14-3 shared neutral

[Rich Grise]

On Thu, 24 Feb 2005 09:00:16 -0500, Beeper top-posted (see below for
context)

Terry, you just said what I was hoping to hear. It is OK if the two seperate
circuits are mechanically connected(if you will) If one trips, the other one
trips also. This was not true in my case and that's why I questioned it. How
about everyone else who knows residential code. Mechanically connected? yes
or no?

They should be mechanically connected (ganged) if you will be using the
two hots for a 220 (240) load down the line. If you don't have anything
like that, and are absolutely certain that you never will, then
independent breakers should be fine. The most the neutral will ever have
to carry will be the current to the one side; otherwise they subtract,
as Terry has pointed out.

If each circuit has its own neutral conductor, then ganging breakers
doesn't make any sense in the first place - they're completely independent
circuits.

Hope This Helps!
Rich

[Context]:

"Terry" <tsanford@nf.sympatico.ca> wrote in message
news:u03Td.14418$uO.496701@news20.bellglobal.com...

"Beeper" <Beeper@echoes.net> wrote in message
news:cvi83301hjc@enews3.newsguy.com...
I'd like some feed back on this one. When I built my house, I had a
very honest Father and Son contractor who were jack of all trades.
They did the wiring also. Sloppy but functional. A few years later,
while making some changes, I noticed they used 14-3 wiring to run 2
seperate circuits. These 2 circuits shared the neutral.
Beeper: I have duplex outlets in my kitchen wired this way. the upper
socket is wired, say to the red, and the lower socket of the duplex to
the black. This is not to get 230 volts between upper and lower but
does allow two 115 volt loads to be plugged in, effectively doubling
the current capacity of the outlet. With 14 AWG that circuit should be
fused/breakered at 15 amps. A double pole breaker should be used to
disconnect both sides 'legs' of the supply to that circuit
simultaneously. Terry

 

[Rich Grise]

On Wed, 23 Feb 2005 18:43:26 -0800, John Larkin wrote:

On Wed, 23 Feb 2005 21:11:22 GMT, Rich Grise <richgrise@example.net
wrote:

On Wed, 23 Feb 2005 09:40:23 -0800, John Larkin wrote:

On Wed, 23 Feb 2005 13:38:01 -0330, "Terry" <tsanford@nf.sympatico.ca
wrote:

Someone wrote:
" Right, so long as the two branches are on different phases".

Err? Different 'Legs' might be a better term?

Well, I'm an electrical engineer, and we don't refer to "legs". By
"different phases" I meant that the voltages are, well, not in phase.

But with a 240V center-tapped transformer, they are exactly in phase -
simply opposite polarity, with respect to the center-tap.

Cheers!
Rich

As I said, to see if they're in phase, merely connect them together
and see what happens. Report back and I'll interpret the experiment
for you.

By this logic, the positive pole of a battery is 180 degrees out of
phase with the negative pole.

Thanks,
Rich

 

[John Larkin]

On Thu, 24 Feb 2005 20:28:24 GMT, Rich Grise <richgrise@example.net>
wrote:

On Wed, 23 Feb 2005 18:43:26 -0800, John Larkin wrote:

On Wed, 23 Feb 2005 21:11:22 GMT, Rich Grise <richgrise@example.net
wrote:

On Wed, 23 Feb 2005 09:40:23 -0800, John Larkin wrote:

On Wed, 23 Feb 2005 13:38:01 -0330, "Terry" <tsanford@nf.sympatico.ca
wrote:

Someone wrote:
" Right, so long as the two branches are on different phases".

Err? Different 'Legs' might be a better term?

Well, I'm an electrical engineer, and we don't refer to "legs". By
"different phases" I meant that the voltages are, well, not in phase.

But with a 240V center-tapped transformer, they are exactly in phase -
simply opposite polarity, with respect to the center-tap.

Cheers!
Rich

As I said, to see if they're in phase, merely connect them together
and see what happens. Report back and I'll interpret the experiment
for you.


By this logic, the positive pole of a battery is 180 degrees out of
phase with the negative pole.

No, phase is meaningless for DC.

John

 

[John Fields]

On Wed, 23 Feb 2005 21:11:22 GMT, Rich Grise <richgrise@example.net>
wrote:

On Wed, 23 Feb 2005 09:40:23 -0800, John Larkin wrote:

On Wed, 23 Feb 2005 13:38:01 -0330, "Terry" <tsanford@nf.sympatico.ca
wrote:

Someone wrote:
" Right, so long as the two branches are on different phases".

Err? Different 'Legs' might be a better term?

Well, I'm an electrical engineer, and we don't refer to "legs". By
"different phases" I meant that the voltages are, well, not in phase.

But with a 240V center-tapped transformer, they are exactly in phase -
simply opposite polarity, with respect to the center-tap.

---
No, they're not.

If you use one end of the transformer secondary as a reference, the
center tap will be in phase with the other end of the winding, (that
is, one positive-going peak will occur at the same time as the other
positive-going peak) but if you use the center tap as the reference
the ends of the winding will be 180° out of phase with each other.
That is, the positive-going peak of one will occur when the
negative-going peak of the other occurs.

--
John Fields

 

[Peter Bennett]

On Thu, 24 Feb 2005 20:27:26 GMT, Rich Grise <richgrise@example.net>
wrote:

On Thu, 24 Feb 2005 09:00:16 -0500, Beeper top-posted (see below for
context)

Terry, you just said what I was hoping to hear. It is OK if the two seperate
circuits are mechanically connected(if you will) If one trips, the other one
trips also. This was not true in my case and that's why I questioned it. How
about everyone else who knows residential code. Mechanically connected? yes
or no?

They should be mechanically connected (ganged) if you will be using the
two hots for a 220 (240) load down the line. If you don't have anything
like that, and are absolutely certain that you never will, then
independent breakers should be fine. The most the neutral will ever have
to carry will be the current to the one side; otherwise they subtract,
as Terry has pointed out.

If two circuits are run in a single 14/3 cable, the breakers feeding
that cable _must_ be mechanically interlocked, so that they will
switch on or off together, whether or not you are using them as a 220
V supply. The reason for this is so that if you turn off one circuit
to work on it, you won't get burned by the other, which will terminate
in the same box.











--
Peter Bennett VE7CEI
email: peterbb4 (at) interchange.ubc.ca
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

 

[Rich Grise]

On Thu, 24 Feb 2005 16:08:35 -0800, Peter Bennett wrote:

On Thu, 24 Feb 2005 20:27:26 GMT, Rich Grise <richgrise@example.net
wrote:

On Thu, 24 Feb 2005 09:00:16 -0500, Beeper top-posted (see below for
context)

Terry, you just said what I was hoping to hear. It is OK if the two seperate
circuits are mechanically connected(if you will) If one trips, the other one
trips also. This was not true in my case and that's why I questioned it. How
about everyone else who knows residential code. Mechanically connected? yes
or no?

They should be mechanically connected (ganged) if you will be using the
two hots for a 220 (240) load down the line. If you don't have anything
like that, and are absolutely certain that you never will, then
independent breakers should be fine. The most the neutral will ever have
to carry will be the current to the one side; otherwise they subtract,
as Terry has pointed out.

If two circuits are run in a single 14/3 cable, the breakers feeding
that cable _must_ be mechanically interlocked, so that they will
switch on or off together, whether or not you are using them as a 220
V supply. The reason for this is so that if you turn off one circuit
to work on it, you won't get burned by the other, which will terminate
in the same box.

I stand corrected. I keep forgetting that regulations are written in
hopes of minimizing the Darwin effect.

Thanks,
Rich

 

[John Larkin]

On Fri, 25 Feb 2005 02:21:57 GMT, Rich Grise <richgrise@example.net>
wrote:

On Thu, 24 Feb 2005 17:48:28 -0600, John Fields wrote:
On Wed, 23 Feb 2005 21:11:22 GMT, Rich Grise <richgrise@example.net

But with a 240V center-tapped transformer, they are exactly in phase -
simply opposite polarity, with respect to the center-tap.

No, they're not.

If you use one end of the transformer secondary as a reference, the
center tap will be in phase with the other end of the winding, (that
is, one positive-going peak will occur at the same time as the other
positive-going peak) but if you use the center tap as the reference
the ends of the winding will be 180° out of phase with each other.
That is, the positive-going peak of one will occur when the
negative-going peak of the other occurs.

Let me put it this way.

A 180 degree phase-shifted sine wave is _visually indistinguishable_
from an instantaneously-inverted sine wave, that is, they _look_
exactly the same, but they are not the same, because they got
created by a different process.

To put it to an extreme example, consider a pulse train:
_ _ _ _ _ _
___| |_____| |_____| |_____| |_____| |_____| |__

Phase-shift it 180 degrees, and you get this:
_ _ _ _ _ _ _
|_____| |_____| |_____| |_____| |_____| |_____| |__

But if you invert it, you get this:
____ _____ _____ _____ _____ _____ ___
|_| |_| |_| |_| |_| |_|


You see, when you're not using a sine wave, it's very easy to tell the
difference between a phase shift and a polarity inversion.

Using a sine wave, however, they _look_ exactly the same, which is
misleading, and leads to tech school instructors (and probably college
profs) teaching their students that they _are_ the same, while in truth,
they're not.

OK. Given a reference sine wave A, please tell us how to tell the
difference between signals B and C, where

B = "A" inverted, and

C = "A" shifted 180 degrees.


Thanks for the education.

John

 

[Rich Grise]

On Thu, 24 Feb 2005 19:53:39 -0800, John Larkin wrote:

On Fri, 25 Feb 2005 02:21:57 GMT, Rich Grise <richgrise@example.net

OK. Given a reference sine wave A, please tell us how to tell the
difference between signals B and C, where

B = "A" inverted, and

C = "A" shifted 180 degrees.

It's more a matter of definition than telling them apart. Like I said,
once they're generated, they look exactly the same.

You look at where they came from. For example, an ordinary inverting
amplifier's output is only phase shifted by whatever reactance the
opamp shows - the output is actually just inverted. Vo = -A * Vi. (plus
some j omega stuff, which they try to compensate out, AIUI.)

In a phase-shift oscillator, the feedback is literally phase-shifted
180 degrees, giving the effect of an inversion at that particular
frequency, ergo positive feedback. The inverted signal and the 180
degree phase-shifted signal add together.

Of course, to throw a monkey wrench into the thing, if you have three-
phase delta, and just put a transformer between e.g. phases A and B, but
center-tap the secondary, _then_ you could call them phases, but not with
respect to the center-tap, only with respect to phase C. (or the
center-point, if it's a 'Y'). And they're 120 degrees from it and each
other, if you look at it that way. But at two ends of the transformer,
with just the center-tap in the middle, there is no third phase to get the
graph up off the X axis!

Yeah, that's it! ;-)

Hope This Helps!
Rich

 

[John Larkin]

On Fri, 25 Feb 2005 05:19:19 GMT, Rich Grise <richgrise@example.net>
wrote:

On Thu, 24 Feb 2005 19:53:39 -0800, John Larkin wrote:
On Fri, 25 Feb 2005 02:21:57 GMT, Rich Grise <richgrise@example.net

OK. Given a reference sine wave A, please tell us how to tell the
difference between signals B and C, where

B = "A" inverted, and

C = "A" shifted 180 degrees.

It's more a matter of definition than telling them apart. Like I said,
once they're generated, they look exactly the same.

You look at where they came from.

Ah, I see now. Suppose two different computers calculate the number
"3". One adds 2+1, and the other takes the square root of 9. These 3's
are different, so there are actually two distinct kinds of "3".

Got it. Thanks.

John

 

[Robert Monsen]

Michael A. Terrell wrote:

John Larkin wrote:

On Fri, 25 Feb 2005 05:19:19 GMT, Rich Grise <richgrise@example.net
wrote:


On Thu, 24 Feb 2005 19:53:39 -0800, John Larkin wrote:

On Fri, 25 Feb 2005 02:21:57 GMT, Rich Grise <richgrise@example.net

OK. Given a reference sine wave A, please tell us how to tell the
difference between signals B and C, where

B = "A" inverted, and

C = "A" shifted 180 degrees.

It's more a matter of definition than telling them apart. Like I said,
once they're generated, they look exactly the same.

You look at where they came from.

Ah, I see now. Suppose two different computers calculate the number
"3". One adds 2+1, and the other takes the square root of 9. These 3's
are different, so there are actually two distinct kinds of "3".

Got it. Thanks.

John


John, I think this may be a better explanation:

If you use a scope to look at the unfiltered output of a full wave 60
Hz rectifier you see 120 bumps in a one second sweep. If there are not
two different phases you would see 60 with wider spaces between them.
This is like the argument of a diode in series with a resistor: Is the
power or the voltage reduced to half. Most people seem to think the
diode will reduce the voltage 50% and refuse to look at the math that
the effect voltage will be reduced from, Say, 120 VAC to an effective 84
VAC rather than 60 VAC.

Actually, in Rich's defense, he was talking about the voltages at the
ends of the secondary of a center tap transformer w.r.t. the center tap,
and indicated that these voltages were inverted in relation to the
center tap, not 'out of phase'. He seems to believe that phase shifts
can only be generated by timing delays. Thus, the argument is really one
of definitions, as in "what is a phase shift?".

For pure sine waves, there is simply no way to a 180 degree time shifted
sine wave from an inverted sine wave, which is what JL's remarks were
pointed at. If it quacks like a duck...

However, if you put a square wave with a duty cycle of 25% into the
primary of the transformer, Rich's point will become apparent. You won't
be able to make the waves match, even with a suitable time shift. You
will need to invert one, and then they will match without any timing delay.

One question I have is can you generate three phase output with the
secondaries of a transformer?

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.

 

[Kitchen Man]

On Sat, 26 Feb 2005 13:02:19 +0000 in sci.electronics.basics, Fred Abse
<excretatauris@cerebrumconfus.it> wrote msg
<pan.2005.02.26.12.09.39.752208@cerebrumconfus.it>:

On Thu, 24 Feb 2005 21:48:13 -0800, John Larkin wrote:

Ah, I see now. Suppose two different computers calculate the number
"3". One adds 2+1, and the other takes the square root of 9. These 3's
are different, so there are actually two distinct kinds of "3".

That's only true for relatively large values of 3

But to get true phase shift, you have to take the limit as 3 approaches
zero.

I believe that Terry's original comment was meant to draw a distinction
between what's available on the two big black wires coming in to the
house, and the three 120 degree phases on the big transmission lines.
Some people are under the mistaken impression that two of those phases
are fed into the residence, rather than one phase split and inverted.
And yes, once you split and invert, you've got a 180 degree phase shift,
as well as a 50% attenuation, on *ahem* each leg. Or should I say bus?

--
http://www.xmission.com/~tiger885/motorbike/NART/nart.html

 

[Kitchen Man]

On Wed, 23 Feb 2005 13:38:01 -0330 in sci.electronics.basics, "Terry"
<tsanford@nf.sympatico.ca> wrote msg
<iL2Td.14401$uO.495799@news20.bellglobal.com>:

if there is load on only one side (leg) of the circuit, the neutral will
carry the same current as the hot lead on that side; and the other hot lead
will be carrying nothing; right?
It is a common mistake to think of the neutral as NOT carrying current; but
all our basic circuit training tells us that current has to flow from a
supply, through a load and return!
That return IS the neutral conductor and it better be intact and in good
shape! The fact that a good neutral is almost or only a volt or two above
ground potential means that it is doing it's job of returning the current to
the low voltage (neutral) side of the supply panel with little loss due to
the resistance of the conductor.

You're absolutely right about this. It is not right to share neutral
circuits. Think of the implications of doing wiring repairs - if a
worker disconnects a neutral wire splice while working on a disconnected
circuit, the currents carried by a shared circuit will start looking for
a place to go. The worker will likely get a little spark surprise at
the same time. I'm surprised that an electrical inspector would allow
it, is such practice really allowed by code?

--
http://www.xmission.com/~tiger885/motorbike/NART/nart.html

 

[Rich Grise]

On Sat, 26 Feb 2005 11:02:17 -0700, Kitchen Man wrote:

On Sat, 26 Feb 2005 13:02:19 +0000 in sci.electronics.basics, Fred Abse
excretatauris@cerebrumconfus.it> wrote msg
pan.2005.02.26.12.09.39.752208@cerebrumconfus.it>:

On Thu, 24 Feb 2005 21:48:13 -0800, John Larkin wrote:

Ah, I see now. Suppose two different computers calculate the number
"3". One adds 2+1, and the other takes the square root of 9. These 3's
are different, so there are actually two distinct kinds of "3".

That's only true for relatively large values of 3

But to get true phase shift, you have to take the limit as 3 approaches
zero.

I believe that Terry's original comment was meant to draw a distinction
between what's available on the two big black wires coming in to the
house, and the three 120 degree phases on the big transmission lines.
Some people are under the mistaken impression that two of those phases
are fed into the residence, rather than one phase split and inverted.
And yes, once you split and invert, you've got a 180 degree phase shift,
as well as a 50% attenuation, on *ahem* each leg. Or should I say bus?

But It Is Not A Phase Shift! It Is Merely A Polarity Inversion!

Some transvestites _look_ just like women - until you get under the
covers!

A phase shift oscillator works because the 180 degree phase shifted
negative feedback _looks_ to the opamp _exactly_ like in-phase positive
feedback. The opamp doesn't know it's in an oscillator - it's only
amplifying.

But just because it _looks_ the same, doesn't mean that it _is_ the
same.

Thanks,
Rich

 

[Rich Grise]

On Sat, 26 Feb 2005 11:02:17 -0700, Kitchen Man wrote:

On Sat, 26 Feb 2005 13:02:19 +0000 in sci.electronics.basics, Fred Abse
excretatauris@cerebrumconfus.it> wrote msg
pan.2005.02.26.12.09.39.752208@cerebrumconfus.it>:

On Thu, 24 Feb 2005 21:48:13 -0800, John Larkin wrote:

Ah, I see now. Suppose two different computers calculate the number
"3". One adds 2+1, and the other takes the square root of 9. These 3's
are different, so there are actually two distinct kinds of "3".

That's only true for relatively large values of 3

But to get true phase shift, you have to take the limit as 3 approaches
zero.

I believe that Terry's original comment was meant to draw a distinction
between what's available on the two big black wires coming in to the
house, and the three 120 degree phases on the big transmission lines.
Some people are under the mistaken impression that two of those phases
are fed into the residence, rather than one phase split and inverted.
And yes, once you split and invert, you've got a 180 degree phase shift,
as well as a 50% attenuation, on *ahem* each leg. Or should I say bus?

OK, Got it.

If the top of the transformer is 180 degrees phase shifted from the bottom,
can you tap the transformer and pick off, say, 30 degrees, 45 degrees, 90
degrees, and so on, until you reach the top, at 180?

Of course not!

Now, do I make myself clear?

Thank you very much.
Rich

 

[John Larkin]

On Sat, 26 Feb 2005 21:27:17 GMT, Rich Grise <richgrise@example.net>
wrote:

On Sat, 26 Feb 2005 11:02:17 -0700, Kitchen Man wrote:

On Sat, 26 Feb 2005 13:02:19 +0000 in sci.electronics.basics, Fred Abse
excretatauris@cerebrumconfus.it> wrote msg
pan.2005.02.26.12.09.39.752208@cerebrumconfus.it>:

On Thu, 24 Feb 2005 21:48:13 -0800, John Larkin wrote:

Ah, I see now. Suppose two different computers calculate the number
"3". One adds 2+1, and the other takes the square root of 9. These 3's
are different, so there are actually two distinct kinds of "3".

That's only true for relatively large values of 3

But to get true phase shift, you have to take the limit as 3 approaches
zero.

I believe that Terry's original comment was meant to draw a distinction
between what's available on the two big black wires coming in to the
house, and the three 120 degree phases on the big transmission lines.
Some people are under the mistaken impression that two of those phases
are fed into the residence, rather than one phase split and inverted.
And yes, once you split and invert, you've got a 180 degree phase shift,
as well as a 50% attenuation, on *ahem* each leg. Or should I say bus?

OK, Got it.

If the top of the transformer is 180 degrees phase shifted from the bottom,
can you tap the transformer and pick off, say, 30 degrees, 45 degrees, 90
degrees, and so on, until you reach the top, at 180?

Of course not!

Of course not. If the only available vectors are 0 and 180 degrees, no
algebraic combination of the two can create any other phase angles.
Taps merely give you different amplitudes at 0 or 180 degrees.

John

 

[Michael A. Terrell]

Kitchen Man wrote:

You're absolutely right about this. It is not right to share neutral
circuits. Think of the implications of doing wiring repairs - if a
worker disconnects a neutral wire splice while working on a disconnected
circuit, the currents carried by a shared circuit will start looking for
a place to go. The worker will likely get a little spark surprise at
the same time. I'm surprised that an electrical inspector would allow
it, is such practice really allowed by code?

Ok, how about this? Two duplex outlets in one double box. Do you?

1. Run two 14-2/G to the box, one for each outlet.

or

2. Run one 14-3/G to the box, and connect the red wire to one outlet,
the black to the other, then connect the white wire and ground to both
outlets? As long as the current in the neutral doesn't add, there is
less current in the neutral than either supply wire.



Method one uses more material, more labor and wires can be mixed between
the devices.

Method two uses only what is needed, takes less labor t install, and the
wiring is rather obvious to anyone capable of doing a later repair.

If it doesn't meet code the inspector can't allow it.

Think about it.

--
Beware of those who post from srvinet.com!

Michael A. Terrell
Central Florida

 

[Fred Abse]

On Thu, 24 Feb 2005 02:45:07 +0000, Rich Grise wrote:

ut they're the same signal! How can a signal be out of phase with itself?
Picking up a voltage from opposite ends of a transformer winding does not
introduce any phase shift, nor does center-tapping that winding and
grounding the center-tap.

OK, ground the center tap and add the signals from each end. You get
zero, not twice the original signal. Hence they are not the same signal.

If you think they're out of phase, please show me the component that
delays the signal by 1/120 second.

Causality doesn't matter. The two signals behave exactly the same as if
you'd used two allpass networks of 90 degrees each. Show me how you would
distinguish between two sets of sinusoidal signals, one set antiphase as
the result of a delay circuit, and the other from a center tapped
transformer. It's only when signals are non-repetitive that you can
perhaps tell.

IMO. it's the use of the word "shift" that's confusing things. Use
"difference", and things get clearer.

"Antiphase" is not "in phase", by definition.

--
Then there's duct tape ...
(Garrison Keillor)

 

[Kitchen Man]

On Sat, 26 Feb 2005 23:05:03 GMT in sci.electronics.basics, "Michael A.
Terrell" <mike.terrell@earthlink.net> wrote msg
<4221009A.B97BE5C9@earthlink.net>:

Kitchen Man wrote:

You're absolutely right about this. It is not right to share neutral
circuits. Think of the implications of doing wiring repairs - if a
worker disconnects a neutral wire splice while working on a disconnected
circuit, the currents carried by a shared circuit will start looking for
a place to go. The worker will likely get a little spark surprise at
the same time. I'm surprised that an electrical inspector would allow
it, is such practice really allowed by code?

Ok, how about this? Two duplex outlets in one double box. Do you?

1. Run two 14-2/G to the box, one for each outlet.

or

2. Run one 14-3/G to the box, and connect the red wire to one outlet,
the black to the other, then connect the white wire and ground to both
outlets? As long as the current in the neutral doesn't add, there is
less current in the neutral than either supply wire.

Maybe I've misunderstood the discussion, because I don't see a problem
with what you're saying, and possibly what I'm asking isn't clear. I've
had experience where three separate circuits, using three separate
circuit breakers, shared neutral paths via wire-nut node boxes
throughout a building. It was my impression that safe practice dictated
that each circuit (defined by a common termination in the breaker box)
should have its neutral line isolated until it also is terminated in the
breaker box.

Method one uses more material, more labor and wires can be mixed between
the devices.

Method two uses only what is needed, takes less labor t install, and the
wiring is rather obvious to anyone capable of doing a later repair.

If it doesn't meet code the inspector can't allow it.

Think about it.

I don't have a copy of the NEC, and I know that the situation I've
described caused unpredictable and, to my eyes, unsafe conditions within
the circuitry. I'd appreciate any insight anyone has to offer.

--
Al Brennan
http://www.xmission.com/~tiger885/motorbike/NART/nart.html

 

[Michael A. Terrell]

Kitchen Man wrote:

Maybe I've misunderstood the discussion, because I don't see a problem
with what you're saying, and possibly what I'm asking isn't clear. I've
had experience where three separate circuits, using three separate
circuit breakers, shared neutral paths via wire-nut node boxes
throughout a building. It was my impression that safe practice dictated
that each circuit (defined by a common termination in the breaker box)
should have its neutral line isolated until it also is terminated in the
breaker box.

I don't have a copy of the NEC, and I know that the situation I've
described caused unpredictable and, to my eyes, unsafe conditions within
the circuitry. I'd appreciate any insight anyone has to offer.

--
Al Brennan

I don't have a current copy of the NEC codebook. It got to expensive
for me after I became disabled.

--
Beware of those who post from srvinet.com!

Michael A. Terrell
Central Florida

 

[Kitchen Man]

On Sat, 26 Feb 2005 21:24:23 GMT in sci.electronics.basics, Rich Grise
<richgrise@example.net> wrote msg
<pan.2005.02.26.21.24.29.841590@example.net>:

And yes, once you split and invert, you've got a 180 degree phase shift,
as well as a 50% attenuation, on *ahem* each leg. Or should I say bus?

But It Is Not A Phase Shift! It Is Merely A Polarity Inversion!

Some transvestites _look_ just like women - until you get under the
covers!

A phase shift oscillator works because the 180 degree phase shifted
negative feedback _looks_ to the opamp _exactly_ like in-phase positive
feedback. The opamp doesn't know it's in an oscillator - it's only
amplifying.

But just because it _looks_ the same, doesn't mean that it _is_ the
same.

Rich, I violently agree. Inversion is the correct term, I think I said
as much. The resultant signals, as we are so adamantly unopposing each
other about, are 180 degrees out of phase with each other. The one
thing we seem to be disagreeing about is the degree of severity of
calling it a "phase shift," since one of the signals was not caused by
some reactance to lead or lag. To me, it isn't that big a deal.

--
Al Brennan
http://www.xmission.com/~tiger885/motorbike/NART/nart.html