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Stupid voltage leak question
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ebastler:
In the specific case of the OP's espresso machine, it all boils down to the question:

* Are those metal parts (by design) meant to be grounded, because there is a risk that they could otherwise come in contact with "hot" mains through just a single fault in the machine? If that is the case, the tingle upon touching them suggests that the parts are not actually grounded, and that's a safety issue that needs to be fixed immediately.
* Or are those parts double-insulated from mains inside the machine, and were never meant to be grounded? In that case, a tingle due to capacitive coupling of some voltage is normal. The machine may still require a properly grounded plug to keep other touchable metal parts safe, but the "tingle" does not give any indication that there is something wrong with that grounding.In practice, I would assume that functional metal parts which are in direct contact with the heater will need to be grounded. E.g. in a typical portafilter machine, the boiler and the group head. But if the machine's outer enclosure is mostly a plastic structure, with some decorative metal parts glued on, those might well be double-insulated and not grounded.

To tell whether specific metal parts were meant to be grounded or not, one could disassemble the machine and look for provided connection points or loose ground wires. But a judgement call "from the outside" may be good enough in some clear-cut cases. @ImpulsiveJames -- which parts specifically caused the tingle when touched? Could you share the specific brand and model, and/or a photo of your machine?
Siwastaja:

--- Quote from: ebastler on January 13, 2024, 07:23:10 am ---In the specific case of the OP's espresso machine, it all boils down to the question:

* Are those metal parts (by design) meant to be grounded, because there is a risk that they could otherwise come in contact with "hot" mains through just a single fault in the machine? If that is the case, the tingle upon touching them suggests that the parts are not actually grounded, and that's a safety issue that needs to be fixed immediately.
* Or are those parts double-insulated from mains inside the machine, and were never meant to be grounded? In that case, a tingle due to capacitive coupling of some voltage is normal. The machine may still require a properly grounded plug to keep other touchable metal parts safe, but the "tingle" does not give any indication that there is something wrong with that grounding.In practice, I would assume that functional metal parts which are in direct contact with the heater will need to be grounded. E.g. in a typical portafilter machine, the boiler and the group head. But if the machine's outer enclosure is mostly a plastic structure, with some decorative metal parts glued on, those might well be double-insulated and not grounded.

To tell whether specific metal parts were meant to be grounded or not, one could disassemble the machine and look for provided connection points or loose ground wires. But a judgement call "from the outside" may be good enough in some clear-cut cases. @ImpulsiveJames -- which parts specifically caused the tingle when touched? Could you share the specific brand and model, and/or a photo of your machine?

--- End quote ---

And here we have the correct answer. Usually a lot of unnecessary noise in threads like this.
Zero999:

--- Quote from: Siwastaja on January 13, 2024, 01:25:48 pm ---And here we have the correct answer. Usually a lot of unnecessary noise in threads like this.

--- End quote ---
Except, if you re-read the thread carefully, you'll find the correct answer. I also dispute part about parasitic capacitances.


--- Quote from: ebastler on January 13, 2024, 07:23:10 am ---Or are those parts double-insulated from mains inside the machine, and were never meant to be grounded? In that case, a tingle due to capacitive coupling of some voltage is normal.
--- End quote ---
I doubt that it's parasitic capacitances, because they'll be far too small to pass enough current to cause a tingling sensation. Y capacitors of course can do that, but not the tiny capacitance between say a metal grip tray and some live parts inside the case. This shouldn't happen, if it has an earth on the mains lead.
ebastler:

--- Quote from: Zero999 on January 13, 2024, 01:49:40 pm ---Except, if you re-read the thread carefully, you'll find the correct answer. I also dispute part about parasitic capacitances.

--- End quote ---

Yes, you pointed out the relevant question before. But I felt that you also jumped to a particular conclusion, which may be the wrong one; hence thought that I should elaborate a bit.

Considering the boundary conditions under which the tingle was felt (barefoot on a cement floor), I would certainly not rule out harmless capacitive coupling to a metal part that is floating by design. What constitutes a "tingle" is a very subjective assessment; it might just be the 60 Hz "vibrations" which are typically felt. Let's wait whether the OP comes back with more details about his espresso machine and the specific metal parts that caused the sensation.
nctnico:

--- Quote from: Zero999 on January 11, 2024, 09:14:09 pm ---You shouldn't feel a tingle from an appliance like that, which should be earthed. It's not the same as a double insulated power supply, with a Y capacitor bridging the primary and secondary sides.

Test the continuity between the exposed metallic parts and the earth pin of the mains plug.

--- End quote ---
Agreed. On a grounded device, all metal parts should be connected to the ground pin. If not, then the unit is faulty and should be checked / replaced. If the coffee maker is OK, then the power cord the next suspect. It is also not unheard of that a grounded outlet doesn't have the ground pin connected.
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