For single phase, 220v ac: what is the difference between 3 and 4 wire
systems?

Most 220 comes into houses with three wires. Two insulated, and one bare.
This implies to me that the bare one is also a ground, as well as the 220v
neutral.

I also observe portable generator to house setups using 4 conductor cable.
Why the difference? Are the 4 conductor setups simply using separate
neutral and ground? If so, is there any practical and/or safety reason to
separate the neutral from ground lead?

Thanks for the response. I believe I hear the following for the 220v stuff
(and I'm not talking code here, but practicality} :

1. The neutral is considered a ground return, in relation to the two hot
220v legs.

2. The neutral may in fact be connected to earth ground at some point along
its way.

3. The 4th wire used in some setups is somewhat redundant, as it could also
be incorporated in with the neutral, thereby eliminating the need for the
4th wire

4. Where a 4th wire is used on a 220v setup, that wire is simply a ground
continuity thing for safety purposes.

Is all this correct? If so, I think I understand it now.

RB wrote:

For single phase, 220v ac: what is the difference between 3 and 4 wire
systems?

Most 220 comes into houses with three wires. Two insulated, and one bare.
This implies to me that the bare one is also a ground, as well as the 220v
neutral.

I also observe portable generator to house setups using 4 conductor cable.
Why the difference? Are the 4 conductor setups simply using separate
neutral and ground? If so, is there any practical and/or safety reason to
separate the neutral from ground lead?


by code, you are to only connect the neutral to the ground electron
point in the Breaker box and not at any other point.
in 4 wire single phase, a forth wire (ground wire) is used many times
to connect the appliance case at the end point, also you can legally
have this ground reconnect to some other remote ground points but never
reconnect the neutral to any ground other than what is in the breaker
box where the main ground electrode comes in.

the same applies to equipment grounds where is you have a neutral
wire (white) running around in the cabinet, only at one point will that
neutral be connected to the cabinet ground using no smaller than a 10-32
stud how ever, multiple cabinet (case) grounds can be connected all over
the place in side etc..
kind of strange i know but that is the way it is.
i have seen in some cases in equipment panels where the neutral side
of the 120 control source never see's a case ground.! oh well!


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

"RB" wrote in message
.. .

Thanks for the response. I believe I hear the following for the 220v
stuff
(and I'm not talking code here, but practicality} :

1. The neutral is considered a ground return, in relation to the two hot
220v legs.

2. The neutral may in fact be connected to earth ground at some point
along
its way.

3. The 4th wire used in some setups is somewhat redundant, as it could
also
be incorporated in with the neutral, thereby eliminating the need for the
4th wire

4. Where a 4th wire is used on a 220v setup, that wire is simply a ground
continuity thing for safety purposes.

Is all this correct? If so, I think I understand it now.

There are excellent articles on the web on MEN (multiple earth neutral)
systems. It would be better for you too look at those first.

N

"RB" wrote in message
.. .
For single phase, 220v ac: what is the difference between 3 and 4 wire
systems?

Most 220 comes into houses with three wires. Two insulated, and one bare.
This implies to me that the bare one is also a ground, as well as the 220v
neutral.

I also observe portable generator to house setups using 4 conductor cable.
Why the difference? Are the 4 conductor setups simply using separate
neutral and ground? If so, is there any practical and/or safety reason to
separate the neutral from ground lead?



In North America it's 120-0-120 which comes from a center tapped
transformer. The center tap is grounded and is also connected to the bare
wire which connects to both the ground and neutral busses in the panel. From
either hot to ground/neutral is 120v, between the two hots is 240v.

RED ALERT
Your undertanding of AC power transmission and connections is flawed
and dangerous.
Gotalk with an electrician explain to him your concept of ac
distribution.
If he laughs ,suck it up and ask him to strainghten you out.
Reference his explainations with your own self study.
mccet
in the biz for quit a while

RB wrote:
For single phase, 220v ac: what is the difference between 3 and 4 wire
systems?

Most 220 comes into houses with three wires. Two insulated, and one bare.
This implies to me that the bare one is also a ground, as well as the 220v
neutral.

I also observe portable generator to house setups using 4 conductor cable.
Why the difference? Are the 4 conductor setups simply using separate
neutral and ground? If so, is there any practical and/or safety reason to
separate the neutral from ground lead?

On Sun, 17 Jul 2005 13:23:43 -0500 "RB"
wrote:

Thanks for the response. I believe I hear the following for the 220v stuff
(and I'm not talking code here, but practicality} :

1. The neutral is considered a ground return, in relation to the two hot
220v legs.

Better to call it a "current return" to avoid confusion with ground.

2. The neutral may in fact be connected to earth ground at some point along
its way.

In the US, it ALWAYS is, or should be if the code is followed.

3. The 4th wire used in some setups is somewhat redundant, as it could also
be incorporated in with the neutral, thereby eliminating the need for the
4th wire

Redundant in the sense that the 2 are at the same voltage. The
redundancy is for safety, however, so that the safety ground wire can
never actually get a voltage on it.

4. Where a 4th wire is used on a 220v setup, that wire is simply a ground
continuity thing for safety purposes.

Yes, as in # 3.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

1. The neutral is considered a ground return, in relation to the two
hot
220v legs

The Neutral is a current carrying conductor, for the 110 in this case.
It is connected to ground in the entrance panel for safety to keep the
hot wires from floating from ground.

Also the neutral is called a grounded conductor.

Ideally the neutral will never return any current to the ground because
loads are ideally supposed to be balanced. Probably rarely achieved.
If the unbalance is sufficient it can raise the ground connection about
ground by several or more volts AC

And FWIW:
The output of the transformer that feeds you house is usually two
windings. Connected so they add to give 220. The two windings are
interspaced with the primary for transformer efficiency among other
reasons.

RB wrote:

For single phase, 220v ac: what is the difference between 3 and 4 wire
systems?

Most 220 comes into houses with three wires. Two insulated, and one bare.
This implies to me that the bare one is also a ground, as well as the 220v
neutral.

I also observe portable generator to house setups using 4 conductor cable.
Why the difference? Are the 4 conductor setups simply using separate
neutral and ground? If so, is there any practical and/or safety reason to
separate the neutral from ground lead?


No one is mentioning a 4-wire system dealing with 3-phase power (Phase
A,B,C + Neutral), where single-phase is available from a neutral
connected from the WYE configured source (generator, transformers,
utility) to any Phase or A to B; A to C; B to C. In countries outside of
the U.S., with 220 VAC single-phase appliances, the system is a 380/220
volt 3-phase 4-wire system. You would have 380 volts single phase
between any two phase wires, or 220 volts from any phase wire to the
neutral. The U.S. equivalent is the 208/120v 3-phase 4-wire system for
small-medium commercial use. Motors rated 208 vac 3-PH (i.e. air
conditioners) could be used and lighting etc. on the 120 VAC from any
leg to the neutral.
The generator you mentioned most likely was a 3-Phase output.

In article . com,
Bob AZ wrote:
The Neutral is a current carrying conductor, for the 110 in this case.
It is connected to ground in the entrance panel for safety to keep the
hot wires from floating from ground.

Eh? Surely in an ideal installation the 'hot' wire will be at equal
potential above both ground and neutral?

--
*A hangover is the wrath of grapes.

Dave Plowman London SW
To e-mail, change noise into sound.

"John J.Turley" writes:

RB wrote:

For single phase, 220v ac: what is the difference between 3 and 4 wire
systems?
Most 220 comes into houses with three wires. Two insulated, and one
bare.

This implies to me that the bare one is also a ground, as well as the 220v
neutral.
I also observe portable generator to house setups using 4 conductor
cable.

Why the difference? Are the 4 conductor setups simply using separate
neutral and ground? If so, is there any practical and/or safety reason to
separate the neutral from ground lead?


No one is mentioning a 4-wire system dealing with 3-phase power (Phase
A,B,C + Neutral), where single-phase is available from a neutral
connected from the WYE configured source (generator, transformers,
utility) to any Phase or A to B; A to C; B to C. In countries outside
of the U.S., with 220 VAC single-phase appliances, the system is a
380/220 volt 3-phase 4-wire system. You would have 380 volts single
phase between any two phase wires, or 220 volts from any phase wire to
the neutral. The U.S. equivalent is the 208/120v 3-phase 4-wire system
for small-medium commercial use. Motors rated 208 vac 3-PH (i.e. air
conditioners) could be used and lighting etc. on the 120 VAC from any
leg to the neutral.

One exception (possibly more) is Norway, where they use 230V three
phase, but one of the phase leads are at 0V potential. All the 230V
"single phase" outlets are connected to two phases.

Norway uses 4 prongs in their three phase connectors, while the rest
of Europe use 5 prongs, thre phases, neutral and ground.


The generator you mentioned most likely was a 3-Phase output.

Thomas

Eh? Surely in an ideal installation the 'hot' wire will be at equal
potential above both ground and neutral?

Each one does. 60 times a second.

Bob AZ

In article .com,
Bob AZ wrote:
Eh? Surely in an ideal installation the 'hot' wire will be at equal
potential above both ground and neutral?

Each one does. 60 times a second.

You've still not explained what you meant. ;-)

--
*A day without sunshine is like... night.

Dave Plowman London SW
To e-mail, change noise into sound.