Angus from makersmuse explains here how he got shocked from a printer with floating ground.


I don't really understand his explanation.

He basically says that if you don't ground the printer properly it wil shock you if you touch it because the ground wire, and thus the printer will be hot?

But why is there voltage on on the pin in the first place?

Does this mean that if I plug my printer in to an ungrounded wall plug and touch the case while I'm grounded I will get shocked?


closed as off-topic by Andy aka, RoyC, Bimpelrekkie, Sparky256, Voltage Spike Jan 24 '18 at 7:49

  • This question does not appear to be about electronics design within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ Why didn't you leave a public comment under that youtube video asking for an explanation? Why haven't you done some research on this - there are plenty of Q&As on this site about electric shock from unearthed appliances. There is plenty of information online about this. \$\endgroup\$ – Andy aka Jan 16 '18 at 9:42
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    \$\begingroup\$ I'm voting to close this question as off-topic because there is tones of info online that can be found about this subject and it is unclear what the OP's level of understanding is so it's difficult to know where to pitch the beginning of an answer if one were deserved. \$\endgroup\$ – Andy aka Jan 16 '18 at 9:44
  • \$\begingroup\$ Also voting to close for above reason plus this site is not a forum for making comments on YouTube videos, which may disappear at some time in the future. \$\endgroup\$ – RoyC Jan 16 '18 at 10:08
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    \$\begingroup\$ I did ask in the comment section but I don't expect to get as detailed of an answer as here. Also I did look if I could find any info about my question but couldn't find any. Perhaps I'm not searching for the right keywords. If you vote to close because of the abundance of info, at least give an example link so I know where to look for further info. \$\endgroup\$ – MeesterPatat Jan 16 '18 at 10:29

GND/Earth is a safety device. If you disable it, things get more unsafe.

A lot of devices have their filters coupled to GND via some capacitor, and some current flows there. If you remove that path and replace it by a resistor (e.g. a human), then that is where the current flows instead.


I'm going to use the Australian terms in my explanation to match the video. Here's the translation if you need it:

  • Aus -> US
  • Earth -> Ground
  • Active -> Hot

There is voltage on the chassis because there is a Y Capacitor between either or both of the active and neutral lines to chassis. The chassis is normally connected to earth but on an unearthed outlet this connection doesn't exist. If it did then the chassis potential would be the same as earth. Without it the chassis can float to a higher potential than earth and therefore give a zap when you touch the chassis and your body forms the connection to earth.

While it is common practice to use Y-Capacitors, if there is enough voltage on the chassis to cause a zap when the supply is unearthed, then there is probably going to be enough current flowing in the earth when the supply is earthed to trip the RCD.

So perhaps your confusion is warranted - no electrical appliance should use earth as a current path, so it ought to raise some eyebrows if a voltage appears on that earth connection. However, Y-Capacitors are often part of a valid design, and they form a conductive path between the incoming voltage and the earth connection. The designer's job is to make sure their conductivity is low enough to be imperceptible.


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