erkal It’s normal for a small boiler, even with very clever software. You introduce a lot of water rapidly when you flush compared to an espresso shot. If the service (steam boiler) is on this can be mitigated a little and if the flush is large. This influx of water chills the boiler down rapidly, especially in the region of the temperature sensor….this encourages the system to produce more heat than is really required. The water mixes and by the time it shows that high reading…it’s too late and then starts the wait for it to cool down.
The temperature effect on the espresso shot is much smaller than the swings seen on the display, as the group has a lot of thermal mass.
The above explains the reason for the swings in temp.
Is this normal or am I doing something wrong?
Yes, you don’t need to be flushing the group between shots…just at the end of a series of shots, also the portafilter only needs brushing out with a dry 1 inch paintbrush after knocking it out…only washing it after the end of a series of shots.