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I'm having a real difficult time understanding the following statements from various sources:

That's what I was told: don't use the earth pin from a power outlet as your earth because it's dangerous.

Source: Q: Using the earth pin on a power outlet as the earth for a crystal radio (while writing this question)

Similarly, on reddit, there are comments telling a very similar story:

Do not connect anything w.r.t. ground to your wall outlet! That‘s a recipe for disaster.

Source: /r/homelab - Grounding your server rack ?

In your house, don't worry about it.

Grounding to the outlet ground is not an earth ground return and potentially dangerous.

Source: /r/homelab - How many of you ground your equipment/server rack? (emphasis mine)

I tried to read and understand the arguments made by the people who claim this is the case, but I don't really understand what they're getting at.

To add further to my confusion, there are people saying the exact opposite of what the above sources say.

Now, I'm not an electrician and I don't consider myself an electrical engineer anymore, but I do have knowledge about electrical engineering. I completed a 4 year apprenticeship on electrical engineering.

I do know that grounding plays a very important role in electrical safety, and to my knowledge, all consumer products made out of metal have the ground pin attached to the housing if they're powered with mains power.

So, if Grounding to the outlet ground is not an earth ground return and potentially dangerous. is the case, why are all these products made out of metal connected directly to it (outlet ground)? That doesn't make any sense to me.

If that makes any difference, yes, this is in the context of grounding a network rack.

However, I don't think that plays a hugely important role, unless I'm missing something here.

Please note: I'm not asking why grounding is done, or what earth's ground is. I'm simply confused by the statements that one shouldn't use the earth from a wall outlet as earth ground: to me, they are the same thing, just with a different "wiring" - lets say.

Context (if this is necessary): I'm living in Switzerland.

Marco
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    If you live in a properly wired place, the protective earth (PE) conductor in your installation wiring is directly connected to the Earth and should never move away more than a few mV (in a fault case). The wall outlet comment might be related to the proximity to accessible live conductors, so accidental connections could be made to live voltages. – tobalt Dec 28 '22 at 19:28
  • @tobalt `the protective earth (PE) conductor in your installation wiring is directly connected to the Earth` that matches my current understanding of how the wiring is done, hence my confusion. `The wall outlet comment might be related to the proximity to accessible live conductors` is that a speculation on your side, or a genuine concern? – Marco Dec 28 '22 at 19:31
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    It is a speculation about why anybody would be concerned of using the PE contact. You know Schuko connectors have the PE permanently exposed. But other outlets such as the Swiss ones, might have the PE in one of the 3 holes, just like the neutral and live wires. So image you are drunk on a bad day, and slide in that earth cable into the wrong hole ;) – tobalt Dec 28 '22 at 19:33
  • Well you could always cut off a wall plug and wire your receiver to that. I would double check that I got it right and then not worry about it. – Drew Dec 28 '22 at 19:35
  • @tobalt `It is a speculation about why anybody would be concerned of using the PE contact.` I can see why some people might have that particular concern, but I think this concern is pretty much void, since consumer electronics that are made out of metal have their PE contact wired to the housing anyway. So if something were to connect to PE then the consumer device would be live. I highly doubt manufacturers would take that risk (PE connecting to something live) into account, since PE is exactly designed for this kind of fault case. – Marco Dec 28 '22 at 19:39
  • @tobalt It's a real mess. In addition to doing my own research I've talked to two friends about this exact question and got two different answers. Further pushing me to ask this question here because the chance is very high to get an answer from someone that is an expert in the field with lots of experience - at least, that's what I'm hoping to get. – Marco Dec 28 '22 at 19:43

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The risk is that in the event of a dead short occurring in between live and earth, the PE could present a significant voltage momentarily until the fuse/breaker trips. The earth connection should present a very low resistance to ground, but if this ground happens to be a spike hammered into the ground then it doesn’t guarantee to be a much better conductor than anyone who happens to be touching the PE at the time. So the risk is small but the fallout could be dire.

Frog
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    I see, so this (effectively) means, **iff** you have the choice to connect to earth, you should do it directly and not through a means that can be compromised? Is that what you mean? :) – Marco Dec 28 '22 at 19:46
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    @marco-a yes exactly – Frog Dec 28 '22 at 19:53
  • Thank you for explaining this. Now it makes a lot of sense. – Marco Dec 28 '22 at 20:58