Error F28 on a Saunier Duval boiler


There are various solutions for the F28 error on a Saunier Duval boiler

Saunier Duval boiler users often feel like the F28 error is like a spell being cast on the unit. They try multiple solutions, and although the error seems to temporarily disappear, it soon reappears again. The “elusive” nature of the F28 error is basically due to the fact that although it is a simple boiler starting error, it is more complicated than it seems and can have a wide range of causes. In this article, we will take a look at all the causes and explain how you can resolve the F28 error in your Saunier Duval boiler for once and for all.

The F28 error in a Saunier Duval boiler is not an isolated error

This start-up error can be due to many different causes. It not only makes the real cause of the error difficult to solve, but it is even more difficult to detect and fix. While it’s true that the problem can be sorted with a simple reboot, this is not always the case. The boiler user might do several reboots, but the boiler might still not be working and can still display the same error code.

In Saunier Duval boilers, the F28 error (or F.28) is universal across all models, meaning the causes of the error display are the same. This does not happen in other brands and there are sometimes notable differences between error code systems across models. So, with this in mind, we can discuss this error code and its related solutions in a general way.

How the manual describes this error code

With the F28 error (which is sometimes related to the F29 error), the manual describes the general cause as a “misfire”and this explains a number of specific, possible causes, many of which are related to gas problems, faulty connectors or broken electronic parts.


Even by simply glancing through the many causes of a misfire, it’s easy to understand why it’s difficult to pinpoint a specific cause for the F28 error and solve it. All the possible causes are in the list below and there are quite a few:

  • Defective or faulty gas meter
  • The gas pressure controller has tripped
  • The gas contains air
  • The gas flow pressure is too low
  • Congested condensation duct
  • Incorrect burner nozzle
  • The thermal locking device (TLD) has blown
  • Incorrect gas nozzle
  • Incorrect ET gas valve
  • Problem with the gas valve
  • The PCB manifold connect is not connected properly
  • Interruption in the wiring system
  • An ignition component is faulty (it could be the transformer, the ignition cable, the ignition connector, or the ignition electrode)
  • Ionization flow interruption, either in the electrode or cable
  • The earthing connection has not been set correctly
  • Faulty electronic components
  • Obstruction with gas intake or gas expulsion

Solutions for error F28 in a Saunier Duval boiler

The actual causes of this error have the following solutions, as per the user manual:

  • In some cases, restarting or rebooting the boiler is enough
  • In other cases (such as broken or cut cables, dirty or misaligned electrodes, clogged smoke ducts and gas intake pipes, congested burner, congested condensation duct, incorrectly placed parts, etc) you can resolve the issue by inspecting the unit, cleaning it and maintaining it regularly.
  • Sometimes, redesigning the unit’s installation is necessary and this can correct errors, such as an incorrectly placed earthing connection or an unsuitable burner nozzle.
  • However, in certain cases, (damaged electronic parts, faulty ignition elements) it is obvious that the faulty parts need to be replaced with new ones.

Here is a link to our store, where you can buy all the boiler spare parts that you need.


Other problems that may give the same error

Sometimes boilers do not behave according to the manual and can still give an F28 error. Here are some scenarios of when boilers display unusual behavior:

  • Boilers often have a long period of inactivity during the summer, and when you switch them on again, they sometimes don’t heat the water and then display the F28 error code. This can remain, even after you’ve used the reset button. Interestingly, this is sometimes not due to any of the problems described in the user manual, but due to a problem with the water pump. There have been isolated cases of this happening, but we don’t want to leave this out as it may be useful to somebody. The solution here would be to service the water pump or replace it with a new part.
  • Since the Saunier Duval gas boiler normally offers instant DHW, it has a small, built-in preheating accumulator so that there is always hot water available. This micro-accumulator can break, and this may be what is interfering with the start-up process and the cause of the F28 error code. A temporary solution that a boiler user can implement (after having contacted a qualified technician) is to activate the boiler’s ecological mode, which prevents the water from being preheated in order to reduce energy consumption. Since the micro-accumulator is deactivated, the F28 error will disappear.

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