High level, simple question about house wiring.

J

John Doe

Guest
(Hello again to one of my favorite Usenet groups. Years ago, my nibble of
electronics design was loads of fun.)

I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
....Two single pole, dual throw switches are used.
....The AC power goes to both switches.
....The ground/neutral goes to both switches.
....The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.

Is that correct?

Assuming that is correct. Given lengthy house wiring, could the AC be
slightly out of sinc enough to produce a very small AC voltage reading
(like five volts) when the two AC sources meet? Maybe that is way off base.
If so, please forget I asked, just curious.

Mostly curious.

Thanks in advance. If my questions are not clear enough, sorry and please
never mind me asking.






--
By "AC" I mean 120 volts AC household stuff (as in the United States).
 
"John Doe" <Usenet@Rocks.com> wrote in message
news:Xns94B887715F02wisdomandfolly@207.115.63.158...
I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.

Is that correct?
Click to expand...
Nope. Close but no see-gar. Rather, it's like this:

....Two single pole, dual throw switches are used.
....Hot goes to the common of the first switch.
....Each pole goes through its own wire, to the corresponding poles of the
second switch.
....Finally, the common of the third switch goes to the light bulb; the other
end of the light bulb goes to ground.

You can see a diagram at http://www.misterfixit.com/3wayswch.htm.

The principle is that you never want a light fixture that is connected to
hot but not connected to neutral. It could be turned off, but if you went
to change the bulb it could actually still be hot and you could get shocked.
So, if the bulb is off, there must be no electricity going to it.

If you are measuring a couple of volts, one possibility is that the switches
are illuminated. A little bit of current trickles through an illuminated
switch even when it's off.
 
On 26 Mar 2004 07:45:33 GMT, the renowned "Walter Harley"
<walterh@cafewalterNOSPAM.com> wrote:

"John Doe" <Usenet@Rocks.com> wrote in message
news:Xns94B887715F02wisdomandfolly@207.115.63.158...
I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.

Is that correct?

Nope. Close but no see-gar. Rather, it's like this:

...Two single pole, dual throw switches are used.
...Hot goes to the common of the first switch.
...Each pole goes through its own wire, to the corresponding poles of the
second switch.
...Finally, the common of the third switch goes to the light bulb; the other
end of the light bulb goes to ground.

You can see a diagram at http://www.misterfixit.com/3wayswch.htm.

The principle is that you never want a light fixture that is connected to
hot but not connected to neutral. It could be turned off, but if you went
to change the bulb it could actually still be hot and you could get shocked.
So, if the bulb is off, there must be no electricity going to it.

If you are measuring a couple of volts, one possibility is that the switches
are illuminated. A little bit of current trickles through an illuminated
switch even when it's off.
Click to expand...
This (non standard, probably not to code) way yields better lamp life
and doesn't suffer the "phase reversal" effect of conventional 3-way
switches ("UP", say, is always on). Uses cheap ordinary SPST switches.



.--------------------------------------------o
|
| L
|-----
' |
| o
- '\ S1
^ \
| o \
.-----
|
|
|
|
'----|
| o
V '\
- \ S2
. o \
| |
' .
| | LAMP1 LAMP2
| | .---. .---. N
'----'---.----| X |---------.--| X |---.-----o
| '---' | | '---' |
| | | |
-------|<------' '---->|----'


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
In article <o9p760pi55ea6id68ilr665j6kh4b7ob2h@4ax.com>, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> writes
On 26 Mar 2004 07:45:33 GMT, the renowned "Walter Harley"
walterh@cafewalterNOSPAM.com> wrote:

"John Doe" <Usenet@Rocks.com> wrote in message
news:Xns94B887715F02wisdomandfolly@207.115.63.158...
I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.

Is that correct?

Nope. Close but no see-gar. Rather, it's like this:

...Two single pole, dual throw switches are used.
...Hot goes to the common of the first switch.
...Each pole goes through its own wire, to the corresponding poles of the
second switch.
...Finally, the common of the third switch goes to the light bulb; the other
end of the light bulb goes to ground.

You can see a diagram at http://www.misterfixit.com/3wayswch.htm.

The principle is that you never want a light fixture that is connected to
hot but not connected to neutral. It could be turned off, but if you went
to change the bulb it could actually still be hot and you could get shocked.
So, if the bulb is off, there must be no electricity going to it.

If you are measuring a couple of volts, one possibility is that the switches
are illuminated. A little bit of current trickles through an illuminated
switch even when it's off.


This (non standard, probably not to code) way yields better lamp life
and doesn't suffer the "phase reversal" effect of conventional 3-way
switches ("UP", say, is always on). Uses cheap ordinary SPST switches.



.--------------------------------------------o
|
| L
|-----
' |
| o
- '\ S1
^ \
| o \
.-----
|
|
|
|
'----|
| o
V '\
- \ S2
. o \
| |
' .
| | LAMP1 LAMP2
| | .---. .---. N
'----'---.----| X |---------.--| X |---.-----o
| '---' | | '---' |
| | | |
-------|<------' '---->|----'
Click to expand...
errr... that doesn't do what he wanted (1 lamp from 2 switches). That's
2 lamps from 2 switches down 1 wire. And in addition it would halve the
lamp brightness and give an annoying line frequency flicker.
--
Tim Mitchell
 
Someone wrote:

I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.
Click to expand...
The following wiring has the advantage that it is fairly easily
retrofitted to existing single- switch systems. Sorry, I can't do ASCII
art (or any other sort).

You need two SPDT switches, call them S1 with A1, B1, C1 and S2 with
A2, B2 and C2 for the two poles (A and B) and common (C) of each switch.

In place of the ususal on- off switch, put S1 with A1 to the neutral
and B1 to the feed to the bulb(s).

Run a 3( +E) core wire (or two 2 cores and leave one core spare) to the
site of the second SPDT S2 - the cores are W1, W2 and W3. At S1 end,
connect W1 to A1, W2 to B1 and W3 to C1.

At S2, connect W1 to A2, W2 to B2, and W3 to C2.

The light will be on when the switches are in positions A1,B2 or A2,B1.

Don't forget the earths.

Voila as they say en francais.
 
On 26 Mar 2004 07:45:33 GMT, Walter Harley wrote:

"John Doe" <Usenet@Rocks.com> wrote in message
news:Xns94B887715F02wisdomandfolly@207.115.63.158...
I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.

Is that correct?

Nope. Close but no see-gar. Rather, it's like this:

...Two single pole, dual throw switches are used.
...Hot goes to the common of the first switch.
...Each pole goes through its own wire, to the corresponding poles of the
second switch.
Click to expand...
The "pole" is the "common" as in single "pole" double throw.

...Finally, the common of the third switch goes to the light bulb; the other
end of the light bulb goes to ground.
Click to expand...
Sorry, neutral.
You can see a diagram at http://www.misterfixit.com/3wayswch.htm.
Click to expand...
Looks good.
The principle is that you never want a light fixture that is connected to
hot but not connected to neutral. It could be turned off, but if you went
to change the bulb it could actually still be hot and you could get shocked.
So, if the bulb is off, there must be no electricity going to it.
Click to expand...
Yup. Unlike automotive switched ground lights. There's a reason for
that, though. The switch housings (e.g. door light switch) are
mounted to the chassis which is der ground.
If you are measuring a couple of volts, one possibility is that the switches
are illuminated. A little bit of current trickles through an illuminated
switch even when it's off.
Click to expand...

--
Best Regards,
Mike
 
On Fri, 26 Mar 2004 11:09:19 +0000, Paul Burke wrote:

Someone wrote:

I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
Click to expand...
Glad to see you check out your hunches, John Doe :)
The following wiring has the advantage that it is fairly easily
retrofitted to existing single- switch systems. Sorry, I can't do ASCII
art (or any other sort).
Click to expand...
then get this program and let it do the art for you, Paul.

This is what Walter was talking about.

S1 S2
red Lamp
o----------o .-.
AC ----o--__ __--o------( X )------+
Black o----------o '-' | White
black |
---
Neutral



+-------- To all metal boxes - use copper or green
|
| some electricians will spray a white tracer on the
=== black wire that goes between switches to
GND indicate it isn't the hot wire.


created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

You need two SPDT switches, call them S1 with A1, B1, C1 and S2 with
A2, B2 and C2 for the two poles (A and B) and common (C) of each switch.

In place of the ususal on- off switch, put S1 with A1 to the neutral
and B1 to the feed to the bulb(s).
Click to expand...
Then you have a hot light when the bulb is off, Paul. A1 should go
to hot, but this ain't the way it's done and code inspectors go by
the book even if your way is better which IMO, it isn't. They'll
fail you for making a better ground if it isn't in der book.

<snip>

--
Best Regards,
Mike
 
On Fri, 26 Mar 2004 14:12:55 GMT, Fred Bloggs wrote:

I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.

Is that correct?


No.

Please view in a fixed-width font such as Courier.

C
+---------+
| o | SW CONNECTS C TO A
| | OR C TO B
| o SW o |
A +---------+ B

TYPE I

+---------+ +--------+
| C | C | |
| +---------+ +----+----+ |
| | o | | o | |
| | | | | |
| | o SW0 o | | o SW1 o | |
--N-------+ | A +---------+ B A +---------+ B |
| | | | /----\ | | |
--L----------|------+-------------|------|------+ | |
| | +-------|------|------------+ |
| +--------------------|------|------------------+
+-------------+ | \----/
| | 3-WIRE EXTENSION
| |
EXISTING-> | | ONE SW MUST BE IN POS A TO PUT
| | LINE ON C
| | -and-
+-+ | ONE SW MUST BE IN POS B TO PUT
| | C ON BULB
| +----+
| |BULB|
| +----+
| |
+---+

TYPE II

+---------+ +--------+
| C | C | |
| +---------+ +----+----+ |
| | o | | o | |
| | | | | |
--L------+ | | o SW0 o | | o SW1 o | |
--N---+ | | A +---------+ B A +---------+ B |
| | | | | /----\ | | |
| | | +-------------|------|------+ | |
| | | +-------|------|------------+ |
| +---|--------------------|------|------------------+
| +------------+ \----/
+-----------------+ | 3-WIRE EXTENSION
| |
EXISTING-> | | REQUIRED
| |
| | BOTH SWITCHES IN POS A
+-+ | -or-
| | BOTH SWITCHES IN POS B
| +----+
| |BULB|
| +----+
| |
+---+

and the superior method is......????? >------+
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TYPE II - only 2-wire wire junctions required .
Click to expand...
Excellent! That must be why it's so common. Type I might pass code
though, since the bulb in both types is never hot when it's off, for
sufficiently long values of T_off.
--
Best Regards,
Mike
 
Active8 wrote:
On Fri, 26 Mar 2004 14:12:55 GMT, Fred Bloggs wrote:


I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.

Is that correct?


No.

Please view in a fixed-width font such as Courier.

C
+---------+
| o | SW CONNECTS C TO A
| | OR C TO B
| o SW o |
A +---------+ B

TYPE I

+---------+ +--------+
| C | C | |
| +---------+ +----+----+ |
| | o | | o | |
| | | | | |
| | o SW0 o | | o SW1 o | |
--N-------+ | A +---------+ B A +---------+ B |
| | | | /----\ | | |
--L----------|------+-------------|------|------+ | |
| | +-------|------|------------+ |
| +--------------------|------|------------------+
+-------------+ | \----/
| | 3-WIRE EXTENSION
| |
EXISTING-> | | ONE SW MUST BE IN POS A TO PUT
| | LINE ON C
| | -and-
+-+ | ONE SW MUST BE IN POS B TO PUT
| | C ON BULB
| +----+
| |BULB|
| +----+
| |
+---+

TYPE II

+---------+ +--------+
| C | C | |
| +---------+ +----+----+ |
| | o | | o | |
| | | | | |
--L------+ | | o SW0 o | | o SW1 o | |
--N---+ | | A +---------+ B A +---------+ B |
| | | | | /----\ | | |
| | | +-------------|------|------+ | |
| | | +-------|------|------------+ |
| +---|--------------------|------|------------------+
| +------------+ \----/
+-----------------+ | 3-WIRE EXTENSION
| |
EXISTING-> | | REQUIRED
| |
| | BOTH SWITCHES IN POS A
+-+ | -or-
| | BOTH SWITCHES IN POS B
| +----+
| |BULB|
| +----+
| |
+---+

and the superior method is......????? >------+
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+-----------------------+
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\ /

TYPE II - only 2-wire wire junctions required .


Excellent! That must be why it's so common. Type I might pass code
though, since the bulb in both types is never hot when it's off, for
sufficiently long values of T_off.
Click to expand...
I do see a problem with TYPE I in the case of indefinite extension with
additional switches SW2, SW3, SW4,... etc where the wiring is a simple
continuation of paralleling connections to the right. With TYPE I,
completing the circuit with an extension switch by moving to position A
will cause conduction to all the other switches in parallel and this may
cause dry contact arcing; whereas with TYPE II, the conduction will
always be through SW0 and the activated extension switch, and no others.
Therefore, in the case of extensions, TYPE II is the only choice for
engineering reasons.
 
Fred Bloggs wrote:
Active8 wrote:

On Fri, 26 Mar 2004 14:12:55 GMT, Fred Bloggs wrote:


I am curious about house wiring, specifically about 3-way switching
(that is, for controlling a lightbulb with two seperate switches).
This is my guess about how that is done. ...Two single pole, dual
throw switches are used. ...The AC power goes to both switches.
...The ground/neutral goes to both switches. ...The single pole of
both switches goes to the light bulb. So at a time, the AC power is
meeting at the bulb but it is alternating in sync, so there is no
current flow.
Is that correct?


No.

Please view in a fixed-width font such as Courier.

C
+---------+
| o | SW CONNECTS C TO A
| | OR C TO B
| o SW o |
A +---------+ B

TYPE I

+---------+ +--------+
| C | C | |
| +---------+ +----+----+ |
| | o | | o | |
| | | | | |
| | o SW0 o | | o SW1 o | |
--N-------+ | A +---------+ B A +---------+ B |
| | | | /----\ | | |
--L----------|------+-------------|------|------+ | |
| | +-------|------|------------+ |
| +--------------------|------|------------------+
+-------------+ | \----/
| | 3-WIRE EXTENSION
| |
EXISTING-> | | ONE SW MUST BE IN POS A TO PUT
| | LINE ON C
| | -and-
+-+ | ONE SW MUST BE IN POS B TO PUT
| | C ON BULB
| +----+
| |BULB|
| +----+
| |
+---+

TYPE II

+---------+ +--------+
| C | C | |
| +---------+ +----+----+ |
| | o | | o | |
| | | | | |
--L------+ | | o SW0 o | | o SW1 o | |
--N---+ | | A +---------+ B A +---------+ B |
| | | | | /----\ | | |
| | | +-------------|------|------+ | |
| | | +-------|------|------------+ |
| +---|--------------------|------|------------------+
| +------------+ \----/
+-----------------+ | 3-WIRE EXTENSION
| |
EXISTING-> | | REQUIRED
| |
| | BOTH SWITCHES IN POS A
+-+ | -or-
| | BOTH SWITCHES IN POS B
| +----+
| |BULB|
| +----+
| |
+---+

and the superior method is......????? >------+
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+-----------------------+
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| <==== hook * line * /sinker
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\ /

TYPE II - only 2-wire wire junctions required .



Excellent! That must be why it's so common. Type I might pass code
though, since the bulb in both types is never hot when it's off, for
sufficiently long values of T_off.


I do see a problem with TYPE I in the case of indefinite extension with
additional switches SW2, SW3, SW4,... etc where the wiring is a simple
continuation of paralleling connections to the right. With TYPE I,
completing the circuit with an extension switch by moving to position A
will cause conduction to all the other switches in parallel and this may
cause dry contact arcing; whereas with TYPE II, the conduction will
always be through SW0 and the activated extension switch, and no others.
Therefore, in the case of extensions, TYPE II is the only choice for
engineering reasons.
Click to expand...
The TYPE I extensions puts all the other switches in parallel when
activating extension to position B too- so this configuration is most
likely in violation of NEC- they really have heartburn over parallel
conduction paths- as well as wiring methods that, by maloperation, may
incite the homeowner to take matters into his own hands.
 
On Fri, 26 Mar 2004 14:46:48 GMT, the renowned Fred Bloggs
<nospam@nospam.com> wrote:

Real bad news to mix those diodes with the line, no approved way of
wiring them in economically,
Click to expand...
True, though they'd probably be safe enough in a metal box with Marr
connectors and shrink-tubing. But not approved.

and where the heck are you going to get
those 84V bulbs?
Click to expand...
No problem, just use regular bulbs and a 170VAC supply.. or live with
the lower light level. There's no appreciable flicker. Some table
lamps have a 1N4005 and a 3-position switch... personally I'd use at
least 3A diodes.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
I read in sci.electronics.design that Fred Bloggs <nospam@nospam.com>
wrote (in <40643A62.2060801@nospam.com>) about 'High level, simple
question about house wiring.', on Fri, 26 Mar 2004:
TYPE II - only 2-wire wire junctions required .
Click to expand...
Type II is the approved method in UK.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
John Doe wrote:
(Hello again to one of my favorite Usenet groups. Years ago, my nibble of
electronics design was loads of fun.)

I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.
Click to expand...
Almost. see:
http://www.easy2diy.com/cm/easy/diy_ht_index.asp?page_id=35693932\

Assuming that is correct. Given lengthy house wiring, could the AC be
slightly out of sinc enough to produce a very small AC voltage reading
(like five volts) when the two AC sources meet? Maybe that is way off base.
If so, please forget I asked, just curious.
Click to expand...
No. The wavelength of 60 Hertz is about 3000 miles, so any wire
inside a house will not have much propagation phase shift with respect
ot any other part. What you will get is small capacitive currents
between various parts of the system (commonly called induced voltage)
so that you might measure small AC voltage between unenergized wires
from the signal they pick up from energized wires, nearby. You will
also find that two wires that leave the same node may not have exactly
the same voltage at their far ends, if they do not carry exactly the
same currents. This is because of resistive and inductive voltage
drops caused by their currents. For this reason, the safety ground
(green, non load carrying wire) will not always have exactly the same
voltage as the neutral (grounded at the fuse box end, but carrying
load current) wire.

During a fault current (short circuit between the hot wire and
neutral) or severe overload condition, almost half of the hot voltage
will be dropped across the neutral wire till the fuse or circuit
breaker opens. That might be enough to shock you, if you were in
contact with both the neutral wire and also in electrical contact with
the Earth. That is why the cases of appliances are connected to a
separate safety ground conductor that does not carry load current.

--
John Popelish
 
On Fri, 26 Mar 2004 15:49:30 GMT, Fred Bloggs wrote:

Fred Bloggs wrote:

Fred Bloggs wrote:



Active8 wrote:

On Fri, 26 Mar 2004 14:12:55 GMT, Fred Bloggs wrote:


I am curious about house wiring, specifically about 3-way switching
(that is, for controlling a lightbulb with two seperate switches).
This is my guess about how that is done. ...Two single pole, dual
throw switches are used. ...The AC power goes to both switches.
...The ground/neutral goes to both switches. ...The single pole of
both switches goes to the light bulb. So at a time, the AC power is
meeting at the bulb but it is alternating in sync, so there is no
current flow.
Is that correct?



No.

Please view in a fixed-width font such as Courier.

C
+---------+
| o | SW CONNECTS C TO A
| | OR C TO B
| o SW o |
A +---------+ B

TYPE I

+---------+ +--------+
| C | C | |
| +---------+ +----+----+ |
| | o | | o | |
| | | | | |
| | o SW0 o | | o SW1 o | |
--N-------+ | A +---------+ B A +---------+ B |
| | | | /----\ | | |
--L----------|------+-------------|------|------+ | |
| | +-------|------|------------+ |
| +--------------------|------|------------------+
+-------------+ | \----/
| | 3-WIRE EXTENSION
| |
EXISTING-> | | ONE SW MUST BE IN POS A TO PUT
| | LINE ON C
| | -and-
+-+ | ONE SW MUST BE IN POS B TO PUT
| | C ON BULB
| +----+
| |BULB|
| +----+
| |
+---+

TYPE II

+---------+ +--------+
| C | C | |
| +---------+ +----+----+ |
| | o | | o | |
| | | | | |
--L------+ | | o SW0 o | | o SW1 o | |
--N---+ | | A +---------+ B A +---------+ B |
| | | | | /----\ | | |
| | | +-------------|------|------+ | |
| | | +-------|------|------------+ |
| +---|--------------------|------|------------------+
| +------------+ \----/
+-----------------+ | 3-WIRE EXTENSION
| |
EXISTING-> | | REQUIRED
| |
| | BOTH SWITCHES IN POS A
+-+ | -or-
| | BOTH SWITCHES IN POS B
| +----+
| |BULB|
| +----+
| |
+---+

and the superior method is......????? >------+
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\ /

TYPE II - only 2-wire wire junctions required .




Excellent! That must be why it's so common. Type I might pass code
though, since the bulb in both types is never hot when it's off, for
sufficiently long values of T_off.



I do see a problem with TYPE I in the case of indefinite extension
with additional switches SW2, SW3, SW4,... etc where the wiring is a
simple continuation of paralleling connections to the right. With TYPE
I, completing the circuit with an extension switch by moving to
position A will cause conduction to all the other switches in parallel
and this may cause dry contact arcing; whereas with TYPE II, the
conduction will always be through SW0 and the activated extension
switch, and no others. Therefore, in the case of extensions, TYPE II
is the only choice for engineering reasons.


The TYPE I extensions puts all the other switches in parallel when
activating extension to position B too- so this configuration is most
likely in violation of NEC- they really have heartburn over parallel
conduction paths- as well as wiring methods that, by maloperation, may
incite the homeowner to take matters into his own hands.


Now that I think about, I don't see why some damned fool can't do the
same thing with TYPE II, moving switches while the bulb is on- so
"extensions" of any kind using these configurations with 3-ways are
against, or should be against, NEC code. This goes to show that things
may get more complicated then they seem at first, so don't try to be
creative, go by the book- most of the techniques were learned the hard
way- the "F" in NFPA means "FIRE".
Click to expand...
And that's most likely why they won't pass something unconventional
and they don't want to hear a lecture about why something should be
passed and how much better it is or "I'm an engineer." I met an EE
gal once who told me how rough it was having to learn her job from
the plant master electrician :) We could've made out buying stock in
index tabs she had so many in her code book ;)

Just to add to your warning... to be totally safe working with
existing circuits, put the breaker in your pocket and use any and
all applicable lockouts. Then stop and think what could go wrong.
--
Best Regards,
Mike
 
On Fri, 26 Mar 2004 15:56:45 GMT, Spehro Pefhany wrote:

On Fri, 26 Mar 2004 14:46:48 GMT, the renowned Fred Bloggs
nospam@nospam.com> wrote:


Real bad news to mix those diodes with the line, no approved way of
wiring them in economically,

True, though they'd probably be safe enough in a metal box with Marr
connectors and shrink-tubing. But not approved.

and where the heck are you going to get
those 84V bulbs?

No problem, just use regular bulbs and a 170VAC supply.. or live with
the lower light level. There's no appreciable flicker. Some table
lamps have a 1N4005 and a 3-position switch... personally I'd use at
least 3A diodes.

Best regards,
Spehro Pefhany
Click to expand...
I'd use 12V before I went through all that. I saw some 12V LED
lights at Autozone. Pricey. 10 or so yr warrantee.
--
Best Regards,
Mike
 
I read in sci.electronics.design that Fred Bloggs <nospam@nospam.com>
wrote (in <40645105.1050801@nospam.com>) about 'High level, simple
question about house wiring.', on Fri, 26 Mar 2004:

the "F" in NFPA means "FIRE".
Click to expand...
One of my US colleagues told me it stood for 'Not a Fornicating Prayer,
A-hole'. I guess he had too many run-ins with the AHJs.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
Hmm, i see there are allot of answers here. some look confusing.
i'll take a stab at it.
you have 2 switches DT (double throw) , lets assume one switch is
upstairs in the hall where the light is and the other is down stairs.
the Light it self gets fead the common from your main source. (white
wire)on the outer side of the fixture. the Center Pole of the upstairs
switch feeds the Hot side of the
lamp. the outer poles of the upstairs switch are fead down to the down
stairs switch and is also connected to the outer poles of that switch.
the down stairs switch Center Pole is connected to your High Side of
source (black wire).
they make 3 wire with ground just for this purpose and i think it has
a red wire in it.
the White wire going up is the common (Neutral), and the Red and
Black are your High Sides that connect the outer poles of each switch
together.
etc...
basically the idea is to use one switch to select which outer pole to
send the high side to and the other switch to select which high side to
use from the outer poles




John Doe wrote:

(Hello again to one of my favorite Usenet groups. Years ago, my nibble of
electronics design was loads of fun.)

I am curious about house wiring, specifically about 3-way switching (that
is, for controlling a lightbulb with two seperate switches).

This is my guess about how that is done.
...Two single pole, dual throw switches are used.
...The AC power goes to both switches.
...The ground/neutral goes to both switches.
...The single pole of both switches goes to the light bulb.
So at a time, the AC power is meeting at the bulb but it is alternating in
sync, so there is no current flow.

Is that correct?

Assuming that is correct. Given lengthy house wiring, could the AC be
slightly out of sinc enough to produce a very small AC voltage reading
(like five volts) when the two AC sources meet? Maybe that is way off base.
If so, please forget I asked, just curious.

Mostly curious.

Thanks in advance. If my questions are not clear enough, sorry and please
never mind me asking.
Click to expand...
 
"Active8" <reply2group@ndbbm.net> wrote in message
news:18pbsd3tpbrzc$.dlg@news.individual.net...
The "pole" is the "common" as in single "pole" double throw.
[...]
Sorry, neutral.
Click to expand...
Guilty on all counts, your honor. Sorry - posting while sleepy... beats
posting while peevish, but not by much.
 
On Fri, 26 Mar 2004 19:27:07 +0000, John Woodgate wrote:

I read in sci.electronics.design that Fred Bloggs <nospam@nospam.com
wrote (in <40645105.1050801@nospam.com>) about 'High level, simple
question about house wiring.', on Fri, 26 Mar 2004:

the "F" in NFPA means "FIRE".

One of my US colleagues told me it stood for 'Not a Fornicating Prayer,
A-hole'. I guess he had too many run-ins with the AHJs.
Click to expand...
Good one!

Inspectors are tough, but once they get tired of seeing your picture
perfect work, they tend to spend more time at the coffee shop. Maybe
12 yrs ago, I asked one if he'd checked any of my work yet today. He
asked who I was, then said, "Oh hell! I don't even look at your
stuff anymore." They like it when you make things easy for them.
--
Best Regards,
Mike
 
On Fri, 26 Mar 2004 14:54:32 -0800, Jamie wrote:

Hmm, i see there are allot of answers here. some look confusing.
i'll take a stab at it.
you have 2 switches DT (double throw) , lets assume one switch is
upstairs in the hall where the light is and the other is down stairs.
the Light it self gets fead the common from your main source.
Click to expand...
feed comes from a feed mill and goes to the livestock.

(white
wire)on the outer side of the fixture.
Click to expand...
neutral to a metal enclosure? I think not. You fail. I'm leaving
now. Call me when it's fixed and I'll schedule a trip back to
reinspect everything. You mean the outside of the socket? That
threaded thingy?

the Center Pole of the upstairs
switch feeds the Hot side of the
lamp.
Click to expand...
yeah...

the outer poles of the upstairs switch are fead down to the down
stairs switch and is also connected to the outer poles of that switch.
the down stairs switch Center Pole is connected to your High Side of
source (black wire).
they make 3 wire with ground just for this purpose and i think it has
a red wire in it.
Click to expand...
it do, but this is Balto city and you have to run conduit. call me
back.

the White wire going up is the common (Neutral), and the Red and
Black are your High Sides that connect the outer poles of each switch
together.
etc...
Click to expand...
what? You stapled it to the studs and the drywallers overran you?
You're screwed.

basically the idea is to use one switch to select which outer pole to
send the high side to and the other switch to select which high side to
use from the outer poles
Click to expand...
Can't I just flip the switch and not worry about all that? ;)
snip
Click to expand...

--
Best Regards,
Mike
 
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