Diagnosis of fully automatic coffee machine

The first part of our series explained the basics, the structure of a fully automatic coffee machine, the individual components and their functions.

Now the second part deals with the different types of faults that can occur and how to rectify them. The focus here is also on the daily cleaning of the machine and the tablet, which can work wonders.

There are two types of faults that need to be distinguished. Constitutional errors and configuration errors occur in the fully automatic coffee machine.

Constitutional errors are based on mechanical errors. A calcified boiler, for example, is a constitutional fault. If the water entering the fully automatic coffee machine is not treated and (partially) softened with an ion exchange filter or a reverse osmosis system specially designed for coffee, limescale and gypsum will build up in the boiler. These deposits can lead to Needle valves to regulate the water flow become blocked and no water flow can take place in the direction of the brewing group/coffee outlet.

However limescale also has a thermally insulating on the machine's sensors. Temperature sensors clogged with limescale do not measure the temperature of the water, but the temperature of the limescale deposits. The actual water temperature is higher. In this case, the machine does not display an error message, it even displays the supposedly correct water temperature, but not the actual water temperature. A water filter should therefore normally always be connected upstream of any type of coffee maker. Since water quality and water hardness vary greatly from region to regionit helps to test water hardness and select the appropriate filter. In addition, an ion exchange filter must be replaced at least once a year.

An equally frequent source of constitutional faults is inadequate cleaning. inadequate cleaning of the fully automatic coffee machine. From a critical point of view, the fully automatic coffee machine has a weak point: the coffee grinder does not like heat and, above all, high humidity. In the case of the fully automatic machine, the grinder is installed in the same housing as the kettle. This means that the guides for the ground coffee very quickly become clogged with ground coffee in the direction of the brewing unit. This leads to inaccurate dosing, and mould spores can also form in these areas. mold spores and this is when things become unappetizing.

This can only be avoided by cleaning the brewing unit daily. This also includes using a cleaning tablet. To be honest, have you ever wondered whether it wouldn't be wise to simply rationalize the tablet for cost reasons? You would be far from alone. However, cleaning a machine without a tablet makes just as much sense as rinsing a salad bowl with clear water. Oils cannot be removed with hot water and the bowl looks even worse afterwards.

The first fully automatic coffee machine manufacturers have now installed sensors in the waste water area that can be used to check whether the fully automatic coffee machine has really been cleaned with the intended cleaning agent. Without wagging the moral finger too much: Take the daily cleaning of your fully automatic coffee machine seriously!

When we talk about the configuration of the fully automatic coffee machine, we are primarily talking about extraction parameters of coffee. In terms of extraction parameters, the same parameters apply to a fully automatic coffee machine as to a standard portafilter machine. This is hardly surprising, as the brewing pressure and water temperature of a fully automatic machine are no different from those of a portafilter machine.

As a rule of thumb an espresso should take between 20 and 30 seconds to extract, a café crème around 40 seconds. Only with reasonable extraction times does the water have enough time to extract the necessary amount of soluble substances from the ground coffee (extraction means nothing other than extraction).

In order to achieve these extraction times, it is essential to use the correct grinding degree and the right amount of powder in each case. Together, the degree of grinding and the amount of powder define the resistance that the water presses against with its brewing pressure. The finer the grind and the more coffee in the brewing chamber, the greater the resistance and the longer the extraction time.

The degree of grinding can be adjusted on modern fully automatic coffee machines via the settings menu finer or coarser. On slightly older machines, the setting can still be made manually. It is important to start a grinding process after each adjustment of the grinding degree and to discard the ground coffee. This is because there are always grinding residues from the previous grinding process, which was carried out with a different grind setting, in the dead space of the grinder. Accordingly, this ground coffee would only be partially representative of the new grind.

At first glance, the amount of ground coffee can be easily adjusted via the Beverage configuration menu menu. But be careful: just because the menu shows a certain amount of coffee does not mean that exactly this amount of coffee will come out of the grinder. Fully automatic coffee machines work with timer-controlled grinders. The set weight is converted by the fully automatic coffee machine into a into a specific grinding timeso a kind of conversion takes place. It is very important that this weight is recalibrated if the grind is changed. During calibration, the fully automatic coffee machine grinds the coffee at the set grinding degree for a certain time (e.g. 5 seconds). You must then weigh how much coffee the grinder has ground during this time (e.g. 14 g).

The weight is stored in the fully automatic machine and the fully automatic coffee machine can then extrapolate the grinding time required to achieve the amount of powder set in the beverage configuration (e.g. 15.5 g for a double espresso). Calibration must always be carried out when the grinding degree is changed. This is because with a finer grind, the grinding disks are closer together, meaning that fewer coffee beans can be ground in the specified time than with a coarser grind, where the grinding disks are correspondingly further apart.