AVPL(-F) is a self-acting differential pressure controller primarily for use in district heating systems. The controller closes on rising differential pressure. The controller has a control valve and an actuator with one control diaphragm. It can be used on primary side of house substations for smaller systems such as one and two-family houses. The controller could be used to control the differential pressure across radiator systems and similar systems to keep a constant differential pressure even with a variable system resistance kva and/or supply pressure Δp0.