How Many Nm Does a Roller Shutter Motor Need?
How many Nm should the tubular motor for my roller shutter have?
The required torque of a tubular motor depends primarily on the actual weight of the roller shutter and not only on its dimensions.
Nm (Newton metres) indicate the amount of force the motor can deliver in order to raise and lower the roller shutter safely.
As a general rule, 1 Nm corresponds to approximately 1.8 kg of load. For example, a 20 Nm motor can theoretically lift approximately 36 kg.
| Torque | Theoretical lifting capacity | Recommended maximum weight |
|---|---|---|
| 10 Nm | 18 kg | 14.5 kg |
| 20 Nm | 36 kg | 29 kg |
| 30 Nm | 54 kg | 43 kg |
| 40 Nm | 72 kg | 57.5 kg |
| 50 Nm | 90 kg | 72 kg |
| 60 Nm | 108 kg | 86.5 kg |
| 80 Nm | 144 kg | 115 kg |
| 100 Nm | 180 kg | 144 kg |
| 120 Nm | 216 kg | 173 kg |
The values above are intended as a practical selection guide rather than an absolute rule. The final choice should take into account the type of shutter curtain, shaft diameter, friction in the guide rails and the frequency of use of the roller shutter.
Why is a safety margin necessary?
In practice, the theoretical calculation alone is not sufficient.
Friction and mechanical losses caused by normal wear of the roller shutter, resistance from the guide rail brushes, possible installation imperfections, or minor deformation of the shaft and shutter curtain must also be taken into account.
For this reason, applying a safety margin of approximately 20% is recommended.
Therefore, although a 20 Nm tubular motor can theoretically lift 36 kg, in practice it is preferable to use it with roller shutters weighing up to approximately 29 kg.
How is the weight of the roller shutter calculated?
The weight does not depend solely on the width and height of the roller shutter, but also on the type of shutter curtain, the thickness and profile of the slats, as well as the material from which they are made, such as aluminium, polyurethane-filled aluminium or PVC.
In practice, the calculation is usually based on the manufacturer's weight tables. When replacing an existing motor, the actual weight of the roller shutter can also be measured where this is practical.
The correct calculation should therefore be based on the actual characteristics of the installation and not solely on a theoretical figure.
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