North American customers beware of Chinese power cords.

[Jeff1946]

Recently I bought an inexpensive 30V 5A power supply.  Been happy with it.  Recently read a comment on a Youtube review of a similar supply that sometimes the neutral and hot leads are reversed.  So as Dave says, "take it apart."  Internal wiring looked fine, but to check plugged it in and found that on the fused side on the power cord socket went to neutral.   With a little investigation found the AC cord was miswired.  Note many cords have an N and an L marked on the female side.  The L (load) should go to the hot lead on the male.  If you hold the female and male plugs facing you with the ground lead down the left and right slots on the female should connect to the left and right slots on the male.

So I replaced the miswired cord with a good one.

Out of curiousity, on 240V systems are both power lines fused and switched?

[wasedadoc]

Out of curiousity, on 240V systems are both power lines fused and switched?

Sometimes both are switched but I've never encountered both being fused.

[dobsonr741]

Yes. Recently bought a USB-C power + switched output extension cord. The outlet Live/Neutral was reversed, and the switch disconnected the neutral, not the live. 
Monoprice did not attempt to repair or replace, they issued a full refund after I reported. The extension cord sold under multiple names, picture is below.

[floobydust]

It's lower manufacturing cost, having mains go to the on/off switch and another lead to the fuse. Gets rid of the jumper. The chinese do this in many products, as well they flip Line and Neutral. It's forbidden to switch or fuse neutral in appliances, according to NA Electrical and Safety Codes.
I guess they don't understand this or have it in their own regional safety standards.

[Manul]

I've seen both lines fused on devices, but it is not typical. In some cases both switched. But at least in my country (which is part of EU) we are not thinking about L or N too much, so to speak. Plugs can go both ways, there is no correct direction, so it means that L and N is not really defined down the stream. You can measure after pluging the cable if you are interested, but that's pretty much it.

[shapirus]

I guess they don't understand this or have it in their own regional safety standards.

not sure about China, but in Europe wall sockets are symmetrical and the plugs can be inserted either way*, so there is no way to predict which of the wires will be live or neutral in the power cord. If it's the same in China, then they probably don't know (or don't care) that some sockets are designed so that live and neutral can't change their positions.

*but there are nuances. there are some designs that enforce a specific arrangement of L and N.

[vk6zgo]

Out of curiousity, on 240V systems are both power lines fused and switched?

Sometimes both are switched but I've never encountered both being fused.

With the USA/NA "split phase" type supply, both legs are "hot" w.r.t. earth (ground), so, yes, some equipment does fuse both legs.
Technically, that does not conform with Australian wiring rules, but I have seen it on quite a lot of equipment used for TV monitoring, etc, so it seems to have "slipped past".

There is not a lot of point in fusing both sides with 230v nominal systems like Oz & EU, etc, as the Neutral & PE (ground) are usually connected together & to an earth spike at the entrance to the premises.

Switching both sides, on the other hand, protects against just such an occurrence as you experienced.

[Psi]

A lot of the cheap china T12/T15 soldering station clones have the power switch mounted in the neutral line.

Since phase and earth are still connected the leakage keeps slowly charging up the PSU capacitors and every so often is enough for the MCU to try turn on and you get a beep and then it instantly dies.

So yeah, if you notice your china soldering station keeps randomly beeping even when power switch is off, that's why

[vk6zgo]

Recently I bought an inexpensive 30V 5A power supply.  Been happy with it.  Recently read a comment on a Youtube review of a similar supply that sometimes the neutral and hot leads are reversed.  So as Dave says, "take it apart."  Internal wiring looked fine, but to check plugged it in and found that on the fused side on the power cord socket went to neutral.   With a little investigation found the AC cord was miswired.  Note many cords have an N and an L marked on the female side.  The L (load) should go to the hot lead on the male.  If you hold the female and male plugs facing you with the ground lead down the left and right slots on the female should connect to the left and right slots on the male.

So I replaced the miswired cord with a good one.

Out of curiousity, on 240V systems are both power lines fused and switched?

"L" stands for "Live" not "load", where "L" means the same as "hot".
The location of L & N on the wall socket & plug are normally a "mirror image", not the same.

The pinout on that end of an "IEC" cord which plugs into the equipment should be the same as the wall socket.

[Doctorandus_P]

I agree with Shapirus, here in Europe nobody cares about swapping neutral and live in applyances. Plugs are bidirectional and from the "safety point of view" both wires are regared "live". The fixed wires in houses does have a color scheme. Blue for neutral and brown for live, but from the outside you can only guess which side is where on a wall socket.

Some appliances can have nasty effects, for example those orange sodium lamps can wear premature if the live wire is connected but the neutral is not. In such cases usually double throw switches are used, or if you want to cheap out, you can measure where the live wire is to put the switch on that side (with fixed installations).

I have a DMM with such a "contactless voltage sense" mode. I sometimes use this to find the neutral wire. I hold one hand over the sensor of the DMM, and put one of the measurement probes (does not matter which) into a wall socket.

[james_s]

A lot of power cords are junk, I've found some that are CCA instead of proper copper wire too.

In North America 240V circuits are fused and switched on both sides because both sides are live 120V to neutral with a split phase system. In other parts of the world there is only one leg, 240V to neutral so it wouldn't make sense to fuse both sides.

[shapirus]

In North America 240V circuits are fused and switched on both sides because both sides are live 120V to neutral with a split phase system.

This fusing concept is curious. The fuses don't always blow both at the same time, right? If one of the fuses is blown, the second wire will still remain live. What's the point of fusing both then?

[Monkeh]

It's forbidden to switch or fuse neutral in appliances, according to NA Electrical and Safety Codes.

You lack polarity control on unearthed equipment. Try that one again without worrying about a functional switch.

In North America 240V circuits are fused and switched on both sides because both sides are live 120V to neutral with a split phase system.

This fusing concept is curious. The fuses don't always blow both at the same time, right? If one of the fuses is blown, the second wire will still remain live. What's the point of fusing both then?

To protect against shorts to ground or overload between one leg and neutral.

[james_s]

This fusing concept is curious. The fuses don't always blow both at the same time, right? If one of the fuses is blown, the second wire will still remain live. What's the point of fusing both then?

Because if either one develops a fault to earth, you want the fuse on that side to blow. The fuse is to protect the wiring from fire, not to completely de-energize the device to prevent a shock.

In practice there is always a circuit breaker in the panel now though, at least in houses built within the past ~60 years and that will be linked so an overload on either side trips the whole breaker.

[MrAl]

Recently I bought an inexpensive 30V 5A power supply.  Been happy with it.  Recently read a comment on a Youtube review of a similar supply that sometimes the neutral and hot leads are reversed.  So as Dave says, "take it apart."  Internal wiring looked fine, but to check plugged it in and found that on the fused side on the power cord socket went to neutral.   With a little investigation found the AC cord was miswired.  Note many cords have an N and an L marked on the female side.  The L (load) should go to the hot lead on the male.  If you hold the female and male plugs facing you with the ground lead down the left and right slots on the female should connect to the left and right slots on the male.

So I replaced the miswired cord with a good one.

Out of curiousity, on 240V systems are both power lines fused and switched?

Do they have a UL or other rating stamp somewhere on the device, like on the back?

[dobsonr741]

One more catch: the IEC320 cable came with my Quicko has reversed Live/Neutral. L/N is written on the C13 end, and it N is live when plugged in to a proper US wall socket. The guts of the Quicko station is wired properly - fuses and disconnects the assumed live. The fault is with the cable they provided. 

That makes a nice 100% failure rate of the Chinese IEC cables I own.  And yes, both cable has UL, the other has also Intertek, CSA and ETV.

[radiolistener]

Out of curiousity, on 240V systems are both power lines fused and switched?

No, just one. There is no difference between N and L lines, because you can plug it into a mains socket in both variant. But there is also a GND line which is designed in that way to not allow connect it to N or L socket hole.

[helius]

You lack polarity control on unearthed equipment. Try that one again without worrying about a functional switch.

Some 2-pole connectors enforce polarity when the cords and sockets are correctly wired. The NEMA 2-15 is such a connector.

Some will ask "Why? For double-insulated equipment it doesn't matter", but the reason goes back farther than that.
It is so lamps with Edison sockets would not make the sleeve live.

[Electro Detective]

I check all equipment current draws, correct fusing and IEC cords etc, I even check the checkers! Who needs drama? 

FWIW I've seen dumbass assembly practices and wiring snafus from back in the day, local and international,

wayyy before China began their monopoly on electronics (and everything else)


i.e. blame yourself for not checking, especially if buying CHEAP

oh, and if it's the wrong fuse value, don't lose sleep if it's on the wrong leg,
the BBQ will happen, regardless of the weather 
 

 

[jonpaul]

Hello: Reversal of Neut/Grd/Hot is a potentially lethal fault/


I would inform the supplier /Amazon/Ebay of the violation and ask for the seller be banned.

As good practice, We use only USA made IEC power cables eg from HP/TEK/GenRad.
 
All junk from  Commie China CAN NEVER BE  trusted especially for compliance or safety.

But you can be sure the ChiComms use the least effort/quality/performance/compliance.

Jon

[Gyro]

"L" stands for "Live" not "load", where "L" means the same as "hot".
The location of L & N on the wall socket & plug are normally a "mirror image", not the same.

The pinout on that end of an "IEC" cord which plugs into the equipment should be the same as the wall socket.

For accuracy rather than nitpicking, L stands for Line, not Live [EDIT: Only for UK/EU apparently, not Oz]. Hence you have Line and Neutral (Line is still live / hot of course).


P.S. I believe the North American equivalent is Phase and Neutral, (or Phase and Phase for 230V outlets) but I might be wrong there.

[vk6zgo]

"L" stands for "Live" not "load", where "L" means the same as "hot".
The location of L & N on the wall socket & plug are normally a "mirror image", not the same.

The pinout on that end of an "IEC" cord which plugs into the equipment should be the same as the wall socket.

For accuracy rather than nitpicking, L stands for Line, not Live. Hence you have Line and Neutral (Line is still live / hot of course).


P.S. I believe the North American equivalent is Phase and Neutral, but I might be wrong there.

Nope, in Oz, it's "Live". "Potatoes, potartoes" sort of thing!

[Gyro]

Don't worry, you'll catch up.

[MrAl]

Nobody answered the question of if they were UL approved or not, or at least had that marking on the product somewhere.

This would tell us if they did not obtain a rating or if they faked it.  Either way would be bad but would be interesting to know.
If they did not obtain a rating then we know what the story is.
If they did fake a rating then we know that they do this now so any of the companies may do that too, so all have to be checked.
Now that i think about it though i think i will check all mine too and all new ones that i get.

[jonpaul]

The Chinese have no ehtics, copy anything to make money,  including trademarked safety symbols, CE, UL, VDE, TUV.

Nothing printed or claimed on a Chinese product has any credence including  safety/PFC/EMI  regulation or compliance testing.

 Jon