There are a number of good brew groups/ concepts for espresso machines. The best known is the E61 brew group. However, since the E61 is not as controllable as we would like, we have preferred a slightly different concept. The idea of the E61 to use the heat from the boiler has remained unchanged with our brew group. The medium is not water but solid 6 mm thick copper. This also results in another advantage that comes into play depending on where you live: The brew group cannot calcify in this area. And it doesn't seem so bulky, which makes the whole machine lighter and look slimmer.
In addition to the copper bridge, which primarily ensures high thermal constancy, the brew group of the machine can also be preheated using 2 heating cartridges. Heating cartridges have the advantage that they bring the brew group body to the desired temperature very quickly. Over time, the copper bridge then maintains the temperature and the heating cartridges are only activated when required.
With 2 x 100 watts, the brew group of the machine reaches the desired temperature after around 12-14 minutes.
The heating cartridges are optionally available with 150 watts. This reduces the heating time by a further 3 minutes.
They are designed in such a way that (analogous to the thermal bridge) they extend almost over the entire length (70 mm) and thus ensure even heating. They are optionally controlled via a screw-in thermostat, which is common on many machines.
A power controller with a PT100 sensor takes over the exact control of the dual boiler version and also allows short-term changes.