Actuators for HVAC Dampers

Actuators are an essential component of virtually every HVAC system or building air conditioning equipment. They are an action element in the field of measuring and regulation technology, which adjusts HVAC or fire dampers or valves to the position required by the control system.

Actuators typically operate within a rotation range of 90°. For special applications, actuators with a range of 180° or 360° are also manufactured. The use of these special actuators is more costly than the standard ninety-degree version.

Such products are offered by the family company Schischek (represented in the Czech Republic by Bola). Their ExMax, RedMax, and InMax actuators are widely used in heavy industry and explosive environments – such as in the pharmaceutical or chemical industry, but also in the automotive industry (specifically in the paint shops of Škoda Auto and Tatra), and even in the maritime sector (for example, oil rigs in the North Sea). Schischek also supplies products to nuclear power plants, the Unipetrol refinery in Litvínov, and the arms factory in Vsetín. Schischek's range of actuators varies according to their suitability for hazardous industrial environments. The InMax range is intended for safe environments. The RedMax and ExMax ranges are designed for use in explosive environments, with RedMax suitable for zone 2 and ExMax for zone 1. Hazard zones are prescribed by ATEX standards.

The product ranges of individual types from all actuator manufacturers distinguish further parameters. The most important of these is the torque, with values ranging from 2 Nm to 40 Nm. Belimo products have individual actuator ranges for HVAC dampers divided by torque: CM with a torque of 2Nm, LM with a torque of 5 Nm, NM with 10 Nm, SM with 20 Nm, and GM with a torque of 40 Nm. At bola.cz, you can also find actuators from other manufacturers, such as Siemens actuators or ESBE. Other established and well-known brands are Sauter and Honeywell.

Another very important parameter when selecting actuators is the power supply and method of electrical control. Power supply options include 100 to 240V AC, 24V AC, or 24V DC. The choice of supply voltage is always determined by the needs of the control system. Actuators for HVAC dampers most commonly have 2 or 3-point control. Two-point control involves open/close positions, where the closing terminal is always under voltage and the opening terminal is connected via a control system switch. Three-point control does not have any terminal under voltage in the basic state. This is widely used to stop the damper rotation in an intermediate position. The control system then switches the control phase between the opening and closing terminals. By timing the opening and closing, the desired intermediate position can be achieved.

Actuators with continuous control are used for smooth regulation of airflow in the HVAC damper. Regulation is achieved by a voltage signal in the range of 0 – 10V: 0.1V represents a certain angle of rotation. The range from 0° to 90° thus corresponds to the control signal range of 0-10V, where 0V represents an angle of 0° and 10V represents an angle of 90°. From Siemens, actuators with 4 to 20mA current loop control can also be supplied. However, voltage continuous control is more common. Currently, there are also actuators with digital control.

If the actuator is correctly addressed on the bus, it additionally provides information about its status (exact position, error messages), and some actuators may be equipped with a flow meter. Using a flow meter, the rotation of the HVAC damper can be controlled, thus regulating the flow very precisely. Automated control of actuator operation is facilitated by connecting actuators to communication buses, especially using the MP-bus protocol from Belimo.

Furthermore, it is necessary to mention the running times of actuators – that is, the time it takes for the actuator to adjust to the end position. Actuators typically rotate from 15 to 150 seconds, but Belimo offers super-fast actuators – in the SMQ range, the adjustment time is 7 seconds, NMQ 4 seconds, and LMQ only two and a half seconds.

Frequent inquiries are made about the so-called emergency function of actuators. The emergency function means that the actuator automatically adjusts to the initial position in the event of a power failure. Actuators with an emergency function thus provide protection, for example, against frost or smoke. Adjustment is usually ensured by a mechanical return spring inside the actuator. Therefore, power supply is not needed for closing even in normal cases. This means that the power phase is used only for opening. A modern approach to the emergency function is the use of a capacitor built into the actuator. It provides enough energy to adjust the actuator.

Belimo emergency actuators have product ranges NFA and SFA. Siemens emergency actuators distinguish between the GCA and GMA ranges. Other manufacturers include Sauter and Honeywell.

Bola also has in its portfolio mounting kits for the proper attachment of actuators to valves. Their experienced team can motorize two-way, three-way, and even four-way valves with actuators. With this accessory, you can install actuators on valves from manufacturers Komextherm, ESBE, and Giacomini.