Mains converter to 110V outputs 220V at neutral-earth?

[German_EE]

Out of curiosity I have been doing some investigating and found the following in our apartment electrical system:

1) Apart from the cooker (three phase) every wall socket is a standard CEE 7/4 device with the live connection on the right. I believe this to be intentional.

2) If a right angled CEE 7/4 plug is inserted with the lead going downwards then the brown lead is connected to live and the blue lead is connected to neutral. The only exception to this was a Chinese made toaster where plugging in with the lead downwards made blue 'live' and I have replaced the power lead. Straight CEE 7/4 plugs have been marked so that the live connection goes to the brown wire.

3) Double insulated appliances can be connected either way and they all have a two pin power plug. Some also have a reversible plug at the other end of the cable but where the power lead is hard-wired I have marked the plug so that the brown and blue wires are correctly energized.

The lesson learned is that most European EEVBlog readers need to be careful when connecting mains powered devices to their supply.

[Monkeh]

Out of curiosity I have been doing some investigating and found the following in our apartment electrical system:

1) Apart from the cooker (three phase) every wall socket is a standard CEE 7/4 device with the live connection on the right. I believe this to be intentional.

It is.

2) If a right angled CEE 7/4 plug is inserted with the lead going downwards then the brown lead is connected to live and the blue lead is connected to neutral. The only exception to this was a Chinese made toaster where plugging in with the lead downwards made blue 'live' and I have replaced the power lead. Straight CEE 7/4 plugs have been marked so that the live connection goes to the brown wire.

3) Double insulated appliances can be connected either way and they all have a two pin power plug. Some also have a reversible plug at the other end of the cable but where the power lead is hard-wired I have marked the plug so that the brown and blue wires are correctly energized.

... Why bother?

[German_EE]

In most cases so that switching is on the live lead.

[Kjelt]

2) If a right angled CEE 7/4 plug is inserted with the lead going downwards then the brown lead is connected to live and the blue lead is connected to neutral.

And how about that second right angled plug in a double socket? That is going to be wrong then 

[Monkeh]

In most cases so that switching is on the live lead.

If it's inside equipment, it just doesn't matter. Unless the equipment for some reason cares, in which case it would have been designed to ensure polarity.

[Richard Crowley]

If it's inside equipment, it just doesn't matter. Unless the equipment for some reason cares, in which case it would have been designed to ensure polarity.

So how do you "ensure polarity" if your country uses symmetrical plugs and indeterminate wiring standards?

[Monkeh]

If it's inside equipment, it just doesn't matter. Unless the equipment for some reason cares, in which case it would have been designed to ensure polarity.

So how do you "ensure polarity" if your country uses symmetrical plugs and indeterminate wiring standards?

You use a polarized plug or hard-wire it.

[Kjelt]

So how do you "ensure polarity" if your country uses symmetrical plugs and indeterminate wiring standards?

You do not. You make sure for instance that with a mains switch inside equipment you always switch both connections to the mains.
Even in our country (netherlands that is) the utilityboard (entrance of electricity to the house) with it's automatic fuses and GFCI's have to switch both poles, so also neutral.
Not all countries are so rigid (germany does not have this for instance).
Most (80%) equipment is double isolated any way, only the washingmachines, dishwasher, fridge etc are not and those need a ground connection for safety.

[Monkeh]

So how do you "ensure polarity" if your country uses symmetrical plugs and indeterminate wiring standards?

You do not. You make sure for instance that with a mains switch inside equipment you always switch both connections to the mains.

No, you don't. There's actually no reason to.

Even in our country (netherlands that is) the utilityboard (entrance of electricity to the house) with it's automatic fuses and GFCI's have to switch both poles, so also neutral.

That has no relevance to switching in an appliance.

[lpc32]

BTW, with the input flipped the neutral is as it should be, but curiously it's 0.13V and not ~0V like the wall. Why might that be?

[Richard Crowley]

BTW, with the input flipped the neutral is as it should be, but curiously it's 0.13V and not ~0V like the wall. Why might that be?

That's not unusual. There are several factors that could be causing that. But unless it is caused by an open circuit, it is nothing to be concerned about.

[lpc32]

I'm curious what causes it, since it's more or less straight through. Not a concern, just knowledge.

[Richard Crowley]

First of all, the measurement of "0V" at the wall is arbitrary by itself.  Relative to WHAT?  There are no perfect ground systems. They all have some amount of series resistance and "source-impedance". Even the crust of the earth itself has "series resistance".

Furthermore, modern meters have rather high impedances, so they can be measuring induced voltages that are "imaginary" in the sense that they are effectively zero when connected to Real World circuits.  And some of the imaginary voltage could be coming from induced signals from adjacent wires (the hot and neutral wires in the power cord), etc. etc.

[lpc32]

Why doesn't it happen (as much) in wall sockets?

[Richard Crowley]

Why doesn't it happen (as much) in wall sockets?

Sorry, I don't understand the question.

[lpc32]

Why no/less induced voltages when measuring directly at the wall?

[Richard Crowley]

Without knowing HOW you are measuring this, it is impossible to attempt any explanation.
When you say that it is 0 volts "at the wall" what does that mean, exactly?  "0 volts" relative to what exactly?
When you say "0.13V" what are you measuring it against?  Under what conditions?

[lpc32]

Neutral-to-Earth measured with a DMM, nothing else connected, at the wall outlet (0V) and the 110V converter output outlet (0.13V). The path through the converter includes a 2m cord, switch, fuse, transformer, socket.

[Richard Crowley]

"Neutral" could very easily be volts above "ground" because of current being drawn by OTHER loads on the same branch circuit.
It gets very tricky when you try to measure these things, there are dozens of factors that must be established in order to understand what you are seeing.

[lpc32]

The 0V "direct from wall" measurement was on the same outlet the converter was connected to when it showed 0.13V (not at the same time). The results were similar on a different wall outlet on another circuit.

[Richard Crowley]

Sorry, apparently I am not communicating clearly here.

When you say you are measuring "0 volts" at some particular point (perhaps a ground pin on a wall outlet), you are presumably probing that point with one side of your DMM.  OK.  That's fine.

But where are you placing the OTHER side of your DMM?  In other words, when you say that point is "0 volts" what are you measuring it AGAINST?  Or to put it another way what is your REFERENCE or DEFINITION for '0 volts"  or "ground"?

In modern building mains wiring schemes, the only point that you can legitimately call "ground" is the big terminal strip where all the green wires connect inside the circuit breaker box.  In most domestic installations in North America (the 115V territories), it is at that ONE point where the green-wire "ground" and the white-wire "neutral" actually connect together.  Everything else is a far extention out from that definitive spot. And there are any number of things that can cause the actual voltage out at the far ends of the branch circuits to deviate from "0 volts" or "ground".

In the photo below, there is a large silver-color terminal block where the white (neutral) and green (safety ground) wires all terminate....

[vk6zgo]

So how do you "ensure polarity" if your country uses symmetrical plugs and indeterminate wiring standards?

You do not. You make sure for instance that with a mains switch inside equipment you always switch both connections to the mains.

No, you don't. There's actually no reason to.

Even in our country (netherlands that is) the utilityboard (entrance of electricity to the house) with it's automatic fuses and GFCI's have to switch both poles, so also neutral.

That has no relevance to switching in an appliance.

Some often used appliances do offer the possibility of contact with exposed Mains .

My daughter received a shock from a Toaster,which had three bad design features.

(1) The element reached up too close to the top of the bread slot.
(2) When it was not in use,but still plugged in,one side of the Mains was still connected to the element.
(3)The power lead was wired with the Active & Neutral inverted.
(In Australia,you can't reverse the plug in the socket,& pin allocation at the power socket is mandated by law)

All would still have been well if the internal switch which opens when the toast pops up had been DPST,instead of SPST,which would have eliminated (2)

In this case,the switch only opened the Neutral line,so no matter how the element was wired,the shock hazard remained.

By the way,she didn't stick a fork into the Toaster,she just reached over the top off it & obviously part of her arm just touched the element (1).

She has a little "El Cheapo" Toaster,but bought this new one because it could toast bigger slices.
On testing,I found that the cheap one did have a DPST switch,so it was put back into service.

[Kjelt]

In the photo below

OMG what a mess! 

[miguelvp]

In the photo below

OMG what a mess! 

You are more than welcome to show us your non messy fuse box

[Kjelt]

Will do when I have time, here it is normal that the inlets are positioned below and then through mains switch and RCD's to the fuses up to all the seperate groups.
Newer systems have bridges where you can bridge the neutral to more fuses so you do not need so many wires, older have more wires but still since it goes from bottom to top it is IMO more clear then the box above.
So they look something like this: