This question has been hunting me for years.

In domestic AC you a Line and a Neutral. Usually there are best practices to make sure that you set loads in the proper way (ie.: when you have a switch and a light bulb, you don't want the line to go directly to the bulb).

Now, in some countries of the world, the power outlets, and the respective plugs don't have a guide to force one way. Basically you can insert the plug in both ways.

enter image description here What are the downstream consequences of having insert the plug in the wrong way? Isn't that bad since you are polarizing the appliance in the opposite way (ie.: assume I have a bad side table lamp, now all of a sudden I have the line that goes directly into the bulb).

Thinking about more sophisticated electronics (like converter, led drivers, etc) this is equivalent to exposing them to constant tension (and consequentially to all the spike of the tension in the house) which, imho, is not a great thing for longevity of some of the components.


1 Answer 1


Appliances are supposed to be approved by a competent testing agency. This might be TUV or CSA, and the EU has a scheme where EU manufacturers can self-certify.

Part of the certification is confirming that the appliance is insulated sufficiently for reverse polarization, assuming it comes with a plug capable of being plugged in backwards. (A non-issue on UK and US plugs which are polarized).

This, however, is only as good as the testing agency. This is where the sea of cheap foreign junk enters the picture. A lot of mail ordered items bypass product safety laws and customs, and have never seen the inside of a testing lab. For those items, your concerns are very much warranted.

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