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Karl — See http://www.coned.com/sales/business/bus_elec.htm for utility-offered savings for 'upgrading' utility-furnished DC service in the NYC area. I don't know how long the program is supposed to last, but I'll bet there are some DC elevators in older apartment buildings in Con Ed service territory.

About 10 years ago, an associate in meter-testing equipment design told me he had been contacted by the Con Ed metering department to make an AC-powered test set for DC-energy meters, for their aged test instrumentation employed lead-acid storage batteries and large resistive-heater load banks for tests, and lugging those in an out of basements was “inconvenient,” to say the least.

[Note that (likely long-existing) 2-phase AC service is still listed as available in Con Ed and PECO systems. It's interesting to note that General Electric shows 2ø 5-wire as one of the available forms for one of their microprocessor-based energy meters—model "kV".]




[This message has been edited by Bjarney (edited 09-15-2003).]

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Karl Riley said:
Quote
In my first apartment as an adult in NYC the power was 110V DC, powered from a generating plant around the corner! Had to get a noisy inverter to play my 78 rpm records. (For those who know New York, it was the lower east side, Ave. C and Stanton).

Yeah. I know that area. They call it "Alphabet City" You should see what's happened to it now!! It's going yuppie!! [Linked Image]

WOW!! 110-volts DC?? What year was this? I thought DC was totally gone from residential applications in this town by the 40s or 50s.

Does anyone know when 110-volt DC for residential applications totally dissapear?

Of course you could get AC/DC radios well into the late 60s & early 1970s (transformer-less 5-tube "all American 5" sets). Reason was they were cheaper because manufacturer could avoid the cost of a transformer.

I heard that there were still a few buildings in New York that were on DC. But these were factory buildings.

I actually wonder if any houses in this country still use 110-volts DC for their appliances.

Wonder if those inverters are still available. I know you can get inverters to power 110-volt AC devices off a 12 volt DC line but that's different.

What types of plugs were used on the 110-volt DC system? Did they wire it with regular NEMA 1-15 and 5-15 sockets or did they use something more like this: ( -- | ) - with one horizontal and one vertical slot ?

That must have been weird if you plugged in your DC - powered fan and it started spinning backwards... [Linked Image]

What about a DC powered blender or electric clock?

"Heyyyy...why is my clock running backwards!! "

*FLIP THE PLUG*

"Oh...much better!" [Linked Image]

[This message has been edited by SvenNYC (edited 09-15-2003).]

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Bjarney, I am amazed reading (on a webpage of all things) an encouragement to change from DC to AC in 2003!

Do I take it therefore that there are still some residential premises powered at 120V dc in NY,NY or is this just for utilities like lifts etc.? It does talk about lighting. Do they use the same NEMA receptacles? It reminds me of the high-pressure hydraulic mains for powering lifts in UK cities whose pipes are still extant - but now tend to contain fibre-optic cables!

Same webpage - steam powered air-conditioning (2003!). I know this is an electrical forum, and I vaguely understand gas refrigerators, but how on earth do these work?

[Sven, our posts crossed in the ether! [Linked Image]]

[This message has been edited by Hutch (edited 09-15-2003).]

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European railways use a vast variety of systems. As far as I know Italy and France are mostly 1500V DC, I think there are 3000V systems, Austria, germany and some other countries have agreed on 15000V 16 2/3 (or more correctly now 16.7) Hz. Tram and subway systems are even worse, they run on 500V, 550V, 650V, 750V, 900V, 950V,... Vienna alone has 650V (not sure, maybe the Trams are 750, not 650), 750V catenary, 750V third rail, 950V (all DC) and 15kV 16 2/3 Hz AC. The Vienna Stadtbahn network that was opened as an urban steam railway system with interconnected lines and trains going as far as 100 or more km out of town is now split up into 3 isolated systems. 1 of the 3 lines uses 750V DC third rail (Vienna subway system), 1 is 750V catenary (tram style, but officially called subway), only the third line is still full railway system, 15kV AC, but the connections to the surrounding area have been chopped as well, even though they could reopen them any day.

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In Britain, rural areas wich were electrified in the later years went straight to AC, but those districts which got electricity early on were wired with 3-wire DC systems.

These were gradually converted to AC over the years, but the central districts of some older towns still had DC mains into the early 1960s.

AC/DC radios and TVs of the time used a cheap half-wave rectifier with one side of the line connected directly to chassis. The tube filaments and dial lamps would be series-wired and connected straight across the incoming AC.

With the reversible 2-pin 5A plugs in common use for radios, plugging in the wrong way to a DC outlet would result in the dial and tube filaments glowing fine, but no B+ supply and thus no sound (or picture).

Where a 3-pin polarized plug was used, those living in homes fed from the negative "outer" would need to wire their radios so that the chassis would be live. With non-identified twin cord, it would be trial-and-error to get the connections the right way, or for color-coded cord they would need to connect the red to neutral and black to live (i.e. the opposite way to "normal").

The problem arose then of course, that the plug would need to be rewired for the set to work in a house wired on the other side of the supply!

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Paul, would this domestic dc be 120V to ground or 240V to ground?

Joined: Aug 2003
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My NYC DC apartment was in 1950 - 52. The plugs were the same as AC. No ground, of course.
For nostalgia sake, the bath tub was in the kitchen, with a cover over it to use as the kitchen counter. There was no heat, but since I was on the 4th floor, enough heat came up from the apartments underneath to make it liveable. Rent, shared with a college buddy: $15/month.

Karl

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For the US, it looks like the current iteration of the NEMA wiring device standard {WD6-1997} does not specify AC or DC for 1-15 plugs and receptacles [simply, 125 volts, 15 amperes, 2-pole, 2-wire.]

[Linked Image from 64.146.180.232]

Note that is not the case with switches—almost all these days are marked AC only. For interrupting DC current—even a purely resistive load—it is a whole different ball game. I don’t know how that meshes with unplugging an appliance from a DC circuit. You would think that arcing could be much greater, for one because AC is momentarily zero every 8.3 milliseconds {each ½ an electrical cycle} allowing a degree of natural arc snuffing. DC does not have that luxury.




[This message has been edited by Bjarney (edited 09-16-2003).]

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Speculatively, in NYC there are probably some old basement motor-generator sets that are owned and maintained by Con Ed for changing the utility’s local AC to DC, presumably upstream of a DC watthour meter. There might also be some “modern” transformer-silicon rectifier-reactor-capacitor converters. Voltage likely would be around 110/220V DC, consistent with the history of ‘Edison 3-wire’ service. Long Shot Guess is that there may some ancient elevator or ventilation motors, and maybe a trace of incandescent lighting in common areas.

Joined: Nov 2002
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The motors would be the universal AC/DC motors, so polarity wouldn't matter.

Well into the 1970s direct line powered radios were sold. Sometime in the 1960s they made them solid state (Have an RCA one somewhere). I won't say valve radios werent, because a record player my mother bought new in 1969 have 50EH5 amp valves.

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