the Opening width indicates how far a window is open. It is given either as a gap in millimetres at the opening edge or as an Opening angle in degrees.
Opening width and stroke length
the Stroke length is the distance the actuator extends. The opening width is what arrives at the window. The two are not always the same: depending on where the actuator sits and how the sash is hinged, the window opens further or less far at the edge than the stroke. The right stroke for your window is calculated by the Chain Length Calculator..
How far must a window open?
- Everyday ventilation: even a gap of a few centimetres ensures air exchange
- Purge ventilation or night cooling: larger opening, more air
- RWA: what counts here is the required opening area specified by the design – not the gap alone
What limits the opening width?
Besides the actuator, fittings also limit the opening, such as the tilt stay or the safety stay. The actuator must never extend further than the window mechanism allows.
Practical example: tiltable windows in the classroom
A tilt window is intended to open electrically for ventilation during breaks. A chain drive with a 200 mm lift, mounted on the top of the wing, opens the edge by about 200 mm. However, if the existing tilt shear already restricts the opening at 150 mm, that’s the end of the story: The drive runs against the fitting and switches over to the Load cut-off ab. In this case, either the fitting is adjusted or a drive with a shorter stroke is selected.
Common mistakes
- Misunderstanding the opening width with the opening area: For the RWA, the required opening area counts (see NRWG), not just the gap
- Choose a larger hub than the fitting or safety stay allow
- For windows at a reachable height, protect the area around the closing edges forgotten
Tip: Always measure the opening width at the edge where the drive engages. Near the bands, a tilt or folding window opens significantly less far.
Frequently asked questions
How do I measure the opening width?
Open the window as wide as you wish and measure the distance between the wing and the frame at the edge where the actuator is to be mounted. Enter this value as the lift.
Can I change the opening width later?
It depends on the drive. The stroke is fixed for many drives. Therefore, plan the opening width already during the selection process, for example using the Chain Length Calculator..
Read more
- Glossary: mounting position
- Open tilt windows electrically
- Chain actuators for façade windows: typical applications
Not sure which actuator fits? Call us: 040 50694631 (Mon–Fri 8 am–5 pm) or use the actuator finder.