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

...





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

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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?- 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.

No, it's not. It's perfectly and absolutely true.
Electricity will NEVER seek any other path but
that of the lowest resistanct/impedance/whatever.

In fact the
current divides inversly proportionally to the
resistance
in the path.

Uhh, yeah, to the lower resistance 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.

Depends.


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.

240Vac (or 220 if that's what you like to call it)
in a Class II constructed appliance is exactly as
safe as 120V in a Class II constructed appliance.
They will not be inherently dangerous.
Even under the scenario being attempted to be
described here, without a fault occurring, there
can be no danger.
The world changes and the NEC, being the first
level of protection, changes with it. Also note
that depending on the NEC can still very easily
result in a non-compliant installation in almost
every North American jurisdiction. Loca code
enforcement always has the last say.

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.

Without knowing what you actually have there, it's
hard to say. You may feel safer, but you aren't
to code whenever you daisy chain an earth
connection like that. Plus, you didn't
necessarily get ALL exposed metal with such a
wire - many metal parts could still be ungrounded,
besides not being arranged in the spedified start
connection required of earthing methods. Earth
has to be the middle of the star, and all
components star connected into it. A dryer cannot
be a star component; all stars must be internal.

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.

Other than missing information having neglected
any local codes, you're very likely out of
complaince. Additionally, how do you know that
ALL exposed metal has been earthed by the addition
of that one wire? I suspect you don't; so you may
well still have the possibility of further points
of access to the theorized voltage.

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.

More. But not completely.


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

It may well violate local codes. Disconnection,
or damage to, the wire can, witout notice, return
you to the previous same situation you had (like,
someone besides you moves one of them, maybe a
service man, next owner, whatever). Codes don't
allow relying on such a thing. UL, CSA and the EC
safety codes are all the same at that point too,
in addition to local codes.
Since UL/CSA/EC/NOMs are required to sell such
a product in NA, you have disturbed the design of
both systems and they are no longer certified.
UL1459 is the only spec that comes to mind right
now, and it's going to have a superceded by ...
note. It's been quite awhile.
Remember, the NEC is MINIMUM requirements, NOT the
BEST! NEC is always specced as the first
requirement, then code offices add their own
additional requirements to them where it's deemed
necessary.

Do you disagree?

Sort of. I think the thread has become disengaged
from reality at some point and too many factors
are missing to try to go back and recapture them.

thanks
Mark

"bud--" wrote in message
.. .
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--

Damn, where you been Bud, I'm exhausted already. What's really interesting
is that the Consumer products safety commission has the data on
electrocutions from household appliances, and there is no difference between
deaths from clothes dryers and any other appliances, in fact airconditioners
cause more deaths than dryers. go figure

No, it's not. *It's perfectly and absolutely true.
Electricity will NEVER seek any other path but
that of the lowest resistanct/impedance/whatever.


So you think if you put a 20 Ohm resistor in parallel with a 1 Ohm
resistor then 0 current will flow through the 20 Ohm resistor and ALL
the current will flow in the 1 Ohm resistor?

If that's what you think, you are ABSOLUTLY WRONG.
I'm not going to debate this with you, its a fact.


Mark

wrote:
No, it's not. It's perfectly and absolutely true.
Electricity will NEVER seek any other path but
that of the lowest resistanct/impedance/whatever.


So you think if you put a 20 Ohm resistor in parallel with a 1 Ohm
resistor then 0 current will flow through the 20 Ohm resistor and ALL
the current will flow in the 1 Ohm resistor?

If that's what you think, you are ABSOLUTLY WRONG.
I'm not going to debate this with you, its a fact.


Mark

This whole thread and that exchagne above are exhibiting the difference
between and electrician and an EE.
EE's are right.
Electricians are practical.

On Tue, 20 Jan 2009 19:18:36 -0500, Tman
wrote:

wrote:
No, it's not. It's perfectly and absolutely true.
Electricity will NEVER seek any other path but
that of the lowest resistanct/impedance/whatever.


So you think if you put a 20 Ohm resistor in parallel with a 1 Ohm
resistor then 0 current will flow through the 20 Ohm resistor and ALL
the current will flow in the 1 Ohm resistor?

If that's what you think, you are ABSOLUTLY WRONG.
I'm not going to debate this with you, its a fact.


Mark

This whole thread and that exchagne above are exhibiting the difference
between and electrician and an EE.
EE's are right.
Electricians are practical.

100-ohm and 200-ohm resistor in parallel across 120V.

Current through the path of least resistance = 1.2A

Current through the 200-ohm resistor = 600mA

Since this (200-ohm resistor) is not the path of least resistance,
practical people WILL NOT be electrocuted :-)

BTW, I did not calculate 1 / ((1 / R1) + (1 / R2))

On Tue, 20 Jan 2009 19:18:36 -0500, Tman
wrote:

wrote:
No, it's not. It's perfectly and absolutely true.
Electricity will NEVER seek any other path but
that of the lowest resistanct/impedance/whatever.


So you think if you put a 20 Ohm resistor in parallel with a 1 Ohm
resistor then 0 current will flow through the 20 Ohm resistor and ALL
the current will flow in the 1 Ohm resistor?

If that's what you think, you are ABSOLUTLY WRONG.
I'm not going to debate this with you, its a fact.


Mark

This whole thread and that exchagne above are exhibiting the difference
between and electrician and an EE.
EE's are right.
Electricians are practical.

We are the AC Borg
Your "path of least resistance" is irrelevant
You are irrelevant
You will be electrocuted

Harry L wrote:
On Tue, 20 Jan 2009 19:18:36 -0500, Tman
wrote:

wrote:
No, it's not. It's perfectly and absolutely true.
Electricity will NEVER seek any other path but
that of the lowest resistanct/impedance/whatever.

So you think if you put a 20 Ohm resistor in parallel with a 1 Ohm
resistor then 0 current will flow through the 20 Ohm resistor and ALL
the current will flow in the 1 Ohm resistor?

If that's what you think, you are ABSOLUTLY WRONG.
I'm not going to debate this with you, its a fact.


Mark
This whole thread and that exchagne above are exhibiting the difference
between and electrician and an EE.
EE's are right.
Electricians are practical.

We are the AC Borg
Your "path of least resistance" is irrelevant
You are irrelevant
You will be electrocuted
I'll die right!

RBM wrote:

Damn, where you been Bud, I'm exhausted already.

I can see why. By the time I get to this newsgroup you've answered all
the questions. (NOT a complaint.) I don't know how you get anything else
done.

What's really interesting
is that the Consumer products safety commission has the data on
electrocutions from household appliances, and there is no difference between
deaths from clothes dryers and any other appliances, in fact airconditioners
cause more deaths than dryers. go figure

Why do you want to go and ruin a good argument with facts???

--
bud--