Actuators are an important part of virtually any building ventilation or air conditioning system. It is an actuation element of applications in the field of measuring and control technology, which moves the air, fire or smoke dampers or other armatures to the position required by the control system.
Actuators usually operate in the range of 90° rotation. Actuators with a range of 180° or 360° are also available for special applications. Using these special actuators is more expensive than the common 90° version.
Schischek ExMax, RedMax and InMax actuators, for example, are widely used in heavy industry and explosive environments - ie in the pharmaceutical or chemical industries, but also in the automotive industry (specifically in Škoda Auto and Tatra paint shops), and even marine (eg oil platforms in the North Sea). Schischek also supplies products to nuclear power plants, the Unipetrol refinery in Litvínov and the armory in Vsetín. Schischek actuator series differ in their intended use in hazardous industrial environments. The InMax series is designed for a safe environment. The RedMax and ExMax series are designed for use in explosive atmospheres, with RedMax in zone 2 and ExMax in zone 1. Danger zones are described by ATEX normatives.
The product lines are also categorized by another parameters. The most important of these is the torque, with values ranging from 2 Nm to 40 Nm. Belimo products have individual series of actuators for air dampers divided according to torque: CM with 2Nm torque, LM with 5 Nm torque, NM with 10 Nm, SM with 20 Nm and GM with 40 Nm torque.
Power supply comes in 100 to 240V AC, 24V AC or 24V DC variants. The voltage must always be selected upon the control system. Actuators for air dampers most often have 2 or 3-position control. In the case of two-position control, these are open / closed positions, meaning the closing terminal is always energized and the opening terminal is connected via the switch of the control system. The three-point control has no terminal in its energized basic state. This is widely used to stop the rotation of the damper in the intermediate position. The control system then switches the control phase between the opening and closing terminals. The desired intermediate position can be achieved by time control of opening and closing.
Actuators with continuous control are used for continuous regulation of the air flow in the damper. The regulation takes place here with a voltage signal in the range 0 - 10V: 0.1V represents a certain angle of rotation. The range from 0° to 90° thus corresponds to the range of the control signal 0-10V, where 0V represents an angle of 0° and 10V represents an angle of 90°. Siemens actuators with 4 to 20 mA current loop control can also be purchased. However, more common continuous control is voltage. Digital actuators are also available.
If the actuator is correctly addressed on the bus, it also provides information about its status (exact position, error messages), some actuators may be equipped with a flow meter. With the help of a flow meter, it is possible to control the rotation of the air damper and thus regulate the flow very precisely. Connection to the communication buses brings automated control of actuator operation, especially when using Belimo's MP-bus protocol.
It is also necessary to mention the running times of the actuators - ie the time during which the drive is reset to the end position. Normally, actuators rotate 15 to 150 seconds, but Belimo super fast actuators in the SMQ series have an adjustment time of 7s, NMQ 4s and LMQ only 2.5s.
Frequently asked questions are about the so-called fail-safe function of actuators. It means that the actuator automatically moves to its initial (zero or emergency) position in the event of a power failure. Fail-safe actuators provide protection against, for example, frost or smoke. The adjustment is usually ensured by a return spring inside the actuator. Therefore, the power supply does not have to be used for closing even in daily operation. This means that voltage is only used for opening. A modern approach to the emergency function is to use a capacitor built into the actuator. It provides enough energy to adjust the acturator.