Window actuator during a power cut: what happens to the window?

During a power cut, an electric window actuator usually stops exactly where it is. An open window stays open and a closed one stays closed. Chain and spindle actuators usually hold the sash securely in position.

What exactly happens?

• The actuator stops immediately; there is no automatic travel to an end position.
• Rain and wind sensors cannot send a close signal without power.
• Push buttons and remote controls only work again once power is restored.

And when the power comes back?

That depends on the control unit. Many ventilation controls do not move on their own after a power cut but wait for the next command. If a rain or wind signal is present, they usually close the windows. How your control behaves is described in its manual.

How do I protect against rain during a power cut?

• Close the windows when leaving the building instead of relying only on the rain sensor.
• For important areas, provide an unterbrechungsfreie Stromversorgung (USV) for the 24 V control – planned by a qualified electrician.
• For roof windows and rooflights, keep the opening width for permanent ventilation small.

And with smoke and heat exhaust systems?

In smoke and heat exhaust systems, an SHEV control panel with backup batteries powers the actuators so they open even during a power cut. Vent Systems does not supply SHEV control panels; our controls are intended for daily ventilation.

Frequently asked questions

Does a window actuator close automatically during a power cut?

No. Without power it stays in its current position. It can only close automatically again once power is back and the control sends a close signal.

Can I close the window by hand during a power cut?

With most chain and spindle actuators not easily, because the actuator holds the sash. Forcing it can damage the actuator and the fittings. Wait for the power to return or ask us about your model.

Read more: Window actuator does not open – finding the causes · Rain sensor for windows