A general word of warning, that was not included in the "manual": Hans (the guy that makes the drivers) warned me, that he tested with some safety items in the circuitry, but they make the valve response less accurate.
Therefore, there is NO protection against short-circuit of the valve output. Please make sure that whatever happens, the connection on the solenoid is arranged in such a way that wire breakage cannot lead to the wires accidentally touching each other, it will burn out the switching transistor.