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Default 1920's wiring....

"bud--" wrote in message
.. .
Existential Angst wrote:

It's funny, we started with copper, went to tinned copper, went back to
copper, slid further back to effing aluminum (goodgawd), learned from
that mistake and went back to copper again. Altho power companies use
aluminum in parts of their service -- and steel!


As several people have said, steel is not used as a conductor.


Yeah, I just looked -- that guy wire I thought was steel indeed appears to
be alum!
--
EA


Aluminum is rather widely used inside buildings for larger sized wire. It
is very common to use aluminum wire for the service wires from the utility
connection to the meter to the service panel. The problems were with 15
and 20A branch circuits. Aluminum can still be used for them too, but not
likely any time soon.

--
bud--



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"bud--" wrote in message
.. .
Existential Angst wrote:
"Jules" wrote in message
news
On Mon, 26 Oct 2009 23:04:48 -0700, terry wrote:

(http://en.wikipedia.org/wiki/Ring_circuit for the curious)


That was VERY inneresting!!!
Am I correct in observing that the diagram shows two "radial" connections
to the ring?


The text talks about "unfused spurs".

It took me a while to grok the "point" of the schematic, and when I did,
it left me with a very big Q:

How does a ring circuit SAVE copper? ?
Yeah, I can see how you can use thinner gauge wire, but now you have to
use twice as much of it!


If you went straight out to a load and straight back there would be twice
the wire. The circuit wanders around the building picking up loads as it
goes.


Excellent point! I see that!! That is really really neat! Iow, the
geometry of the installation is sort of part of the schematic!!


Current capacity (density) is directly proportional to cross-sectional
area, so it seems to me this system is 6 of one, half a dozen of the
other, mass-wise in copper.
The article pointed out some potent disadvantages, as well -- somewhat
dicey, eh?


Seems really weird from the perspective of the US. Must be quite reliable
because it is still being used. I was really surprised when I heard how
different UK wiring is.

Interestingly, NYC still has DC running to some older commercial
buildings!


Ended about 2 years ago.
http://cityroom.blogs.nytimes.com/2007/11/14/off-goes-the-power-current-started-by-thomas-edison/

And, NYC's 3 phase is 208, not 220 or 240 V, like most of the rest of the
country -- 208 is EXACTLY the rms voltage difference between two 120 V
sine waves 120 deg out of phase, making it, I think, the "purest" type of
3 phase.


The vast majority of 3 phase power in the US (that supplies 120V loads) is
208V (wye connection). New 240V (delta connection) systems are probably
quite uncommon.


Well, on the various ng concerned with machines all over the country, over
about 10 yrs I think I'm the ONLY one to reference 208 V, via NYC. Maybe
208 dominates in big industrial cities?
Even Long Island (NY) which perhaps has one of the highest concentration of
"small" machine shops ( 10,000 sq ft) in the country, uses 240 V.

But here's my Q:
For a given voltage, what difference would the end user see in terms of a
delta or wye connection?
And why is 208 wye, and 240 V delta?

And, is each leg of the 240 V delta 3 ph separated by equal 120 deg shifts,
like the 208?
I argue that it is not, that two of the phases *must* be 180 deg out of
phase, as that's the only way you could get 240 from two 120 legs. The 3rd
phase must be 90 deg to these two.
Visavis 208/120 V systems, which is exactly consistent with 120 phase angle.

I argue this, but others hotly disagree, but without really being able to
tell me wye.

If the above is correct, I surmise the reason is that the 208 3 ph is
supplied right from the generator, whilst 240 3 ph comes off of pole
transformers.

--
EA




--
bud--



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bud-- wrote:
Existential Angst wrote:

It's funny, we started with copper, went to tinned copper, went back
to copper, slid further back to effing aluminum (goodgawd), learned
from that mistake and went back to copper again. Altho power
companies use aluminum in parts of their service -- and steel!


As several people have said, steel is not used as a conductor.

Aluminum is rather widely used inside buildings for larger sized wire.
It is very common to use aluminum wire for the service wires from the
utility connection to the meter to the service panel. The problems were
with 15 and 20A branch circuits. Aluminum can still be used for them
too, but not likely any time soon.


Around here #2 aluminum is the smallest you are allowed to use
in a home. Usually for the electric range.

TDD
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On Tue, 27 Oct 2009 15:38:12 -0400, Existential Angst wrote:
Seems so. Although it is more hassle to set up, and I'm never quite
convinced of the loading benefits given that the ring could fail yet still
appear to work; at least with a radial system if a connection goes bad
it's pretty obvious that it's done so.

(http://en.wikipedia.org/wiki/Ring_circuit for the curious)


That was VERY inneresting!!!
Am I correct in observing that the diagram shows two "radial" connections to
the ring?


Yes, such spur connections seem reasonably common for things like attics,
garages, and where rooms are later added on to buildings - and in that
respect they're not really much different to US wiring layouts, I suppose
(apart from they feed back to the ring, not always back to the service
panel).

It took me a while to grok the "point" of the schematic, and when I did,
it left me with a very big Q:

How does a ring circuit SAVE copper? ?


As Bud says, you have multiple loads on the ring, and the ring's quite
large, so from any given outlet the run length of the two routes back to
the consumer unit (service panel) is never quite equal.

The article pointed out some potent disadvantages, as well -- somewhat
dicey, eh?


Certainly can be. Hazards with any system, I suppose.

Aside: I can never quite decide whether I prefer UK-style outlets/plugs or
US ones. Remember that all plugs for UK appliances have their own fuse,
rather than relying on tripping a breaker back in the service panel, and
all outlets there have a live/neutral/earth connection - as a result the
plugs are quite large (although not as chunky as US 240V plugs,
thankfully), but the built-in fuse is nice to have.

OTOH I like how compact US plugs are - particularly on things like wall
warts where the pins fold away for storage.

OTOH (again) US plugs can be knocked such that they expose the pins, which
seems like a major safety hazard...

Interestingly, NYC still has DC running to some older commercial
buildings!


Yeah, so I've heard. I really like big old DC stuff - shame just about all
of it's gone to the junkyard these days. It appeals to the mad scientist
in me ;-)

But, I thought Europe was all 220, ie, two hot legs, residentially??


Yeah, I think it's all technically 230V these days actually - the UK
lowered theirs slightly (as did others) whilst some other countries on
220V upped theirs a little. It's just too ingrained in my mind such that
I'll always call the UK system 240V...

I'm curious how much 120V is used outside of the US, actually - I'm not
sure what other places in the world are using.

g-dAmerica never quite gets it right, unless it comes to fleecing their
public. Who needs a junta or a dictatorship when you have a Congress
blowing Wall Street, using the Media as a condom??


:-) I think the US system just evolved slowly over time, and with such a
high population it's hard to put the brakes on and simply change over to
something else; the European picture was a bit different because it was
all such a mess after WWII that there was a far more opportunity to start
over with different systems and standards. Not that they always got it
right, of course!

(I still find black wires as being 'hot' kind of weird in the US -
after doing a lot of electronics work over the years it was
surprising to me when I found that the wire that makes you go ouch is
the black one, not the white one ;-)

Altho amazingly our vitamins are a lot more available, fwiu. Whazzup
wit dat, over there???


No comment, really. Never been one to buy vitamins - although I've heard
that medicine's generally a lot cheaper over there (or free, given the
NHS) than it is in the US.

cheers!

Jules

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Existential Angst wrote:
"Jules" wrote in message
news
On Mon, 26 Oct 2009 23:04:48 -0700, terry wrote:

(http://en.wikipedia.org/wiki/Ring_circuit for the curious)


That was VERY inneresting!!!
Am I correct in observing that the diagram shows two "radial" connections to
the ring?


The text talks about "unfused spurs".

It took me a while to grok the "point" of the schematic, and when I did, it
left me with a very big Q:

How does a ring circuit SAVE copper? ?
Yeah, I can see how you can use thinner gauge wire, but now you have to use
twice as much of it!


If you went straight out to a load and straight back there would be
twice the wire. The circuit wanders around the building picking up loads
as it goes.

Current capacity (density) is directly proportional to cross-sectional
area, so it seems to me this system is 6 of one, half a dozen of the other,
mass-wise in copper.
The article pointed out some potent disadvantages, as well -- somewhat
dicey, eh?


Seems really weird from the perspective of the US. Must be quite
reliable because it is still being used. I was really surprised when I
heard how different UK wiring is.

Interestingly, NYC still has DC running to some older commercial buildings!


Ended about 2 years ago.
http://cityroom.blogs.nytimes.com/2007/11/14/off-goes-the-power-current-started-by-thomas-edison/

And, NYC's 3 phase is 208, not 220 or 240 V, like most of the rest of the
country -- 208 is EXACTLY the rms voltage difference between two 120 V sine
waves 120 deg out of phase, making it, I think, the "purest" type of 3
phase.


The vast majority of 3 phase power in the US (that supplies 120V loads)
is 208V (wye connection). New 240V (delta connection) systems are
probably quite uncommon.

--
bud--


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Existential Angst wrote:

It's funny, we started with copper, went to tinned copper, went back to
copper, slid further back to effing aluminum (goodgawd), learned from that
mistake and went back to copper again. Altho power companies use aluminum
in parts of their service -- and steel!


As several people have said, steel is not used as a conductor.

Aluminum is rather widely used inside buildings for larger sized wire.
It is very common to use aluminum wire for the service wires from the
utility connection to the meter to the service panel. The problems were
with 15 and 20A branch circuits. Aluminum can still be used for them
too, but not likely any time soon.

--
bud--
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"Jules" wrote in message
news
On Tue, 27 Oct 2009 15:38:12 -0400, Existential Angst wrote:
Seems so. Although it is more hassle to set up, and I'm never quite
convinced of the loading benefits given that the ring could fail yet
still
appear to work; at least with a radial system if a connection goes bad
it's pretty obvious that it's done so.

(http://en.wikipedia.org/wiki/Ring_circuit for the curious)


That was VERY inneresting!!!
Am I correct in observing that the diagram shows two "radial" connections
to
the ring?


Yes, such spur connections seem reasonably common for things like attics,
garages, and where rooms are later added on to buildings - and in that
respect they're not really much different to US wiring layouts, I suppose
(apart from they feed back to the ring, not always back to the service
panel).

It took me a while to grok the "point" of the schematic, and when I did,
it left me with a very big Q:

How does a ring circuit SAVE copper? ?


As Bud says, you have multiple loads on the ring, and the ring's quite
large, so from any given outlet the run length of the two routes back to
the consumer unit (service panel) is never quite equal.

The article pointed out some potent disadvantages, as well -- somewhat
dicey, eh?


Certainly can be. Hazards with any system, I suppose.

Aside: I can never quite decide whether I prefer UK-style outlets/plugs or
US ones. Remember that all plugs for UK appliances have their own fuse,
rather than relying on tripping a breaker back in the service panel, and
all outlets there have a live/neutral/earth connection - as a result the
plugs are quite large (although not as chunky as US 240V plugs,
thankfully), but the built-in fuse is nice to have.

OTOH I like how compact US plugs are - particularly on things like wall
warts where the pins fold away for storage.

OTOH (again) US plugs can be knocked such that they expose the pins, which
seems like a major safety hazard...

Interestingly, NYC still has DC running to some older commercial
buildings!


Yeah, so I've heard. I really like big old DC stuff - shame just about all
of it's gone to the junkyard these days. It appeals to the mad scientist
in me ;-)

But, I thought Europe was all 220, ie, two hot legs, residentially??


Yeah, I think it's all technically 230V these days actually - the UK
lowered theirs slightly (as did others) whilst some other countries on
220V upped theirs a little. It's just too ingrained in my mind such that
I'll always call the UK system 240V...


Is your 220/230 V from one hot leg to a neutral, or between two hot legs?

The ring diagam would seem to indicate that it's one hot leg to a neutral.
--
EA






I'm curious how much 120V is used outside of the US, actually - I'm not
sure what other places in the world are using.

g-dAmerica never quite gets it right, unless it comes to fleecing their
public. Who needs a junta or a dictatorship when you have a Congress
blowing Wall Street, using the Media as a condom??


:-) I think the US system just evolved slowly over time, and with such a
high population it's hard to put the brakes on and simply change over to
something else; the European picture was a bit different because it was
all such a mess after WWII that there was a far more opportunity to start
over with different systems and standards. Not that they always got it
right, of course!

(I still find black wires as being 'hot' kind of weird in the US -
after doing a lot of electronics work over the years it was
surprising to me when I found that the wire that makes you go ouch is
the black one, not the white one ;-)

Altho amazingly our vitamins are a lot more available, fwiu. Whazzup
wit dat, over there???


No comment, really. Never been one to buy vitamins - although I've heard
that medicine's generally a lot cheaper over there (or free, given the
NHS) than it is in the US.

cheers!

Jules



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Existential Angst wrote:
"bud--" wrote in message
.. .
Existential Angst wrote:
It's funny, we started with copper, went to tinned copper, went back to
copper, slid further back to effing aluminum (goodgawd), learned from
that mistake and went back to copper again. Altho power companies use
aluminum in parts of their service -- and steel!


As several people have said, steel is not used as a conductor.


Yeah, I just looked -- that guy wire I thought was steel indeed appears to
be alum!


ACSR - aluminum cable steel reinforced. The neutral is bare aluminum
with one of the strands steel to support the drop. I think someone else
said about the same thing.

--
bud--
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On 10/28/2009 7:01 AM Stormin Mormon spake thus:

makes sign of the pentagon


Did you mean the sign of the *pentagram*, or the sign of the Pentagon?

Go with Satan, my son from the dark side.


Whatever.


--
Who needs a junta or a dictatorship when you have a Congress
blowing Wall Street, using the media as a condom?

- harvested from Usenet
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Existential Angst wrote:
The vast majority of 3 phase power in the US (that supplies 120V loads) is
208V (wye connection). New 240V (delta connection) systems are probably
quite uncommon.


Well, on the various ng concerned with machines all over the country, over
about 10 yrs I think I'm the ONLY one to reference 208 V, via NYC. Maybe
208 dominates in big industrial cities?
Even Long Island (NY) which perhaps has one of the highest concentration of
"small" machine shops ( 10,000 sq ft) in the country, uses 240 V.


120/208V dominates in general. Machine shops may want 240V because
machines may be commonly made for 240V. That may be historical - it may
be how early machines were made and was continued for compatibility with
older equipment. I have seen some machine tools in use that probably
predate Columbus.

But here's my Q:
For a given voltage, what difference would the end user see in terms of a
delta or wye connection?
And why is 208 wye, and 240 V delta?


208V has 3 - 120V transformers. One endpoint of each transformer is
connected together to form a "neutral". You have 120V from each of the
phase conductors to the neutral. That is a major advantage when you are
supplying 120V loads (compare to 240V delta). The voltage between phase
conductors is 208V. A 3-phase motor would be 208V. A diagram of the
transformer connections looks like a Y-wye (or star).

The major power distribution in a large building is likely 277/480V wye.
The 3 transformers are 277V with one end connected to a common neutral.
The voltage between phase conductors is 480V. Higher voltage means less
copper is used in wiring. A lot fluorescent (and non-incandescent)
lightning is 277V .For motors 480V 3-phase is nice. Stepdown
transformers to 120/208V wye are installed in electrical rooms where
necessary. [You could also get 240V delta.]

A 240V delta system starts out with a 120/240 transformer like is used
for a residential service. The center tap is the neutral, just like with
a residential service. For the 3-phase, 2 transformers are added, one
end of each connected to the ends of the original transformer and the
other end connected together to be the 3 phase "high leg". A diagram of
the transformer connections looks like a triangle or delta. The voltage
from the high leg to neutral is 208V. There may only be 2 transformers
(open delta). I suspect this system came from original 120/240V single
phase systems where some 3-phase load had to be added. You can add a
transformer, which can be much smaller than the original one (depending
on the 3 phase load). And there used to be a "delta breaker" (may still
exist) which I believe allowed 3 phase to be kludged into original
single phase services. I suspect this is how 3 phase came to many
machine shops. You have 120V from only 2 phases to the neutral and it is
much harder to "balance" the current in the 3 legs. If not balanced, the
voltages between phases may be different which increases motor heating.
If there are 3 transformers imbalance also causes "circulating" currents.

And, is each leg of the 240 V delta 3 ph separated by equal 120 deg shifts,
like the 208?


Yup.

I argue that it is not, that two of the phases *must* be 180 deg out of
phase, as that's the only way you could get 240 from two 120 legs. The 3rd
phase must be 90 deg to these two.


Not how delta works.

There did used to be 2-phase power (90 degrees). Niagra, which was
probably the first large hydro generation, was originally 2-phase.

Visavis 208/120 V systems, which is exactly consistent with 120 phase angle.

I argue this, but others hotly disagree, but without really being able to
tell me wye.

If the above is correct, I surmise the reason is that the 208 3 ph is
supplied right from the generator, whilst 240 3 ph comes off of pole
transformers.


Nope.

You could look at machine shops and see if there are only 2 transformers
(open delta) and one is much smaller (most of the load is single phase).
For delta, one of the transformers has a 3rd connection (neutral).

--
bud--


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Jules wrote:
On Tue, 27 Oct 2009 15:38:12 -0400, Existential Angst wrote:
Seems so. Although it is more hassle to set up, and I'm never quite
convinced of the loading benefits given that the ring could fail yet still
appear to work; at least with a radial system if a connection goes bad
it's pretty obvious that it's done so.

(http://en.wikipedia.org/wiki/Ring_circuit for the curious)

That was VERY inneresting!!!
Am I correct in observing that the diagram shows two "radial" connections to
the ring?


Yes, such spur connections seem reasonably common for things like attics,
garages, and where rooms are later added on to buildings - and in that
respect they're not really much different to US wiring layouts, I suppose
(apart from they feed back to the ring, not always back to the service
panel).


A question is whether the spur is ring-wire-size or 'full-wire-size'.
The Wiki article sounds like it is ring-wire-size with limitation on the
number of outlets or possible fuses.

Aside: I can never quite decide whether I prefer UK-style outlets/plugs or
US ones. Remember that all plugs for UK appliances have their own fuse,
rather than relying on tripping a breaker back in the service panel, and
all outlets there have a live/neutral/earth connection - as a result the
plugs are quite large (although not as chunky as US 240V plugs,
thankfully), but the built-in fuse is nice to have.


I assume a major purpose of the fuse is that you are connecting a cord
with rather limited current rating to a 30/32A ring circuit.

OTOH I like how compact US plugs are - particularly on things like wall
warts where the pins fold away for storage.

OTOH (again) US plugs can be knocked such that they expose the pins, which
seems like a major safety hazard...

But, I thought Europe was all 220, ie, two hot legs, residentially??


Yeah, I think it's all technically 230V these days actually - the UK
lowered theirs slightly (as did others) whilst some other countries on
220V upped theirs a little. It's just too ingrained in my mind such that
I'll always call the UK system 240V...


All 3-phase at utility end, from what I have read, with hot and neutral
supplied. You may get 2 of the phases. And in some countries I have read
you get all 3 phases.

:-) I think the US system just evolved slowly over time, and with such a
high population it's hard to put the brakes on and simply change over to
something else; the European picture was a bit different because it was
all such a mess after WWII that there was a far more opportunity to start
over with different systems and standards. Not that they always got it
right, of course!


The UK, in particular, does seem to be a much more 'engineered' system.
Not sure how much the 'cowboy' mentality in the US would allow that.
Receptacle configurations have changed even since WWII if I read the
Wiki article right.

Surprising how much even the names of parts are different from this side
the pond (like "consumer unit" in the Wiki article).

--
bud--
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On Wed, 28 Oct 2009 13:26:40 -0600, bud-- wrote:
A question is whether the spur is ring-wire-size or 'full-wire-size'.
The Wiki article sounds like it is ring-wire-size with limitation on the
number of outlets or possible fuses.


Yeah, normally ring-wire-size from installations I've seen, so some care
has to be taken when adding new services (although I suppose that's true
of any type of electrical system)

Aside: I can never quite decide whether I prefer UK-style outlets/plugs
or US ones. Remember that all plugs for UK appliances have their own
fuse, rather than relying on tripping a breaker back in the service
panel, and all outlets there have a live/neutral/earth connection - as
a result the plugs are quite large (although not as chunky as US 240V
plugs, thankfully), but the built-in fuse is nice to have.


I assume a major purpose of the fuse is that you are connecting a cord
with rather limited current rating to a 30/32A ring circuit.


Well, not just the cord, but the device itself too; it's nice if the
device doesn't have to wait for the main ring fuse to blow (or breaker to
trip) if there's a fault. Fuses in plugs were commonly 3A, 5A or 13A -
although ISTR seeing 2A before, and in reality most things end up using
13A with some smaller stuff (lamps etc.) using 3A.

OTOH I like how compact US plugs are - particularly on things like wall
warts where the pins fold away for storage.

OTOH (again) US plugs can be knocked such that they expose the pins,
which seems like a major safety hazard...

But, I thought Europe was all 220, ie, two hot legs, residentially??


Yeah, I think it's all technically 230V these days actually - the UK
lowered theirs slightly (as did others) whilst some other countries on
220V upped theirs a little. It's just too ingrained in my mind such
that I'll always call the UK system 240V...


All 3-phase at utility end, from what I have read, with hot and neutral
supplied. You may get 2 of the phases. And in some countries I have read
you get all 3 phases.


Yes, some larger houses can end up with a couple of phases (in the UK).
Typically they're just a single phase, though. Not sure what the rest of
Europe's like.

The UK, in particular, does seem to be a much more 'engineered' system.
Not sure how much the 'cowboy' mentality in the US would allow that.
Receptacle configurations have changed even since WWII if I read the
Wiki article right.


Yeah, there have been some changes to outlet designs, plugs and light
fittings - plus of course at some point fuse boxes started disappearing
and were replaced by breakers.

Surprising how much even the names of parts are different from this side
the pond (like "consumer unit" in the Wiki article).


Uh huh. Cord vs. cable, outlet vs. socket etc... although having done the
move from one country to another there's a lot of commonality, too. Enough
that the US system more or less makes sense to me now ;-)

Oh, I found a world map of the various voltages/frequencies in use which
may be of interest:

http://en.wikipedia.org/wiki/File:Wo...6Frequency.png

cheers

Jules

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On Wed, 28 Oct 2009 13:32:44 -0400, Existential Angst wrote:
Yeah, I think it's all technically 230V these days actually - the UK
lowered theirs slightly (as did others) whilst some other countries on
220V upped theirs a little. It's just too ingrained in my mind such that
I'll always call the UK system 240V...


Is your 220/230 V from one hot leg to a neutral, or between two hot legs?

The ring diagam would seem to indicate that it's one hot leg to a neutral.


Yep, 'live' gives 240V (well, technically 230V) with respect to the
neutral, rather than there being two 'hots' of 120V like the US system.

Power over there is at 50Hz too rather than 60, which can have an impact
on things which derive timing from the power input (or on things with
inductive components - if I remember right the problem's in bringing
things designed for a 60Hz environment into a 50Hz one as there can be
overheating issues)

cheers

Jules


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wrote in message
...
On Wed, 28 Oct 2009 11:52:26 -0600, bud--
wrote:

Existential Angst wrote:
"bud--" wrote in message
.. .
Existential Angst wrote:
It's funny, we started with copper, went to tinned copper, went back
to
copper, slid further back to effing aluminum (goodgawd), learned from
that mistake and went back to copper again. Altho power companies use
aluminum in parts of their service -- and steel!

As several people have said, steel is not used as a conductor.

Yeah, I just looked -- that guy wire I thought was steel indeed appears
to
be alum!


ACSR - aluminum cable steel reinforced. The neutral is bare aluminum
with one of the strands steel to support the drop. I think someone else
said about the same thing.



Most domestic service drops I have seen are just AAC, no steel core.



Everyone I've ever seen used by NYSEG and ConEd are aluminum with a steel
core



Phelps Dodge has a pretty good web site talking about the various
service drop cables.



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wrote:
On Wed, 28 Oct 2009 13:03:03 -0600, bud--
wrote:


But here's my Q:
For a given voltage, what difference would the end user see in terms of a
delta or wye connection?
And why is 208 wye, and 240 V delta?


208V has 3 - 120V transformers. One endpoint of each transformer is
connected together to form a "neutral". You have 120V from each of the
phase conductors to the neutral. That is a major advantage when you are
supplying 120V loads (compare to 240V delta). The voltage between phase
conductors is 208V. A 3-phase motor would be 208V. A diagram of the
transformer connections looks like a Y-wye (or star).


This is a picture of one of those transformer arrays. The incoming
phases to the customer is black,red.blue

http://gfretwell.com/electrical/3_p_wye-wye.jpg

A picture is worth a thousand words.

Where do you get the wire with the neon insulation? (nice touch)


A 240V delta system starts out with a 120/240 transformer like is used
for a residential service. The center tap is the neutral, just like with
a residential service. For the 3-phase, 2 transformers are added, one
end of each connected to the ends of the original transformer and the
other end connected together to be the 3 phase "high leg". A diagram of
the transformer connections looks like a triangle or delta. The voltage
from the high leg to neutral is 208V. There may only be 2 transformers
(open delta). I suspect this system came from original 120/240V single
phase systems where some 3-phase load had to be added. You can add a
transformer, which can be much smaller than the original one (depending
on the 3 phase load).


This is a picture of that transformer array, the 120/240 phases are
typically black & red and the high leg is required to be orange by
code.


http://gfretwell.com/electrical/High...ransormers.jpg


Another nice pic. 2 transformers means open delta. Notice the right
transformer has 3 connections - the center one is the neutral. Left
transformer only has 2 connections.


There is another way you can see delta in a place that doesn't need
any 120v load. They make a standard delta with either 2 or 3
transformers and ground one phase leg AKA "corner grounded delta".
That will look a lot like single phase to someone who is not aware
since there will just be 2 ungrounded conductors and the 3d phase will
be white. The equipment will look like single phase with 2 pole
breakers.

That is one place where you will need those 2 pole "delta" rated
breakers.



I have never seen an installation with a delta breaker. Catalog pictures
what I remember is a delta breaker has 2 bus stabs and a wire. The wire
goes to the neutral bar?
Is this the only way delta breakers are used?


You can also have ungrounded delta but that will be in a special place
like a glass factory where the first fault to ground won't bring down
the power. There are special monitoring requirements for that.

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wrote:
On Thu, 29 Oct 2009 10:50:29 -0600, bud--
wrote:

I have never seen an installation with a delta breaker. Catalog pictures
what I remember is a delta breaker has 2 bus stabs and a wire. The wire
goes to the neutral bar?
Is this the only way delta breakers are used?


"Delta" breakers are really only telling you they have higher line to
ground ratings. The normal breaker you see in 120/240 is really only
rated 120v nominal to ground. In a delta you always have at least one
leg above 200v to ground. In corner delta you have 2 at 240v above
ground. The place you are likely to see corner delta is in a sewer
lift station where the only load is the pump and a control panel that
runs l/l at 240v. That will usually be open delta too.
The panel will look like a single pole (2 hots and a grounded leg)
unit but the tip off is 240v to ground and 3 p loads. That is really
the one you have to look for "delta" breakers in. All 3p breakers I
have ever seen are rated that way.
Although a corner delta panel looks exactly like a 120/240 panel, it
still needs to be listed for delta (higher voltage). I suspect it may
only be the label ;-)

An example would be to compare a QO230H "delta" breaker $200
with a QO230 120/240 breaker (the one on your water heater) $67

That is list price, you will beat that by up to 60% on the regular
breaker but you might not on the delta breaker.


Interesting.

A few posts back I mentioned a "delta breaker" then you mentioned "delta
rated breakers". My last post confused the distinction. I looked in the
SquareD catalog and your delta ratings are easy to find. They are
supposed to have a catalog for corner grounded delta but I haven't
searched for it yet. Should reinforce the info you provided above.

I looked in an my old electrician's handbook and it shows a "delta
breaker" as a 3-phase breaker except it only has 2 bus connections. The
third connection comes out to an additional lug. In use, you have high
leg delta service entrance wires but a single phase panel. The delta
breaker plugs into the panel and picks up the 120V legs. The service
high leg connects directly to the additional lug on the breaker. The
only 3-phase available is on the load side of the delta breaker - to
equipment or a subpanel. Everything else in the service panel is single
phase. I suspect they were used to add some 3-phase load to a single
phase panel - you just add 3-phase service wires and meter to the
existing single phase panel. To be safe you also add a 3-phase common
trip circuit breaker as a separate service disconnect. They could also
be used as one of the service disconnects in a split bus panel.

I looked on google (Holt) and delta breakers have not been allowed in
panelboards since 1978 (408.36). I sure have never seen one. But I
remembered seeing them in the NEC which is why I was interested.

--
bud--
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Posted to alt.home.repair
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Default 1920's wiring....

wrote:
On Thu, 29 Oct 2009 10:50:29 -0600, bud--
wrote:

I have never seen an installation with a delta breaker. Catalog pictures
what I remember is a delta breaker has 2 bus stabs and a wire. The wire
goes to the neutral bar?
Is this the only way delta breakers are used?


"Delta" breakers are really only telling you they have higher line to
ground ratings. The normal breaker you see in 120/240 is really only
rated 120v nominal to ground. In a delta you always have at least one
leg above 200v to ground. In corner delta you have 2 at 240v above
ground. The place you are likely to see corner delta is in a sewer
lift station where the only load is the pump and a control panel that
runs l/l at 240v. That will usually be open delta too.
The panel will look like a single pole (2 hots and a grounded leg)
unit but the tip off is 240v to ground and 3 p loads. That is really
the one you have to look for "delta" breakers in. All 3p breakers I
have ever seen are rated that way.
Although a corner delta panel looks exactly like a 120/240 panel, it
still needs to be listed for delta (higher voltage). I suspect it may
only be the label ;-)

An example would be to compare a QO230H "delta" breaker $200
with a QO230 120/240 breaker (the one on your water heater) $67

That is list price, you will beat that by up to 60% on the regular
breaker but you might not on the delta breaker.


Interesting.

A few posts back I mentioned a "delta breaker" then you mentioned "delta
rated breakers". My last post confused the distinction. I looked in the
SquareD catalog and your delta ratings are easy to find. They are
supposed to have a catalog for corner grounded delta but I haven't
searched for it yet. Should reinforce the info you provided above.

I looked in an my old electrician's handbook and it shows a "delta
breaker" as a 3-phase breaker except it only has 2 bus connections. The
third connection comes out to an additional lug. In use, you have high
leg delta service entrance wires but a single phase panel. The delta
breaker plugs into the panel and picks up the 120V legs. The service
high leg connects directly to the additional lug on the breaker. The
only 3-phase available is on the load side of the delta breaker - to
equipment or a subpanel. Everything else in the service panel is single
phase. I suspect they were used to add some 3-phase load to a single
phase panel - you just add 3-phase service wires and meter to the
existing single phase panel. To be safe you also add a 3-phase common
trip circuit breaker as a separate service disconnect. They could also
be used as one of the service disconnects in a split bus panel.

I looked on google (Holt) and delta breakers have not been allowed in
panelboards since 1978 (408.36). I sure have never seen one. But I
remembered seeing them in the NEC which is why I was interested.

--
bud--
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