One for Loring!

[RodKirby]

I have an idiot acquaintance (I guess we all have at least one) and he wanted to argue (for no particular reason), that "It doesn't matter if you swap the active and neutral wires"

Some Oz facts:
Normal power supply 240V 50Hz.
Other than changing plugs it MUST be a qualified Electrician to do electrical work.
ALL plugs, sockets, power boards CLEARLY indicate the "active" connection - red or blue wire. "Neutral" is always black. Earth is green or green/white striped.

Whenever I do anything to plugs, sockets (powerboards - don't tell!), I have a tester which will indicate if I've messed up.

My question:

Why should the active/neutral be connected "properly"? My googling just made things more confusing. Some answers said "doesn't matter", others said "it does matter" but no specific reason. Some answers seemed to indicate that the active connection is earthed but the neutral is not.

Please help

[Pappy]

Reverse the wires on a table lamp then touch the metal sleeve around the socket. The answer will be shockingly apparent.....

[LCHIEN]

actually its been an issue at work recently.
Most power systems in the world be they 110/120VAC or 220/240V have nuetral at or near ground (grounded in the Breaker box) and a hot wire which carries the voltage.

In such a system usually the hot side is fused or circuit-breakered and the power switch is on the hot side. In other words all the power interrupting portions are on the hot side.

Functionally the equipment and the power switch will work when the power is reversed and the neutral side is interrupted. However, this has the disadvantage of leaving the majority of the components on the hot side and thus energized with the mains voltage - anyone touching any parts inside and earth/ground simultaneously will be shocked, even though significant current is blocked by the interrupting devices.

Conversely in a properly interrupted system (switches, fuses on the Hot side) all the components of the equipment (except the switch and fuse which are generally very limited to the power inlet point) will be grounded- no shock potential.

in the US mostly hot is black (terminals are brass), white is neutral (terminals are silver). In Europe hot is brown, neutral is light blue. THis is the first I've heard of, but can see thorough world confusion if Australia is red or blue=hot and black =neutral.

Anyway, Reversed sockets are quite a common ocurrence. I estimate from experience if there's 2 ways things can be connected and only one is correct and there's no special provision for making sure it can fit only one way other than color coding that around 1% of such connections will be reversed by workers with normal attentiveness.


Maybe the attached graphic will help...

some advice that may help you deal with this fool, two things i have learned:
1 Never try to teach a pig to sing. It wastes your time and annoys the pig.
2 Never argue with a fool. He'll bring you down to his level and then beat you with experience.

I hope i have lived up to your expectations, Rod.

[woodturner]

THis is the first I've heard of, but can see thorough world confusion if Australia is red or blue=hot and black =neutral.

I'm not specifically familiar with the Australian power system either, but from the OP it appears he meant two "hots" with no neutral - i.e. no 120 VAC power.

If that is the case, I would assume and hope that the "hot" he called the neutral is grounded. As you note, the appliance doesn't care, it's a safety issue.

[LCHIEN]

Some 220V distribution - the US residential for example, utilize what we call L1 and L2 without a grounded neutral. I call it split phase maybe, where L1 is 110V above neutral/Earth/Ground and L2 is also 110 V above Neutral/Earth/ground but of opposite phase. THose who understand transformers will not this uses a center tapped transformer and L1 /N and L2/N would be hots for two 110V-grounded neutral branch circuits.

This would seem to suggest using two ganged circuit interrupters for split phase L1/L2 220V equipment in the US. It is actually the case, most breaker boxes furnishing 220V to residential branch circuits like ovens, clothes dryers, stoves, and HVAC have ganged breakers that will physically trip both sides if either trips due to current.

[RAFlorida]

The reason for a "correct" wiring is

safety. As Loring points out, here in the States, White is neutral, green equals grounded, and black is hot relevant to ground or neutral. If we all follow this system, we'll have less surprises.
(It does get more complicated though; Gray is the neutral for a 277 lighting system.)
Surfice it to heed Lorings post.

[woodturner]

Some 220V distribution - the US residential for example, utilize what we call L1 and L2 without a grounded neutral. I call it split phase maybe, where L1 is 110V above neutral/Earth/Ground and L2 is also 110 V above Neutral/Earth/ground but of opposite phase.

Agreed, the two-phase center-tapped transformer is the norm for residential power in the US.

I infer from the OPs post, though, that they are using no center-tap, so they would have 240 VAC between the "hot" and the "neutral". That's what I meant when I speculated that they ground one "hot", since there is no neutral.

If that assumption is correct, their color code is consistent with ours, sort of. The "neutral" would be black because it is really a "hot" - but if they ground it, it becomes a neutral.

Decided to search for information rather than speculating:

This IEEE link has connector information
http://www.ewh.ieee.org/r10/nsw/subp...connectors.pdf

This site suggests the 240 VAC is a single phase derived from 3 phase:
http://www.physicsforums.com/archive.../t-128535.html

So, assuming that link is accurate, they could use a center-tap transformer to get two phases as we do, but the voltage per phase would be 240 VAC.

In other words, they are wiring their 240 V circuits like we wire 120 V circuits, so the one "hot" is in fact the neutral.

[RodKirby]

actually its been an issue at work recently.
Most power systems in the world be they 110/120VAC or 220/240V have nuetral at or near ground (grounded in the Breaker box) and a hot wire which carries the voltage.

In such a system usually the hot side is fused or circuit-breakered and the power switch is on the hot side. In other words all the power interrupting portions are on the hot side.

Functionally the equipment and the power switch will work when the power is reversed and the neutral side is interrupted. However, this has the disadvantage of leaving the majority of the components on the hot side and thus energized with the mains voltage - anyone touching any parts inside and earth/ground simultaneously will be shocked, even though significant current is blocked by the interrupting devices.

Conversely in a properly interrupted system (switches, fuses on the Hot side) all the components of the equipment (except the switch and fuse which are generally very limited to the power inlet point) will be grounded- no shock potential.

in the US mostly hot is black (terminals are brass), white is neutral (terminals are silver). In Europe hot is brown, neutral is light blue. THis is the first I've heard of, but can see thorough world confusion if Australia is red or blue=hot and black =neutral.

Anyway, Reversed sockets are quite a common ocurrence. I estimate from experience if there's 2 ways things can be connected and only one is correct and there's no special provision for making sure it can fit only one way other than color coding that around 1% of such connections will be reversed by workers with normal attentiveness.


Maybe the attached graphic will help...

some advice that may help you deal with this fool, two things i have learned:
1 Never try to teach a pig to sing. It wastes your time and annoys the pig.
2 Never argue with a fool. He'll bring you down to his level and then beat you with experience.

I hope i have lived up to your expectations, Rod.

Many thanks, Loring

And to others for their notes.

[LCHIEN]

Agreed, the two-phase center-tapped transformer is the norm for residential power in the US.

...

In other words, they are wiring their 240 V circuits like we wire 120 V circuits, so the one "hot" is in fact the neutral.

That is correct, that is the model I was discussing. In my diagram 110 or 220V labels would be interchangeable when discussing US vs Aussie wiring.