4 ms·

>That's an interesting issue, since in continential Europe (and a lot of the rest of the world) the plugs are symmetrical and don't distinguish between active a

>That's an interesting issue, since in continential Europe (and a lot of the rest of the world) the plugs are symmetrical and don't distinguish between active and neutral. It really doesn't matter much with A/C since the voltage is always flip flopping. You're basically a bird on a wire at all times but that wire is the earth itself. I can't think of any situation where a properly manufactured device would care which contact is neutral and which one is power. Ground is (in theory) always separate from neutral on the device (it should go without saying that it's separate from the line otherwise you have a short to ground). Plugs in the US used to be symmetrical too. Edit: Since apparently I'm Wrong(TM) does anyone want to tell me why?

gowld 8y ago
(1) Your advice could kill people, and (2) it's not reasonable to claim that decades of expensive electrical mains and appliance design&manufacturing was done for no benefit. The ground wire connects to non-electrified portion of the device, as a protection against accidental electrification. Neutral closes the mains circuit also is grounded, protecting the electrified portion against accidental activation. https://en.wikipedia.org/wiki/Ground_and_neutral https://en.wikipedia.org/wiki/Ground_and_neutral That article also has a section about how mechanized-farm cow milk production is harmed by the issue discussed in the OP
- dsfyu404ed 8y ago
  Of course you don't want to use the ground as your neutral. In normal wiring it's not designed to do that job so it sucks at it. I'm talking about the polarity of the line and the load as it relates to the device being powered. Your comment seems like a complete and total non-sequitur to that. I'm talking about a directional plug here. > Your advice could kill people, I am not giving any advice. I'm saying that unless you're doing something complex involving the neutral and ground no technical reason the neutral and the hot contacts on any given device are not interchangeable because the electrons are going both directions anyway. > it's not reasonable to claim that decades of expensive electrical mains and appliance design&manufacturing was done for no benefit. You can still get devices in 2019 that are not grounded (common) and do not have a directional plug (rare). >Neutral closes the mains circuit also is grounded, protecting the electrified portion against accidental activation. How is this related to what I said? Yes neutral and ground are both "grounded to the ground" at some point (usually the panel) but the device being plugged in doesn't know the difference between the neutral and the live wire because its getting its electrons from both (because AC).
  - pgeorgi 8y ago
    > and do not have a directional plug (rare). https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Schuko_%28CEE_7-3%29_socket-outlets%2C_with_and_without_shutters.jpg/800px-Schuko_%28CEE_7-3%29_socket-outlets%2C_with_and_without_shutters.jpg https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Sc... What would a directional plug for this socket look like?
    - dsfyu404ed 8y ago
      I don't know. A non-directional/non-polarized plug would just omit the features that engage the key-ways on the side enabling you to plug it in whichever way you want. If you want to make it directional/polarized just engage the key-ways so the user can only plug it in one way. In North America we have these[1] for things that don't have a metal case and on cheaper devices both blades are often the same size allowing you to plug it into an outlet whichever way you want. [1]https://cdn.sparkfun.com/assets/5/1/0/d/c/51154c1cce395f903d000001.jpg https://cdn.sparkfun.com/assets/5/1/0/d/c/51154c1cce395f903d...
      - wongarsu 8y ago
        What parent is getting at is that Socket Type F "Schuko", one of the most popular socket types, is completely symmetrical and inherently non-polarized. Since any plug compatible with Schuko is non-directional calling non-directional plugs rare is factually wrong (if we talk globally). It also proves your point that the difference between life and neutral largely doesn't matter, since in about half the world wall sockets don't care about the difference.
  - jlokier 8y ago
    > I'm saying that unless you're doing something complex involving the neutral and ground no technical reason the neutral and the hot contacts on any given device are not interchangeable because the electrons are going both directions anyway. They are not interchangable for safety, electric shock, or EMC purposes, because the AC voltage range at neutral and hot contacts are very different. This is when the voltage is measured relative to the nearby environment. Roughly speaking, the neutral AC voltage may oscillate around +/-2V (that's all), relative to the surrounding environment.[] If it's more than that you probably have a fault. Whereas the hot AC voltage will oscillate around the full range you'd expect (~110V RMS or ~230V RMS depending on country). This makes them very different, with regard to human safety, other safety (such as sparking against an earthed pipe, causing fire, contact with water), and current flow to the environment via capacitive coupling. [] - Neutral is bonded to ground somewhere, but not at the mains outlet. The reason it's not zero and a small voltage appears, is because all the devices plugged in closer than the neutral-to-earth bond contribute a small "pull" to the neutral voltage, competing with the bonded voltage.
wongarsu 8y ago
I agree that in a device without exposed metal and with a two-pronged plug it doesn't matter. And those devices extremely common at least in Europe. It's mostly problematic if you make assumptions around knowing which pin in neutral that turn out to be wrong: for example on a lamp socket you could put the exposed part on Neutral, making it safe to touch. That becomes dangerous if you switch Neutral and Life. If you assume you don't know which is neutral you obviously wouldn't design it that way and protect any metal surface with some isolator (plastic) or ground it.
hundt 8y ago
> Since apparently I'm Wrong(TM) does anyone want to tell me why? I think because some devices are designed such that incidental contact with neutral (before the load) is possible under normal circumstances, which means (if the internal circuit in the device is not complete) you could get shocked if hot and neutral are swapped. An example of such a device is a plug-in light fixture with a screw-in bulb. You might easily touch the edge or side of the socket while there is no bulb in there. You are much less likely to touch the contact deep within the socket. So the fixture is wired to make the socket neutral and the contact hot.

gowld 8y ago

(1) Your advice could kill people, and (2) it's not reasonable to claim that decades of expensive electrical mains and appliance design&manufacturing was done for no benefit. The ground wire connects to non-electrified portion of the device, as a protection against accidental electrification. Neutral closes the mains circuit also is grounded, protecting the electrified portion against accidental activation. https://en.wikipedia.org/wiki/Ground_and_neutral https://en.wikipedia.org/wiki/Ground_and_neutral That article also has a section about how mechanized-farm cow milk production is harmed by the issue discussed in the OP

dsfyu404ed 8y ago
Of course you don't want to use the ground as your neutral. In normal wiring it's not designed to do that job so it sucks at it. I'm talking about the polarity of the line and the load as it relates to the device being powered. Your comment seems like a complete and total non-sequitur to that. I'm talking about a directional plug here. > Your advice could kill people, I am not giving any advice. I'm saying that unless you're doing something complex involving the neutral and ground no technical reason the neutral and the hot contacts on any given device are not interchangeable because the electrons are going both directions anyway. > it's not reasonable to claim that decades of expensive electrical mains and appliance design&manufacturing was done for no benefit. You can still get devices in 2019 that are not grounded (common) and do not have a directional plug (rare). >Neutral closes the mains circuit also is grounded, protecting the electrified portion against accidental activation. How is this related to what I said? Yes neutral and ground are both "grounded to the ground" at some point (usually the panel) but the device being plugged in doesn't know the difference between the neutral and the live wire because its getting its electrons from both (because AC).
- pgeorgi 8y ago
  > and do not have a directional plug (rare). https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Schuko_%28CEE_7-3%29_socket-outlets%2C_with_and_without_shutters.jpg/800px-Schuko_%28CEE_7-3%29_socket-outlets%2C_with_and_without_shutters.jpg https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Sc... What would a directional plug for this socket look like?
  - dsfyu404ed 8y ago
    I don't know. A non-directional/non-polarized plug would just omit the features that engage the key-ways on the side enabling you to plug it in whichever way you want. If you want to make it directional/polarized just engage the key-ways so the user can only plug it in one way. In North America we have these[1] for things that don't have a metal case and on cheaper devices both blades are often the same size allowing you to plug it into an outlet whichever way you want. [1]https://cdn.sparkfun.com/assets/5/1/0/d/c/51154c1cce395f903d000001.jpg https://cdn.sparkfun.com/assets/5/1/0/d/c/51154c1cce395f903d...
    - wongarsu 8y ago
      What parent is getting at is that Socket Type F "Schuko", one of the most popular socket types, is completely symmetrical and inherently non-polarized. Since any plug compatible with Schuko is non-directional calling non-directional plugs rare is factually wrong (if we talk globally). It also proves your point that the difference between life and neutral largely doesn't matter, since in about half the world wall sockets don't care about the difference.
- jlokier 8y ago
  > I'm saying that unless you're doing something complex involving the neutral and ground no technical reason the neutral and the hot contacts on any given device are not interchangeable because the electrons are going both directions anyway. They are not interchangable for safety, electric shock, or EMC purposes, because the AC voltage range at neutral and hot contacts are very different. This is when the voltage is measured relative to the nearby environment. Roughly speaking, the neutral AC voltage may oscillate around +/-2V (that's all), relative to the surrounding environment.[] If it's more than that you probably have a fault. Whereas the hot AC voltage will oscillate around the full range you'd expect (~110V RMS or ~230V RMS depending on country). This makes them very different, with regard to human safety, other safety (such as sparking against an earthed pipe, causing fire, contact with water), and current flow to the environment via capacitive coupling. [] - Neutral is bonded to ground somewhere, but not at the mains outlet. The reason it's not zero and a small voltage appears, is because all the devices plugged in closer than the neutral-to-earth bond contribute a small "pull" to the neutral voltage, competing with the bonded voltage.

wongarsu 8y ago

I agree that in a device without exposed metal and with a two-pronged plug it doesn't matter. And those devices extremely common at least in Europe. It's mostly problematic if you make assumptions around knowing which pin in neutral that turn out to be wrong: for example on a lamp socket you could put the exposed part on Neutral, making it safe to touch. That becomes dangerous if you switch Neutral and Life. If you assume you don't know which is neutral you obviously wouldn't design it that way and protect any metal surface with some isolator (plastic) or ground it.

hundt 8y ago

> Since apparently I'm Wrong(TM) does anyone want to tell me why? I think because some devices are designed such that incidental contact with neutral (before the load) is possible under normal circumstances, which means (if the internal circuit in the device is not complete) you could get shocked if hot and neutral are swapped. An example of such a device is a plug-in light fixture with a screw-in bulb. You might easily touch the edge or side of the socket while there is no bulb in there. You are much less likely to touch the contact deep within the socket. So the fixture is wired to make the socket neutral and the contact hot.