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From: Robert M. Riches Jr. on 15 Oct 2007 13:34
On 2007-10-14, Unruh <unruh-spam(a)physics.ubc.ca> wrote:
> "Peter D." <psd(a)live.home.invalid> writes:
>
>>on Saturday 13 October 2007 10:13
>>in the Usenet newsgroup alt.os.linux.mandrake
>>Adam wrote:
>
>>> Peter D. wrote:
>
>>[snip]
>>> 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.
>
>>I was assuming each house had a street supply of 220V and a transformer
>>with a single phase 110V output, but a two phase system could be used.
>>I am not the man to ask about US power supply techniques.
>
> Nope, each house gets 220 volts swinging in opposite phases WRT ground.
> Thus by using ground ( a big copper rod driven 6 ft into the ground) you
> get two 110 volt outputs. If something goes wrong with the ground, you get
> a 220 running through the two phased 110 circuits in series.

In all installations I have seen, the neutral has been
supported by a third wire from the transformer on the street
to the panel in the house. The ground rod does not normally
carry any substantial amount of current.

--
Robert Riches
spamtrap42(a)verizon.net
(Yes, that is one of my email addresses.)
From: Robert M. Riches Jr. on 15 Oct 2007 13:35
On 2007-10-14, Peter D. <psd(a)live.home.invalid> wrote:
> on Saturday 13 October 2007 10:43
> in the Usenet newsgroup alt.os.linux.mandrake
> Robert M. Riches Jr. wrote:
>
>> 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.
>
> Center tap, implies a transformer. 220V single phase on the
> supply side, and 220V (plus centre tap) on the user's side?

The transformer in question is owned by the utility. It
resides on a pole or in a big dark green box near the curb.
The primary is normally several thousand volts. The
secondary that feeds the house is 220VCT.

--
Robert Riches
spamtrap42(a)verizon.net
(Yes, that is one of my email addresses.)
From: Robert M. Riches Jr. on 15 Oct 2007 13:37
On 2007-10-14, Unruh <unruh-spam(a)physics.ubc.ca> wrote:
> "Peter D." <psd(a)live.home.invalid> writes:
>
>>on Saturday 13 October 2007 10:43
>>in the Usenet newsgroup alt.os.linux.mandrake
>>Robert M. Riches Jr. wrote:
>
>>> 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.
>
> No. The transformer is on the pole outside your and your neighbour's house.
>
> 600---- ---------------------- +110
> S C
> S C________
> S C -
> ___S C .
> | C______________________ -110
> _
> -
> .
>
> The two 110 lines come into the house with 220V between them. In the house
> you connect the neutral to ground.
>
>>Center tap, implies a transformer. 220V single phase on the
>>supply side, and 220V (plus centre tap) on the user's side?
>
> 600 or 2000 on the supply side. You know, that single wire way up at the
> top of the poles, with big glass conductors setting it off from the poles?
> (ground is the return path. Cheaper than copper).

The neutral is _always_ carried by a wire just as big as the
wires that carry L1 and L2. Modern installations I have
seen have used aluminum wire rather than copper. The ground
rod does not normally carry substantial current.

--
Robert Riches
spamtrap42(a)verizon.net
(Yes, that is one of my email addresses.)
From: Robert M. Riches Jr. on 15 Oct 2007 13:38
On 2007-10-15, Peter D. <psd(a)live.home.invalid> wrote:
> on Monday 15 October 2007 08:38
> in the Usenet newsgroup alt.os.linux.mandrake
> Unruh wrote:
>
>> "Peter D." <psd(a)live.home.invalid> writes:
>>
>>>on Saturday 13 October 2007 10:43
>>>in the Usenet newsgroup alt.os.linux.mandrake
>>>Robert M. Riches Jr. wrote:
>>
>>>> On 2007-10-13, Adam <look(a)bottom.for.address> wrote:
>
> [snip]
>>>> Right. The "somehow" is the feed coming into the house is
>>>> essentially 220V with a center tap.
>>
>> No. The transformer is on the pole outside your and your neighbour's
>> house.
>>
>> 600---- ---------------------- +110
>> S C
>> S C________
>> S C -
>> ___S C .
>> | C______________________ -110
>> _
>> -
>> .
>>
>> The two 110 lines come into the house with 220V between them. In the house
>> you connect the neutral to ground.
>
> Good ASCII art.
>
>>>Center tap, implies a transformer. 220V single phase on the
>>>supply side, and 220V (plus centre tap) on the user's side?
>>
>> 600 or 2000 on the supply side. You know, that single wire way up at the
>> top of the poles, with big glass conductors setting it off from the poles?
>
> No, I can't see it from here. My eyes are poor and I'm 8,000 miles away.
> ;-)
>
>> (ground is the return path. Cheaper than copper).
> [snip]
>
> That depends on local soil properties. It works very well in some places.

Soil has nothing to do with it. The third wire does.

--
Robert Riches
spamtrap42(a)verizon.net
(Yes, that is one of my email addresses.)
From: Unruh on 15 Oct 2007 13:48
"Peter D." <psd(a)live.home.invalid> writes:

>on Monday 15 October 2007 08:38
>in the Usenet newsgroup alt.os.linux.mandrake
>Unruh wrote:

>> "Peter D." <psd(a)live.home.invalid> writes:
>>
>>>on Saturday 13 October 2007 10:43
>>>in the Usenet newsgroup alt.os.linux.mandrake
>>>Robert M. Riches Jr. wrote:
>>
>>>> On 2007-10-13, Adam <look(a)bottom.for.address> wrote:

>[snip]
>>>> Right. The "somehow" is the feed coming into the house is
>>>> essentially 220V with a center tap.
>>
>> No. The transformer is on the pole outside your and your neighbour's
>> house.
>>
>> 600---- ---------------------- +110
>> S C
>> S C________
>> S C -
>> ___S C .
>> | C______________________ -110
>> _
>> -
>> .
>>
>> The two 110 lines come into the house with 220V between them. In the house
>> you connect the neutral to ground.

>Good ASCII art.

>>>Center tap, implies a transformer. 220V single phase on the
>>>supply side, and 220V (plus centre tap) on the user's side?
>>
>> 600 or 2000 on the supply side. You know, that single wire way up at the
>> top of the poles, with big glass conductors setting it off from the poles?

>No, I can't see it from here. My eyes are poor and I'm 8,000 miles away.
>;-)

How does the power come into your home? Is it underground?



>> (ground is the return path. Cheaper than copper).
>[snip]

>That depends on local soil properties. It works very well in some places.

Agreed, which is why the grounding rods are supposed to go down to the
water table, which is a good conductor. That is easy here in VAncouver. On
the other hand in Phoenix say, it might be more difficult.

I will have to have a look-- it may be that they also use a third neutral
from the pole to the house as well as the two hot lines.




>--
>sig goes here...
>Peter D.
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