can i detect if the hot and neutral lines reversed?

sdowney717

Joined Jul 18, 2012
648
Maybe American outlets do. Here in the Netherlands our outlets are not polarized.
For many decades they have been physically polarized, so it is impossible to plug them in the wrong way. Some electrical devices do not have a polarized plug, likely cause with them it does not matter or they are old.

My boat has a polarized twist lock 30 amp plug, can only plug in one way. Then on the neutral wire are small neon lamp connected to ground, if it lights up, you know the polarity is reversed.
https://en.wikipedia.org/wiki/NEMA_connector
 

panic mode

Joined Oct 10, 2011
1,868
For many decades they have been physically polarized, so it is impossible to plug them in the wrong way.
As stated before, that is the case in SOME countries (such as USA). This is NOT the case in many European countries (drawing shows 230V single phase).

Btw. I find European plugs/receptacles way nicer than North American. Same goes for terminals (Marrets are just crap).
 
As stated before, that is the case in SOME countries (such as USA). This is NOT the case in many European countries (drawing shows 230V single phase).

Btw. I find European plugs/receptacles way nicer than North American. Same goes for terminals (Marrets are just crap).
Off topic: Definitely agree that our connectors are better. Same goes for our voltage system. (3 phase 380v, phase to neutral 230v)
 

cmartinez

Joined Jan 17, 2007
7,243
I'd rather be connected across 110V than 230V :eek:
Down here we have 110 VAC, but some engineers have the opinion that that level of voltage will "freeze" and electrocute you more easily than 220VAC. This because 220VAC will shock you so hard that your body will be jerked and launched away from the source... but maybe that's just an urban legend... I've never been electrocuted before, luckily.
 

MrAl

Joined Jun 17, 2014
7,961
Hi,

I would rather have 230vac than 120vac because the wire size for 230vac can be smaller for more power delivery. At 120vac we use #12 AWG wire for normal 20 amps circuits and that amounts to a max of 2400 watts, but at 230vac that same wire would deliver 4600 watts. That is very significant. That would fix a lot of problems we have with the grid in parts of the USA if the generators could handle the power because current draw lowers the voltage due to long wire resistances.
#14 AWG wire (not used anymore i dont think) in older houses is good for 15 amps normally, and so that limits the 120vac system to 1800 watts where in the 230vac system it would be 3450 watts. That's almost double the power.
 

AlbertHall

Joined Jun 4, 2014
10,904
Down here we have 110 VAC, but some engineers have the opinion that that level of voltage will "freeze" and electrocute you more easily than 220VAC. This because 220VAC will shock you so hard that your body will be jerked and launched away from the source... but maybe that's just an urban legend... I've never been electrocuted before, luckily.
In my case it just meant that I couldn't let go...
I still have the burn scars on my fingers - but I did survive.
 
What always mixes me up is which 'prong' is the hot, the wider one or the more narrow one.
The smaller one makes sense for hot. Now is it the left or right one? Depends if you mount it ground prong up (the industrial way) or down (the pretty way). With the ground prong up, a sheet of metal would have a harder time shorting N and H. The "pretty way" looks like a face.

Now the ( blue or brown) to (white or black) relationship, I have a hard time with.
 

WBahn

Joined Mar 31, 2012
26,398
What always mixes me up is which 'prong' is the hot, the wider one or the more narrow one.
Think of which situation you would more likely want to avoid.

Connecting the power input to a piece of equipment to the neutral because you can insert a narrow power prong into a wide neutral socket, or connecting the chassis of a piece of equipment to the live wire because you can insert a narrow neutral prong into a wide hot socket.
 

MaxHeadRoom

Joined Jul 18, 2013
22,341
The smaller one makes sense for hot. Now is it the left or right one? Depends if you mount it ground prong up (the industrial way) or down (the pretty way). With the ground prong up, a sheet of metal would have a harder time shorting N and H. The "pretty way" looks like a face.

Now the ( blue or brown) to (white or black) relationship, I have a hard time with.
The original method/theory was to wire the GND pin at the bottom on the thinking that if the plug were to 'sag' down, the last pin out would be the Earth pin.
Then a case came up where a waitress in a restaurant dropped a metal tray down a wall where the plug had drooped slightly and the tray hit the L & N pins causing a flash a gave here a serious shock, so after that the recommendation was to place the GND pin at the top.

Two 120v sockets.
Max.
upload_2018-7-31_12-38-18.jpeg
 

AlbertHall

Joined Jun 4, 2014
10,904
The smaller one makes sense for hot. Now is it the left or right one? Depends if you mount it ground prong up (the industrial way) or down (the pretty way). With the ground prong up, a sheet of metal would have a harder time shorting N and H. The "pretty way" looks like a face.

Now the ( blue or brown) to (white or black) relationship, I have a hard time with.
UK used to have red-live, black-neutral, and green-earth.
In my first job I was to repair an instrument which had no plug on the mains cable and wasn't one we had seen before.
The mains cable was red/black/green but as the instrument was German I decided to check, not make the obvious guess, and it is just as well I did as the red wire was connected to the chassis.
 

MrAl

Joined Jun 17, 2014
7,961
The smaller one makes sense for hot. Now is it the left or right one? Depends if you mount it ground prong up (the industrial way) or down (the pretty way). With the ground prong up, a sheet of metal would have a harder time shorting N and H. The "pretty way" looks like a face.

Now the ( blue or brown) to (white or black) relationship, I have a hard time with.
Hi,

Yes left and right are tricky too. I try to go by the size narrow or wide so i dont make a mistake because of handedness. I dont have to wire this kind of thing up that much though so i tend to forget over time. I look it up on the net and see that some sites show it incorrectly.
 

sdowney717

Joined Jul 18, 2012
648
The original method/theory was to wire the GND pin at the bottom on the thinking that if the plug were to 'sag' down, the last pin out would be the Earth pin.
Then a case came up where a waitress in a restaurant dropped a metal tray down a wall where the plug had drooped slightly and the tray hit the L & N pins causing a flash a gave here a serious shock, so after that the recommendation was to place the GND pin at the top.

Two 120v sockets.
Max.
View attachment 157298
looks like a sad face on the left, and angry face on the right, LOL.

Local hospital where I used to work mounted them all ground up saying they are safer.
 

MrAl

Joined Jun 17, 2014
7,961
Think of which situation you would more likely want to avoid.

Connecting the power input to a piece of equipment to the neutral because you can insert a narrow power prong into a wide neutral socket, or connecting the chassis of a piece of equipment to the live wire because you can insert a narrow neutral prong into a wide hot socket.
Hi,

Yes and i gather you are implying that a larger item is harder to stick into a smaller hole so the universe of objects that can fit into the narrow hole is smaller than the universe of objects that can fit into the larger hole thus making the smaller hole voltage potential less likely to be accidentally connected to thus making it safer to use the smaller hole as the 'hot'. I think i might remember this now because of your way of looking at it.
In the past, i kept forgetting which is which and what made it worse was i looked on some web sites and found them to be incorrectly showing the connections (backwards). That was not nice to see.
I also got mixed up thinking sometimes that the larger hole or prong could carry more current so it should be 'hot'. As we know though that is not right. Perhaps to avoid that we could imagine that it would not matter if could carry more current or not because the current has to be equal in both hot and neutral wires.
 
`All 100% true the NET is always right isn't true here. In an Explorer's Post at HP (Hewlett-Packard) I wa sin my teens and knew which wire should go to the middle of a glass fuseholder. My mentor didn't.

The three prong line cords don't have the wide blades when 3 prongs are present. What about the guys that cut the third prong off. Fortunately, I don;t see any non-polarized duplex outlets anywhere, but I do have some (unconnected ones) at home.

Many a times, I would grab a line cord, orient it as though I was plugging it in and take a meter to figure out whether or not brown or blue was hot or neutral. I still haven't learned.

When RED became ALWAYS NEGATIVE and I didn;t know any better, you learn. In the thermocouple world RED is negative. Then with copper tubing fittings, a 7/8 elbow is a 3/4 elbow. Same exact fitting. Just depends on where you buy it.

The last annoying thing I ran into was that a machinist measures flat head (overall length) and pan head (thread length) screws differently. In another discipline (eyeglasses) all screws are measure OAL.
 

MaxHeadRoom

Joined Jul 18, 2013
22,341
Perhaps to avoid that we could imagine that it would not matter if could carry more current or not because the current has to be equal in both hot and neutral wires.
One 'Slight' exception was when the regulation for kitchen duplex outlets were required for each to be wired across 240v, IOW top one L1 & N, bottom L2 & N.
Because each Live is out of phase to each other a single N was allowed, in this case IF the load on each were equal the N current is Zero!
Max.
 

WBahn

Joined Mar 31, 2012
26,398
One 'Slight' exception was when the regulation for kitchen duplex outlets were required for each to be wired across 240v, IOW top one L1 & N, bottom L2 & N.
Because each Live is out of phase to each other a single N was allowed, in this case IF the load on each were equal the N current is Zero!
Max.
I wonder, in the age of highly non-linear loads, is it now possible for the neutral current in such an arrangement to actually be greater than either of the live wires?

Or even with linear loads, what about if one is capacitive and the other is inductive? I wonder if the standard allowed for that possibility, or chose to discount it because of the unlikelihood of its occurrence in such a way as to be an issue.
 

ebp

Joined Feb 8, 2018
2,332
Neutral current became something of an instant huge problem in commercial buildings a few decades back when offices rather suddenly filled up with electronic equipment. It tended to be blamed on computers with switch mode power supplies, but the reality was that anything that ran on DC was just as bad. With rectified and capacitively-filtered supplies, virtually 100% of the sum of the phase currents in 3-phase installations is returned via the neutral. There just isn't any cancellation at all, instead neutral gets six "pulses" of current of high RMS-to-average ratio, all nicely spaced 60 degrees apart. At the same time, the total loads often were increased simply because more things were being plugged in. A computer and a monitor replaced a Selectric typewriter. Photocopiers and laser printers displaced supplies cabinets. Family photos on executives' desk got shoved aside to accommodate monitors and computers furiously running NO-OPs. Neutral conductors with melted insulation sometimes resulted.

Active power factor correction has improved matters, but still is not that widely used in North America, especially in the multitude of low power switchers that abound.

Compact fluorescent lamps with built-in electronics had terrible power factor. Some of the newer LED lamp power supplies have good power factor - if the lamp is narrow voltage range and dimmable, the PF (no, not the Procurator Fiscal) is probably good. Wide input range non-dimmable lamps often have simple flyback drivers with bad PF.
 

MaxHeadRoom

Joined Jul 18, 2013
22,341
The Province power supplier here recently offered a 1 day seminar on the current problem of electronic equipment responsible for poor power factor and the means and ways to correct it, very interesting.
Max.
 
We had 36 Air to water heat pumps in our building. They did decide to put in active power factor correction. Auto switchable capacitor bank.

When I went to a IEEE lecture, some interesting parts were that a solar plant can be used for local power factor correction mostly and each source of power has its own strengths and weaknesses. So, nuclear is hard to throttle. Hydro is just as bad. Wind is totally wierd because you never know when your gonna get it. Solar helps meet peek demand. Natural gas is very easy to throttle. I forget what they had to say about coal.

So, inverter based plants can do a lot more with respect to power factor correction at the "local grid" level.
 
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