Buderus GB022 Heating Issues: Error 2F, Flow/Safety Temperature Sensors & Exchanger Replacement

Hello,

I have a problem with the Buderus GB022 stove. Error 2F has appeared for some time.

I checked in the service manual - it could be related to the flow sensor or the safety temperature sensor. I checked both sensors with a multimeter and they did not show significant differences in readings for a given temperature (differences of a few ohms).

This error occurs when starting the burner. It helps to switch the stove off and on several times.

During these types of reboots, the 2F error often reappears. After starting the stove, the symbols OU-> OC-> OL-> H (with lower and upper lines) appear in sequence. The 2F error appears immediately after H (H is visible for a fraction of a second).

I called the service technician Buderus to the topic several times and at this point I do not know what to do with this stove. The service technician claimed that it was a matter of a worn exchanger and replaced it, later stated that the stove should be thoroughly cleaned and he did it too. Then something changed in the configuration. None of this helped.

Can you help with the topic?

Hehe, I like it when an authorized service technician replaces parts at random, but the fault persists.
Because of such bunglers, the rest of these true professionals later lose.
A field of poverty as this is a free warranty repair, but if the customer pays, for me it is a fraud and taking out the money.

As I understood correctly, the error is related to the boiler overheating shortly after its start.
If I were you, I would check to what values the temperature rises on these sensors before this error appears. Maybe the sensor works well at room temperature, and at a higher burner it is freaking out. I assume that, for example, in the boiler service settings, you can check the current temperature readings on each of these sensors.

Out of curiosity, I took a look at your boiler service manual and the error 2F means:

Quote:

The flow sensor and the safety temperature sensor have not seen an increase
heating water temperature after burner start or temperature difference between
flow sensor and safety temperature sensor is too high.

For me, this means that the error will pop up if the sensors do not respond quickly to temperature changes or one of them is damaged, which will result in significant discrepancies between the indications of one and the other sensor.
Therefore, the above-mentioned temperature readings can be crucial and extremely meaningful here.
Besides, the process of "fixing" this error is described in chapter 25, although it seems trivial, it is worth checking all these elements.
I do not know what your sensors look like, but in the Vaillant boiler I have such almost hermetically sealed ones, which, after dismantling, reacted to temperature changes caused by the air blowing on them from the mouth.
You could use a test to see if the sensors will react and will have the same resistance, but simulating a higher temperature, similar to the one in the installation after firing the burner. For example, I could soak mine in hot water and measure the resistance, but apparently not every sensor is that waterproof.

Thanks for the answer.

Today I recorded a video of how the stove behaves right after it is turned on - it does not even start heating (the temperature does not increase) and the error 2F appears immediately. So it is not due to the difference in temperature readings on the sensors during heating (at higher temperatures).

[movie: ad81e811eb] https://filmy.elektroda.pl/49_1497353595.mp4 [/ movie: ad81e811eb]

Anyone have any ideas what to do?

At first I was scared that your boiler works like a concrete mixer, but it's probably the washing machine that makes so much noise

The video shows that the burner turns on for a moment (the flame icon and the temperature changes by a few degrees), and this is also the result of the instructions that when you turn it on, it fires the burner for a moment.

The 2F error according to the instructions suggests that the problem lies in the temperature sensors, or if not in the sensors themselves, then I would look for a problem in another element that indirectly affects errors in temperature readings, e.g. no / disturbed water flow in the boiler system.
You still haven't done the sensor test, which in my opinion is the basis for further considerations, and as you can see, the boiler locks up at 45 degrees.
It is enough for one sensor to react properly and show, for example, 45 degrees, and the other one is distorting, indicating too low or too high temperature. This condition can be read by the electronics as a failure, which results in blocking the boiler to protect it from potential overheating.

You have a great service manual, quite detailed test procedures, I'm also impressed.
In chapter 111 you have given the resistance of the sensors in 5 degrees steps, so you can accurately determine in amateur conditions whether they are operational and work properly according to their characteristics.

According to the instructions, the sensor resistance at the temperature:
- 35 degrees is 6,754 Ohm
- 40 degrees is 5 594 Ohm
- 45 degrees is 4,656 Ohm
- 50 degrees is 3,893 Ohm
Since you had 45 degrees on the display, you already know how much more or less the multimeter should show. It would be useful to check how much the second sensor shows on the display, but even if you do not have any insight, the resistance measurement will give you the answer, how it is recording the temperature at the moment and how much it differs from the first sensor.

If you claim that your boiler does not turn on the burner at all, the more you have the sensor released, because a cold boiler without burner operation cannot reach 45 degrees in practice. In my case, a cold boiler in the current "hot weather" has 25/26 degrees on the supply sensor and the hot water exchanger sensor and this is a real value.

1) Is the boiler well vented?
2) Open valves under the boiler?
3) After removing the casing, what is the temperature of water at the outlet from the combustion chamber?

Thanks for all the tips and tricks.

Today I sat down to the topic and checked both sensors again with a multimeter.

It is interesting that at the beginning the stove showed a temperature of 47 oC, and after turning it off and on it started to show 23 oC.

Below are records of indications for different temperatures (safety sensor - CB; flow sensor - CZ):
23 oC: CB = 11590; CZ = 11480
27 oC: CB = 9030; CZ = 10,020
30 oC: CB = 6900; CZ = 8200
32 oC: CB = 7680; CZ = 8050
37 oC: CB = 5240; CZ = 6850
45 oC: CB = 3300; CZ = 4900

Comparing it with the data from the manual and the auxiliary graph (I attach, it may be useful to someone), it turns out that the safety sensor will be hit. What do you think about it?

Five times the eye looks like the display shows the temperature from the flow sensor (CZ), which is located somewhere at the bottom next to the plate exchanger. In turn, the safety sensor (CB) is on the top near the burner, so it is assumed to have a slightly higher temperature, which is also confirmed by your measurements.
It would be nice to see if you can see the current CB readings on the display.
With CB, it is only at measurements for 30 and 32 degrees that it has cooled down, i.e. the burner had to turn off for a while, then it turned on again and increased the temperature.
But despite everything, I do not see any disturbing differences, so my variant with too large a temperature difference between the two sensors is rather out of the question.

In turn, I am wondering that the sensor showed 47 degrees, and after restarting the power supply, suddenly 23 degrees appeared.
Assuming that the display shows CZ indications, it can be assumed that he is freaking out.
It would be nice to know the resistance of the sensors at 47 degrees and at 23 after a power restart to see if this is a sensor problem that randomly loses resistance, or it is an electronics fault.
Electronics is a big expense, so if the sensor has not been cleaned, disassemble it and clean it, check the electrical connections, and if there is any loss of resistance, it is not so called cable problem.
If both sensors are identical, you can try to swap them and then do the tests.

Finally, you can take the risk and buy a new sensor, but bear in mind that this could be a motherboard problem.

Thanks to everyone for your help on the topic. I tried cleaning the power sensor, but it eventually helped replacing it. The stove has been working without any problems for 2-3 weeks now