Dimmer switch wiring *peace of mind question*

[securespark]

yankey sparky

when I said effectively I meant that there is a connection from neutral through the lamp and down the switchwire when the light is off. If there was no neutral connection however you define it the neon would not light.

 

[sterose]

Sterose - that isn't actually how it works at all.

The voltage of the phase conductor relative to neutral alternates from +340V to -340V 50 times a second. At no point is the neutral at anything other than 0V.

Also there is no neutral in a light switch, be it a dimmer or a simple on-off.

And whilst a simple rheostat will work whichever way round you connect it, I remain unconvinced that the generic case of an electronic circuit would be the same, but if everybody is sure that you can connect the supply to the output of a dimmer and the load to the input and that it will work, then I will have to revise that opinion.

Again, there is a lack of knowledge of basic physics.

If the live is -240v then the neutral is +240v.

The reason we do not get shocked by the neutral, is because we arent touching the live.

This is in the same way as touching the live does nothing unless you are touching neutral (neutral is effectively earth, by the way).

Remember, electricity runs around a *circuit*.

 

[sterose]

Incidentally, this is why electric pylons only carry 3 or 6 live conductors, and 1 earth on top. Because the ground is used as neutral.

 

[hsiboy]

Although, technically speaking, a switchwire effectively becomes a neutral when the light is off (with lamp in situ).

I fear we're getting too far off topic here, but I cannot agree with this statement. The switchwire is at zero volts with respect to earth, true, but I will not call it a neutral because it is not a grounded conductor. (Earthed conductor? What's the UK term?)

This isn't just semantics, this lies at the very heart of what it means to be a neutral wire. It's not even "effectively" a neutral wire because of the fact that it is possible to raise it significantly above earth ground, which cannot be done with a true neutral conductor.

Ahem. in brit parlance it is called the neutral wire.
earth is earth, neutral is neutral no matter what your earthing system TT IT PME whatever.

Stuart.

 

[hsiboy]

I quite like this thread, some good stuff in here.

But lets not mess about with the laws of physics ok?

Phase line alternates between + and - with respect to neutral and earth. why? (i'm not asking, i want you to think about it)

Does the neutral line terminate at the star on the transformers windings (LV side)? which other point is also earthed?

which has less resistance, the cpc from the transformer to the cutout or the earth/dirt/ground? think about it.

In a PME what happens?

A dimmer will work any way around. why?

So will all electronic equipment, why?

Think about it. how many countries have two pin plugs that can go in either way.

Here in the uk, before double insulated circuits, we used to earth the chassis. How does the fuse blow if there is a short from live to the chassis?

Its beautifully simple, simply beautiful.

Bonus question. why do building sites in the uk use 100v supplies?

Stuart.

 

[securespark]

How about you put your ideas up??????????

 

[hsiboy]

How about you put your ideas up??????????

<sharp intake of breath>cost yah </sharp intake of breath>

Nope. better let them think about it.

i have had a good rummage in the past threads on here. and often a good piece of advice is shot down by a caustic remark or comment. This forum is about helping people, not scoring brownie points for the best smart alec reply is it not?

Although you wouldn't know it.

And this thread was a fine example.

Stuart.

 

[sterose]

I quite like this thread, some good stuff in here.

But lets not mess about with the laws of physics ok?

Phase line alternates between + and - with respect to neutral and earth. why? (i'm not asking, i want you to think about it)

Does the neutral line terminate at the star on the transformers windings (LV side)? which other point is also earthed?

which has less resistance, the cpc from the transformer to the cutout or the earth/dirt/ground? think about it.

In a PME what happens?

A dimmer will work any way around. why?

So will all electronic equipment, why?

Think about it. how many countries have two pin plugs that can go in either way.

Here in the uk, before double insulated circuits, we used to earth the chassis. How does the fuse blow if there is a short from live to the chassis?

Its beautifully simple, simply beautiful.

Bonus question. why do building sites in the uk use 100v supplies?

Stuart.

I think you should cut down on the rhetoric, and actually put forth your own answers.

"Phase line alternates between + and - with respect to neutral and earth. why? (i'm not asking, i want you to think about it)"
Mainly because transformers only work with AC.

"Does the neutral line terminate at the star on the transformers windings (LV side)? which other point is also earthed?"
Don't understand the question.

"which has less resistance, the cpc from the transformer to the cutout or the earth/dirt/ground? think about it."
The earth has little resistance.

"A dimmer will work any way around. why?
So will all electronic equipment, why?
Think about it. how many countries have two pin plugs that can go in either way.
Here in the uk, before double insulated circuits, we used to earth the chassis. How does the fuse blow if there is a short from live to the chassis?"
I have already explained the AC theory.
The fuse blows because ther is excess current.

"Its beautifully simple, simply beautiful."
You're descent into madness, is beautiful.

 

[yankey-sparky]

Again, there is a lack of knowledge of basic physics.
If the live is -240v then the neutral is +240v.

This is wrong WRONG WRONG!!!

The neutral is always at zero volts! Always! The live goes from +240 to -240 but the neutral always remains at zero due to its connection to the earth!

Sterose, please tell me where you are getting this information. You have been led astray at some point. Are you an electrician? What are your qualifications to be giving advice on this forum?

P.S. The neutral will typically have a small voltage due to the resistance of the wire itself, but never more than a few volts

 

[hsiboy]

ah sterose,

You're descent into madness, is beautiful.

There yah go. couldnt help it could you. another smart alec comment.

You also said earlier

Because of the nature of AC (i.e. alternating current), it does not matter which way around you wire components into the mains.

correct. it doesnt matter. it will still work.

however...

In alternating current, the current actually reverses 50 times a second. This means the neutral is actually the 'live' side for a split second every second.

is not quite right. so, you dont fully understand what is happening.

But if you read what other people are saying, and think about it, you will see where you went wrong.

Stuart.

 

[breezer]

just noticed this bit

Incidentally, this is why electric pylons only carry 3 or 6 live conductors, and 1 earth on top. Because the ground is used as neutral.

yeah right, course it is. NOT

 

[hsiboy]

"Phase line alternates between + and - with respect to neutral and earth. why? (i'm not asking, i want you to think about it)"
Mainly because transformers only work with AC.

The current alternates because it was induced by moving a magnetic field close to a coil of wire. A magnet has two poles N & S. if you alternate the poles of a magnet close to a coil of wire, a current will appear at the terminals of the coil that has a relationship with the position of the magnetic poles of the magnet. The easiest method of moving the magnetic field is by rotation, hence the sinusoidal waveform produced. 360 degree rotation. In Three phase power each phase is 120 degrees apart. This why we can split the phases and obtain 230v even though we call it a 400v supply.

"Does the neutral line terminate at the star on the transformers windings (LV side)? which other point is also earthed?"
Don't understand the question.

the power is delivered into the local area on HT lines, and stepped down via a transformer. The neutral line has not been carried to the site only the phases. At the transformer, the middle tap is taken to earth (ground in the US) it is this point that becomes the neutral line that is delivered.

"which has less resistance, the cpc from the transformer to the cutout or the earth/dirt/ground? think about it."
The earth has little resistance.

The earth (ground) is a very poor conductor. How do you think they manage in hot countries? Its much easier for the current to flow along a metallic conductor.

Here in the uk, before double insulated circuits, we used to earth the chassis. How does the fuse blow if there is a short from live to the chassis?"
I have already explained the AC theory.
The fuse blows because ther is excess current.

Did you know the current will flow all the way back to the transformer? Did you know that this current can be many hundreds of amps, even just for a simple kettle with a fault? The fuse does not blow because there is an excess of current.

Stuart.

 

[yankey-sparky]

I'm afraid there is a great deal of incorrect information in this thread, much of it from Sterose and Hsiboy.

I will attempt to clear up some of the confusion.

If the live is -240v then the neutral is +240v.

As I stated before, but am including here again for completeness' sake: at no point is the neutral ever above earth potential. The live switches between +340V and -340V 50 times per second (averaging out to be 240V, but there's no need to get into that right now), but the neutral remains at 0V at all times because it is connected to the earth conductor.

The reason we do not get shocked by the neutral, is because we arent touching the live.
This is in the same way as touching the live does nothing unless you are touching neutral (neutral is effectively earth, by the way).

You do not get shocked (if everything is operating correctly, which you should never assume) very badly from the neutral because, despite the fact that it has current running through it, both you and the neutral are at roughly zero volts. There is little or no potential difference between you and the neutral so little or no current will pass between you.
You WILL get shocked from the live whether or not you are touching the neutral because you have a very large potential difference between you and the live conductor. It is irresponsible to an unbelievable degree that you have stated otherwise! Again I must ask where you are getting your information from!?
The real reasons touching both the live and the neutral is "more" dangerous is
1) because this creates an ideal situation for the current to flow directly across your heart
2) because touching the neutral provides a nearly resistance-free return path on the other side of your body, much better than through your shoes into the floor.

Incidentally, this is why electric pylons only carry 3 or 6 live conductors, and 1 earth on top. Because the ground is used as neutral.

The reason there is no neutral is because the electric pylons are connected in a delta configuration, not a star. There is no neutral in a delta connection, which is why it is important to balance your loads on the three phases. The ground is not used as a neutral, there is no neutral. The earth conductor at the top is used to keep the pylons at earth potential and as a degree of protection against lightning strikes.

I will not call it a neutral because it is not a grounded conductor. (Earthed conductor? What's the UK term?)
Ahem. in brit parlance it is called the neutral wire.
earth is earth, neutral is neutral no matter what your earthing system TT IT PME whatever.

In the US, there is a distinction between the grounded conductor and the grounding conductor. The grounding conductor is the earth connection, that is, the path to the earthing rod or what have you. In normal operation, the grounding conductor should be at zero volts and should not have a current flowing through it.
The grounded conductor, called the neutral, is so called because it is attached to the grounding conductor so that it remains at (well, close to anyway) zero volts despite the fact that it has a current flowing through it. In normal operation, the grounded conductor should be at zero volts but may have a current flowing through it.
I was wondering if the UK has similar terminology to differentiate the two.

A dimmer will work any way around. why?
So will all electronic equipment, why?

NOT all electronic equipment will work any way around, although anything designed for AC use must. Bipolar junction transistors, diodes, and many other DC components will only work in one configuration because the semiconductor junction will only allow current to pass through one way. Also, many semiconductors require the load to be on a certain side because of how the current to the base is detected.

the power is delivered into the local area on HT lines, and stepped down via a transformer. The neutral line has not been carried to the site only the phases. At the transformer, the middle tap is taken to earth (ground in the US) it is this point that becomes the neutral line that is delivered.

The high tension lines are in a delta configuration, and therefore have no neutral line to carry anywhere in the first place. At the transformer, a number of things can happen depending on the type of transformer and how it is connected. A three phase delta-to-star transformer will have an earthed neutral conductor connecting one side of each of the three phases to each other, as your picture shows.
To call this a middle tap is incorrect. A tap on a transformer is a connection in one of various locations along a winding, and they are used to configure the voltage that a transformer supplies to the secondary side. At this point I must stop, because I don't know the configuration of the utility's transformer feeding a residence in the UK, only the US.

The earth (ground) is a very poor conductor. How do you think they manage in hot countries? Its much easier for the current to flow along a metallic conductor.

The earth (ground) can have a very wide range of resistances depending on soil type and moisture content, but if your earthing rod isn't buried in low-resistance ground then you will have a big problem in your electrical system.
Your confusion may arise from thinking about using the earth as a return path all the way from the source of the earthing back to the electrical supply to complete a circuit. This is not the case, since the planet Earth has a virtually unlimited ability to absorb current (due primarily to the fact that it is rather large), any connection to ground results in a completed circuit. The current is dissipated at the point where it is earthed, it does not need to go anywhere from there.

Here in the uk, before double insulated circuits, we used to earth the chassis. How does the fuse blow if there is a short from live to the chassis?"
Did you know the current will flow all the way back to the transformer? Did you know that this current can be many hundreds of amps, even just for a simple kettle with a fault? The fuse does not blow because there is an excess of current.

The fuse blows if there is a short from the live to the chassis because a circuit is completed between the live and the planet Earth. There is no need for the current to be able to make it back to the transformer, it only needs to be dissipated into the ground. The excellent conductive path in question in this case is the earth bonding between the chassis and the ground, and this is what creates the large current which blows the fuse.

Please check your facts before posting! Stating incorrect information as if you know what you are talking about could get people hurt!

 

[hsiboy]

I'm afraid there is a great deal of incorrect information in this thread, much of it from Sterose and Hsiboy.

I will attempt to clear up some of the confusion.

i don't think you have at all.

I will not call it a neutral because it is not a grounded conductor. (Earthed conductor? What's the UK term?)

Ahem. in brit parlance it is called the neutral wire.

The point i was making is that you were busy telling us how it wasn't semantics, but then your argument is 100% semantic. At what point did i say the neutral is not at zero volts with respect to earth/ground ??

NOT all electronic equipment will work any way around, although anything designed for AC use must.

Are you being deliberately obtuse? we are talking about uk mains supply, which has not been DC since the late 1920s.

At this point I must stop, because I don't know the configuration of the utility's transformer feeding a residence in the UK, only the US.

Then what are you arguing? The image is correct. Could i have used a better choice of word other than tap? Maybe, however with respect to the three phases it becomes center tap 0v.

The earth (ground) can have a very wide range of resistances depending on soil type and moisture content, but if your earthing rod isn't buried in low-resistance ground then you will have a big problem in your electrical system.
Your confusion may arise from thinking about using the earth as a return path all the way from the source of the earthing back to the electrical supply to complete a circuit. This is not the case, since the planet Earth has a virtually unlimited ability to absorb current (due primarily to the fact that it is rather large), any connection to ground results in a completed circuit. The current is dissipated at the point where it is earthed, it does not need to go anywhere from there.

What the hell are you on about? This is primary school (8th grade is it?) physics. The current flows in a circuit, there is no magical absorbtion properties of the earth, no matter how wet is soil is, or how deep your earth rod is. If that were not the case why would electrical engineers, designers and electricians measure the resistance of the earth rod/grid with respect to the electrical system? Do you think we earth things just to mop up surplus electrons that might leak out?

The fuse blows if there is a short from the live to the chassis because a circuit is completed between the live and the planet Earth. There is no need for the current to be able to make it back to the transformer, it only needs to be dissipated into the ground.

dissipated into ground? are you trolling me? since when did we power houses, factories, hospitals schools with static/atmospheric electricity?
You need to learn about the fundamental laws of physics, then the fundamental principles of electricity. The earth is not a sponge for electromotive forces.

The excellent conductive path in question in this case is the earth bonding between the chassis and the ground, and this is what creates the large current which blows the fuse.

The excellent conductive path you talk about may in fact be twice as resistive as the phase conductor. The higher the resistance of the fault current path the higher the voltage present on all conductive parts of the path, and greater the risk to humans and livestock.

Please check your facts before posting! Stating incorrect information as if you know what you are talking about could get people hurt!

LOL touche!

Stuart.

 

[yankey-sparky]

Hsiboy
Re: neutral conductors. The statement made (by Securespark, not you), which I cannot agree with, was that a conductor which is on the other side of a resistive load can be considered to be a netural conductor. This is wrong because part of the definition of a neutral conductor is the fact that it is directly tied to ground, not tied to ground on the other side of a resistive load (for example, a light bulb). It happens to be a conductor that is at zero volts at the moment, but it is not a neutral conductor.
To clear up the terminology being used, I was wondering if the UK has a term such as "grounded conductor" to describe the neutral. The fact that it is grounded is essential to the definition of a neutral.

Re: electronic equipment. The statement made was that all electronic equipment would work either way around. This is incorrect as it only applies to AC electronic equipment, regardless of how commonplace DC equipment is or is not (ignoring the fact that your DVD players, cell phones, computers, and hundreds of other modern electronic devices are loaded with them).

Re: "center tapped" transformers. A center tapped transformer is a completely different configuration from what you have described. Center tapping a transformer is a method of splitting, for example, a single 240V winding into two 120V windings while maintaining the capability of using the full 240V if you need it. What you have described is not a center tapped transformer, it is a three phase transformer with one side of the phases connected and grounded, that is to say, a star configuration.
Please stop saying "tap." That connection is not a tap.

Re: grounding. The Earth is in fact a giant electron sponge that we use to "mop up surplus electrons" as you put it. The earth resistance is measured to ensure that the earthing rod can effectively dissipate the stray currents into the ground so that the earthed components never rise above zero volts, as they would with a poorly connected earthing system.
How would an electron "know" the way back to the transformer during a ground fault? All electrons do is follow a path from low voltage potential to high voltage potential (curse you, Ben Franklin!). The Earth, being at zero volts at all times, provides no obvious path back to the transformer supplying the power that has been ground faulted.