Within the facade/window automation sector there are 3 main types of electric actuators-
- Chain drive actuators
- Linear drive actuators
- Rotary drive actuators
Within these three actuator categories there are countless variables and their uses vary greatly.
Chain drive actuators are available in 24v DC and 230v AC (main powered). There are 12v DC chain drive actuators on the market which are configured to be used on wireless networks such as z-wave, these have limited capability.
Chain actuators are available in single chain or twin chain bodies for wider windows where two push points are required. Alternatively there are actuators that can be used in tandem or even in sets of up to four which are generally used on parallel opening windows. On standard awning type windows where two push points are required the twin chain single bodied actuators offer a more aesthetically pleasing option.
230v AC are suitable for many applications from domestic to commercial installations. They are generally used on non metallic or high level windows where if the power cables are damaged the risk/consequences of electrifying the window frame are not life threatening. Installations to Aluminium or Steel windows particularly at low level or into Curtain Walling screens are generally 24v DC systems to reduce the previously mentioned risk.
The 230v AC actuators usually work on a 4 wire system. Earth, Neutral then L1 & L2 which dictate the direction of drive. These can be controlled by simple wall switches or intelligent controllers.
Both 230v AC and 24v DC actuators are available in a variety of chain stroke lengths and Newton Force (N) strengths which are generally dictated by the application, size and weight of the window.
24v DC chain drive actuators generally work on a two wire, reverse polarity basis so some type of controller with 24v DC transformer is required. This can come in the form of a simple integrated switch transformer such as the SE Controls 3A 24v DC transformer with touch sensitive switch or more complicated intelligent controls that can be integrated with Building Management System (BMS) or home automation systems such as Z-wave, CBus or Control4. This type of controller generally has inputs for rain, wind, temperature and other common sensors. One example of this type of controller is the NV PSU, this controller also has the option of an add on room controller module the NVLogiQ. This has the ability to monitor Co2 levels within the room along with internal/external temperatures and will operate the windows automatically to suite the desired room climate setting.
24v DC systems can also incorporate a battery back-up system, in the event of a power failure the system can still operate for a certain amount of time. This can be useful in the event of power failure when the windows are in the open position and it starts to rain. The windows can be closed via the battery back-up system preventing any water ingress into the building. This system is also useful if window actuators are controlling bush fire rated windows, the windows can still be closed even in the event of a power outage.
One of the main uses for battery back-up controllers is as part of a fire smoke control system. Upon receipt of a signal from the fire alarm panel or smoke detector the windows can be closed or opened depending on the particular smoke control strategy for that particular installation. These systems generally use fire rated cables between the control panel and actuators, so in the event of a fire and power outage the windows will open/close as preset without the fear of the cables being destroyed stopping operation.
Linear Drive Actuators are powered in similar ways to the chain drives and are available in AC and DC versions. They are also available in different stroke lengths and forces. Generally stroke lengths can be between 50-1000mm and forces can be up to 2000N which is approximately 200kg.
Linear drive are available in two main types, a standard linear where the motor drives a screw drive to power the linear shaft open/close. The second type is a rack and pinion actuator, with this type an externally mounted motor attached to the pinion drives the rack up or down.
Linear drive actuators are used to drive windows, roof lights, solar shading or operable louvres. They can be used singularly, tandem or in multiples. A tandem limit switch is required when operating multiple actuators on the same application to ensure the drives operated together at the same time. If one actuator fails or an obstruction occurs inhibiting the operation of one of the actuators then the limit switch automatically stops the remaining actuators to eradicate the chance of damage to the window,etc.
The final type of actuator is a rotary drive actuator. This type of actuator generally drives dampers/louvres or roof ventilators. They are available in both AC and DC versions depending o application. Fail safe spring return versions are also available where permanent power is required to power the actuator one way, the release of power enables the actuator to fully return to the start position until power is re-applied. This function is useful in smoke control/fire systems where is power failure occurs the actuator powers open or close via the fail safe spring opening or closing the vent as required. Rotary actuators generally rotate a maximum of approximately 90 degrees and usually have adjustable limit stops that can be positioned between the zero and maximum rotation positions.