Electric actuator for the control valve - how does it work and which one to choose for the heating system?
What is an electric actuator and how it works with a control valve?
Electric actuators for control valves are a key component of automation in heating and cooling systems. They are responsible for repositioning of the valve (e.g., opening or closing the flow of the medium) according to the signal from the controller. This allows precise temperature and flow control without manual adjustment. Below we explain what such an actuator is, how it works in conjunction with different types of valves (globe and rotary), and what to look for when selecting an actuator for your heating system. We also suggest which models are worth considering - with a special focus on Danfoss offerings - and what mistakes are most often made when selecting these devices.
Electric actuator is a device that converts electricity into motion to control the valve. In practice, it consists of a motor (e.g., a synchronous or stepper motor) and a gearbox, which together move the stem or rotate the valve plug/valve valve. The actuator is mounted on the valve (usually without special tools, using a nut or an adapter) - once mounted, it becomes an integral part of the valve and can change its setting under the influence of a control signal.
Operation of the actuator with a mushroom (linear) control valve: in such a valve, the regulating element is a plug (piston) moving reciprocating (linear) motion up and down, changing the passage of the valve. The electric actuator in the linear version exerts pressure on the valve stem, moving it along the axis - this way it opens or closes the valve. For example, in Danfoss plug valves of the type VS, VM, VB etc., aMV series actuators press the stem, regulating the flow of the medium. At the moment of power failure, some actuators retract the stem thanks to a built-in spring (so-called safety function) - this causes the valve to close or open to a preset safe position (depending on the design). Linear actuators are usually characterized by parameters such as pressure force (N) and stroke (mm) - they must provide sufficient force to overcome the resistance of the valve (e.g., pressure of the medium at differential pressure), and their maximum stroke should correspond to the stroke of the valve to allow full opening and closing.
Operation of an actuator with a rotary (mixing) valve: in rotary valves (e.g., 3- or 4-way mixing, ball or butterfly valves), the control element rotates within a certain angular range (e.g., 90°), changing the direction or proportion of flow. The actuator designed for such a valve performs a motion rotatable - most often by means of torque transmitted to the valve shaft. Mounting is done through a coupling that attaches the actuator to the axis of the mixing valve. An example is the Danfoss rotary actuators of the series AMB, which are used to control mixing and diverting valves - for example, the AMB 162/182 model is used for 3- and 4-way Danfoss rotary valves types HRB, HRE, HFE in installations c.o.. This type of actuator generates a specific torque (Nm) and rotates the valve by a given angle (usually 90°). Rotary motion is physically limited in the actuator (e.g., by limit switches or mechanical stops) to the operating range of the valve.
With both linear and rotary actuators, control is automatic - the actuator receives a signal from a thermostat or controller and moves the valve to the appropriate position. When the extreme position is reached, a limit switch or electronic system usually operates to cut off power to the motor to prevent overloading the mechanism. Modern actuators often have auto-adaptation functions - for example, the actuators themselves adjust stroke length to valve end positions, which speeds up the startup and calibration of the system. They also have safety features, such as built-in overload switches to protect against stem blockage, and the ability to manually reposition the valve in the event of a power failure (e.g., via a hand clutch or knob).
Applications for actuators in heating and HVAC systems
Electric valve actuators are widely used in all kinds of heating, cooling and ventilation systems. They allow automatic flow and temperature control, which improves energy efficiency and comfort. Typical application areas include m.in.:
Central heating (c.o.) - Control of mixing valves in the boiler room (maintaining the set temperature on the supply of heating circuits), control of radiator valves in large systems or zone valves, as well as heat exchangers in district heating systems.
Domestic hot water (c.w.u.) - actuators control mixing valves that maintain a constant temperature in storage tanks or domestic water mixing systems. They are also used in priority switching valves c.w.u., which divert power from the boiler to the water heater or to the c.o.
Air conditioning and ventilation (HVAC) installations - Actuators are installed in air handling and air conditioning units to control cooling or heating water control valves (e.g., in heaters, coolers, exchangers). Enable smooth control of supply air temperature. They are also used in cooling systems (chilled water) and in fan-coils and fan coil units (exchanger flow control).
Underfloor heating - in underfloor systems, a 3-way mixing valve with an actuator is often installed to reduce the temperature of water from the boiler to an appropriate level. The actuator ensures automatic operation of such a mixing valve depending on the temperature of the floor or rooms.
Solar systems - In solar systems, actuators can control valves that switch circuits (e.g., directing heat to the c.w.u. or to a buffer) or mixing valves to prevent overheating.
Industrial HVAC and heating systems - large actuators (high force/momentum) are used in heat exchanges, municipal grids, and industrial applications for the control of low-pressure steam, hot water, etc. - Wherever precise control of medium flow in heating and cooling processes is required.
As you can see, we will meet electric actuators both in small domestic boiler rooms (e.g., for the floor mixer) and in large HVAC systems in commercial or industrial buildings. Automation of valves with actuators brings the benefits of stable control, energy savings (due to more accurate heat metering) and convenience - the system becomes largely maintenance-free for the user.
Linear vs. rotary actuator - differences and choices depending on valve type
The type of actuator movement must correspond to the type of valve, to be controlled. In practice, we divide actuators (and valves) into two main categories because of their movement: linear and rotatingâ.
Linear actuators - designed for valves with reciprocating motion, such as globe valves (a.k.a. globe valves) or needle valves. A linear actuator produces a rectilinear motion (pushing or pulling the stem). Examples include danfoss actuators AMV/AME series cooperating with valves of type VS, VM, VB, etc., but also actuators from other manufacturers for plug valves (e.g. Siemens sCC/SAX series for valves with spindle or Samson type 5824/5825 for their valves). A feature of linear actuators is the feeding forces (N) - e.g. 200 N, 450 N, 1000 N - determining the ability to move the pin under load. Also important is jump (the maximum distance the pin will travel, such as 5 mm, 10 mm, 20 mm). Linear actuators are usually mounted with a nut on the valve body (the thread standard sometimes varies, such as M30x1.5 on small Danfoss valves).
Rotary actuators - used for valves in which the regulating element performs a rotary motion. This applies to m.in. 3- and 4-way mixing valves, quarter-turn ball valves or butterfly valves. The rotary actuator generates torque and rotates the valve shaft to a specific angle (usually 90° for quarter-turn valves, but there are also valves that require 180° or other angles). Examples of rotary actuators include the aforementioned Danfoss AMB (for HRB/HRE/HFE mixing valves) or popular actuators for mixing valves from other companies, e.g. ESBE ARA series, Afriso, Siemens SQN/SQR etc. Rotary actuators are characterized by torque (Nm) - e.g. 5 Nm, 10 Nm, 20 Nm - and the time of rotation for a given angle (e.g., 60 seconds/90°). They are mounted by direct mounting on the mixing valve stem or with dedicated brackets/adapters.
Key difference: A linear actuator moves the valve straight (top-down), and rotary - in rotation(around the axis). In addition, linear actuators are used where greater precision is required with small displacements (e.g., accurate flow control in a plug valve), while rotary actuators are ideal for mixing or switching flow between branches (e.g., in mixers, where the angle of rotation of a 3-way valve determines the proportion of mixed medium). In practice, the choice comes down to this, what kind of valve we have or plan to have - do not mount a linear actuator on a rotary valve and vice versa.
It is also worth noting that manufacturers often offer sets of valve + actuator compatible. ESBE, for example, has a range of globe valves with matching linear actuators to guarantee precise control in HVAC systems. For its mixing valves, on the other hand, it offers ARA series rotary actuators and larger 90 series actuators for larger diameters. Matching actuator type to valve is therefore the first and basic step in the selection - if you buy a control valve, it is worthwhile to immediately select the right type of actuator for it.
Types of actuator control: 2-point, 3-point, modulating
Electric actuators can differ not only in construction (linear vs. rotary), but also in control method. Choosing the right type of control is important because it depends on what signal we will control the valve in our automation system. There are three main types of actuator control:
2-point control (ON/OFF) - Also called two-position, two-position or simply on/off. An actuator with this control behaves like a switch: either completely opens, or completely closes the valve. The control signal is usually the supply or cutoff of power at the corresponding input. An example is the control of a zone valve by a room thermostat: when there is a need for heating, the thermostat gives voltage to the actuator, which opens the valve; when the temperature is reached - the voltage is cut off and the valve closes (often closed by a spring). The 2-point actuators are easiest, most common in small installations (e.g., thermoelectric actuators at floor manifolds or simple on/off actuators at ball valves). The disadvantage is the lack of intermediate control - the valve is either fully open or closed. Advantage - simple integration, for example, with a thermostat (all you need is a 0-1 signal).
3-point control (so-called "floating") - is a very popular mode in HVAC systems. The 3-point actuator usually has three control cables: common and two directional (opening and closing). Applying voltage to the "open" wire causes the actuator to move toward the opening of the valve, applying voltage to "close" - movement toward closing. When voltage is not applied to any of them, the actuator stops at the current position. The controller (PID controller) sends pulsed open/close signals to move the valve to the correct intermediate position. There is no single analogue value signal here - the adjustment is done by the switching time control signals. An example is the Danfoss AMV 3-point actuator - it works with controllers equipped with triac or floating relay outputs (open/close). This type of control is simpler than modulation, but allows positioning of the valve. Most 3-point actuators do not have position feedback (they are assumed to reach the desired position after a reasonable amount of time). In 3-point heating systems, the m is controlled.in. mixing valves and multiple plug valves in air conditioning systems. Danfoss offers many actuators in 3-point versions (designation AMV), e.g. AMV 10, 20, 30, etc., as well as rotary AMBs in 2- or 3-point versions.
Modulation control (proportional, analog) - in this mode, the actuator accepts a continuous control signal, mostly standard 0-10 V DC or 4-20 mA (0-20 mA, 2-10 V, etc. are also encountered.). The analog signal represents the desired valve position (e.g. 0 V - closed, 10 V - 100% open). The modulating actuator has built-in electronics (positioner) that sets the valve opening in proportion to the input signal. It provides very smooth and accurate adjustment - the valve can occupy any position in the range, and the actuator maintains this position with feedback. This type of control is used in more advanced systems with analog controllers or BMS systems. An example is the actuator Danfoss AME 20, which, when supplied with 24 V AC, responds to a 0(2)-10 V or 0(4)-20 mA signal. Siemens, on the other hand, offers the SKD/SKC/SKB series - they require a 24-volt power supply and also accept a 0-10 volt or 4-20 mA analog signal, proportionally controlling the valve. Modulating actuators often have additional features: output feedback (e.g. 0-10 V position signal), options to change the characteristics (linear/equal percentage) or the ability to set parameters (such as signal range). Danfoss marks modulating actuators with the symbol AME (e.g. AME 10, AME 20, AME 435).
In practice, selection of control type depends on the automation system: if we have a simple on/off thermostat - we use a 2-point actuator (ew. 3-point as 2-point can also be used, although it is a waste of its capabilities). If you have a weather controller or PLC with 3-point output - take a 3-point actuator. For advanced analog controllers or smart systems - preferably a modulating actuator. It is worth noting that rotary actuators for mixing valves often come in all three signal variants. For example, you can get the Danfoss AMB 162/182 as a 2-point, 3-point or analog 0-10 V/4-20 mA - They then differ by the model end or DIP setting. Similarly, actuators from other brands (e.g. Siemens, Belimo) have options with different types of control. It is important to actuator control was compatible with the controller in the plant.
Choosing an actuator step by step - what to pay attention to?
When selecting an electric actuator for a control valve in a heating system, it is worth approaching the subject step by step. Improper selection can result in malfunctions ranging from inability to close the valve, to unstable system operation, to actuator or valve failure. Here's key criteria for actuator selection:
Valve type and required movement: Determine whether you need a linear or rotary actuator (see above). This is a basic criterion - other actuators fit mushroom valves and others fit mixing valves. Also specify the size (DN diameter) of the valve and the stem stroke or angle of rotation. Each actuator has a stroke/rotation limit for which it is designed - make sure it is compatible with your valve. E.g. for "smaller" valves (DN ≤ 50) fit compact actuators, and for larger diameters more powerful actuators are needed. The manufacturer usually states with which series and sizes of valves a given actuator model works (sometimes a mechanical adapter is required - you need to check this in the documentation).
Control signal (control function): Decide what type of control you want the actuator to have - 2-point, 3-point or modulating. It depends on the controller/thermostat you have. If the system is simple and works on/off - choose a 2-point actuator (or a 3-point one, which you will control binary). If you have a regulator with a triac or open/close relay output - the following will be suitable 3-point actuator. When a controller (such as one built into a furnace or BMS system) has an analog output of 0-10 V - modulating actuator will be the best. Remember that it is impossible to achieve smooth analog control with an ordinary on/off actuator - it must be a model with built-in electronics and a suitable signal input. Example: if the weather controller requires the connection of a 3-point actuator, and we mistakenly buy a 0-10 V modulating actuator, then without an additional module it will not work properly (no suitable control signal).
Supply voltage: The most popular actuators come in two power versions - 24 V AC (low voltage) or 230 V AC. It also meets 24 V DC in some modulating. Choose a voltage that is compatible with the electrical installation and control. 24-volt actuators are usually safer (low potential, often used in BMS), but require a safety transformer. 230 V can be powered directly from the mains, which is sometimes convenient, but care must be taken. Some types (e.g., zone valves, thermoelectric actuators) are more likely to be 230 V, others (e.g., larger proportional actuators) - usually 24 V. Also note whether the controller can give control to 230 V or only to 24 V. Incorrect selection of supply voltage is unfortunately a fairly common mistake - For example, it happens to connect a 24-volt actuator to the 230-volt network, which ends up destroying it. So choose the right version and make sure the wiring is adjusted. (Note: Analog modulating actuators are generally 24 V; 230 V modulating actuators are rare - for example, the Samson 5824-30K operates at 85-264 V AC thanks to a built-in power supply).
The force or torque required to move the valve: Each valve needs a certain force/momentum to change its setting - especially under pressure. If the actuator is too weak, the valve will not close fully at high ΔP (pressure difference) or the actuator will be constantly overloaded (risk of damage). Valve manufacturers often quote the so-called "valve". required closing force for a given ΔP or torque needed for a given diameter. Select an actuator with a force/momentum equal to or greater than the required one. E.g. small DN15 valves may only need ~100-200 N, but DN50 valves already ~1000 N, and large flaps even several thousand newtons. The Danfoss AMV 20, for example, has a force of 450 N, which is sufficient for most DN15-50 valves; Siemens SKB electrohydraulic actuators reach 2,800 N for DN100 valves. Insufficient force will be manifested by the fact that, despite the operation of the actuator, the flow is not throttled to zero or the regulation is unstable.
Pitch or angle of rotation and speed of operation: The linear actuator must have jump not less than the stroke of the valve (otherwise it will not open it fully). Too much actuator stroke is not a problem if it is automatically adjusted (many actuators have auto-adaptive stroke), but the too small means a limitation of the valve capacity. For rotary actuator rotation angle (e.g., 90°) must coincide with the required rotation of the valve. Equally important is speed of the actuator, i.e. the time it takes to cover the full range of the. The speed is selected according to the dynamics of the system: for slow systems (like floor heating with high inertia) slower actuators are better, to avoid temperature oscillations. On the other hand, in systems that require rapid response (e.g., temperature control c.w.u. in the plate heat exchanger, where sudden water intake requires rapid correction of the valve) will work well for high-speed actuators. Danfoss, for example, offers actuators with different times: AMV 35 needs only approx. 3 s/mm (very fast), and AMV 25 approx. 11 s/mm. For mixing valves, ESBE recommends a turn time of ~240 s/90° in floor circuits, while for c.w.u. whether the heaters use a time of 30-120 s/90°. Let's pay attention to these values and let's choose the switching time appropriate to the characteristics of the installation.
Mechanical compatibility (assembly): Make sure that the selected actuator can be mounted on the selected valve. If you buy an actuator and a valve from the same company designed to work together - usually there is no problem. But if, for example, you want to put a universal actuator on a valve from another manufacturer, you may need an adapter, or it may not even be possible. Check the mounting standard: for small plug valves, the M30x1.5 thread is often used (e.g. Danfoss, Oventrop, Heimeier - here there are some compatibility between brands), but for larger valves, manufacturers have their own mounts (e.g. Danfoss VS or Siemens need dedicated adapters for other actuators). With rotary valves, make sure that the diameter and shape of the valve stem matches the actuator coupling (e.g., 10 mm square, 8x8 mm flat seat, etc.).) or if there is a suitable mounting kit. No mechanical fit this is a common mistake - the actuator will not physically manage to move the valve properly if it is not properly installed.
Additional features (optional): Consider whether you need safety functions (fail-safe). If the valve is to automatically close or open in the event of a power failure, choose a model with a spring return or emergency power supply. For example, Danfoss offers actuator versions with the notation "SU/SD" (spring up/down) - after a power failure, the spring moves the valve to the safety position. Other manufacturers (Belimo, Johnson Controls) have actuators with a spring or with a built-in supercapacitor to ensure closing. If the application requires it (e.g., solid fuel boiler - the mixing valve must open to full at power failure to protect the boiler from overheating), then be sure to select an actuator with such a function. Other additions can be: manual control (useful in case of service - many actuators have this option), additional limit switches or feedback signal (for valve position signaling, e.g. Danfoss offers sets of additional switches for its actuators), or resistance to environmental conditions (IP rating, ambient temperature). In special cases, these factors can also affect the selection of the.
In summary, selecting an actuator comes down to making sure that type, signal, power, force, pitch and mounting are appropriate. If in doubt, it is worth using manufacturers' configurators or consulting a supplier - many companies (such as Assured Automation or manufacturers themselves like Danfoss) provide selection tools or tables, taking into account the above factors. A well-chosen actuator will ensure many years of trouble-free operation and optimal control of the installation.
Typical errors in the selection and use of actuators
When selecting and installing electric actuators, it is worth avoiding some common mistakes that can negate the benefits of automation. Here is a list of common mistakes and problems and tips on how to avoid them:
Incorrect supply voltage: As mentioned, confusing 24 volts vs 230 volts is dangerous. Connecting a low-voltage actuator under 230 volts will immediately damage it. On the other hand, using a 230-volt actuator where the controller provides only 24 volts will result in unresponsiveness (or damage to the controller). Always check the labeling - manufacturers often label the versions /.../24 or /.../230 in the model. Example of error: trying to use a Danfoss 24 V 3-point actuator on a 230 V regulator output - this will end up damaging the triac in the regulator or the actuator itself. Council: make sure that both the actuator and the control are on the same voltage and properly connected.
Control signal inconsistency: A common problem is signal mismatch - For example, we buy a 0-10 V modulation actuator, and the controller has only relay outputs on/off, or vice versa - we have an analog controller, and the actuator only 3-point. In both cases, we will not get modulation. Council: Identify the type of control signal in your system before purchasing an actuator and select a model that expects exactly that (or has the ability to switch modes).
Poor strength or lack of spring function where needed: There is sometimes an underestimation of the required force - for example, putting a small actuator of 200 N on a valve that requires 400 N, resulting in the valve not closing under heavy load. Another mistake is to omit the security function where it is important. E.g. in a solid fuel boiler system mixing valve should open automatically on power failure - if you give an ordinary actuator without a spring, then in the absence of electricity the valve will remain in the current position, which can lead to a dangerous increase in the temperature of the boiler. Council: always compare the valve's requirements (from the documentation) with the actuator's data and take into account emergency scenarios - if necessary, choose a more powerful or fail-safe version.
Inappropriate stroke or torque - mismatch with the valve: As an example, if you try to use an actuator with a 5 mm stroke on a valve that has a 10 mm stroke - the valve will never fully open, limiting the maximum flow rate. In the case of rotary actuators - using too weak (e.g., 5 Nm) on a large-diameter valve that needs 15 Nm will cause the valve to "stutter" and not reach its end positions. Council:check the valve data (required stroke, torque, resistance) and select an actuator that exceeds these requirements by some margin. The manufacturer often indicates which series of actuators fit which diameter range - it is worth taking advantage of this.
An actuator that is too fast or too slow for the application: Although less frequently noticed, this error affects the quality of regulation. Too fast actuator in a system with high inertia can cause oscillations (overheating, underheating alternately), because it reacts faster than the system can stabilize. E.g. if you give an actuator that changes position in 30 seconds to an underfloor heating system (slow responding), it may result in instability. ESBE even mentions "too short a turnover time" as a selection error - recommends 240 s for the floor instead of 60 s, for example. The opposite situation: an actuator that is too slow in a system that requires a quick response (such as a three-way valve switching hot water to the boiler) - may not be able to keep up with changes in demand. Council: select the conversion time with the specific function in mind: for floor heating rather slower, for c.w.u. fast, for standard heaters - medium (60-120 s). You can find information on times in catalogs (e.g. Danfoss AMV 35 - 3 s/mm is fast, AMV 25 - 11 s/mm slower).
Lack of mechanical fit (poor assembly): Here the errors appear at the installation stage. Examples: actuator not tightened properly to the valve (it slips, does not transmit movement), confusion of the adapter (for example, using an actuator of another brand without an adapter - the thread does not fit, so someone "combines" with a makeshift mount). Another problem is mounting the actuator in the wrong position - for example. upside down in a humid environment, which may result in flooding of the case and failure of the. Council: always follow the manufacturer's installation instructions - there are recommendations for position (e.g., most actuators can be mounted in any position except "up with the motor down" so that condensation does not flow inside). Use dedicated adapters if you are combining different brands. Check that the valve stem is properly clamped in the actuator coupling. After installation test traffic - manually (if there is such an option) or with a short signal - to make sure that the valve actually moves full range.
Inadequate control or wiring: Often underestimated issue - even a well-chosen actuator may not work properly if, for example, the control output in the controller is not able to handle it. Example: many electric actuators have quite a high inrush current (especially 230 V). Regulators with relay outputs must have adequate contact load capacity. Danfoss in the documentation recommends for high-speed actuators (AMV 150) to use relays for min current. 40 A starting - which shows that a typical small relay can stick together under such a load. Council: check the power consumption of the actuator (VA or W) and make sure that the controller/thermostat has outputs with adequate load capacity or use an additional intermediate relay. Also take care to connect the cables correctly according to the diagram (confusing the "open" and "close" wires in a 3-point actuator will result in reverse operation, which can confuse at startup).
Awareness of the above mistakes will help avoid them. When in doubt, it's always a good idea to look into Manufacturer's FAQor instructions - often there are answers to common problems. Remember that an actuator is an actuating device that must be properly selected and installed to fulfill its role. Its proper functioning is crucial for trouble-free and efficient operation the entire heating system.
Examples of recommended actuator models (Danfoss, Siemens, Samson)
The market offers many models of electric actuators for control valves. Here are some popular and proven suggestions - mostly brands Danfoss, as well as equivalents from Siemens i Samson - Along with their characteristics:
Danfoss AMV 10 / AMV 13 - compact linear actuators with a force of approx. 300 N and a stroke of ~5 mm (small valves). Designed mainly for Danfoss valves of VS, VM, VB series with small diameters (AMV 10 even works with the special miniser valve VMV). Control: 3-point. AMV 10 is the standard version, AMV 13 has security function - a return spring that automatically repositions the valve at the loss of power (the spring acts "down", that is, usually closes the valve). These models are available in 24 V and 230 V versions. They have a compact design and speed ok. 14 s/mm pitch, which means approx. 140 s for a full 5 mm opening - fast enough for typical radiator applications. They feature simple installation and overload protection, protecting against excessive pressure on the valve plug.
Danfoss AMV 20 / AMV 23 - Medium-sized universal linear actuators, force 450 N, stroke up to ~10 mm. Commonly used for DN15-50 valves in c.o. i c.w.u. (e.g., valves of the VS, VM, VB types, as well as PICV valves of the AB-QM type). These are actuators 3-point, available in 24 V and 230 V versions. AMV 20 - basic version, AMV 23 - with safety function (return spring according to EN 14597). The operating speed of the AMV 20/23 is approx. 15 s/mm(i.e. ~150 s for 10 mm). These models are valued for their robustness - IP54 housing, quiet operation and lack of maintenance. Automatically calibrate the valve stroke on first startup. They are often used in heat exchanges, air handling units, etc. as the "workhorse" of automation. It is worth mentioning that Danfoss also has modulating equivalents for these actuators: AME 20 (24 V, analog signal 0-10 V/4-20 mA, with manual override). The AME 20 has similar mechanical performance (450 N, 10 mm, 15 s/mm) as the AMV 20, but allows precise valve positioning and has a feedback output.
Danfoss AMV 30 / AMV 33 - Actuators similar in size to the AMV20, but made as a high-speed drives. The turnaround time is only 3 s/mm, which is about 30 seconds for a full stroke of ~10 mm - several times faster than the standard. This makes them suitable for applications requiring dynamic control (e.g., maintaining a constant temperature in DHW exchangers, where changes in demand are sudden). The force remains 450 N. AMV 30 - 3-Point Standard Version, AMV 33 - with safety function (spring, complies with DIN EN 14597). Keep in mind that fast running time also means higher inrush current, which requires appropriate controllers (triacs/relays with high load capacity). These models work well in systems where fast response to disturbances is important. Assembly and mechanical features as in AMV20.
Danfoss AMV 435 - larger linear actuator for large valves. Designed for 2- and 3-way valves type VRB, VRG, VF, VL up to DN80. It has 400 N force i long stroke 20 mmâ. It is powered by 24 V AC/DC or 230 V AC (versions) and is 3-point controlled. A distinctive feature is selectable speed - 7.5 s/mm or 15 s/mm (adjustable, e.g. with a switch). This provides flexibility: you can set it to fast mode (full stroke ~150 s) or slower mode (approx. 300 s) depending on the regulation requirements. AMV 435 has lED signaling indicating operation (LED changes color when moving, reaching position) and the possibility of manual control and connection of additional limit switches. This model is dedicated to larger installations (e.g., heating risers, large air conditioning units). There is also a modulation version AME 435 QM, cooperating with AB-QM (PICV) valves up to DN100 - accepts analog signal and has anti-oscillation and characteristic adaptation functions. If you need to control a large valve with analog precision, AME 435 will be the right choice; for 3-point control, AMV 435 will suffice.
Other Danfoss actuators: It is worth mentioning that Danfoss also offers a whole range of aMB rotary actuators for mixing valves (e.g. AMB 162, 182 - 5 Nm and 10 Nm, different times, 2/3-point or analog control) and smaller thermoelectric actuators tWA/QT series for small manifolds and zone valves (they operate 2-point, slower, but are cheap and simple). However, in the context of heating system automation, the focus is on the AMV/AME models described above - they provide greater functionality and are suitable for central system components (mixers, main control valves).
Siemens - popular solutions: Siemens (series Acvatix) is one of the leaders in valves and actuators. Their product range includes both small electro-thermal actuators (e.g. SSA, STL for small valves) and large ones electromotive and electrohydraulic actuators. For example, Siemens SKD/SKC/SKB is a series of large actuators for plug valves with strokes of 20/40 mm - these are electrohydraulic actuators with high force: the SKD62 or SKB62 models reach approx. 1000 N and 2800 N forces with 24 V supply and modulation signal. Siemens offers them in 3-point versions (ozn. ...53) or with a 0-10 V positioner (ozn. ...62). For medium-sized valves (e.g., DN15-50), Siemens has SAX series linear actuators (400 N, 20 mm, various times) and MXG/MVI modulines. For mixing and ball valves, Siemens offers rotary actuators type GDB/GLB (5 Nm, 10 Nm) - similar to Danfoss AMB - also in 3-point and modbus/analog versions. Generally Siemens is famous for its reliability - many older models (Landis&Staefa) have been working in boiler houses for several decades. When choosing a Siemens, pay attention to the markings: for example. SAX31 - 3-Point 230 V, SAX61 - 0-10V 24 V analog, SAX81 - control via bus (in modern systems).
Samson - solutions for industry and HVAC: German Samson specializes in control fittings and their electric actuators are often found in heating and industry. Examples of these models are Samson series 5824, 5825 - are linear actuators for Samson valves (but can also drive other valves using adapters). Type 5825 is a 3-point version, such as 230 V AC, while the 5824 has a built-in positioner (analog control) and a universal power supply of 24-240 V. Samsons feature a robust design and a choice of different strokes (e.g. 7.5mm, 12mm) and safety options (spring return versions are also available). They are often used together with Samson flange valves in district heating substations. For mixers and smaller zone valves, Samson has a less extensive offering - mixers with other actuators are often used.
Summary of model selection: If you are looking for an actuator for a typical domestic boiler room - for example, for a DN25 3-way mixing valve - consider a ~10 Nm rotary actuator (Danfoss AMB 162 or ESBE ARA661). For solid fuel boiler with protection - actuator with spring (e.g., LTA (Afriso) with spring return or Danfoss AMB 162 with safety function, if available). For the mushroom valve at the weather-controlled gas furnace - Danfoss AMV 20 or Siemens SAX. For larger installations: for a DN50 valve - Danfoss AMV 25 (1000 N) will be suitable, and for really large valves DN100 - Siemens SKB or Belimo electro-hydraulic actuator with several thousand newtons. It is important that the brand is proven and the device has service and parts availability. Danfoss, Siemens, Samsonare reputable companies and their models discussed above are sure to provide durability and technical support. The final choice depends on the specific requirements of your installation - always follow the manufacturer's specifications and recommendations.
Summary
Automation of the heating system with electric actuators brings tangible benefits: more stable room temperature, fuel/energy savings and operating convenience. Electric actuator for control valve is a device that does the work of regulation for us - whether by moving the valve plug linearly or rotating mixing streams. The key to success is informed choice of actuator: proper type (linear vs rotary), proper control signal, matching supply voltage, sufficient force, and mechanically compatible with the valve. In the article, we presented the most important selection criteria and typical pitfalls to avoid. We hope that with this information, both installers and end users will better understand the operation of the actuators and make a thoughtful choice when upgrading or building your heating system. By automating the valves with properly selected actuators, we will gain more efficient, safe and comfortable heating system - and it's an investment that is sure to pay off.
