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Unwind cable completely

Why should you always unwind the cable completely and completely untangle an extension cable?

You have probably already noticed when looking at the label on a cable reel or cable box that the following instructions are listed, for example:

Unwind cable completely

(These instructions are for your own safety and should be followed as much as possible.)

You can find out quite easily how much power each device used actually has by reading these details on the “type plate”.

But why does a cable reel have to be fully unwound in the event of high loads?

Cable winding devices, such as cable reels or cable boxes become extremely hot in the centre of the rolled up cable. For this reason, temperature switches (overheating protection) are prescribed which interrupt the flow at about 65° C. Without this overheating protection, the cable insulation can melt and lead to the destruction of the winding device or - in the worst case - can lead to fire.

A set of hedge clippers, for example, has approx. between 500 and 700 watts. This means that if you want to sort out your hedge and just plug the hedge clippers into the cable reel or cable box, there is no risk if you don’t completely unwind the cable, as this is <1,000 watts.

An electric lawnmower, however, can already have over approx. 1,500 watts and should therefore only be used with a completely unwound cable (from the cable reel).

And when is the overheating protection triggered and how does it work?

The overheating protection is triggered if the temperature in the centre of the reel is too high. This occurs if the cable has not been sufficiently unwound and if heat is created due to a high current flow to the connected consumers (coil effect). This effect can also occur through other heat sources, such as direct sunlight or machines in enclosed spaces, for example.

Procedure when the overheating protection is triggered:

If the current has been interrupted by the overheating protection switch (bimetal), please pull the plug from the power outlet and unplug all the consumers. Unwind the whole cable and leave the cable unwinding device to cool. After a few minutes you can briefly press the button on the outlet plate and plug in the power plug again. The current flow should now be restored. If this is not the case after a longer period of time, it may be that the switch is damaged by overload and must be replaced.

However, to prevent unnecessary overheating of the cable, this should always be completely unwound from the drum.