode |
| S.39 | Burner off contact has been triggered | Burner shut off due to thermostat or condensate pump issue |
| S.40 | Comfort safety mode active | Boiler in safety mode to ensure comfort |
| S.41 | Water pressure > 2.8 bar | Water pressure exceeds 2.8 bar |
| S.42 | Flue non-return flap return signal blocks burner operation | Flue flap issue blocking burner operation |
| S.46 | Comfort safety mode flame loss at minimum load | Flame loss in safety mode at minimum load |
| S.53 | Boiler is in waiting period of modulation function due to water shortage | Boiler waiting due to water shortage affecting modulation |
| S.54 | Boiler is in waiting period of operation, blocking function as a result | Operation blocked due to waiting period |
| S.57 | Waiting period comfort safety mode | Boiler in waiting period due to safety mode |
| S.58 | Modulation limitation due to noise/wind error | Modulation limited due to noise or wind error |
| S.61 | Gas family check unsuccessful | Failed gas family check |
7. Vaillant EcoTEC Plus Regular Gas Boiler
The Vaillant EcoTEC Plus Regular Gas Boiler combines robust performance with energy efficiency, ideal for homes that require a dependable and consistent heating source. For any operational issues, check the error codes below to help identify and resolve common problems with this model.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| S.20 | Warnstar demand | Demand signal error for Warnstar system |
| S.21 | Fan running | Fan is operating |
| S.22 | Pump running | Pump is operating |
| S.23 | Ignition sequence | Issue with the ignition sequence |
| S.24 | Burner ignited | Burner has ignited successfully |
| S.25 | Fan and water pump running | Both fan and water pump are operating |
| S.26 | Fan overrun | Fan running longer than expected |
| S.27 | Pump overrun | Pump running longer than expected |
| S.28 | Anti-cycling mode | Mode to prevent rapid cycling of the burner |
| S.30 | No heating demand from external controls | No heating demand detected from external controls |
| S.31 | Central heating thermostat knob turned off | Thermostat knob is set to off |
| S.32 | Heat exchanger antifreeze active due to high fan speed variation | Anti-freeze mode activated due to fan speed variation |
| S.34 | Anti-frost mode is active | Anti-frost protection mode is active |
| S.36 | Not heating demand from low voltage | Low voltage issue affecting heating demand |
| S.41 | Water pressure greater than 2.9 bar | Water pressure exceeds 2.9 bar |
| S.42 | Response from accessory module or defective condensate pump blocking burner operation | Accessory module or condensate pump issue blocking burner |
| S.53 | Appliance in waiting period of block operation function due to water shortage | Waiting period due to water shortage affecting block operation |
| S.54 | Appliance in waiting period of block operation due to water shortage | Waiting period due to water shortage affecting block operation |
| S.96 | Return sensor error | Error with the return sensor |
| S.98 | Flow return sensor check is running demand is blocked | Flow return sensor check in progress with blocked demand |
8. Vaillant EcoTEC Plus Gas Boiler
The Vaillant EcoTEC Plus Gas Boiler is known for its high efficiency and reliable heating performance, suited for various home heating needs. If you face any difficulties with your EcoTEC Plus, the error codes provided here will aid in diagnosing and fixing common issues effectively.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| P.00 | Heating circuit and hot water circuit are purged | The circuits are being purged. |
| P.01 | Maximum load test program error | Error during the maximum load test program. |
| P.02 | Minimum load test program | Error during the minimum load test program. |
| P.06 | Filling mode test program | Error during the filling mode test program. |
9. Vaillant EcoTEC Gas Boiler error codes
Designed to offer excellent heating efficiency, the Vaillant EcoTEC Gas Boiler is a versatile choice for residential heating. For any operational concerns, consult the following error codes to help pinpoint and resolve issues that may arise with this model.
| Fault Code | Possible Cause | Meaning |
|---|---|---|
| D.0 | Heating part load error | Error with heating part load. |
| D.1 | Water pump overrun – time for heat mode | The water pump is running longer than necessary. |
| D.2 | Max burner anti-cycling period at 20°C flow temperature | Burner anti-cycling period exceeded at 20°C. |
| D.3 | Hot water flow temperature reading | Reading issue with the hot water flow temperature. |
| D.4 | Current temperature for warm stat sensor | Issue with the warm stat sensor temperature reading. |
| D.5 | Set value of flow temperature or target value of return | Incorrect set value for flow or return temperature. |
| D.7 | Warm start temperature target value | Issue with the warm start temperature target. |
| D.8 | External controls heat demand | Problem with heat demand from external controls. |
| D.9 | Flow target temperature from external analogue regulator terminal | Incorrect flow target temperature from external regulator. |
| D.10 | Status internal heating pump error | Error with the internal heating pump status. |
| D.11 | Status external heating pump error | Error with the external heating pump status. |
| D.12 | Cylinder charging pump via accessory module | Issue with the cylinder charging pump. |
| D.13 | Hot water circulation pump | Problem with the hot water circulation pump. |
10. Vaillant Error Codes F28 and F29
If your Vaillant boiler is showing either error code F28 or F29, then the condensate pipe has frozen and needs to be thawed.
This issue can occur during the colder months as the pipe runs outside but can be resolved fairly easily without the need for an engineer, as the pipe just needs to be thawed out.
How do you clear faults on a Vaillant boiler?
Clearing faults on a Vaillant boiler depends on the specific error code or issue. In many cases, a simple reset can clear minor faults like a temporary pressure drop or ignition failure. To clear a fault code on a Vaillant boiler, locate the reset button on the boiler's control panel, which usually looks like a flame with a line through it, and press and hold it for a few seconds until the error code disappears.
Before resetting, it’s worth checking a couple of things:
- Boiler pressure: If your boiler pressure is too low (below 1 bar), you may need to top it up using the filling loop.
- Gas and power supply: Ensure your gas supply is working (try other gas appliances) and that there are no electrical issues, such as a tripped fuse.
If you’ve checked these and the fault persists after resetting, it’s best to contact a Gas Safe registered engineer. Repeatedly resetting your boiler without addressing the underlying issue can cause further damage.
Which is the reset button on a Vaillant boiler?
The reset button on a Vaillant boiler is usually located on the front panel and marked with a flame symbol and a line through it or simply labelled “RESET.” On most models, it’s a small button that you need to press and hold for a few seconds (typically 3-5 seconds) to initiate a reset. If you’re unsure where it is on your specific model, check your boiler’s manual or look for a button near the display screen. Once pressed, your boiler should attempt to restart. If the fault continues, there may be an issue that needs professional attention.
FAQs about Vaillant boiler error codes
Is it safe to reset a Vaillant boiler?
Yes, resetting a Vaillant boiler is generally safe as long as you follow the manufacturer’s instructions. If your boiler has locked out due to a minor issue - like a temporary pressure drop or a power cut - a reset can often get it running again. However, if your boiler keeps locking out or displaying an error code, it could indicate a deeper issue. In that case, it’s best to call a Gas Safe registered engineer rather than repeatedly resetting it.
What does the flashing flame symbol mean on a Vaillant boiler?
The flashing flame symbol on a Vaillant boiler usually means the burner is in operation, which is normal when your heating or hot water is on. However, if the flame symbol is flashing and your boiler isn’t providing heat or hot water, it could point to an ignition fault, gas supply issue, or another problem. Checking the pressure gauge and error codes can help pinpoint the issue - if in doubt, a professional should take a look.
Why is my Vaillant boiler giving me hot water but no heating?
If your Vaillant boiler is providing hot water but not heating your home, the issue could be with the thermostat, diverter valve, or system pressure. For common causes and simple fixes for this issue, read our guide: Hot water but no heating? Here's what to do.
When to call a professional
Some boiler problems can be solved with a few simple checks, but anything involving the gas supply, the inside of the boiler, or a fault that keeps coming back needs a Gas Safe registered engineer. Never remove the boiler casing or attempt internal repairs yourself.
JustFix engineers can diagnose the fault, explain what's needed and what it'll cost before any work starts, and get your heating and hot water back up and running. All our work is backed by our 12-month workmanship guarantee.
Need a hand? Tell us what's going on and we'll take it from there.
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