Electrothermal valve actuators for heating, ventilation and air conditioning systems. The actuator is very space-saving thanks to its compact design. The tapered design, especially in the mounting area of the nut, makes installation easy to handle. The fixing cable is not located in the area of the fixing nut. This reduces the likelihood of contact with devices carrying hot water. As the fixing nut allows the valve to be screwed onto the thread continuously, it is possible to open the valve in a de-energized state by turning the nut back by two to three thread turns, unlike bayonet and snap-on couplings. Leaking water is drained away via a drainage system. A special design eliminates the need for seals. The current valve position is displayed at 2 positions (top and side). Due to their M 30 x 1.5 mounting and their characteristics (normally closed), the valve actuators are suitable for the following valve and distributor brands: Beulco, Empur, Heimeier, Kamo, Oventrop, Purmo, SBK, SKV, Strawa, Taconova, Watts.