The rotary or impeller pump has a round brass body and is driven by an electric motor usually bolted to the bottom of the chassis of thr machine. The body of the motor is a grey finned arrangement. If the A1 has this and I have no reason to doubt, it is quite easy to find when you look inside the back of the machine. The electric vibrating (solenoid) pump takes up a lot less space as it does not require a hefty electric motor to drive it and is used in semi commercial machines because overall they are much smaller (and therefore have a lot less available space inside) than a regular sized commercial machine. You have to be careful with what is written about the differences between rotary and solenoid pumps, on the net, in coffee "head" type sites...speaking with many years experieince in business in the coffee and machine game...in domestic use you would find NO difference in the performance of your espresso machine if you changed it from one type of pump to the other. The solenoid and rotary pumps are both set (in an espresso machine) to operate at the same pressure, and both are able to be regulated by those with the requisite experience to do so, but only if a pressure adjustment is required. In fact, in the real world where domestic machines fitted with solenoid pumps probably outnumber commercial machines fitted with rotary pumps, we see many more failed rotary pumps than we do solenoid pumps. This may well be due to the fact that commercial machines get a lot more use than domestic machines, however the fact remains that we get very few problematic solenoid pumps in practice. A rotary (impeller) pump costs a lot more than a solenoid (vibrating) pump. The rotary pump requires an expensive electric motor to drive it. Therefore to set up a machine with a rotary pump costs quite a bit more than to set one up with a vibrating pump. This adds to the cost of manufacture of the commercial, over an semi-commercial machine. During the brewing of espresso the water pump (irrespective of type) is set to operate at between 8 and 10 bars or atmospheres pressure. The max RATED pumping pressure of either vibrating or rotary pumps intended for this purpose is usually in the vicinity of 16 bars so both operate way under their max capacity. Hope this helps, FC.
