Why you should always unwind a cable reel completely and untangle an extension cable completely

Unwind cable completely

Surely you have noticed on the label of a cable reel or a cable box that the following information is listed:

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(This information is for your own safety and should be followed as closely as possible)

Such a label indicates how many watts, or maximum power, can be connected in the rolled up and unrolled state. You can easily find out how much power the connected, used device actually has by reading this information on the so-called "nameplate". Different devices, or in this case consumers, cause different loads.

Why unwind the cable completely at high load?

Where electricity flows, the use of electrical devices also generates heat. If more electricity flows through the use of several consumers, more heat is also generated. If electrical cables are wound up like the cable of a cable reel, the heat is naturally difficult to dissipate. To avoid overheating the cable, it should always be completely unwound from the drum body.

Cable rewinding devices, such as cable reels or cable boxes become extremely hot in the core of the coiled cable. Therefore temperature switches, also known as overheating protection, are mandatory. Without this mechanism and the overheating protection, the cable insulation can melt and lead to destruction - or in the worst case - to fire of the rewinder.

Kabel komplett abrollen Brobusta

Kabel komplett abrollen Garant G

How strong is the cable reel when rolled up?

Unwind cable completely - An example to help you understand

A hedge trimmer, for example, has approximately between 500 and 700 watts. This means that if you are getting your hedge into shape and only plug the hedge trimmer into the cable reel or cable box, you are not taking any risks even if the cable is not completely unrolled, as the hedge trimmer has an output of less than 1,000 watts.

An electric lawnmower, on the other hand, can already have over 1,500 watts and should therefore only be used in conjunction with a completely unwound cable.

When does the overheat protection trip and how does it work?

The overheating protection triggers if excessive temperatures occur in the drum core. At a temperature of approx. 65°C the current is interrupted. Such high temperatures occur if the cable has not been sufficiently unrolled and if heat is generated due to excessive current flow through the connected loads. This is also called the coil effect.

However, it should be noted that overheating can also be caused by other heat sources, such as solar radiation or machines in closed rooms. The heat generated during use therefore adds up with the ambient temperature.

Procedure for tripping the overheat protection

If the overheating protection switch (bimetal) has interrupted the current, please disconnect the plug from the mains and unplug all loads. Please unroll the cable completely and let the cable unrolling device cool down. After a few minutes you can briefly press the push button on the socket board and plug the power plug back in. Now the current flow should be restored.

If this is not the case even after a long period of time, the switch may be damaged by overload and must be replaced. It is easier to use the device always completely unrolled to avoid triggering the overheating protection.