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Old 2020-08-28, 03:07   #56
lavalamp
 
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The only way I can see this being dangerous is if the voltages supplied inside the computer are referenced to the "neutral" wire. So the "grounds" (black wires on molex/sata connectors) in the PC might actually be live 120V AC, and the 5V, 12V DC output of the PSU would be referenced to that. Probably worth checking.
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Old 2020-08-28, 03:53   #57
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Based on Xyzzy's description of what is happening I agree with PhilF and switching the neutral on a 120V device in the USA is a bad thing. The dangerous part is not when it is working normally, because it will probably work just fine. The dangerous part comes into play when (not if) something goes wrong.

Hypothetical:

You need do something on the inside of your computer, it is just a quick fix, your not pulling anything major apart so you turn the power supply switch to the off position and do not unplug the computer from the wall. If the switch is on the neutral wire as PhilF described, the computer is not disconnected from the line(hot) wire and if you touch the wrong wire inside the computer, something or someone could get hurt or worse.

That is just one simple example of things going wrong. History is full of far worse examples.
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Old 2020-08-28, 07:07   #58
retina
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Wow, so many incorrect beliefs here about mains power.

In most switch mode power supplies (and all consumer versions) live and neutral are completely arbitrary. Swap them over and it makes no difference. The input is completely isolated from any ground via a transformer. All that matters is that the voltage difference between the two incoming power lines is within the range the PSU is designed for.

All those little double insulated wall-wart switch mode PSUs everyone has now don't even have a ground, or anything to tell you which pin is hot and which is neutral. Because it makes no difference which way you plug them in.

And working on a system plugged in, but unpowered is perfectly fine. The ground line keeps everything well ordered. Don't worry about it, the fuse would have blown long ago if somehow live was connected to the grounded metal casing.

Last fiddled with by retina on 2020-08-28 at 07:14
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Old 2020-08-28, 07:19   #59
LaurV
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If you ask me, picture in post #42 is right, and the one in #51 is wrong. Think about when you match the cables, female connectors always have pin 1 in the opposite side of male connectors, if it is supposed that pin 1 is matched with pin 1. What's kinda wrong, is the switch - again, if you ask me, it should use DPST, to cut both lines. Was the manufacturer trying to save 6-7 cents by using a SPST switch?

About safety, you MUST check. Don't expect the manufacturers to care about your safety.

Also, there is nothing like "two lines/hots" for a single-phase plug (that is an absurdity, unless you have two phases, in which case the cable has 3 wires, excluding the earth, four wires with the earth). The 220 is EXACTLY like in US, except the voltage is higher, so the current (and therefore the loss in the wire by heat) is lower.

Working in electronic design/manufacturing for 30+ years, designed power supplies for industrial use in US, Germany, etc.

Edit: One thing you could look for, try to see if you have any cable in house which is actually marked - many of them are, like those from "brand" houses (Dell, HP, etc). It has to be marked in both sides, like for example:

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Last fiddled with by LaurV on 2020-08-28 at 07:29
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Old 2020-08-28, 13:05   #60
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Quote:
Originally Posted by retina View Post
Wow, so many incorrect beliefs here about mains power.

In most switch mode power supplies (and all consumer versions) live and neutral are completely arbitrary.
Retina, you are absolutely WRONG. You NEVER switch neutral without switching hot also. PERIOD. I have 50+ years of experience with AC power in the USA backing me up.

Also, the better quality switching power supplies have integrated line filters to prevent high frequency trash from being injected back into the incoming power line. Depending on the design of the filter, it could definitely care which side was hot and which was neutral.

Please Mike, either fix that cord or DO NOT USE IT.

EDIT: This question has already evoked more responses than it deserves. Even if there were a question as to it being safe (which there isn't), it seems to me like a no-brainer to err on the side of caution and fix it. If nothing else, that cord assembly is illegal to sell in the USA. It breaks the AC wiring codes. Protect yourself both physically and legally by fixing it and putting this section of the thread to bed.

Last fiddled with by PhilF on 2020-08-28 at 13:56
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Old 2020-08-28, 13:37   #61
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Quote:
Originally Posted by PhilF View Post
Please Mike, either fix that cord or DO NOT USE IT.
We won't use it. Thanks!



Too bad the manufacturer won't replace it.

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Old 2020-08-28, 14:28   #62
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Quote:
Originally Posted by Xyzzy View Post
Too bad the manufacturer won't replace it.

They probably have a pile of many thousands of them, all wired wrong.
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Old 2020-08-28, 19:34   #63
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They want to replace the switch:
Quote:
Thank you for getting back with us. According to our team, this might be an on/off switch issue; therefore, we can ship you a replacement on/off switch if you can provide us with your full shipping information (name, address, phone number).
We are going to try to convince them that the cord itself is the issue. (When we run a continuity test on the "hot" wire the switch actually works. Too bad the "hot" is really the neutral!)

PS - ELI5: What is the neutral for? (We view electricity like water in a pipe (pressure=volts & flow=amps) so maybe we are looking at it wrong?)
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Old 2020-08-28, 19:49   #64
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Quote:
Originally Posted by Xyzzy View Post
They want to replace the switch:We are going to try to convince them that the cord itself is the issue. (When we run a continuity test on the "hot" wire the switch actually works. Too bad the "hot" is really the neutral!)

PS - ELI5: What is the neutral for? (We view electricity like water in a pipe (pressure=volts & flow=amps) so maybe we are looking at it wrong?)
Is the product UL listed? If it is sold in the USA it should be. Let them know you are contacting the UL market surveillance group to see if they are interested in defective products being sold.

I used to work for a UL listed manufacturer. They had a complaint that was substantiated. It was a painful experience.
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Old 2020-08-28, 19:52   #65
chalsall
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Quote:
Originally Posted by Xyzzy View Post
What is the neutral for?
It carries the current from "Hot" back to the panel, after doing whatever work it is the device does.

It is very similar to Ground (AKA "Earth"), and in fact Neutral and Ground are tied together at the panel.

BUT, importantly... Ground should never actually carry any current. It's there as a safety feature (and some devices don't even use it). There's a reason bathroom outlets, for example, have Ground Fault Interrupters (GFI) which kill the Hot the instant any current is detected passing back through the Ground.
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Old 2020-08-28, 20:00   #66
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Quote:
Originally Posted by Xyzzy View Post
PS - ELI5: What is the neutral for? (We view electricity like water in a pipe (pressure=volts & flow=amps) so maybe we are looking at it wrong?)
In the water analogy the neutral is the drain pipe. The ground is the sink over flow or the floor drain that discharges outside.
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