Ferroli boiler FH code


Ferroli boilers and the FH “error”: The air purging cycle

The “automatic air purging cycle” is an intelligent feature that Ferroli boilers have. These boiler users often call this function the FH error. In reality, however, this is not actually an error, and it’s also not included in the Ferroli boiler user manual’s list of fault codes: FH is simply an acronym that this display shows while performing the air purging cycle. This article will discuss the so-called FH error in Ferroli boilers, why it is erroneously considered as a fault, its actual meaning, and more details that can be useful and valuable to you.

Why is the FH acronym mistaken for an error code?

It can be tedious reading through the manual when you’ve just bought a boiler. This is understandable because the information contained in the manual is often common sense. However, this is not the case with the topic we are discussing in this article. When it comes to complex appliances, like boilers, reading the manual can’t hurt.


After reading the manual, you’ll notice that the FH acronym on a Ferroli boiler doesn’t mean that there is an error. Instead, it represents an intelligent and automatic process that the boiler carries out every now and then (later on, we will understand under which circumstances it carries this out). Some people, however, interpret the FH acronym as an error code, an opinion that is backed up by the following:

  • Error codes are normally indicated with acronyms, or by acronyms with numbers. From this aspect, the FH acronym seems very similar to an error code.
  • When it appears on the display, the FH code is often displayed in red (a color that is associated with problems) and it may also blink repeatedly which, in addition to the fact that the boiler isn’t starting up, is normally associated with a malfunction or breakdown.
  • The fact that the purging cycle has several steps lasting 300 seconds (5 minutes) in total can give the impression that it is a neverending process, which is also the case with many other error codes.

All of the above reasons make it easy to think that the FH acronym is an error code. However, it is not included in the error code table. We recommend reading through a Ferroli boiler manual to see that the FH acronym is not only excluded from the error code tables but is explained as one of the boiler’s normal processes.

Automatic air purging stages

The air purging cycle is what is popularly known as a pre-purge. It can take up to 4-5 minutes depending on the model, and it’s best to be patient and wait for it to end. It’s important that you don’t press any buttons while the boiler is purging as this can prevent it from performing the purge properly.

Depending on the Ferroli boiler model, during the purge cycle, there may be 2 variants of the FH acronym where the letter H changes from uppercase to lowercase on the display to indicate the change of stage: it will first appear as FH (“Air purging with the fan running”), and it will then appear as Fh (“air purging with the fan off”). Taking this into account, the air purging cycle stages are:

  1. During the initial 5 seconds, the display shows the card software’s version number that the boiler is using.
  2. In the next 20 seconds, the boiler carries out the first stage of the purging cycle using the fan. The code appears on the display as FH, with an uppercase H.
  3. For the next 280 seconds (4.7 minutes), the boiler carries out the second stage of the automatic purging cycle, this time without using a fan. The code on the display is Fh, with a lowercase h.
  4. Finally, the boiler will start working when it needs to maintain the temperature that was programmed into the room’s thermostat, or whenever there is a demand for domestic hot water.

Depending on the model, the display might only show the letters FH with no variation on upper or lowercase. However, the pre-purging process will be the same.

Instants when the initials FH appear on the display

  • When installing the boiler for the first time, after connecting the boiler to the mains and opening the gas inlet valve, an air purging cycle will be routinely performed. The pump needs to draw air inwards and inside the heating circuit.
  • When the gas and boiler are turned on after a long interruption in the gas or electrical supply, an air purging cycle is normally performed automatically. It is important that when this happens, there is no demand for DHW or heating on the room’s thermostat as the boiler could then lock up.
  • After error code F37 (pressure is too low). According to the boiler’s hygrometer, the load pressure in a cold installation should be about 1 bar. If the system pressure is less than 1 bar, the boiler will shut down and error code F37 will appear on the display. When this happens, the filling valve should be opened to help increase the pressure (after which, it is important to close it). After this procedure, the boiler will automatically understand that it needs to perform an air purging cycle before starting up.

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