BOREAS, a cryogenic propellant rocket engine demonstrator using LOX and LH2, is one of the current projects under study at the CNES. This demonstration platform aims to test and prove new technologies for future liquid-propellant rockets. BOREAS is characterized by a bleed cycle feed system controlled by a set of valves that allow to have a wide nominal functioning domain and additionally low-thrust working points. The aim of this work is to extend the existing model of BOREAS on the 0D fluid network modeling software CARFONC to predict its behavior during test bench trials, simulating low-thrust points and reproducing transient phases, in particular those concerning these same points, such as the starting transient.