IEC plug/socket... live vs neutral?

[KL27x]

I have 2 power cords. They plug into the 110 mains socket on one end. They have a IEC 320 C14 looking plug on the other end. The kind that goes into a 3 prong socket like you find on a monitor or computer psu, etc.

The live and neutral are wired opposite to each other on these cords. 

The only reason I noticed is because I am wiring up a transformer to an IEC socket. I picked up the nearest power cord to figure out which pin of the socket I should fuse. Later, I am testing the transformer and I notice I have it backwards. Then I see I'm using a different cord. And I find out the cords are wired differently.

Is there a standard? If so, which one do I throw out?

[Zbig]

I will evade the question by expressing my opinion that if your equipement is not live/neutral "agnostic", it's not designed properly. For instance, that's the kind of mains socket prevalent throughout many parts of Europe:



The live/neutral assignment ("polarity" if you will) depends on whether you stick the plug into the upper or the lower socket.

[KL27x]

Sure. Double-insulation and all. But if the cords are not manufactured the same way, that's just insanity. Maybe I have cords from different countries with different standards?

It bothers me because. If I wanted polarity to be random, I'd make the plug so it can be flipped. The earth pin could be directly in the middle, or what not. Then the plug could go in either way, like a figure 8 plug/socket. If it can go in just one way, it should be wired the same way every time, for sake of order, if nothing more.

[alm]

This site lists a pin-out. I am sure you could find the definite reference in IEC 60320 if you feel like paying the fees or can find a copy somewhere. Do you not have a box with a dozen of these that you could measure to figure out if there is a consistent polarity?

[magnusbh]

Hi, you have to remeber that there is no guarantee for how the wires are connected inside the wall, the only guarantee is the GND. Live and neutral has no standard in the mains socket that you could trust (even if some manufactures mark them with "N" and "L".

BR
Magnus

[drussell]

Egads!  I had no idea there were places in the world where it was random!

Certainly here in North America it is controlled (well, at least since the 1950s-60s)...  The small blade is the hot, large blade is the neutral and even simple appliances or things like lamps are wired to switch the hot so that the socket and the base of the bulb is not live when the power switch is off!

Sure, you see the occasional wall plug where they were wired backwards by someone who didn't know what the were doing... (always a dead giveaway and to me always means check every damn outlet in the house!)

For the IEC connector end, it should be like this:



If you find a cord that is wired incorrectly, I would chop it in half and discard it immediately!  I suppose if it seems to be reasonable quality (doubtful if they didn't even get the wiring polarity correct!) you could keep whichever end was wired with the proper colors. 

P.S. Zbig, are you sure that plug you show doesn't swap the terminals internally?  It seems insane to me that it wouldn't be properly marked and consistent!

[Ranayna]

Well, the plugs here in Germany definetly are not polarized:

[alm]

Given that most of the plugs that fit in the socket Zbig posted will also fit a German Schuko socket which is non-polarized, I could see how the designers of the socket might not worry too much about consistent polarization.

[drussell]

Yeah, I'm shocked!   

I just looked it up and, yeah, sure enough the Schuko and Europlug styles do not specify a line vs neutral.  Crazy! 

The giant UK style ones are specified, as are the Australian style but not the rest of Europe, apparently!  Well, well...  You learn something new every day! 

[Nusa]

This is one of those cases where not showing a country tag will affect the relevancy of the answers to the question.

[drussell]

This is one of those cases where not showing a country tag will affect the relevancy of the answers to the question.

Indeed!

I made the assumption that we were talking about North America, though, when KL27x said:

I have 2 power cords. They plug into the 110 mains socket on one end.

As an aside, I like the way the Badcaps forum has a "mains voltage and frequency" field for user profiles.

[glarsson]

I just looked it up and, yeah, sure enough the Schuko and Europlug styles do not specify a line vs neutral.  Crazy!

In my view this is a safety feature. If the safety of a lightbulb depends on all parts connecting the line and neutral correctly then the safety is easily compromised. Better to build the safety of devices without knowledge on how line and neutral are connected.

[ejeffrey]

Yeah, it is crazy.  For most applications it shouldn't matter -- grounded and double insulated appliances should treat the live and neutral equivalently.  Old appliances that connect neutral to the frame (!) or are not double insulated by designed so that a single fault connects the neutral to the frame are really obsolete.  But there are still cases out there such as Edison light sockets and exposed heating elements in toasters where putting the less dangerous terminal towards the user makes sense, and lack of consistent polarization of outlets is not really what you want.  But in most of Europe that is what you have.

Worse yet, the shucko and similar plugs are designed so that they will mate with non-grounded outlets, which are common and AFAIK, actually still code compliant in some European countries for new residential wiring in dry rooms.  This is total madness, and compared to that, the polarized plug thing is a minor detail.

[ejeffrey]

I just looked it up and, yeah, sure enough the Schuko and Europlug styles do not specify a line vs neutral.  Crazy!

In my view this is a safety feature. If the safety of a lightbulb depends on all parts connecting the line and neutral correctly then the safety is easily compromised. Better to build the safety of devices without knowledge on how line and neutral are connected.

As long as you use Edison light sockets, that is impossible.  A major point of a polarized plug is that the outer shell of the lamp is supposed to be neutral, and the hot wire is recessed and much harder to accidentally contact.

[alm]

Fixed light sockets should be installed with neutral to the screw thread. And other lamps should be unplugged before changing the bulb. I agree that this is one of the (old) connectors where polarization would improve safety, but for any new design hot and neutral polarity should not affect safety. What if your device is used on a ship that might have both wires hot and no neutral?

As for the grounded plugs in ungrounded sockets, what else are you going to do with a large installed base of ungrounded sockets? Tell people they are not allowed to buy modern appliances? Replace the electrical systems everywhere? It would probably only slightly less painful than switching the US to 230 V/50 Hz.

[hermit]

For most applications it shouldn't matter

If it has an on/off switch it matters.  You switch the hot side so nothing is live on the other side.

[glarsson]

If it has an on/off switch it matters.  You switch the hot side so nothing is live on the other side.

No. The switch should switch both wires.

[alm]

You switch the hot side so nothing is live on the other side.

That is a dangerous assumption. You should always unplug something if you are going to service it. If you are not, what do you care that some wires inside the appliance are hot? It is not like any current is going to flow.

[hermit]

If it has an on/off switch it matters.  You switch the hot side so nothing is live on the other side.

No. The switch should switch both wires.

Well, you are free to implement what you want, but this isn't how it is done in the real world.  Neutral eventually ties back to Earth ground so if you switch it out you are disabling a potential safety.

[RGB255_0_0]

If it has an on/off switch it matters.  You switch the hot side so nothing is live on the other side.

No. The switch should switch both wires.

Well, you are free to implement what you want, but this isn't how it is done in the real world.  Neutral eventually ties back to Earth ground so if you switch it out you are disabling a potential safety.

Not always.

[hermit]

You switch the hot side so nothing is live on the other side.

That is a dangerous assumption. You should always unplug something if you are going to service it. If you are not, what do you care that some wires inside the appliance are hot? It is not like any current is going to flow.

I simply stated what is normally considered 'code'.  It has nothing to do with repair and everything to do with what can happen while it is sitting there doing nothing.  Having live current in an an otherwise idle device can do many things and probably most of them are bad.  That is why you switch the hot side.  If wired correctly the neutral side can act as Earth ground.  Which side would you switch?

[RGB255_0_0]

If wired correctly the neutral side can act as Earth ground.

[hermit]

Not always.

Not always WHAT?  Please not the use of the word "potential" in my post.  My job is not code enforcement but it is to know what the code is.

[hermit]

If wired correctly the neutral side can act as Earth ground.

Ah.  Now I get it.  Trolling.  I was there when the electrician installed my new panel.  I can assure you my neutral is correctly installed and is tied to ground.  If you want to ignore the totality of a posting please just ignore it all.

[Tepe]

Not always.

Not always WHAT?  Please not the use of the word "potential" in my post.  My job is not code enforcement but it is to know what the code is.

I guess the point was that the code differs with geography.