neutral

[Thomasj845]

Your intermediate switch would have 4 wires and the luminaire is controlled from 3 or more locations, \

Tom

 

[Stoday]

That's right, Tom

 

[ninebob]

Tom,

Some posters here get on their high horse, and rightly so. Please understand what I said previously: this is a UK forum.

American electrics are very different from those here. I could probably rewire my own house in the UK from top to bottom, if I tried to rewire yours in the states I'd likely kill myself.

If you want DIY advice, look to the forum I pointed out in an earlier post, which is relevant to the USA. If you want to learn about UK electrics, then welcome to the forum, but please listen.

Simon

 

[kevplumb]

cant one of the sparks post a uk wiring diagram it might help

 

[Paul_C]

Guys,

I think the disagreement here is due simply to definitions and common usage.

Tom is quite correct in his pure definition of a neutral conductor in that it carries the imbalance of current. The way that the American NEC is worded makes it pretty clear that this is the intent. When talking about a simple 2-wire circuit, that conductor which would be called a neutral in Britain is referred to as the GROUNDED conductor. Thus in NEC usage, the incoming grounded conductor on a standard 3-wire residential service is a neutral; the white wire on a 240V dryer circuit is also a neutral, but the white wire on a 120V general purpose circuit is not. Of course, that wire connects to the neutral bus at the main panel, and from there backward to source it is a neutral.

The British IEE however, has a somewhat broader definition of a neutral conductor which you probably have not seen Tom. That broader definition has been around a long time -- Here's the IEE's definition from way back in 1955:

Neutral conductor. The neutral conductor of a 3-phase 4-wire system, the conductor of a single-phase or d.c. installation which is earthed by the supply undertaking (or otherwise at the source of the supply), or the middle wire or common return conductor of a 3-wire d.c. or single-phase a.c. system.

Notice that they explicity include the grounded conductor of a 2-wire system as being a neutral. That's why my fellow Brits are so insistent that this usage is correct. And yes, I'm aware of the fact that the first part of the IEE's definition in relation to a 3-ph 4-w system is rather circular in its nature and not the best way they could have defined it!

 

[notb665]

In case you are lost in this thread, here's a picture: -

Why would a house need two different voltages? Surely appliances can be designed to work on one voltage like in the, er, UK.

 

[Paul_C]

We call the two conductors Live and Neutral. You call yours Hot and Grounded, I believe?

BAS,

"Hot" is really only a colloquialism. The NEC terminology is UNGROUNDED conductor.

 

[Paul_C]

Why would a house need two different voltages? Surely appliances can be designed to work on one voltage like in the, er, UK.

They can, but it's a matter of historical development. In earlier times American homes did take a 2-wire 120V-only service (some are still in existence). When higher-powered appliances started to become more common, and homes started to use greater quantities of power in general, 240V supplies were provided. To have changed to a straight 240V 2-wire service would have rendered existing 120V equipment redundant.

By the way, Britain had 120/240V (or thereabouts) 3-wire systems in the very early days too. It's just that we abandoned the lower voltage and adopted 200 to 250V as standard much earlier, before there were enough appliances around to make the change impractical.

There are many such instances of history affecting modern usage: Look at how long Britain ran dual standard TV broadcasts (405 and 625 line), for example, or how despite changes in wiring methods and equipment, the basic electrical characteristics of telephones lines are pretty much the same as they were 100 years ago.

 

[Lectrician]

When having a 240volt 'receptical', is it fed from a double pole breaker, or 2 single pole breakers??

Anyone got a good schematic for our distribution system?? I have somehwere...

 

[ryanj]

Here are some good drawings of the UK systems by PaulC:

http://electrical-contractor.net/theory/ukold1a.gif
http://electrical-contractor.net/theory/ukold2a.gif
http://electrical-contractor.net/theory/ukold3a.gif

When having a 240volt 'receptical', is fed from a double pole breaker, or 2 single pole breakers??

I'm pretty sure they use two seperate breakers, perhaps Paul can elaborate.

 

[Paul_C]

When having a 240volt 'receptical', is it fed from a double pole breaker, or 2 single pole breakers?

A double-pole breaker is the norm, but two single-pole breakers are also permissible so long as an approved handle tie is used so that both poles will open simultaneously. (A standard residential panel has the busbars interleaved so that adjacent slots will always be on opposite poles.)

 

[Thomasj845]

Your explanation is Excellent, thanks for helping me out.
I am beginning to love the brits.

 

[plugwash]

note that if the supply system is 3 phase the higher voltage will be 208V rather than 240V

i belive that 3 phase in the USA is uncommon in houses but common in commercial buildings and blocks of flats.

 

[andy]

Would you agree or dis agree that a neutral conductor is a conductor designed to carry unbalanced current?

TOm

both. the neutral is designed to carry the unbalanced load, so in a 3 phase system, if it is equally balanced then there will be nothing on the neutral. if they we unbalanced there would be load on the neutral. in a single phase system there is only 1 phase and one neutral, so the neutral has to take all the load.

but its the same in a 3 phase system where single phase items are concered. i.e sockets. the neutral takes the load but only to the neutral block in the DB, if equally balanced. (bit like you americans)

however, houses are fed from a 3 phase supply where all the neutral are together, so if there are 3 houses, all using the same current, then the neutral only carries the load to the neutral in the 3 phase cable, and not back to the transformer since its balanced, therefore it does only carry the unbalanced load

does that make any sense?

 

[Lectrician]

A double-pole breaker is the norm, but two single-pole breakers are also permissible so long as an approved handle tie is used so that both poles will open simultaneously. (A standard residential panel has the busbars interleaved so that adjacent slots will always be on opposite poles.)

From the diagram above, It looked like there where two sides inside the board. Makes more sense now. We can have two phase boards over here, or use them as switched neutral boards.

The american setup is called split-phase over here, and is seen on farms etc in rural areas. However, we have the two 'phases' at 240v to the neutral, with 480v between them. Our distribution network uses the split phase very often, but only distributes one of the phases and the neutral to the property, so again, our neutral is carrying all the current until it hits the street.

To clarify - We have two 'live' conductors - one known as PHASE and the other as NEUTRAL. It is improper to call the red or brown the 'live', it should be referred to as 'phase', even in single phase supplies. BUT, most people, including sparks will call it live - and sockets etc are marked up with an L