1920's wiring....

[Existential Angst]

Indeed, it does look like that twisted support/guy wire is aluminum!

So what is a 1350 alloy, visavis a 6061 alloy? Do you know the ohms per foot of each, vs. that of copper?

[Existential Angst]

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

[Existential Angst]

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

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&#39;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&#39;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.

[The Daring Dufas]

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

TDD

[Jules]

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&#39;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).

As Bud says, you have multiple loads on the ring, and the ring&#39;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.

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...

Yeah, so I&#39;ve heard. I really like big old DC stuff - shame just about all of it&#39;s gone to the junkyard these days. It appeals to the mad scientist in me ;-)

Yeah, I think it&#39;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&#39;s just too ingrained in my mind such that I&#39;ll always call the UK system 240V...

I&#39;m curious how much 120V is used outside of the US, actually - I&#39;m not sure what other places in the world are using.

:-) I think the US system just evolved slowly over time, and with such a high population it&#39;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 &#39;hot&#39; 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 ;-)

No comment, really. Never been one to buy vitamins - although I&#39;ve heard that medicine&#39;s generally a lot cheaper over there (or free, given the NHS) than it is in the US.

cheers!

Jules

[bud--]

The text talks about "unfused spurs".

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.

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.

Ended about 2 years ago.

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--]

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.

[gfretwell]

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

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

[bud--]

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.

[gfretwell]

I am not sure what 6061 is but the 1350 is 99.5% aluminum.

According to table 8 in the NEC the resistance for #2 (typical residential service drop up to 200a) is .194 ohms per 1000 ft copper .319 ohms per 1000 ft aluminum

[Existential Angst]

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&#39;s one hot leg to a neutral.

[David Nebenzahl]

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

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

Whatever.

[bud--]

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.

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.

Yup.

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.

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--]

A question is whether the spur is ring-wire-size or &#39;full-wire-size&#39;. The Wiki article sounds like it is ring-wire-size with limitation on the number of outlets or possible fuses.

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.

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.

The UK, in particular, does seem to be a much more &#39;engineered&#39; system. Not sure how much the &#39;cowboy&#39; 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).

[Jules]

Yeah, normally ring-wire-size from installations I&#39;ve seen, so some care has to be taken when adding new services (although I suppose that&#39;s true of any type of electrical system)

Well, not just the cord, but the device itself too; it&#39;s nice if the device doesn&#39;t have to wait for the main ring fuse to blow (or breaker to trip) if there&#39;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.

Yes, some larger houses can end up with a couple of phases (in the UK). Typically they&#39;re just a single phase, though. Not sure what the rest of Europe&#39;s like.

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.

Uh huh. Cord vs. cable, outlet vs. socket etc... although having done the move from one country to another there&#39;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:

cheers

Jules

[Jules]

Yep, &#39;live&#39; gives 240V (well, technically 230V) with respect to the neutral, rather than there being two &#39;hots&#39; 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&#39;s in bringing things designed for a 60Hz environment into a 50Hz one as there can be overheating issues)

cheers

Jules

[RBM]

Everyone I&#39;ve ever seen used by NYSEG and ConEd are aluminum with a steel core

[clare]

I still do, when parts are available. Getting hard to buy non surface mount components as simple as capacitors though.

[clare]

I&#39;ve got a "loifetime supply" of about 8 500g rolls.

[gfretwell]

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

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.

There is another way you can see delta in a place that doesn&#39;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.

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&#39;t bring down the power. There are special monitoring requirements for that.