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Comment by chociej | Hacker News Reader

Nobody's pointed it out yet, so I'll mention it:

US voltage is 120 V (240 V phase to phase), not 110 V. And while 115 V is within service tolerances specified by ANSI C84.1 (114 V to 126 V), that's not the nominal value.

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It's a bit of a pet peeve of mine. We've been standardized on 240/120 since 1967, and still many people insist on saying 110 and 220. It hasn't been 110V since well before 1967, either -- it was increasing over time before they locked it at 120.

220, 221, whatever it takes.

Humor is often not well received here.

Reference is to Mr. Mom for anyone unfamiliar.

https://www.youtube.com/watch?v=II4-HnWRQK0

Its been 120VAC in the vast majority of the US since quite some time like the 1940's - 1960's.'

A minority are still 115-120VAC but very few still at 110VAC or even 110VDC.

But 110V line voltage is still too common of a misconception still lingering overseas.

This can be seen in some power transformers which are built overseas with multiple primary windings intended for international use. Often these will step-up or step-down the incoming line voltage to the working level correctly using the 240V primary when 230-240V is actually powering the transformer through that winding. But when used in the USA with the 110V primary, the transformer powers the working circuit with almost 10 percent higher voltage than the engineers thought they were going to get.

Thanks, I'm in canada and I know we're 120, I was wondering if there was some reason the US was different and I'd just never heard about it. Iirc Japan, at least part of it, may actually be 110.

https://electronics.stackexchange.com/questions/614270/why-d...

Japan uses 100V and 50/60 Hz depending on where you are in the country.

It's really annoying as Japan has lots of wonderful vintage secondhand synthesizers for sale, but being domestic market models they often have non-switching power supplies that require 100 V.

Yup! I've got a 120->100V step down transformer for my Minidisc player.

Speaking of Japan and frequency differences, one funny indirect consequence of the power differences is the video game Super Smash Bros Melee having separate NTSC and PAL versions, one at 60Hz and another at 50Hz, and consequently running at 60fps or 50fps (unless you override this at start). For good players, 50fps changed the game a lot, so they'd always use NTSC or override to 60. But PAL Melee also had other gameplay changes.

A lot of games on the Mega Drive / Genesis didn't properly adjust their speed for PAL/NTSC, for example Sonic 1. They'd just run slower/faster according to VDP clock.

All video games and consoles had separate NTSC and PAL versions until relatively recently. PAL, which is 50Hz was/is used in Europe most of the world except a handful of countries including USA and Japan.

Japan standardized on NTSC/60Hz well before the video game era, for both the 50Hz and 60Hz mains power regions. The frequency is decoupled from mains power frequency even though it was historically based on American 60Hz power.

This is partially done to compensate for terrible wiring. Lots of people are fond of using small wires and going long distances leading to a lot of voltage drop. They often send 125v or so from the transformer which is 123-124 at the panel, 120 v or so at the receptacle, and >100v after someone decides to run something on a few hundred feet of #18 extension cord.

Sure, but the nominal value is still 120 V.

It's about looking at supply vs demand. Electrical devices are often labeled by the minimum voltage they require to operate. 110 V is commonly used because the device can operate reliably on a 120 V distribution system.

I learned recently that Japan is often on 100V power so I'd think a lot of international components would support 100-240V.

It's mostly just a misnomer. A 110 V device with a 5% tolerance, for example, would not work on nominal US circuits.

While it's true, the US does supply 120V±5%, appliances and equipment are operable on a much wider range.

For example, my laptop charger is rated for 100-240V, which is not uncommon.

120V-5% is still greater than 110V.

Power supplies are rated for 100V because that's the voltage in Japan. Though the tolerance would probably be useful for running a really long US extension cord.

Technically they function fine as low as 95V for the worst case scenario, if they're well built.

My old computer started burning in some internal cabling about 30 years ago. Turns out our power wasn't 230 V when the power company came and set up a machine to make a graph. Some times of the day it could be much lower and that made my ancient atari converted to a towerbox to burn the cable to the harddrive on booting.

Nothing to do with well built usually, just designed to work in all regions (specifically, Japan, which has 100V power for because of... reasons).

That's a fairly recent development, mainly limited to switchmode power supplies.

Laptops and other electronics are often the same between North America and europe, just with a different plug, thus the wide tolerance. For anything with a motor or coil this probably won't work

The 100V low end is there due to Japan.

100-240V 50-60Hz switching supplies are common "worldwide" or "universal" adapters, definitely not an indication of service voltage standard here.

110V is the Room Mean Squared (RMS) voltage.

https://www.electrical4u.com/rms-or-root-mean-square-value-o...

No, 120V is the nominal RMS voltage; the peak is 120V*sqrt(2)≈170V.

The *root mean square is 120V.

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