Automatic compact charging unit with BA-type backflow prevention valve. The compact automatic charging unit is composed of a shut-off valve with an inspectable strainer, a BA-type controllable reduced pressure zone backflow preventer and an automatic filling unit. It is installed on the water inlet piping in closed circuit heating systems. It maintains the pressure of the system stable at a set value, automatically topping up with water as required. The backflow preventer prevents the contaminated water of the closed heating circuit from flowing back into the domestic water supply, in accordance with the provisions of EN 1717. The device is supplied complete with preformed shell insulation and features a compact design to facilitate installation.