Increased AC mains voltages in the US--why?

[Rhodesplyr]

For years, I've heard about how AC mains voltages in the US have crept upwards since the 1950s, but it occurred to me the other day that I know absolutely nothing about the reason for this trend from ~110V to 115V to 117V to 120V and beyond.

What drove/drives this trend?

Will we eventually hit 240V? :-)

[Steve Conner]

Isn't it just that everyone got more power hungry, but the power companies couldn't be bothered upgrading their wiring?

So they just bumped the voltage up in order that it would still stay above the legal minimum even when sagging at peak demand times.

In the USA it is effectively 240V already, 120 is only for smaller appliances

We had the opposite trend, we started at 240 and are supposed to be coming down to 230 to meet the European standard. In practice it never changed.

[g1]

Line losses are probably the main reason. Lower voltage requires higher current and thicker wire to supply the same amount of wattage as higher voltage. So the cost of the wire thickness may be a factor. Also you generally have more power loss (heat) at poorer connections with higher current. Automotive seems to be trending toward 24V rather than 12V (or the 6V it used to be). Regulation may also be a factor.
I just wish they would pick a number and stick with it. Incandescent bulbs are now 130V, 115 won't cut it anymore. All your appliances use more power as the voltage creeps up, and are subjected to more stress. I'm sure all the manufacturers have no beef with reduced life expectancy.
As Steve pointed out, you already have 240V (250 at our house) coming into your house, where it is then split in half. I don't think it would be feasable to convert our household use to 240V, and that would probably just keep creeping up anyway.
I believe 3 phase 208V is supposed to be the best solution, but don't know much about it.

[Enzo]

130v bulbs are more about lasting longer than meeting rising mains voltages. You'd see some super long life bulb in the store, and look at the label and see it was 130v and also a lot lower lumen output per wattage than normal bulbs. 130v bulbs on 120v or 125v will last longer.

[g1]

130v bulbs on 120v or 125v will last longer.

Can I twist your words around and say 120V bulbs on 125v or 130v will last less longer?
I won't argue that the intent may not have been to meet rising mains voltage, but I don't see anything less than 130V bulbs in our stores anymore.
A little anecdote an electrician friend told me: He had an elderly lady call to get the wiring corrected in one room because the light bulb kept blowing. He couldn't find any problem but the bulbs kept blowing and after returning several times he realized she had a case of old 115V bulbs and that was what she was using. Put in a 130V and never heard back from her again. Or so that was his story...
Anyway, my main point was that rising voltage can only add to the stress put on items designed for lower voltages. Biggest issue for me is filter cap voltage ratings. I mentioned in another thread an amp I saw recently approx. 5 yrs. old. Solid state with 63V caps. Mains labelled as 120V. Voltage on caps 63V with 125VAC on the mains. Never bothered checking filter cap voltages on SS stuff before, now I pay more attention. Same with heater voltages. 7V on the heaters (@125V mains) isn't exactly tube friendly. That was another 5 yr. old amp but labelled for 120V mains (though the PT was marked 115V). If memory serves the 6BQ5's were idling around 14W each.

[Enzo]

No argument over that. Just pointing out the genesis of 130v lamps was reliability and life. They were the items specially sold as extra long life lamps, and places like schools and institutions used them to save $$$. 130v bulbs have been around for a long time.

I am sure Canadian rules differ from ours, but as the USA tries to phase out common incandescent lamps, the new rule is higher efficiency, so the CFLs are mainly what they sell, but I wouldn;t be surprised if the colder lamps were not also an effort to increase overall efficiency in the product line to help meet standards. I know they are selling "higher efficiency" incandescents too. Our requirement changes tnd to leak across the border, just as RoHS tends to leak into ours.

[Tom Phillips]

Although 130V incandescent bulbs have been aroud for a long time I have rarely, if ever, been able to find them in the common home stores in my area. Even the "Long life" bulbs in those stores are 120V. As Enzo pointed out they are concentrating on the compact florecents so the stock of incandecents are shrinking. In my neck of the woods I need to go to the pro electrical supply stores or do mail order to get the 130V bulbs in common sizes.

[J M Fahey]

AFAIK, USA often had 2x110V (nominal) lines in series, with the center tap grounded.
This provides both 110V and 220V in the same house, depending on wall plug wiring. Cool.
At the same time no live wire is ever more than 110V away from ground, which is safe. Cool.
Problem is, it´s still monophasic and not very efficient transformer-distribution wise.
I *think* they are aiming for 220V house wiring (such as used in Europe and most of the World) sometime in the future, with more efficient 3x220V triphasic.
Old 220V equipment would work perfectly with those 220V, phase-to-phase, would still have both wires floating (as now) and no phase would be more than 127V away from ground; sort of having your cake and eating it.
Problem is those 127V at household taps would burn 110V lamps quickly , and make a lot of 110V equipment suffer.
So I *guess* they have been raising "old system" voltages steadily, 110>113>115>117>120V so you end up having equipment which can freely operate with 127V lines (as I said=3x220V triphasic).
Old wiring would still be usable (the Zillions of Dollars invested so far) and *new* wiring would be straight "127"/3x220.
It´s being done now in Brazil, where a lot of old fine tube equipment now has lots of problems.
Lamps and appliances sold there are already 127V (or straight 220V, take your pick).
In Argentina we have the old European standard: 3x380V , with neutral; providing 220V phase to ground, and 3x380V phase-to-phase.
jm2c

[Steve Conner]

Yup. It's not the "old" European standard, it's how it is just now as well.

We use 240/415V, but the European standard has a tolerance wide enough to include that. Some European countries run 3-phase power to every home and use the 400V for larger appliances, but we don't. Some government bureaucrat probably thought it was too dangerous.

Incandescent lamps get more efficient the hotter you run them. The light output goes up faster than the heat output. The problem is that the life goes down faster still.

[Rhodesplyr]

So, is the consensus that the increase over the last sixty years in typical AC mains voltages in the United States is primarily the power companies' response to regulatory stipulations that voltages not fall below a certain point even under extremely heavy demand?

[J M Fahey]

Hi Steve.
I´m lucky enough that since our power system *is* 3x380V triphasic, with the 220V line being a "poor relative" derived from it, I do in fact have 3x380V at my door´s distribution box.
I mean lucky because my "big" magnetiser needs it but if I ordered it "officially" I would have to register my home shop as an Industry, go through a lot of red tape , pay a relatively high fixed price, all for a few minutes use in a month.
Magnetizing a speaker takes seconds.
So at nights or on Sundays I dress in black Ninja clothes, paint my face black and go out with a *heavy" 3 phase wire and 3 car battery type clamps .... and as Nike says, "just do it".
Oh well, the delights of trying to keep a small industry alive.

[soundguruman]

This is a big problem when your old Marshall amp is made to run 110 Volts. You almost have to modify it to stop it from over-voltaging, running too hot.

[Steve Conner]

Yup, see RG Keen's "Vintage Voltage Adapter" for details.

[soundguruman]

The ratio of the high voltage winding is 1:4
and so if your plexi says "110 V" on the voltage selector, you are over voltage by 40 volts or more.
This makes the transformers hot as Hades, meltdown eminent.
Pay attention to this problem.

[J M Fahey]

Sorry but I very much doubt that a 10% voltage increase applied to a power transformer primary (120V vs 110V) sends it close to a meltdown just by itself.