Determining Proper A/C Polarity

Sure there is polarity in your AC, one pin is phase, the other return. Around here in germany, the electrical Schuko-plug/outlet system does not determine, which is which, so electrical equipment is supposed to assume both pins could be phase/hot (in the middle is earth as a third line for safety reasons). Therefore e.g. BOTH poles have to be switched by a device's on/off power switch (SHOULD, but obviously, just switching one pole is cheaper, so.....you understand the difference, if phase/hot is connected to the whole circuit or not?). E.g., you could touch the cold line without any harm, not so the hot pole...
It becomes interesting, if you count in grounding into equation and actually, there is a difference in some audio gear and you actually get lower noise floor when connecting one way, but not the other.
This is actually not something a manufacturer intended as a feature when it happens. It is a design flaw at the end.

There is a correct way. Every electrical permit issued is done so by a qualified electrical inspector and inspected by another qualified inspector. Your electrician/ contractor who hooks everything up went to school and learned how to do this VERY basic thing. There are brass and white metal lugs on each outlet specifying which is hot and which is return line. It is nearly impossible to eff up and there are three LICENSED qualified technicians who are involved.

Only someone without a clue doing your wiring as a DYI project could possibly screw it up. It is really that basic.

Simple test:[/b]
If you plug a lamp with a dimmer switch into an outlet, using a dimmable florescent bulb, it won't work properly if the wiring is backwards. If it's wired correctly, no problems.

Ok, lemme set some things straight in case of confusion..

In the USA we have a "polarized" plug/socket system for our AC power. This means the physical orientation of the plug into the socket, not the polarity of the power. The polarity of the plug/socket is so that the devices that have only a single fuse and/or power switch will always have the fuse/power switch on the "Line" side. Line is sometimes referred to as "Hot".

USA:
Line/Hot/Phase = Current source
Neutral = Current return
Ground = Safety ground

Secondly, in the USA we also have "Neutral" and "Ground" conductors in our AC wiring. Neutral is the current return for the Line power. Ground is ONLY for safety and should not be used for current return. Neutral and ground are tied together and earth grounded at the fuse/circuit breaker panel and will be a relatively similar voltage. However, since current and resistance are different on different conductors, you WILL have slightly different voltages on Neutral and Ground and this is not a problem unless it's caused by poor ground bonding.

Thirdly, and most importantly for the discussion of audio gear is that most power systems in audio gear don't care if your Line and Neutral are backwards, aside from the safety aspect.

A power transformer doesn't care what primary conductors your Line and Neutral inputs are attached to. The bridge rectifier on the output of the power transformer doesn't care either.  The transformers are never marked for signal "polarity".  Bridge rectifiers only have ~ ~ symbols for the AC inputs because at that point the AC is now completely differential in nature and not referenced to ground.

A SMPS power supply doesn't care either since the Line and Neutral are rectified immediately and usually isolated from the rest of the circuit.

If the article were confused and talking about mixing up Ground and Neutral, you have a recipe for disaster anyway.

As for your wiring in NZ, a quick search shows a similar single phase approach but using 220VAC/50HZ.  

You'd think it'd be hard to mess up hot and neutral..

When renovating my house after I bought it, I wanted to remove a ceiling fan, paint the ceiling and then put up a light fixture instead..

Turning the switch off on the wall should be sufficient to cut the power to the fan, no?

When I reached up to grab the base of the unit, I got a tickle..

Turns out they wired the fan backwards and the chassis was connected to HOT.  But about that switch..

Turns out they also hooked into an outlet on the wall and hooked up the hot and neutral backwards so the switch was on neutral.  Looks like they sprayed the walls white and the wires were all white with paint, so you couldn't even tell which one was which, ground not connected, etc.  

Lets just say that the house was full of these kinds of issues.  I'm pretty surprised it didn't burn down at some point in time before I fixed all the wiring.

NEVER EVER do work on a fixture without turning off the breaker  (unless is an ICU and you are not allowed to turn the feed off) Regardless of the switch position you will most likely still have an active feed looping thru the roof from fixture to fixture even when the switch is off your fixture still has power on the active side.

Interesting.  None of the dozen houses I've worked on for myself, family or friends built from the 60's to the 90's have been bonded at the meter, only in the breaker box like such:





However, I do see the code that says "service disconnect".  I suppose at some point the code was changed.