VAILLANT. Error F.28
Causes and solutions:
- Boiler power supply failures: Reset the boiler There is an appropriate button on the panel of Vaillant gas boilers (crossed out flame symbol or RESET sign).
It is strictly recommended to connect heating boilers through a stabilizer (for the boiler) or UPS, this will save unnecessary costs of replacing the control board.
- Failures in the gas supply to the house: often the gas pressure on the main line decreases and the boiler does not work. Checking involves ignition of all the burners on the hob at maximum power. The characteristic color of the flames indicates that there is no problem with the fuel supply, while their intensity and stability indicates that the pressure is constant and normal.
- The gas valve is clogged / defective: it is easy to disassemble it, but not desirable:
- Vaillant connectors have miniature latches. Users often break them when removing the valve from the boiler.
- A special grease is applied to the rod. Which one. is not an idle question.
- It is possible to knock down the setting of Vaillant fittings by the gas pressure at the inlet to the boiler burner.
But if you still dare, then after removing the stepper motor and removing the cap you can see the rod, which is responsible for moving the diaphragm that regulates the gas supply to the burner of Vaillant boiler. In the process of operation, it gets dirty and deposits prevent it from moving freely. It is enough to wash in any liquid on an alcohol basis, put it back and assemble in the reverse order.
- Faulty ionization sensor and / or electrode: If the boiler ignites and sparks, the boiler ignites and extinguishes, this means that the flame control electrode (ionization sensor) “does not see” the flame.
Depending on the type of boiler ionization electrode stands alone or already in conjunction with the ignition electrode.
Often the electrodes become contaminated with soot and burnt dust and it is often sufficient to wipe them with the fingers and the boiler will work again. If the electrode has not been serviced for a long time, you need to clean its tips with an abrasive emery cloth with a minimum grain.
- Failure of the modulation coil / ignition transformer: its malfunction can be judged by the absence of spark between the electrodes and the burner during ignition. If you have experience, you need to test the windings with a multimeter to detect a breakage.
Any diagnosis and repair of the boiler should be performed by a certified professional with a valid certificate issued by Rostekhnadzor.
Causes of failure
To possible reviews about the boilers of this brand were favorable, it is necessary to pay great attention to the prevention of malfunctions and their elimination. It is worth noting that not all problems are indicated by codes, some occur without warning. The situation when the boiler does not turn on at all, can occur due to incorrect connection of “zero” and “phase”.
Also, the malfunction can be related to the following:
- Air is abundantly mixed with gas;
- Low pressure in the gas line;
- Grounding errors;
- The cables are torn;
- Unreasonable connection to the gas line.
When there is no hot water at all or the boiler does not heat it well, it is necessary to evaluate the condition of the flow sensor. Sometimes it gets dirty, the liquid moves, but the automation does not give the command to the fan to blow the furnace and fan the fire. Bleed water from the hot water circuit to ensure that the pipes are saturated with air. Following this, it is necessary to sharply unlock and tighten the water taps in front of the boiler to remove the dirt from the fan or sensor due to the pressure drop. If the pressure rises or falls unpredictably and hot water drips from a cold tap, the secondary heat exchanger could be damaged.
Sometimes the boiler buzzes when turned on. no need to be afraid to open it. It is required to see that no pipes or other parts are in contact with the body. Then there is definitely no problem with extraneous noise either.
You should also check the following reasons:
Features of regulation
Boilers of this manufacturer are notable for the ease of control. However, this does not mean that everyone can handle such a task on their own. It is best to make adjustments in pairs, with one person turning the faucet and the other tracking the position of the pressure arrow. To make adjustments to the temperature of water or heating, you can use special valves that are located on the control panel. In doing so, how hot the water is will be shown on the display. Thanks to this you can increase the temperature or decrease it by turning the valve to the desired position.
Also, that it is time to figure out how to eliminate error F28 in the boiler Vaillant, can signal special light sensors on the panel of the device. The green lamp lights up during the use of heated water. Yellow light indicates gas combustion is occurring. If the red LED lights up, it indicates a malfunction in the system. It is also worth paying attention to the fact that the boiler is filled exclusively with water. You should not make any experiments.
Main error codes (f28, f75) and their short decoding
The codes for various errors or malfunctions are numerous.
Let’s see the most common ones:
| Code | Explanation of |
| F00 | Supply thermistor circuit interrupted |
| F01 | Reverse mowing line thermistor circuit breakage |
| F02-03 | Opening of the temperature thermistor or storage sensor |
| F04 | Breakage of return thermistor |
| F10 | Supply thermistor short circuit (exceeding 130°) |
| F11, F14 | Short circuit of the return thermistor (exceeding 130°) |
| F22 | Dry run (pump malfunction) |
| F23 | Lack of water. Determined by temperature difference between forward and return lines |
| F27 | Parasitic flame |
| F28 | Blockage of the ignition |
| F29 | Failure in operating mode (occurs when the flame goes out and the ignition attempt fails) |
| F35 | Fault in the gas exhaust system |
| F37 | Unstable or abnormal fan speed |
| F72 | Forward and/or reverse mowing line sensor reading error |
| F75 | The pump is unable to raise the pressure |
| F76 | Primary heat exchanger has overheated |
In addition to error codes marked with F, there are status codes marked with S. They inform about the ongoing process and are not errors.
Fault, malfunction and error codes for Vaillant boilers
F13. Vaillant VUW: short-circuit in the warm start/storage temperature sensor VUW with actoSTOR: short-circuit in the storage sensor, only in conjunction with F91.
NTC faulty, short circuit in wiring harness, cable/housing
F20. Error: Vaillant boiler safety shutdown. temperature limiter
Malfunction of “mass” connection of the wire harness to the product, malfunction of NTC supply or return line (unreliable contact), breakdown through ignition cable, ignition plug or ignition electrode
F22. Safety shut-off: lack of water
No or insufficient water in the product, defective water pressure sensor, cable to the pump or water pressure sensor unreliably connected / not connected / defective
F23. Safety shutdown: Temperature difference too great
Pump blocked, pump capacity too low, air in the product NTC flow or return NTC return lines mixed up
F24. Safety shutdown: Temperature rise too fast
Pump blocked, reduced pump capacity, air in product, system pressure too low, gravity check valve blocked or incorrectly installed
F25. Exhaust gas temperature too high, in case of safety shutoff
Optional safety temperature limiter (STB) plug connection interrupted, broken wiring harness
F26. Fault: gas fitting does not work
Gas valve servomotor not connected, wrong connector on board, breakage in wiring harness, gas valve servomotor defective, electronics malfunction
F27. Safety switch-off: flame simulation
Moisture in electronics unit, electronics unit (flame control device) defective, solenoid gas valve defective
F28. Error when starting the Vaillant boiler: ignition failed
Faulty gas meter or triggered gas pressure switch, air in the gas, gas pressure too low, thermal shut-off device (TAE) triggered, condensate drain line clogged, wrong gas nozzle, wrong gas fitting ET, gas fitting error, Multi-pin plug not correctly connected to the electronic board, wire harness breakage, ignition system faulty (ignition transformer, ignition cable, ignition plug, ignition electrode), breakage in ionisation circuit (cable, electrode), product grounding is not correct, electronic unit faulty
F29. Error during operation: Unsuccessful reignition
Interruption of gas supply from time to time, recirculation of flue gas, blocked condensate drain line, incorrect product grounding, ignition of ignition transformer failure
Plug incorrectly connected to the fan, multi-pin plug incorrectly connected to the electronics board, broken wiring harness, fan blocked, defective hall sensor, defective electronics board
F42. Error: Encoder resistor (possibly in conjunction with F70)
Short circuit/breakage of coding resistor for output value (in the cable harness on the heat exchanger) or gas group resistance (on the electronic board)
Vaillant boiler error F 28
F49. eBUS error eBUS data bus short circuit, eBUS data bus overload or duplicated eBUS data bus power supply with different polarities
F52. Bad contact: Mass flow sensor / Venturi device
Mass flow sensor/Venturi not connected to the mains
Combustion control has detected an error
F54. Error in gas supply to Vaillant boiler (in combination with F28/F29)
Existing gas supply is insufficient to operate the appliance
Components in the combustion control are defective
F57. Comfort mode active Comfort mode has detected an adjustment fault
Ignition electrode is heavily corroded
F61. Control error of the gas fitting
Control of the gas fitting is not possible
F62. Delayed shut-down of the gas fitting of the Vaillant boiler
Gas valve shut off delay detected
Short circuit NTC feed or return line, electronics unit defective
Vaillant Boiler Fault Code F.28 and F.29
F65. Electronics block temperature error
Excessive heat produced by external influences, electronics unit defective
Invalid flame signal, electronics unit defective
Air in the gas, too low gas pressure, unsuitable excess air, clogged condensate drain ducts, unsuitable gas nozzle, ionisation current circuit breakage (wire, electrode), exhaust gas recirculation, condensate drain duct
F70. Invalid device code (DSN)
Spare parts installed: Display and printed circuit board are replaced at the same time, and the new code of the appliance is not set up, the coding resistance of the power value is incorrect or missing
F71. Mower feed line temperature sensor failure
Temperature sensor in mowing line supply line reports constant value:
F72. Mowing line supply or return temperature sensor failure
Temperature differential between supply and return NTC sensor lines is too high. Mower supply or return temperature sensor defective
F73. Water pressure sensor signal is in wrong range (too low)
Water pressure sensor open/short circuit, open/short to ground in water pressure sensor lead or defective water pressure sensor
F74. Water pressure sensor signal is in wrong range (too high)
The wire to the water pressure sensor is shorted to 5V/24V or there is an internal error in the water pressure sensor
F75. No detection of pressure surge on start of Vaillant boiler pump
Water pressure sensor or/and pump defective, air in heating system, too little water in product; check adjustable bypass, connect expansion tank to return mowing line
F76. Fault: Overheating protection on the primary heat exchanger has tripped
Cable or cable connections of the fuse in the primary heat exchanger are defective or the primary heat exchanger is defective
F77. Exhaust valve/condensate pump error
No return signal from flue gas valve or condensate pump defective
F78. Open circuit in hot water outlet sensor on external controller
UK link box connected, but hot water NTC not closed
F80. Secondary heat exchanger inlet sensor open or short circuit; only in combination with F91
NTC defective, NTC cable defective, defective plug connection on the NTC, defective plug connection on actoSTOR electronics unit. Plug on the sensor has a short circuit to frame, short circuit in the cable harness, sensor defective
F81. Load pump defective; only in conjunction with F91
After a certain time the tank is not completely loaded
F83. Fault on temperature change of flow or return sensor
When starting the burner, either the flow or return sensor detects no temperature change or too low a value.
F84. Error: Invalid difference between flow and return sensor temperature
Feed and return line sensors are reporting incorrect values
F85. Mowing line supply or return temperature sensor not assembled correctly
Temperature sensors for supply and/or return mowing line mounted on the same pipe or not on their pipes
F90. Communication with the actoSTOR module has been interrupted
Check the cable harness from the product to the actoSTOR module (PEBus). If the product is to be operated without the actoSTOR module, set D.092 = 0.
F91. Sensor/actuator error on actoSTOR
The coding resistor on the PCB is not suitable for the specified gas group: check the resistance, recheck the gas type and specify the correct gas group.
Combustion adjustment detects poor combustion quality
Status message codes for Vaillant boiler
S.0. No heat request. S.1. Fan start. S.2. Pump pre-run. S.3. Firing process. S.4. Burner operation. S.5. Fan and pump run out. S.6. Fan run out. S.7. Pump runout. S.8. Burner lockout after heating operation.
S.10. Heat demand for hot water preparation (determined DHW flow rate). S.11. Fan startup. S.13. Ignition process. S.14. Burner operation. S.15. Fan and pump run out. S.16. Run out fan. S.17. Pump run out.
Hot start / water heater heating mode
S.20. Pump pre-run. S.21. Fan start. S.23. Ignition process. S.24. Burner operation. S.25. Fan and pump run out. S.26. Fan run out. S.27. Pump run out. S.28. Burner lockout after hot start/heating water heater operation (beat suppression).
Special cases of status messages (system effects)
S.30. Room thermostat 230 V/24 V block heating mode.
S.31. Summer mode on; eBus controller or integrated timer locks heating mode.
S.33. Exchanger freeze protection mode active, because the contacts of the gas-air circuit relay did not close. Boiler blocked and on stand-by for 20 minutes (turbotec only).
S.34. Freeze protection mode active.
S.36. Continuous regulator setpoint is over 20 C, so the external regulator is blocking the heating mode.
S.41. System pressure too high. 2.8 bar. 4.5 bar.
S.42. The burner is blocked due to:
S.51. Waste gas output into the room is detected, the boiler is in 55 sec mode. No sensitivity to flue gas outlet (atmotec).
S.52. Exhaust gas outlet into the room is recognized, the boiler is blocked and is in 20-minute standby mode (atmotec).
S.53. The boiler is in a 2.5-minute standby time due to lack of water (too much difference between the temperature of the supply and return mowing line).
S.54. Appliance is on standby in 20 minutes due to lack of water (temperature rise too fast).
S.96. Mowing line return sensor is testing, heating requests are blocked.
S.97. Water pressure sensor testing is occurring, heating requests are blocked.
S.98. Supply and return line sensor test in progress, heating requests blocked.
Additional information on gas boiler models: Characteristics, operating functions, accessories, controls and adjustments, troubleshooting.
Trouble Causes
For possible reviews of boilers of this brand to be favorable, great care must be taken to prevent malfunctions and troubleshooting. It is worth noting that not all problems are indicated by codes, some occur without warning. The situation when the boiler doesn’t start at all can occur because of wrong connection of “zero” and “phase”.
The malfunction may also be related to the following:
- air abundantly mixed with gas;
- Low pressure in the gas line;
- Grounding mistakes;
- torn cables;
- illiterate connection to the gas pipeline.
When there is no hot water at all or the boiler does not heat it well, you need to assess the status of the flow sensor. Sometimes it gets dirty, the liquid flows, but the automatics does not let the fan blow through the furnace and blow up the fire. Releasing water from the hot water supply line, achieve saturation of the pipes with air. Following this, the water taps in front of the boiler must be sharply unlocked and tightened to remove the dirt from the fan or sensor due to pressure variations. If the pressure rises or falls unpredictably, while hot water is dripping from a cold tap, you can assume damage to the secondary heat exchanger.
Sometimes the boiler buzzes when switching on. no need to be afraid to open it. Required to see that no pipes or other parts do not come into contact with the body. Then there will not be any problems with extraneous noise.
You should also check the following causes:
Installation recommendations
Error F28 gas boiler Vaillant can give out because of the incorrect installation of the unit. Therefore, it is necessary to coordinate the installation of the device with the gas distribution company.
It is also necessary to correctly determine in which hole in the wall the chimney will pass. Some parts of the construction of the house may be too strong and thick for such equipment.
When connecting the boiler for the first time, it is necessary to use a voltage regulator. It is important to follow the polarity.
In order not to encounter the fact that the boiler Vaillant gives error F28, it is necessary to make the connection correctly. It is necessary to understand that only professional specialists can perform this procedure in accordance with all requirements.
If the installation is made independently, it is necessary to make a project of the heating system and certify it in the appropriate authorities. At independent or low-quality installation can cause serious problems.
Problems of gas boilers Vaillant: error f28, how to eliminate it, as well as possible malfunctions and owners’ reviews
The European company Vaillant is well known to specialists and users of heating equipment.
Founded more than 100 years ago, the company has accumulated vast manufacturing and technological experience, developed a lot of own patented components and parts.
Gas boilers, manufactured by this company, are known far beyond Europe and exported not only to Russia, but also in most countries of the world.
The units are renowned for their reliability and resistance to external loads and are adapted to the technical conditions of the country where they will be used.
Emerging problems are immediately diagnosed by a system of sensors that sends a signal to the display about the appearance of a problem.
Knowing the error codes of Vaillant boiler you can diagnose almost any problem. And having experience in repairing heating equipment, nothing prevents you from solving the problem yourself. Codes are displayed on digital indicators, representing two-digit numbers with letter F. Let’s break them down in more detail.
F28 error
A fairly common error that occurs when the ignition unit fails to start. As a result, the equipment can not start. Error F28 in Vaillant boilers can indicate breakage of system board and other components. high voltage ignition transformer, gas magnet, gas valve, ignition sensor and many others. It appears when there is a wire break or insufficient pressure in the line. It is often caused by a trivial closed gas valve.
To fix error F28, follow these steps:
- Check all electrical connections.
- Test the gas equipment.
- Make sure that there is a gas supply to the Vaillant boiler.
- Remove impurities from the ignition sensor.
If all nodes are intact, there is a high probability of error directly on the system board. In this case it is necessary to address to Vaillant service for its repair or complete replacement.
Error F75 can also indicate problems with the onboard water pressure sensor. it can not detect pressure increase after the start of the pump.
F75 error
Another common sign of malfunction. F75 error in Vaillant boilers indicates problems with pressure in the heating system. It appears after the start of the circulation pump. Usually in this case, the pressure rises by about 0.2-0.4 atmospheres. If this does not happen, the problem may be in the wrong installation of the system. First it is necessary to check the serviceability and correctness of the connection of the expansion tank (expansomate), then conduct the bleeding of the circuit.
After that check the efficiency of the pump. it must pump the coolant through the loop. Faulty pump must be replaced, they are usually not repairable.
F0, F1, F2, F3 and F4 errors
The first two occur in Vaillant heating boilers in the case, if the coolant temperature sensor (NTC sensor) failed. It must be replaced by a sensor of the same model. Although there is no vibration, some connection wires can be damaged, so check for continuity with a multimeter. Also you need to inspect quality of connections, connectors. it’s often the case that codes are appearing due to oxidation of contacts. F2, F3 and F4 codes are caused by the storage sensor.
F5 and F6 codes (also F15 and F16)
This code is characteristic for Vaillant Atmo series boilers with atmospheric burners. It indicates breakage of draught sensor or breakage in connecting wires. Recommend to check continuity of wires, test sensor itself. If the breakage appeared after disassembling-assembling of the equipment, check the correctness of all connections. In turbine units occur codes F15 and F16.
Codes F10 and F11
Their appearance means a short circuit in the circuits of supply and return temperature sensors. Not only wires need to be checked, but also the temperature sensors themselves. Similarly test the connector connections.
Faults F13 and F14
If the digital display shows one of these codes, it means that the coolant overheated. it heated to a temperature of 130 degrees. For Vaillant boilers this value is critical, so the equipment shuts down immediately. If the water in the circuit is clearly cooler, there is a short circuit in the sensor itself or in the connecting wires.
F20 code
Indicates a problem with the supply temperature sensor. It needs to be checked, similarly all connections are checked. In some cases, the code indicates overheating of the coolant.
At error F22 all circuits that are responsible for the work of the circulation pump and coolant pressure sensor in the circuit should be tested.
Codes F22, F23 and F24
F22 error is the general, showing the most various malfunctions. It appears when there is no water in the heating circuit. Water can leak through the smallest cracks and crevices, there could also be problems with the pressostat and circulation pump. In rare cases, the system board is to blame.
F23 at the first start-up indicates a problem with the coolant. it is not enough or the installer managed to mix up the supply and return pipes. In other cases, the culprit is the circulation pump, which needs to be checked and replaced. Code F24 indicates too high temperature of heating medium in the flow pipe. check the pump, temperature sensors and circuits. The last place to blame is on the board.
F25 error
In Vaillant boilers it indicates too high temperature of products of combustion in the flue. When registering the overheating the equipment shuts down. If gas equipment and heat exchanger are normal, we test the sensors and electric connections.
Code F27
Some errors in Vaillant boilers indicate several possible problems:
- The sensor of flame presence has broken. despite the absence of fire, the boiler “sees” it.
- Gas solenoid valve breakage.
- There was a serious malfunction in the work of the system board.
In the last case we switch off equipment, wait a few minutes, then restart.
Error F29 is possible if the ignition system malfunctions. check all components.
F29 error
Widespread and occurs if there is a banal drop in pressure in the gas line or if the gas supply is completely cut off. As the result the flame goes out, equipment turns off, the above mentioned code appears on the display.
F32 error
Characteristic only for the Vaillant condensing boilers. Diagnose malfunction of the fan responsible for removal of combustion products. In this case check the fan and connecting wires. Sometimes the fault is in the circuit board that controls the equipment.
F35 and F36 errors
If these codes appear, open windows and ventilate the room, check for foreign odors. It’s possible that instead of flue gases may go directly to the room. Codes are shown on the display even if the fresh air supply is interrupted. The situation is typical only for atmospheric boilers Vaillant.
Code F61
Serious error related to the operation of gas valves. Indicates their malfunction and breakage of electronic board. Rarely, code is displayed if connecting wires are broken.
Code F62
Boiler “sees” the flame for more than four seconds after closing the gas valve. Possible causes:
- The valve is broken. it must be repaired or better completely replaced (may cause leakage).
- Need to clean the burner.
- System board malfunction. reset or test at the nearest Vaillant service center.
Codes F74 and F74
Faulty water pressure sensor in the heating circuit. In this case, the module must be replaced, because it gives wrong data.
