Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break,
then the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break, then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave swinging up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror images
of each other. If you measure the peak of either wave to ground, it is
120v, if you measure the top peak of one wave to the bottom of the other, it
is 240v. There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.

Tman wrote:
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.
...
OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the neutral conductor to the breaker box.

At one time the National Electrical Code (USA) allowed 120/240 volt
ranges and dryers to have a shared grounding and neutral conductor if it
was being fed directly from the service equipment. Because of the
potential danger with an open neutral, the Code now requires four wires.

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break, then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T
This used to be permitted on residential dryers and ranges on the assumption
that the robust connections would be properly made by a qualified installer
and very unlikely to come loose. This was in the time before 120V grounding
receptacles and small appliances were not grounded. There were (are?) some
dryers with a center tapped heating element to provide the 120V for the
timer. Not a very good design.

Don Young

Tman wrote:
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break,
then the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T


It's theoretically not as safe as having separate neutral and ground
wires. But the unbalanced current is very small, the conductor is very
large, and a 240/120V 3-wire circuit is only allowed when connected to
the main panel (not a subpanel), where the ground and neutral are bonded
to the same buss.

If the neutral wire were to inexplicably come loose, I *think* the timer
relay would open and remove power to the drum motor. So the 120V on the
chassis would be current limited by the series resistance of the timer.
(I could be way wrong on this last point)

Bob

Oddly enough, the third wire is not a neutral for the main
220 volt heater element. Since the current flows through the
black wires, or black and red. But doesn't need a neutral.

The only time the third wire behaves as a neutral, if there
is a 110 volt timer.

It's a bit strange, but seems to have worked for all these
years.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v).
I've always
wondered how they serve up 240 V with 120V components (e.g.
timer motor)
on only three wires.

You see, I always thought that the grounded conductor should
never be
current-carrying, in the theory that if the ground feed
should break,
then the metal chassis of the appliance does not get
energized.

Well looks like that "3rd" wire, is a neutral, and judging
by the dryer
schematic, is both used as a chassis ground and a
current-carrying
conductor for the 120V items on the dryer -- such as timer
and drum motor.

OK -- am I totally wrong about the code and theory, or is
this unsafe?
Seems to me that dryer would get real "hot" should their be
a fault in
the neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I
am aware.
Someone please inform me?
T

"Stormin Mormon" wrote in message
...
Oddly enough, the third wire is not a neutral for the main
220 volt heater element. Since the current flows through the
black wires, or black and red. But doesn't need a neutral.

The only time the third wire behaves as a neutral, if there
is a 110 volt timer.

It's a bit strange, but seems to have worked for all these
years.

The motors are generally 120 volt as well

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.


"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v).
I've always
wondered how they serve up 240 V with 120V components (e.g.
timer motor)
on only three wires.

You see, I always thought that the grounded conductor should
never be
current-carrying, in the theory that if the ground feed
should break,
then the metal chassis of the appliance does not get
energized.

Well looks like that "3rd" wire, is a neutral, and judging
by the dryer
schematic, is both used as a chassis ground and a
current-carrying
conductor for the 120V items on the dryer -- such as timer
and drum motor.

OK -- am I totally wrong about the code and theory, or is
this unsafe?
Seems to me that dryer would get real "hot" should their be
a fault in
the neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I
am aware.
Someone please inform me?
T

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break, then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T


It was acceptable when installed as others have described, it's no longer
acceptable in NEW installations, but since there aren't piles of
electrocuted housewives across the country, existing installations are still
acceptable

RBM wrote:

It was acceptable when installed as others have described, it's no longer
acceptable in NEW installations, but since there aren't piles of
electrocuted housewives across the country, existing installations are still
acceptable

My house was built in 2000, fwiw.
Also, BTW there is a non-trivial 120v load through that neutral -- not
just the timer motor, but also both main motors (mine is a combined
washer / dryer stacked unit)...
T

On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:


"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break, then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave swinging up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror images
of each other. If you measure the peak of either wave to ground, it is
120v

Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)

if you measure the top peak of one wave to the bottom of the other, it
is 240v.

340V. Shut up, reality :-)

There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.

On 2009-01-16, Tman wrote:

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break,
then the metal chassis of the appliance does not get energized.

The term you want here is "grounding conductor", since "grounded
conductor" is another (better) term for what is commonly called the
neutral.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?

As others have mentioned, this arrangement was once allowed but is no
longer allowed in new installations. Existing installations are
grandfathered, so if you buy a new electric dryer, you should have a
choice of cords: a 3-wire cord (with a bond on the machine between the
chassis and the neutral) or a 4-wire cord (where the bond on the
machine should be removed).

I'm not sure of the reason for the original rule allowing a 3-wire
circuit, although I have heard that it was a conservation measure
during World War II. If so, it was judged that the copper savings was
more valuable than the increased risk in the event the neutral
conductor was compromised.

Cheers, Wayne

On Jan 16, 7:05*am, "RBM" wrote:
"Tman" wrote in message

...





Took a look at the schematic today for the dryer (240v). *I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break, then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

It was acceptable *when installed as others have described, it's no longer
acceptable in NEW installations, but since there aren't piles of
electrocuted housewives across the country, existing installations are still
acceptable- Hide quoted text -

- Show quoted text -

"since there aren't piles of electrocuted _housewives_ across the
country"

A rather sexist comment right there...unless you are implying that
women are more sucsebtible to electrocution than men.

On Jan 16, 3:57*am, "RBM" wrote:
"Stormin Mormon" wrote in message

...

Oddly enough, the third wire is not a neutral for the main
220 volt heater element. Since the current flows through the
black wires, or black and red. But doesn't need a neutral.

The only time the third wire behaves as a neutral, if there
is a 110 volt timer.

It's a bit strange, but seems to have worked for all these
years.

The motors are generally 120 volt as well





--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v).
I've always
wondered how they serve up 240 V with 120V components (e.g.
timer motor)
on only three wires.

You see, I always thought that the grounded conductor should
never be
current-carrying, in the theory that if the ground feed
should break,
then the metal chassis of the appliance does not get
energized.

Well looks like that "3rd" wire, is a neutral, and judging
by the dryer
schematic, is both used as a chassis ground and a
current-carrying
conductor for the 120V items on the dryer -- such as timer
and drum motor.

OK -- am I totally wrong about the code and theory, or is
this unsafe?
Seems to me that dryer would get real "hot" should their be
a fault in
the neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I
am aware.
Someone please inform me?
T- Hide quoted text -

- Show quoted text -

Yeah. It took me some time to figure out how a shop was getting 240
on only two wires. Used to be common wiring back when.

Harry K

"Tman" wrote in message
...
RBM wrote:

It was acceptable when installed as others have described, it's no
longer acceptable in NEW installations, but since there aren't piles of
electrocuted housewives across the country, existing installations are
still acceptable

My house was built in 2000, fwiw.
Also, BTW there is a non-trivial 120v load through that neutral -- not
just the timer motor, but also both main motors (mine is a combined washer
/ dryer stacked unit)...
T


You are quite correct, it was not I that suggested it was only the timer
motor. Clearly there have been few incidents as a result of the wiring
method or the NEC would have demanded it be changed years ago

"DerbyDad03" wrote in message
...
On Jan 16, 7:05 am, "RBM" wrote:
"Tman" wrote in message

...





Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break,
then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

It was acceptable when installed as others have described, it's no longer
acceptable in NEW installations, but since there aren't piles of
electrocuted housewives across the country, existing installations are
still
acceptable- Hide quoted text -

- Show quoted text -

"since there aren't piles of electrocuted _housewives_ across the
country"

A rather sexist comment right there...unless you are implying that
women are more sucsebtible to electrocution than men.


Not at all, my reference merely dates back to the mid century when it was
typically women that used these machines almost exclusively

Tman wrote:
RBM wrote:

It was acceptable when installed as others have described, it's no
longer acceptable in NEW installations, but since there aren't piles
of electrocuted housewives across the country, existing installations
are still acceptable

My house was built in 2000, fwiw.
Also, BTW there is a non-trivial 120v load through that neutral -- not
just the timer motor, but also both main motors (mine is a combined
washer / dryer stacked unit)...
T


I believe the NEC switch to 4 wires for dryer circuits was about 1996.
I would think your house has one. (You may have to look in the box
behind the dryer outlet to find out, or in the service panel.)

Any recent dryer would have an isolated neutral circuit that comes out
to a connection terminal. The terminal is then jumpered to the dryer
"ground" (or a jumper is available). For old houses where the dryer
circuit is 3-wire combined neutral-ground, the jumper is left. For newer
houses (which should include yours), the jumper is removed and a 4 wire
cord is used.

IMHO manufacturers should make dryers and ranges that operate on 240V
(do not need a neutral). It would eliminate the problems and confusion.
Couldn't cost that much more.

--
bud--

A rather sexist comment right there...unless you are implying that
women are more sucsebtible to electrocution than men.
I didn't read it as such at all. I'm sure a lot of men get electrocuted
every day just as well --- while slaving away bringing home the bacon,
so that wifey can have a nice hot meal on the table when he comes home!

T

bud-- wrote:


I believe the NEC switch to 4 wires for dryer circuits was about 1996.
I would think your house has one. (You may have to look in the box
behind the dryer outlet to find out, or in the service panel.)

Well i looked closer and learned something today...

My house, built circa 2000 does in fact have a 4x (2H, 1N, 1G)
receptacle (sp?).

The dryer, cheapest Kenmore unit bought in 2000 also and delivered by
the dryer guy, has a 3 wire plug -- current carrying neutral-- jumpered
to the chassis ground at the dryer end of it.

It's just that the 3-prong cord plugs into the 4-x outlet, leaving the
central ground unused (and, until now, unnoticed).

Oh well, just one more reason to replace the clunker....

T

On Jan 16, 6:23�pm, Tman wrote:
bud-- wrote:

I believe the NEC switch to 4 wires for dryer �circuits was about 1996.
I would think your house has one. (You may have to look in the box
behind the dryer outlet to find out, or in the service panel.)

Well i looked closer and learned something today...

My house, built circa 2000 does in fact have a 4x (2H, 1N, 1G)
receptacle (sp?).

The dryer, cheapest Kenmore unit bought in 2000 also and delivered by
the dryer guy, has a 3 wire plug -- current carrying neutral-- jumpered
to the chassis ground at the dryer end of it.

It's just that the 3-prong cord plugs into the 4-x outlet, leaving the
central ground unused (and, until now, unnoticed).

Oh well, just one more reason to replace the clunker....

T

yeah I look and wonder but things keep changing over time. in most
cases its safer and more energy efficent

Tman wrote:
bud-- wrote:


I believe the NEC switch to 4 wires for dryer circuits was about
1996. I would think your house has one. (You may have to look in the
box behind the dryer outlet to find out, or in the service panel.)

Well i looked closer and learned something today...

My house, built circa 2000 does in fact have a 4x (2H, 1N, 1G)
receptacle (sp?).

The dryer, cheapest Kenmore unit bought in 2000 also and delivered by
the dryer guy, has a 3 wire plug -- current carrying neutral-- jumpered
to the chassis ground at the dryer end of it.

It's just that the 3-prong cord plugs into the 4-x outlet, leaving the
central ground unused (and, until now, unnoticed).

Oh well, just one more reason to replace the clunker....

T

I didn't know you could do that. learn something new every day.

If this bothers you, a new dryer cord is as close as your local hardware
store, simply replace the cord with a 4-wire cord whose plug fits your
outlet and remove the bonding jumper. It's not a HUGE deal, but I
believe it is technically a code violation to use a 3-wire cord where a
4-wire receptacle is available.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

"Gary H" wrote in message
...
On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:


"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break,
then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave swinging
up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it is
120v

Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)

if you measure the top peak of one wave to the bottom of the other, it
is 240v.

340V. Shut up, reality :-)

There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.


I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't more
technical, do you think he would have understood your numbers better in
relation to his dryer?

On Jan 17, 12:32*pm, "Buerste" wrote:
"Gary H" wrote in message

...





On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). *I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break,
then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware..
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each other.

wrote in message
...
On Jan 17, 12:32 pm, "Buerste" wrote:
"Gary H" wrote in message

...





On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break,
then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave swinging
up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it is
120v

Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)

if you measure the top peak of one wave to the bottom of the other, it
is 240v.

340V. Shut up, reality :-)

There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.

I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't more
technical, do you think he would have understood your numbers better in
relation to his dryer?- Hide quoted text -

- Show quoted text -

To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do that
as an extra saftey feature.
Good question
Mark


I would recommend using a 3 wire dryer circuit just as it was intended to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through your
plumbing or other appliances

Buerste wrote:
"Gary H" wrote in message
...
On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each other.
The potential between either phase and ground/neutral is 120v. The
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it is
120v
Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)
I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't more
technical, do you think he would have understood your numbers better in
relation to his dryer?


LOL, OP here. I took a couple EE courses when working on my MS
aerospace engineering and did an internship where I designed one of the
lightest 400Hz DC-AC inverter for aerospace use. I get the split phase,
peak / RMS business quite fine. I'm just not totally up to speed with
what's code and what's not -- and this rig seemed to be amiss.

I guess in the name of being pedantic, I'll point out that the two hots
probably are not exactly "180 degrees" out of phase and "mirror
images" of each other; close but in real life situations the reactive
loads will not be [perfectly] identical across both phases, making the
out-of-phase, well just a little bit different than pi radians

T

"Tman" wrote in message
...

LOL, OP here. I took a couple EE courses when working on my MS aerospace
engineering and did an internship where I designed one of the lightest
400Hz DC-AC inverter for aerospace use. I get the split phase, peak / RMS
business quite fine. I'm just not totally up to speed with what's code
and what's not -- and this rig seemed to be amiss.

I guess in the name of being pedantic, I'll point out that the two hots
probably are not exactly "180 degrees" out of phase and "mirror images" of
each other; close but in real life situations the reactive loads will not
be [perfectly] identical across both phases, making the out-of-phase, well
just a little bit different than pi radians

T

What you are calling two hots are comming from a center tapped transformer.
There is only one phase. They can not be out of phase with each other by
any ammount not counting a couple of inches of wire from the transfromer
windings to the load.

Ralph Mowery wrote:

What you are calling two hots are comming from a center tapped transformer.
There is only one phase. They can not be out of phase with each other by
any ammount not counting a couple of inches of wire from the transfromer
windings to the load.


Think of the extreme where one H-N has a purely resistive load, and the
other H-N has a highly reactive (say inductive) load, and remember that
both the transformer and the wires have an inherent inductance. The
voltage peaks as measured at the load will not be exactly 180 deg out of
phase.
T

On Sun, 18 Jan 2009 22:04:22 -0500, "Ralph Mowery"
wrote:


"Tman" wrote in message
...

LOL, OP here. I took a couple EE courses when working on my MS aerospace
engineering and did an internship where I designed one of the lightest
400Hz DC-AC inverter for aerospace use. I get the split phase, peak / RMS
business quite fine. I'm just not totally up to speed with what's code
and what's not -- and this rig seemed to be amiss.

I guess in the name of being pedantic, I'll point out that the two hots
probably are not exactly "180 degrees" out of phase and "mirror images" of
each other; close but in real life situations the reactive loads will not
be [perfectly] identical across both phases, making the out-of-phase, well
just a little bit different than pi radians

T

What you are calling two hots are comming from a center tapped transformer.
There is only one phase. They can not be out of phase with each other by
any ammount not counting a couple of inches of wire from the transfromer
windings to the load.


It depends on your point of reference. The normal point of reference
(for wiring on the transformer secondary) is in the MIDDLE
(center-tapped coil). Points are measured from that. That is, 2
phases.

What may be confusing to some, is these 2 phases are not 2 of the 3
phases being supplied to the transformer.

On Jan 17, 4:05*pm, "RBM" wrote:
wrote in message

...
On Jan 17, 12:32 pm, "Buerste" wrote:





"Gary H" wrote in message

.. .

On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break,
then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in
the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave swinging
up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it is
120v

Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)

if you measure the top peak of one wave to the bottom of the other, it
is 240v.

340V. Shut up, reality :-)

There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.

I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't more
technical, do you think he would have understood your numbers better in
relation to his dryer?- Hide quoted text -

- Show quoted text -

To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. *NEC code as
picky as it is used to allow this. *I think it is now not allowed in
new homes. *I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. *This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. *You
can also connect it to a cold water pipe. *I would suggest you do that
as an extra saftey feature.
Good question
Mark

I would recommend *using a 3 wire dryer circuit just as it was intended to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.

Mark

wrote in message
...
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message

...
On Jan 17, 12:32 pm, "Buerste" wrote:





"Gary H" wrote in message

.. .

On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.

You see, I always thought that the grounded conductor should never
be
current-carrying, in the theory that if the ground feed should
break,
then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.

OK -- am I totally wrong about the code and theory, or is this
unsafe?
Seems to me that dryer would get real "hot" should their be a fault
in
the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am
aware.
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave
swinging
up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it is
120v

Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)

if you measure the top peak of one wave to the bottom of the other,
it
is 240v.

340V. Shut up, reality :-)

There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.

I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't more
technical, do you think he would have understood your numbers better in
relation to his dryer?- Hide quoted text -

- Show quoted text -

To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was intended to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through
your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.

Mark


What you are proposing to do, routes dangerous line voltage fault current
from the dryer to another circuits grounding conductor, or worse, a water
pipe, which was not designed for that purpose, and is not only dangerous,
but illegal as well. I suggest you get an NEC code book and research
"grounding"

RBM wrote:
wrote in message
...
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message

...
On Jan 17, 12:32 pm, "Buerste" wrote:





"Gary H" wrote in message
...
On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:
"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.
You see, I always thought that the grounded conductor should never
be
current-carrying, in the theory that if the ground feed should
break,
then
the metal chassis of the appliance does not get energized.
Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.
OK -- am I totally wrong about the code and theory, or is this
unsafe?
Seems to me that dryer would get real "hot" should their be a fault
in
the
neutral conductor to the breaker box.
I know I'm missing something here as this is SOP as far as I am
aware.
Someone please inform me?
T
Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave
swinging
up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it is
120v
Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)
if you measure the top peak of one wave to the bottom of the other,
it
is 240v.
340V. Shut up, reality :-)
There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.
I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't more
technical, do you think he would have understood your numbers better in
relation to his dryer?- Hide quoted text -
- Show quoted text -
To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was intended to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through
your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.

Mark


What you are proposing to do, routes dangerous line voltage fault current
from the dryer to another circuits grounding conductor, or worse, a water
pipe, which was not designed for that purpose, and is not only dangerous,
but illegal as well. I suggest you get an NEC code book and research
"grounding"



Correct me if I'm mistaken, but doesn't the NEC allow you, in a retrofit
type situation, to replace an ungrounded receptacle with a grounded one
so long as you ground the receptacle and box to any convenient point "in
the grounding system" which would include a copper water pipe? I agree,
would be far better to drag it back to the panel... I honestly don't
know what it says running a ground wire from a plug-connected
appliance to a water pipe. I'd sooner replace the recep. with a 4-wire
and use the exception there; then replace the dryer cord with a 4-wire
and remove the bonding jumper in the dryer.

Disclaimer: IANAE, I'm posting this for feedback and comment, not as advice.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

"Gary H" wrote in message
...
On Sun, 18 Jan 2009 22:04:22 -0500, "Ralph Mowery"
wrote:


"Tman" wrote in message
...

LOL, OP here. I took a couple EE courses when working on my MS
aerospace
engineering and did an internship where I designed one of the lightest
400Hz DC-AC inverter for aerospace use. I get the split phase, peak /
RMS
business quite fine. I'm just not totally up to speed with what's code
and what's not -- and this rig seemed to be amiss.

I guess in the name of being pedantic, I'll point out that the two hots
probably are not exactly "180 degrees" out of phase and "mirror images"
of
each other; close but in real life situations the reactive loads will
not
be [perfectly] identical across both phases, making the out-of-phase,
well
just a little bit different than pi radians

T

What you are calling two hots are comming from a center tapped
transformer.
There is only one phase. They can not be out of phase with each other by
any ammount not counting a couple of inches of wire from the transfromer
windings to the load.


It depends on your point of reference. The normal point of reference
(for wiring on the transformer secondary) is in the MIDDLE
(center-tapped coil). Points are measured from that. That is, 2
phases.

What may be confusing to some, is these 2 phases are not 2 of the 3
phases being supplied to the transformer.

The wiring comming into a normal house in the US is single phase. Not two
phase. True two phase power has the phases 90 deg out instead of the so
called 180 deg .

Two phase powe can be made from a 3 phase circuit, but it requires more than
a simple center tapped transformer the normal house has.

"Nate Nagel" wrote in message
...
RBM wrote:
wrote in message
...
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message

...
On Jan 17, 12:32 pm, "Buerste" wrote:





"Gary H" wrote in message
...
On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:
"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.
You see, I always thought that the grounded conductor should never
be
current-carrying, in the theory that if the ground feed should
break,
then
the metal chassis of the appliance does not get energized.
Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.
OK -- am I totally wrong about the code and theory, or is this
unsafe?
Seems to me that dryer would get real "hot" should their be a fault
in
the
neutral conductor to the breaker box.
I know I'm missing something here as this is SOP as far as I am
aware.
Someone please inform me?
T
Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave
swinging
up
and down. With split phase, it looks like 2 waves on the scope. As
one
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it
is
120v
Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)
if you measure the top peak of one wave to the bottom of the other,
it
is 240v.
340V. Shut up, reality :-)
There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.
I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't
more
technical, do you think he would have understood your numbers better in
relation to his dryer?- Hide quoted text -
- Show quoted text -
To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was intended
to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through
your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.

Mark


What you are proposing to do, routes dangerous line voltage fault current
from the dryer to another circuits grounding conductor, or worse, a water
pipe, which was not designed for that purpose, and is not only
dangerous, but illegal as well. I suggest you get an NEC code book and
research "grounding"



Correct me if I'm mistaken, but doesn't the NEC allow you, in a retrofit
type situation, to replace an ungrounded receptacle with a grounded one so
long as you ground the receptacle and box to any convenient point "in the
grounding system" which would include a copper water pipe? I agree, would
be far better to drag it back to the panel... I honestly don't know what
it says running a ground wire from a plug-connected appliance to a
water pipe. I'd sooner replace the recep. with a 4-wire and use the
exception there; then replace the dryer cord with a 4-wire and remove the
bonding jumper in the dryer.

Disclaimer: IANAE, I'm posting this for feedback and comment, not as
advice.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel


First of all, the code doesn't allow you to ground a receptacle to a water
pipe. It allows you to ground it to any point along the "grounding electrode
system", which will include the metallic water pipe feeding the building,
but only the first 5 feet of it. A properly installed 3 wire dryer circuit
must meet 4 conditions to be acceptable. The whole idea is to have a better
quality circuit than just some old piece of Romex making the connection.
Most importantly, electricity takes the path of least resistance. What
happens if this guy's auxiliary ground, which he believes is to protect
someone, is a better path for the normal motor circuit currents to run
through? Now current that should be running through a properly sized
conductor is running through what? And if it's running through some section
of plumbing, and some plumbing work requires cutting that particular pipe,
what happens to the plumber?

On Jan 19, 8:02*pm, "RBM" wrote:
"Nate Nagel" wrote in message

...





RBM wrote:
wrote in message
....
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message

....
On Jan 17, 12:32 pm, "Buerste" wrote:

"Gary H" wrote in message
m...
On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:
"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.
You see, I always thought that the grounded conductor should never
be
current-carrying, in the theory that if the ground feed should
break,
then
the metal chassis of the appliance does not get energized.
Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.
OK -- am I totally wrong about the code and theory, or is this
unsafe?
Seems to me that dryer would get real "hot" should their be a fault
in
the
neutral conductor to the breaker box.
I know I'm missing something here as this is SOP as far as I am
aware.
Someone please inform me?
T
Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave
swinging
up
and down. With split phase, it looks like 2 waves on the scope. As
one
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it
is
120v
Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)
if you measure the top peak of one wave to the bottom of the other,
it
is 240v.
340V. Shut up, reality :-)
There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.
I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't
more
technical, do you think he would have understood your numbers better in
relation to his dryer?- Hide quoted text -
- Show quoted text -
To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was intended
to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through
your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. *It is more technically correct
to say two POLARITIES of one phase.

Mark

What you are proposing to do, routes dangerous line voltage fault current
from the dryer to another circuits grounding conductor, or worse, a water
pipe, which was not designed for that *purpose, and is not only
dangerous, but illegal as well. I suggest you get an NEC code book and
research "grounding"

Correct me if I'm mistaken, but doesn't the NEC allow you, in a retrofit
type situation, to replace an ungrounded receptacle with a grounded one so
long as you ground the receptacle and box to any convenient point "in the
grounding system" which would include a copper water pipe? *I agree, would
be far better to drag it back to the panel... *I honestly don't know what
it says running a ground wire from a plug-connected appliance to a
water pipe. *I'd sooner replace the recep. with a 4-wire and use the
exception there; then replace the dryer cord with a 4-wire and remove the
bonding jumper in the dryer.

Disclaimer: IANAE, I'm posting this for feedback and comment, not as
advice.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

First of all, the code doesn't allow you to ground a receptacle to a water
pipe. It allows you to ground it to any point along the "grounding electrode
system", which will include the metallic water pipe feeding the building,
but only the first 5 feet of it. A properly installed 3 wire dryer circuit
must meet 4 conditions to be acceptable. The whole idea is to have a better
quality circuit than just some old piece of Romex making the connection.
Most importantly, electricity takes the path of least resistance. What
happens if this guy's auxiliary ground, which he believes is to protect
someone, is a better path for the normal motor circuit currents to run
through? Now current that should be running through a properly sized
conductor is running through what? And if it's running through some section
of plumbing, and some plumbing work requires cutting that particular pipe,
what happens to the plumber?- Hide quoted text -

- Show quoted text -

Nothing...

You have the normal neutral/ground wire in parallel with the aux
ground wire. "Electricity takes the path of least resistance" is an
oversimplfication. In fact the current divides inversly
proportionally to the resistance in the path. Yes some of the motor
current may flow through the auxiallry ground. But if that ground
should be opened by the plumber then all the current will flow through
the original ground. The only voltage across the water pipe will be
the small drop due to the resistance of the wire.

I agree this is not an ideal situation, but the problem started
becasue the NEC made a mistake in the first place and allowed 3 wire
220V circuits which are inherently dangerous for all the reasons you
are pointing out. The BEST way to fix this is to replace the 3 wire
system with a 4 wire system , which could requires pulling a new 4
wire cable to replace the existing 3 wire cable. Thats a big job. A
second best altternative is to connect an auxiallry ground so that in
case the ground/neutral in the orignal 3 wire circuit should fail OPEN
which is unusal but can happen, and if it does it hapen it places a
LETHAL voltage on the case of the dryer. This is unacceptable to me!
But I'm not going to pull a new 4 wire cable. An auxialry ground will
prevent electrocution due to a single open failure in the original 3
wire NEC approved system. In my case the auxially ground is the case
of the washer right next to the dryer and the washer is plugged in via
a 3 prong 120V plug. I didn't modify the outlet or cords in any way,
I simply connected a wire between the metal frame of the washer and
dryer. This is legal and makes it safer.

Bottom line for me is.... the big green wire I added connecting the
washer case and dryer case ensure that whatever else might happen,
there can be no dangerous voltage across those two applicances. The
orignal NEC approved 3 wire system did not ensure that.

Answer these two questions and then I am done ..

1) Does adding a big green wire between a washer and dryer case make
the system more or less safe? I say more.

2) Does adding a big green wire between a washer and dryer case
violate any code? I say no.

Do you disagree?

thanks
Mark

wrote in message
...
On Jan 19, 8:02 pm, "RBM" wrote:
"Nate Nagel" wrote in message

...





RBM wrote:
wrote in message
...
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message

...
On Jan 17, 12:32 pm, "Buerste" wrote:

"Gary H" wrote in message
m...
On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste"
wrote:
"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've
always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.
You see, I always thought that the grounded conductor should never
be
current-carrying, in the theory that if the ground feed should
break,
then
the metal chassis of the appliance does not get energized.
Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and
drum
motor.
OK -- am I totally wrong about the code and theory, or is this
unsafe?
Seems to me that dryer would get real "hot" should their be a
fault
in
the
neutral conductor to the breaker box.
I know I'm missing something here as this is SOP as far as I am
aware.
Someone please inform me?
T
Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of
Alternating
current looks like a sine wave on an oscilloscope with the wave
swinging
up
and down. With split phase, it looks like 2 waves on the scope. As
one
wave is bottoming out the other is topping out. They are like
mirror
images
of each other. If you measure the peak of either wave to ground, it
is
120v
Actually, the peak is 170V (RMS * 1.414) but you don't need reality
to
get in the way here :-)
if you measure the top peak of one wave to the bottom of the other,
it
is 240v.
340V. Shut up, reality :-)
There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.
I understand, however to make it a bit clearer I used numbers that
more
easily translated to the OP's ability to understand. Sorry I wasn't
more
technical, do you think he would have understood your numbers better
in
relation to his dryer?- Hide quoted text -
- Show quoted text -
To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was intended
to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through
your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.

Mark

What you are proposing to do, routes dangerous line voltage fault
current
from the dryer to another circuits grounding conductor, or worse, a
water
pipe, which was not designed for that purpose, and is not only
dangerous, but illegal as well. I suggest you get an NEC code book and
research "grounding"

Correct me if I'm mistaken, but doesn't the NEC allow you, in a retrofit
type situation, to replace an ungrounded receptacle with a grounded one
so
long as you ground the receptacle and box to any convenient point "in
the
grounding system" which would include a copper water pipe? I agree,
would
be far better to drag it back to the panel... I honestly don't know what
it says running a ground wire from a plug-connected appliance to a
water pipe. I'd sooner replace the recep. with a 4-wire and use the
exception there; then replace the dryer cord with a 4-wire and remove
the
bonding jumper in the dryer.

Disclaimer: IANAE, I'm posting this for feedback and comment, not as
advice.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

First of all, the code doesn't allow you to ground a receptacle to a water
pipe. It allows you to ground it to any point along the "grounding
electrode
system", which will include the metallic water pipe feeding the building,
but only the first 5 feet of it. A properly installed 3 wire dryer circuit
must meet 4 conditions to be acceptable. The whole idea is to have a
better
quality circuit than just some old piece of Romex making the connection.
Most importantly, electricity takes the path of least resistance. What
happens if this guy's auxiliary ground, which he believes is to protect
someone, is a better path for the normal motor circuit currents to run
through? Now current that should be running through a properly sized
conductor is running through what? And if it's running through some
section
of plumbing, and some plumbing work requires cutting that particular pipe,
what happens to the plumber?- Hide quoted text -

- Show quoted text -

Nothing...

You have the normal neutral/ground wire in parallel with the aux
ground wire. "Electricity takes the path of least resistance" is an
oversimplfication. In fact the current divides inversly
proportionally to the resistance in the path. Yes some of the motor
current may flow through the auxiallry ground. But if that ground
should be opened by the plumber then all the current will flow through
the original ground. The only voltage across the water pipe will be
the small drop due to the resistance of the wire.

I agree this is not an ideal situation, but the problem started
becasue the NEC made a mistake in the first place and allowed 3 wire
220V circuits which are inherently dangerous for all the reasons you
are pointing out. The BEST way to fix this is to replace the 3 wire
system with a 4 wire system , which could requires pulling a new 4
wire cable to replace the existing 3 wire cable. Thats a big job. A
second best altternative is to connect an auxiallry ground so that in
case the ground/neutral in the orignal 3 wire circuit should fail OPEN
which is unusal but can happen, and if it does it hapen it places a
LETHAL voltage on the case of the dryer. This is unacceptable to me!
But I'm not going to pull a new 4 wire cable. An auxialry ground will
prevent electrocution due to a single open failure in the original 3
wire NEC approved system. In my case the auxially ground is the case
of the washer right next to the dryer and the washer is plugged in via
a 3 prong 120V plug. I didn't modify the outlet or cords in any way,
I simply connected a wire between the metal frame of the washer and
dryer. This is legal and makes it safer.

Bottom line for me is.... the big green wire I added connecting the
washer case and dryer case ensure that whatever else might happen,
there can be no dangerous voltage across those two applicances. The
orignal NEC approved 3 wire system did not ensure that.

Answer these two questions and then I am done ..

1) Does adding a big green wire between a washer and dryer case make
the system more or less safe? I say more.

2) Does adding a big green wire between a washer and dryer case
violate any code? I say no.

Do you disagree?

thanks
Mark


I disagree on both counts. The first for the reasons already stated, and
no,the NEC does not approve your method

On Jan 20, 7:02*am, "RBM" wrote:
wrote in message

...
On Jan 19, 8:02 pm, "RBM" wrote:





"Nate Nagel" wrote in message

...

RBM wrote:
wrote in message
...
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message

...
On Jan 17, 12:32 pm, "Buerste" wrote:

"Gary H" wrote in message
m...
On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste"
wrote:
"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've
always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.
You see, I always thought that the grounded conductor should never
be
current-carrying, in the theory that if the ground feed should
break,
then
the metal chassis of the appliance does not get energized.
Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and
drum
motor.
OK -- am I totally wrong about the code and theory, or is this
unsafe?
Seems to me that dryer would get real "hot" should their be a
fault
in
the
neutral conductor to the breaker box.
I know I'm missing something here as this is SOP as far as I am
aware.
Someone please inform me?
T
Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of
Alternating
current looks like a sine wave on an oscilloscope with the wave
swinging
up
and down. With split phase, it looks like 2 waves on the scope. As
one
wave is bottoming out the other is topping out. They are like
mirror
images
of each other. If you measure the peak of either wave to ground, it
is
120v
Actually, the peak is 170V (RMS * 1.414) but you don't need reality
to
get in the way here :-)
if you measure the top peak of one wave to the bottom of the other,
it
is 240v.
340V. Shut up, reality :-)
There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.
I understand, however to make it a bit clearer I used numbers that
more
easily translated to the OP's ability to understand. Sorry I wasn't
more
technical, do you think he would have understood your numbers better
in
relation to his dryer?- Hide quoted text -
- Show quoted text -
To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was intended
to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through
your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.

Mark

What you are proposing to do, routes dangerous line voltage fault
current
from the dryer to another circuits grounding conductor, or worse, a
water
pipe, which was not designed for that purpose, and is not only
dangerous, but illegal as well. I suggest you get an NEC code book and
research "grounding"

Correct me if I'm mistaken, but doesn't the NEC allow you, in a retrofit
type situation, to replace an ungrounded receptacle with a grounded one
so
long as you ground the receptacle and box to any convenient point "in
the
grounding system" which would include a copper water pipe? I agree,
would
be far better to drag it back to the panel... I honestly don't know what
it says running a ground wire from a plug-connected appliance to a
water pipe. I'd sooner replace the recep. with a 4-wire and use the
exception there; then replace the dryer cord with a 4-wire and remove
the
bonding jumper in the dryer.

Disclaimer: IANAE, I'm posting this for feedback and comment, not as
advice.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

First of all, the code doesn't allow you to ground a receptacle to a water
pipe. It allows you to ground it to any point along the "grounding
electrode
system", which will include the metallic water pipe feeding the building,
but only the first 5 feet of it. A properly installed 3 wire dryer circuit
must meet 4 conditions to be acceptable. The whole idea is to have a
better
quality circuit than just some old piece of Romex making the connection..
Most importantly, electricity takes the path of least resistance. What
happens if this guy's auxiliary ground, which he believes is to protect
someone, is a better path for the normal motor circuit currents to run
through? Now current that should be running through a properly sized
conductor is running through what? And if it's running through some
section
of plumbing, and some plumbing work requires cutting that particular pipe,
what happens to the plumber?- Hide quoted text -

- Show quoted text -

Nothing...

You have the normal neutral/ground *wire in parallel with *the aux
ground wire. * "Electricity takes the path of least resistance" is an
oversimplfication. *In fact the current divides inversly
proportionally to the resistance in the path. *Yes some of the motor
current may flow through the auxiallry ground. *But if that ground
should be opened by the plumber then all the current will flow through
the original ground. *The only voltage across the water pipe will be
the small drop due to the resistance of the wire.

I agree this is not an ideal situation, but the problem started
becasue the NEC made a mistake in the first place and allowed 3 wire
220V circuits which are inherently dangerous for all the reasons you
are pointing out. *The BEST way to fix this is to replace the 3 wire
system with a 4 wire system , which could requires *pulling a new 4
wire cable to replace the existing 3 wire cable. Thats a big job. *A
second best altternative is to connect an auxiallry ground so that in
case the ground/neutral in the orignal 3 wire circuit should fail OPEN
which is unusal but can happen, and if it does it hapen it places a
LETHAL voltage on the case of the dryer. *This is unacceptable to me!
But I'm not going to pull a new 4 wire cable. *An auxialry ground will
prevent electrocution due to a single open failure in the original 3
wire NEC approved system. In my case the auxially ground is the case
of the washer right next to the dryer and the washer is plugged in via
a 3 prong 120V plug. *I didn't modify the outlet or cords in any way,
I simply connected a wire between the metal frame of the washer and
dryer. *This is legal and makes it safer.

Bottom line for me is.... the big green wire I added connecting the
washer case *and dryer case ensure that whatever else might happen,
there can be no dangerous voltage across those two applicances. *The
orignal NEC approved 3 wire system did not ensure that.

Answer these two questions and then I am done ..

1) Does adding a big green wire between a washer and dryer case make
the system more or less safe? *I say more.

2) Does adding a big green wire between a washer and dryer case
violate any code? *I say no.

Do you disagree?

thanks
Mark

I disagree on both counts. The first for the reasons already stated, and
no,the NEC does not approve your method- Hide quoted text -

- Show quoted text -

Out of curiousity, what exactly in the NEC says you can't bond the
metal cases of two appliances together? In some cases, SPAs for
example, code specifically requires that all metal within a certain
distance be bonded together. So, if that washer or dryer happened to
be within the specified distance from a spa, it would have to be
bonded to the spa pump, heater, etc.

I see both sides to this discussion. I'm generally not in favor of
rube goldberg adaptions. But on the other hand, not sure what says
you can't bond two metal objects together. Also, in the case of the
washer/dryer, bonding would seem to be a good idea, because the washer
is a very likely object to come in contact with simultaneously with
the dryer, so having them at equi potential seems like a good idea.

wrote in message
...
On Jan 20, 7:02 am, "RBM" wrote:
wrote in message

...
On Jan 19, 8:02 pm, "RBM" wrote:





"Nate Nagel" wrote in message

...

RBM wrote:
wrote in message
...
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message

...
On Jan 17, 12:32 pm, "Buerste" wrote:

"Gary H" wrote in message
m...
On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste"
wrote:
"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've
always
wondered how they serve up 240 V with 120V components (e.g.
timer
motor)
on only three wires.
You see, I always thought that the grounded conductor should
never
be
current-carrying, in the theory that if the ground feed should
break,
then
the metal chassis of the appliance does not get energized.
Well looks like that "3rd" wire, is a neutral, and judging by
the
dryer
schematic, is both used as a chassis ground and a
current-carrying
conductor for the 120V items on the dryer -- such as timer and
drum
motor.
OK -- am I totally wrong about the code and theory, or is this
unsafe?
Seems to me that dryer would get real "hot" should their be a
fault
in
the
neutral conductor to the breaker box.
I know I'm missing something here as this is SOP as far as I am
aware.
Someone please inform me?
T
Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with
each
other.
The potential between either phase and ground/neutral is 120v.
The
potential between the two hots is 240v. A single phase of
Alternating
current looks like a sine wave on an oscilloscope with the wave
swinging
up
and down. With split phase, it looks like 2 waves on the scope.
As
one
wave is bottoming out the other is topping out. They are like
mirror
images
of each other. If you measure the peak of either wave to ground,
it
is
120v
Actually, the peak is 170V (RMS * 1.414) but you don't need
reality
to
get in the way here :-)
if you measure the top peak of one wave to the bottom of the
other,
it
is 240v.
340V. Shut up, reality :-)
There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.
I understand, however to make it a bit clearer I used numbers that
more
easily translated to the OP's ability to understand. Sorry I wasn't
more
technical, do you think he would have understood your numbers
better
in
relation to his dryer?- Hide quoted text -
- Show quoted text -
To the OP, you are exactly correct, the 3 wire system can be
dangerous
if the "ground neutral" wire opens becasue most dryers have a 120
volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do
that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was
intended
to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current
through
your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage
appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this
dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.

Mark

What you are proposing to do, routes dangerous line voltage fault
current
from the dryer to another circuits grounding conductor, or worse, a
water
pipe, which was not designed for that purpose, and is not only
dangerous, but illegal as well. I suggest you get an NEC code book
and
research "grounding"

Correct me if I'm mistaken, but doesn't the NEC allow you, in a
retrofit
type situation, to replace an ungrounded receptacle with a grounded
one
so
long as you ground the receptacle and box to any convenient point "in
the
grounding system" which would include a copper water pipe? I agree,
would
be far better to drag it back to the panel... I honestly don't know
what
it says running a ground wire from a plug-connected appliance to a
water pipe. I'd sooner replace the recep. with a 4-wire and use the
exception there; then replace the dryer cord with a 4-wire and remove
the
bonding jumper in the dryer.

Disclaimer: IANAE, I'm posting this for feedback and comment, not as
advice.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

First of all, the code doesn't allow you to ground a receptacle to a
water
pipe. It allows you to ground it to any point along the "grounding
electrode
system", which will include the metallic water pipe feeding the
building,
but only the first 5 feet of it. A properly installed 3 wire dryer
circuit
must meet 4 conditions to be acceptable. The whole idea is to have a
better
quality circuit than just some old piece of Romex making the connection.
Most importantly, electricity takes the path of least resistance. What
happens if this guy's auxiliary ground, which he believes is to protect
someone, is a better path for the normal motor circuit currents to run
through? Now current that should be running through a properly sized
conductor is running through what? And if it's running through some
section
of plumbing, and some plumbing work requires cutting that particular
pipe,
what happens to the plumber?- Hide quoted text -

- Show quoted text -

Nothing...

You have the normal neutral/ground wire in parallel with the aux
ground wire. "Electricity takes the path of least resistance" is an
oversimplfication. In fact the current divides inversly
proportionally to the resistance in the path. Yes some of the motor
current may flow through the auxiallry ground. But if that ground
should be opened by the plumber then all the current will flow through
the original ground. The only voltage across the water pipe will be
the small drop due to the resistance of the wire.

I agree this is not an ideal situation, but the problem started
becasue the NEC made a mistake in the first place and allowed 3 wire
220V circuits which are inherently dangerous for all the reasons you
are pointing out. The BEST way to fix this is to replace the 3 wire
system with a 4 wire system , which could requires pulling a new 4
wire cable to replace the existing 3 wire cable. Thats a big job. A
second best altternative is to connect an auxiallry ground so that in
case the ground/neutral in the orignal 3 wire circuit should fail OPEN
which is unusal but can happen, and if it does it hapen it places a
LETHAL voltage on the case of the dryer. This is unacceptable to me!
But I'm not going to pull a new 4 wire cable. An auxialry ground will
prevent electrocution due to a single open failure in the original 3
wire NEC approved system. In my case the auxially ground is the case
of the washer right next to the dryer and the washer is plugged in via
a 3 prong 120V plug. I didn't modify the outlet or cords in any way,
I simply connected a wire between the metal frame of the washer and
dryer. This is legal and makes it safer.

Bottom line for me is.... the big green wire I added connecting the
washer case and dryer case ensure that whatever else might happen,
there can be no dangerous voltage across those two applicances. The
orignal NEC approved 3 wire system did not ensure that.

Answer these two questions and then I am done ..

1) Does adding a big green wire between a washer and dryer case make
the system more or less safe? I say more.

2) Does adding a big green wire between a washer and dryer case
violate any code? I say no.

Do you disagree?

thanks
Mark

I disagree on both counts. The first for the reasons already stated, and
no,the NEC does not approve your method- Hide quoted text -

- Show quoted text -

Out of curiousity, what exactly in the NEC says you can't bond the
metal cases of two appliances together? In some cases, SPAs for
example, code specifically requires that all metal within a certain
distance be bonded together. So, if that washer or dryer happened to
be within the specified distance from a spa, it would have to be
bonded to the spa pump, heater, etc.

I see both sides to this discussion. I'm generally not in favor of
rube goldberg adaptions. But on the other hand, not sure what says
you can't bond two metal objects together. Also, in the case of the
washer/dryer, bonding would seem to be a good idea, because the washer
is a very likely object to come in contact with simultaneously with
the dryer, so having them at equi potential seems like a good idea.

With a hot tub, you want anything within reach, likely to become energized,
to be bonded to the very substantial grounding system of the tub

Three wire electric dryers are more of an isolated application, so typical
laws or rules that normally make sense, don't apply. The body of the machine
is part of the live circuit, not just fault currents. It requires a special
cable (SE) or insulated ground/neutral, originating only from a main service
panel. Under no circumstances would you want the grounding system of another
circuit to become or act as a live neutral conductor from a clothes dryer,
or potentially more dangerous would be using an internal plumbing system. In
the event you lose your neutral/ ground on a three wire dryer circuit, the
motor won't turn and although the chassis of the machine would be live,
you'd still know that a problem existed, and would have it fixed. If you add
a supplemental ground to the neighboring washer, you'd have no way of even
knowing that dangerous neutral currents were running through the washer
outlet's grounding system

On Mon, 19 Jan 2009 17:06:16 -0500, "RBM" wrote:


wrote in message
...
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message

...
On Jan 17, 12:32 pm, "Buerste" wrote:





"Gary H" wrote in message

.. .

On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:

"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer
motor)
on only three wires.

You see, I always thought that the grounded conductor should never
be
current-carrying, in the theory that if the ground feed should
break,
then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the
dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum
motor.

OK -- am I totally wrong about the code and theory, or is this
unsafe?
Seems to me that dryer would get real "hot" should their be a fault
in
the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am
aware.
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each
other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave
swinging
up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror
images
of each other. If you measure the peak of either wave to ground, it is
120v

Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)

if you measure the top peak of one wave to the bottom of the other,
it
is 240v.

340V. Shut up, reality :-)

There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.

I understand, however to make it a bit clearer I used numbers that more
easily translated to the OP's ability to understand. Sorry I wasn't more
technical, do you think he would have understood your numbers better in
relation to his dryer?- Hide quoted text -

- Show quoted text -

To the OP, you are exactly correct, the 3 wire system can be dangerous
if the "ground neutral" wire opens becasue most dryers have a 120 volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was intended to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current through
your
plumbing or other appliances- Hide quoted text -

- Show quoted text -

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage appearing
on the dryer frame which is far more dangerous..

Using the 3 wire system "as it was intended" can create this dangerous
condition, that's why they changed it.

I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..

To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.


Are you sure you mean POLARITY there? The polarity is reversing 120
times per second. That sounds like "phase".

Mark


What you are proposing to do, routes dangerous line voltage fault current
from the dryer to another circuits grounding conductor, or worse, a water
pipe, which was not designed for that purpose, and is not only dangerous,
but illegal as well. I suggest you get an NEC code book and research
"grounding"

On Mon, 19 Jan 2009 19:13:57 -0500, "Ralph Mowery"
wrote:


"Gary H" wrote in message
.. .
On Sun, 18 Jan 2009 22:04:22 -0500, "Ralph Mowery"
wrote:


"Tman" wrote in message
...

LOL, OP here. I took a couple EE courses when working on my MS
aerospace
engineering and did an internship where I designed one of the lightest
400Hz DC-AC inverter for aerospace use. I get the split phase, peak /
RMS
business quite fine. I'm just not totally up to speed with what's code
and what's not -- and this rig seemed to be amiss.

I guess in the name of being pedantic, I'll point out that the two hots
probably are not exactly "180 degrees" out of phase and "mirror images"
of
each other; close but in real life situations the reactive loads will
not
be [perfectly] identical across both phases, making the out-of-phase,
well
just a little bit different than pi radians

T

What you are calling two hots are comming from a center tapped
transformer.
There is only one phase. They can not be out of phase with each other by
any ammount not counting a couple of inches of wire from the transfromer
windings to the load.


It depends on your point of reference. The normal point of reference
(for wiring on the transformer secondary) is in the MIDDLE
(center-tapped coil). Points are measured from that. That is, 2
phases.

What may be confusing to some, is these 2 phases are not 2 of the 3
phases being supplied to the transformer.

The wiring comming into a normal house in the US is single phase. Not two
phase. True two phase power has the phases 90 deg out instead of the so
called 180 deg .


The problem with that is that "phase" already means something.
Something that applies equally well to your (I mean the 90-deg apart
one) 2-phase system, 3-phase power, and the normal system used in
houses. Measurements are made in reference to a common point (ground)
which is in the middle of that (residential) transformer. Measuring
the ends of the transformer with a dual-trace scope will show TWO
PHASES. In this case, one leg will show 90 degrees (most positive)
while the other leg will show 270 degrees (most negative) at the same
time. That's two different phases.

Two phase powe can be made from a 3 phase circuit, but it requires more than
a simple center tapped transformer the normal house has.

RBM wrote:
wrote in message
...
On Jan 20, 7:02 am, "RBM" wrote:
wrote in message
On Jan 19, 8:02 pm, "RBM" wrote:
"Nate Nagel" wrote in message
...
RBM wrote:
wrote in message
...
On Jan 17, 4:05 pm, "RBM" wrote:
wrote in message
...
On Jan 17, 12:32 pm, "Buerste" wrote:

To the OP, you are exactly correct, the 3 wire system can be
dangerous
if the "ground neutral" wire opens becasue most dryers have a 120
volt
motor so that current flows through the neutral ground. NEC code as
picky as it is used to allow this. I think it is now not allowed in
new homes. I have a 3 wire dryer and I added a ground wire connected
from the frame of the dryer to the frame of the washer. This way,
whatever else happens there can be no voltage across those two
appliances and the washer has a 3 prong plug so it is grounded. You
can also connect it to a cold water pipe. I would suggest you do
that
as an extra saftey feature.
Good question
Mark

I would recommend using a 3 wire dryer circuit just as it was
intended
to
be used or replace it with a proper 4 wire system. Installing a Rube
Goldberg grounding addition isn't helping the situation, and could
potentially cause more harm running line voltage fault current
through
your
plumbing or other appliances-

an additional ground wire connected to the dryer frame helps the
situation becasue it prevents the possiblity of line voltage
appearing
on the dryer frame which is far more dangerous..
Using the 3 wire system "as it was intended" can create this
dangerous
condition, that's why they changed it.
I agree, changing over to a 4 wire system is a better option, but if
you have a 3 wire cable it is not easy to do..
To the op re being an EE and calling it 220 VAC two phases, it is
common usgage but technically wrong. It is more technically correct
to say two POLARITIES of one phase.
Mark

What you are proposing to do, routes dangerous line voltage fault
current
from the dryer to another circuits grounding conductor, or worse, a
water
pipe, which was not designed for that purpose, and is not only
dangerous, but illegal as well. I suggest you get an NEC code book
and
research "grounding"

Correct me if I'm mistaken, but doesn't the NEC allow you, in a
retrofit
type situation, to replace an ungrounded receptacle with a grounded
one
so
long as you ground the receptacle and box to any convenient point "in
the
grounding system" which would include a copper water pipe?

Applies if there is not a grounding conductor at the receptacle. In this
case there is.

Don't think there is a prohibition against a redundant ground, except in
this case it becomes a parallel neutral conductor.

I agree,
would
be far better to drag it back to the panel... I honestly don't know
what
it says running a ground wire from a plug-connected appliance to a
water pipe. I'd sooner replace the recep. with a 4-wire and use the
exception there; then replace the dryer cord with a 4-wire and remove
the
bonding jumper in the dryer.
Disclaimer: IANAE, I'm posting this for feedback and comment, not as
advice.
nate


First of all, the code doesn't allow you to ground a receptacle to a
water
pipe. It allows you to ground it to any point along the "grounding
electrode
system", which will include the metallic water pipe feeding the
building,
but only the first 5 feet of it. A properly installed 3 wire dryer
circuit
must meet 4 conditions to be acceptable. The whole idea is to have a
better
quality circuit than just some old piece of Romex making the connection.
Most importantly, electricity takes the path of least resistance. What
happens if this guy's auxiliary ground, which he believes is to protect
someone, is a better path for the normal motor circuit currents to run
through? Now current that should be running through a properly sized
conductor is running through what? And if it's running through some
section
of plumbing, and some plumbing work requires cutting that particular
pipe,
what happens to the plumber?

Nothing...

You have the normal neutral/ground wire in parallel with the aux
ground wire. "Electricity takes the path of least resistance" is an
oversimplfication. In fact the current divides inversly
proportionally to the resistance in the path. Yes some of the motor
current may flow through the auxiallry ground. But if that ground
should be opened by the plumber then all the current will flow through
the original ground. The only voltage across the water pipe will be
the small drop due to the resistance of the wire.

I agree this is not an ideal situation, but the problem started
becasue the NEC made a mistake in the first place and allowed 3 wire
220V circuits which are inherently dangerous for all the reasons you
are pointing out.

The NEC allowed this "dangerous" method for about 30 years. Apparently
the NEC didn't think it was particularly "dangerous". And since the best
way to get the code changed is to show dead bodies, apparently it was
not a "dangerous" method.

The BEST way to fix this is to replace the 3 wire
system with a 4 wire system , which could requires pulling a new 4
wire cable to replace the existing 3 wire cable.

If I had an electric dryer with a 3-wire circuit I might replace the
wiring if it was easy. If not I would use the existing 3-wire circuit.
As Roy pointed out, there were major limitations on how these circuits
were wired. Like for instance you couldn't use Romex.

Thats a big job. A
second best altternative is to connect an auxiallry ground so that in
case the ground/neutral in the orignal 3 wire circuit should fail OPEN
which is unusal but can happen, and if it does it hapen it places a
LETHAL voltage on the case of the dryer. This is unacceptable to me!
But I'm not going to pull a new 4 wire cable. An auxialry ground will
prevent electrocution due to a single open failure in the original 3
wire NEC approved system. In my case the auxially ground is the case
of the washer right next to the dryer and the washer is plugged in via
a 3 prong 120V plug. I didn't modify the outlet or cords in any way,
I simply connected a wire between the metal frame of the washer and
dryer. This is legal and makes it safer.

Bottom line for me is.... the big green wire I added connecting the
washer case and dryer case ensure that whatever else might happen,
there can be no dangerous voltage across those two applicances. The
orignal NEC approved 3 wire system did not ensure that.

Answer these two questions and then I am done ..

1) Does adding a big green wire between a washer and dryer case make
the system more or less safe? I say more.

2) Does adding a big green wire between a washer and dryer case
violate any code? I say no.

Do you disagree?

thanks
Mark

I disagree on both counts. The first for the reasons already stated, and
no,the NEC does not approve your method

- Show quoted text -
It would be nice to edit these things out.

Out of curiousity, what exactly in the NEC says you can't bond the
metal cases of two appliances together?

The argument that can be made in this case is that the alternate ground
path also becomes an alternate neutral return. That puts some normal
neutral current on the grounding conductor which is verbotten. Just like
bonding neutral and ground at a subpanel.

In some cases, SPAs for
example, code specifically requires that all metal within a certain
distance be bonded together.

Without looking it up, I believe it is isolated metal that might become
energized.

So, if that washer or dryer happened to
be within the specified distance from a spa, it would have to be
bonded to the spa pump, heater, etc.

I believe the specified distance is 5 feet (so you can be in contact
with the spa and the other metal). You can't have receptacles in that
area. You wouldn't want a hypothetical dryer either.

I see both sides to this discussion. I'm generally not in favor of
rube goldberg adaptions. But on the other hand, not sure what says
you can't bond two metal objects together. Also, in the case of the
washer/dryer, bonding would seem to be a good idea, because the washer
is a very likely object to come in contact with simultaneously with
the dryer, so having them at equi potential seems like a good idea.

One can certainly argue both sides. I agree with Roy.

--
bud--

"Gary H" wrote in
message
...
On Sun, 18 Jan 2009 22:04:22 -0500, "Ralph
Mowery"
wrote:


"Tman" wrote in
message
...

LOL, OP here. I took a couple EE courses
when working
on my MS aerospace
engineering and did an internship where I
designed one
of the lightest 400Hz DC-AC inverter for
aerospace
use. I get the split phase, peak / RMS
business quite fine. I'm just not totally up
to speed
with what's code and what's not -- and this
rig seemed
to be amiss. I guess in the name of being
pedantic, I'll point out
that the two hots probably are not exactly
"180
degrees" out of phase and "mirror images" of
each other; close but in real life situations
the
reactive loads will not
be [perfectly] identical across both phases,
making
the out-of-phase, well
just a little bit different than pi radians


T

What you are calling two hots are comming from
a center
tapped transformer.
There is only one phase. They can not be out
of phase
with each other by any ammount not counting a
couple of
inches of wire from the transfromer windings
to the
load.

It depends on your point of reference. The
normal point
of reference (for wiring on the transformer
secondary)
is in the MIDDLE (center-tapped coil). Points
are
measured from that. That is, 2 phases.

What may be confusing to some, is these 2
phases are not
2 of the 3 phases being supplied to the
transformer.

The wiring comming into a normal house in the US
is
single phase. Not two phase. True two phase
power has
the phases 90 deg out instead of the so called
180 deg .

Two phase powe can be made from a 3 phase
circuit, but it
requires more than a simple center tapped
transformer the
normal house has.

Technicall it's called split phase.