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From: Adam on 12 Oct 2007 20:13
Peter D. wrote:
>> would it be possible, in theory, to build a gadget that
>> would plug into a household electric outlet and automatically switch in
>> inductors or capacitors as needed?
>
> Yes, definitely. The better computer power supplies have Automatic
> Power Factor Correction. Unfortunately if you have to ask questions
> about this you are not the man to do the job. Mains voltage is
> *dangerous*.

Thanks, Peter! I didn't know this was already being done on a small
scale. I wasn't planning on building one, just wondering if it was
possible. A separate question, that I won't even go into, is whether
the money saved would be worth the time and expense of building or
buying such a thing.

> I am not an American.

I noticed your posts were timestamped UCT +1000.

> Don't they have 220V supplied to the house which is then distributed
> around the house twice, as 220V "high" voltage and 110V "standard"
> voltage? The meter (and the best place to do power factor correction
> is at the 220V connection.

I don't know much about this and hope someone will correct me, but as I
understand it, your typical American house has two 110-120V feeds out of
phase. The entire house is wired for 120V (plug has vertical prongs
plus ground pin). Somehow the two feeds are combined to get 220-240V
(plug has horizontal prongs plus ground pin, or sometimes circular
prongs), but that's only run to the few places where 240V appliances
would be, typically the range (stove/oven), clothes dryer, and larger
air conditioners.

> Yes that is the folklore I was repeating. The low voltage was
> chosen for good electrical safety, at the expense of poor fire
> (and overall) safety.

What may be of slight interest was the choice of AC over DC in the U.S.
From http://www.richard.clark32.btinternet.co.uk/chair.html :

"In the 1880's, electricity was a new and novel power source. Thomas
Edison and George Westinghouse were the two major players in the
struggle to control electrical utilities. Technical and economic
circumstances made Westinghouse's alternating current superior to
Edison's direct current. Alternating current was soon adopted as the
standard for electrical transmission worldwide. Edison had tried to
convince everyone that Westinghouse's AC current was unsafe and was
delighted when New York State introduced the electric chair, which
required alternating current."

> Is everybody trying to set a record for the biggest most off topic
> thread? This should have been broken up into dozens of threads.

I suppose that's my fault. The thread has changed topics numerous
times, and I've tried to keep changing the subject line to reflect this,
but sometimes one sentence in one of my posts sparks a whole new
discussion about something else, using the "old" subject line. I've
tried, like spinning off the "Temperature Sensors" thread, but meanwhile
the original thread, which at one point was about batteries, now seems
to be about house wiring. If you could somehow fix this, I'd be very
grateful!

Adam

From: Robert M. Riches Jr. on 12 Oct 2007 20:43
On 2007-10-13, Adam <look(a)bottom.for.address> wrote:
>
> I don't know much about this and hope someone will correct me, but as I
> understand it, your typical American house has two 110-120V feeds out of
> phase. The entire house is wired for 120V (plug has vertical prongs
> plus ground pin). Somehow the two feeds are combined to get 220-240V
> (plug has horizontal prongs plus ground pin, or sometimes circular
> prongs), but that's only run to the few places where 240V appliances
> would be, typically the range (stove/oven), clothes dryer, and larger
> air conditioners.

Right. The "somehow" is the feed coming into the house is
essentially 220V with a center tap. The two outer lines are
called L1 and L2. The center tap is called N, for neutral,
and it is grounded at building entrances. (That's where the
power lines enter the building, not at the doors.) L1 and
L2 have 220V between them. L* and N have 110V between them.
Safety ground is routed separately from N, because N at an
outlet can be a few/several volts above ground, enough to
taste wild if one were to hold onto one and stick one's
tongue on the other.

--
Robert Riches
spamtrap42(a)verizon.net
(Yes, that is one of my email addresses.)
From: Moe Trin on 13 Oct 2007 17:54
On Sat, 13 Oct 2007, in the Usenet newsgroup alt.os.linux.mandrake, in article
<slrnfh054r.mnq.rob(a)one.localnet>, Robert M. Riches Jr. wrote:

>Adam <look(a)bottom.for.address> wrote:

>> The entire house is wired for 120V (plug has vertical prongs
>> plus ground pin).

Well... let's clarify that as pins that are parallel like | | where
the 'return' pin usually is taller than the 'hot' pin. The ground is
there in construction done in the past 30 or so years, but before that
it might only be 2 pin polarized or even the original 2 pin unpolarized.

>> Somehow the two feeds are combined to get 220-240V (plug has
>> horizontal prongs plus ground pin, or sometimes circular prongs),

Well..

>> but that's only run to the few places where 240V appliances would be,
>> typically the range (stove/oven), clothes dryer, and larger air
>> conditioners.

I haven't seen appliances with the connector the same dimension as the
"standard" 110 volt plug. Invariably, those are using larger connectors
with 1/2 x 1/8 inch blades, rather than 1/4 (or 5/16) x 1/16. Length
of the pins differ too.

>Right. The "somehow" is the feed coming into the house is
>essentially 220V with a center tap. The two outer lines are
>called L1 and L2. The center tap is called N, for neutral,
>and it is grounded at building entrances. (That's where the
>power lines enter the building, not at the doors.) L1 and
>L2 have 220V between them. L* and N have 110V between them.

The exception is buildings with much larger power consumption (like
large apartment buildings) which _MAY_ get a 3 phase star (4 wire)
feed, and houses on a street with lots of homes where there are
three transformers up on the pole. In these less common cases, Line
to Neutral is nominally 120V, and Line to Line is nominally 208V
(with a 120 degree phase shift between lines rather than 180).

>Safety ground is routed separately from N, because N at an
>outlet can be a few/several volts above ground, enough to
>taste wild if one were to hold onto one and stick one's
>tongue on the other.

The cause is current flow in the neutral times the resistance of
the wires and connections. A "worst case" might be 15 Amperes in
a 14 AWG wire over a distance of 100 feet (~0.25 Ohm x 15 Amps =
3.75 Volts for the wire alone).

Old guy
From: Unruh on 13 Oct 2007 18:08
Adam <look(a)bottom.for.address> writes:

>Peter D. wrote:

>> Don't they have 220V supplied to the house which is then distributed
>> around the house twice, as 220V "high" voltage and 110V "standard"
>> voltage? The meter (and the best place to do power factor correction
>> is at the 220V connection.

>I don't know much about this and hope someone will correct me, but as I
>understand it, your typical American house has two 110-120V feeds out of
>phase. The entire house is wired for 120V (plug has vertical prongs
>plus ground pin). Somehow the two feeds are combined to get 220-240V
>(plug has horizontal prongs plus ground pin, or sometimes circular
>prongs), but that's only run to the few places where 240V appliances
>would be, typically the range (stove/oven), clothes dryer, and larger
>air conditioners.

If you look at your breaker box, each alternate breaker is a different
phase line. parts of your house is wired with three wire cable ( hot black,
hot red and neutral white) which connect to alternative breakers. There is
220V between the black and red, and 110 between either the red and white or
black and white. Most plug outlets take only one or the other of those, but
in the kitchen many codes require the two plugs in a receptical to be on
separate lines . Thus between the top plug hot and the bottom hot there is
220 volts. In stoves and some dryers, the connection goes between those two
hot plugs (ie 220 volts).



>> Yes that is the folklore I was repeating. The low voltage was
>> chosen for good electrical safety, at the expense of poor fire
>> (and overall) safety.

Actually it is not clear it is safer. The crucial issue is the amperage
going through the body with a critical zone. Higher than that and the
muscles around the heart clamp the heart and do not allow it to go into
fib. Thus 220 volts can well protect you because the higher voltage drives
more current through you. (This is how people hit by 600V or 2000V survive)
110 is pretty close to being ideal for driving current in just the critical
band through you.



>What may be of slight interest was the choice of AC over DC in the U.S.
> From http://www.richard.clark32.btinternet.co.uk/chair.html :

>"In the 1880's, electricity was a new and novel power source. Thomas
>Edison and George Westinghouse were the two major players in the
>struggle to control electrical utilities. Technical and economic
>circumstances made Westinghouse's alternating current superior to

The technical issue was the necessity of driving the long distance lines at
high voltage, or the losses were prohibitive. And converting DV voltage
levels is very difficult esp then. Thus Westinhouse could set up generators
in Niagra falls and deliver power to New York city, while Edison basically
had to have his generators within the city.


>Edison's direct current. Alternating current was soon adopted as the
>standard for electrical transmission worldwide. Edison had tried to
>convince everyone that Westinghouse's AC current was unsafe and was
>delighted when New York State introduced the electric chair, which
>required alternating current."


From: Unruh on 14 Oct 2007 00:49
ibuprofin(a)painkiller.example.tld (Moe Trin) writes:

>On Sat, 13 Oct 2007, in the Usenet newsgroup alt.os.linux.mandrake, in article
><slrnfh054r.mnq.rob(a)one.localnet>, Robert M. Riches Jr. wrote:

>>Adam <look(a)bottom.for.address> wrote:

>>> The entire house is wired for 120V (plug has vertical prongs
>>> plus ground pin).

>Well... let's clarify that as pins that are parallel like | | where
>the 'return' pin usually is taller than the 'hot' pin. The ground is
>there in construction done in the past 30 or so years, but before that
>it might only be 2 pin polarized or even the original 2 pin unpolarized.

>>> Somehow the two feeds are combined to get 220-240V (plug has
>>> horizontal prongs plus ground pin, or sometimes circular prongs),

>Well..

>>> but that's only run to the few places where 240V appliances would be,
>>> typically the range (stove/oven), clothes dryer, and larger air
>>> conditioners.

>I haven't seen appliances with the connector the same dimension as the
>"standard" 110 volt plug. Invariably, those are using larger connectors
>with 1/2 x 1/8 inch blades, rather than 1/4 (or 5/16) x 1/16. Length
>of the pins differ too.

>>Right. The "somehow" is the feed coming into the house is
>>essentially 220V with a center tap. The two outer lines are
>>called L1 and L2. The center tap is called N, for neutral,
>>and it is grounded at building entrances. (That's where the
>>power lines enter the building, not at the doors.) L1 and
>>L2 have 220V between them. L* and N have 110V between them.

>The exception is buildings with much larger power consumption (like
>large apartment buildings) which _MAY_ get a 3 phase star (4 wire)
>feed, and houses on a street with lots of homes where there are
>three transformers up on the pole. In these less common cases, Line
>to Neutral is nominally 120V, and Line to Line is nominally 208V
>(with a 120 degree phase shift between lines rather than 180).

>>Safety ground is routed separately from N, because N at an
>>outlet can be a few/several volts above ground, enough to
>>taste wild if one were to hold onto one and stick one's
>>tongue on the other.

>The cause is current flow in the neutral times the resistance of
>the wires and connections. A "worst case" might be 15 Amperes in
>a 14 AWG wire over a distance of 100 feet (~0.25 Ohm x 15 Amps =
>3.75 Volts for the wire alone).

Course the real fun part ( and the real "wprst case") is on one of those 3 wire lines ( red black white)
when teh neutral gets disconnectd for some reason down at the box. Now the
neutral is at 110 volts, and the return flow is through the other line. Ie,
if something is plugged in or turned on on that other line, the amount of
current in this one depends on how many things are on the other line. I had
this once, where the lights in the bathroom worked only if the lights in
the dining room were turned on. Took me a while to figure that one out!
(It as actually an old knob and tube where the two circuits shared a
neutral, and the lights in the various rooms were on separate phases.)


> Old guy
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