When referring to main s voltage in USA, why do some people say 110/220v, or 115/230v, and others 120/240v?
I have always measured the lines in my home at 120/240v. What that different in the past, or in different regions of the U.S.?
- LGLv 71 year agoFavorite Answer
The voltage standard in the U.S. for residential line/mains voltage is 120V +/-6%, and it has been this way since 1984.
Supposedly, in the days of Edison, power stations supplied 110V in hopes that it would be at least 100V by the time it got to a residence. And then in the 30's the standard went to 115V at the residence. But I think the "110" nomenclature never got completely lost and is why some people still say "the 110". And there are probably some older systems still in use that are at 115 nominal. But for new installations, it's always 120V.
The voltage is regulated at the power station level, the substation level, and the distribution level via taps in transformers that can be changed depending on the load.
Many appliances say "115V" on the back. And I can only guess this is to be able to tolerate that +/-6% in voltage variation.
- Homer BufflekillLv 41 year ago
For the same reason some people refer to a breaker box as a "fuse" box...old technology.
- M.Lv 71 year ago
The power in USA used to be different long ago.
Today, people are repeating terms their father and grandfather said.
In the USA, single-phase domestic/residential power is 120/240 volts, 60 Hz.
There is NO 220 volts! Anybody who thinks there is, obviously has never connected a proper AC voltmeter to the power line (called "mains" in the UK) and looked.
During my lifetime (65 years), I have seen equipment with 110, 113, 115, 117 and 120 volts written on it. I have been doing electrical things since single-digit age.
I did some searching and found this:
- Mr. Un-couthLv 71 year ago
The 110, 115 or 120 Volts is the hoped for Voltage present on the single phase Voltage supplied to a standard user. A (1:2)V steped up center tapped secondary transformer is installed at each user location which has an end to end secondary Voltage of 220, 230, or 240 Volts. Each of the two ends to center taps are 110,115, or 120 Volts but the two are 180 degrees out of phase with each other. Thus the user has available two, (either 110 or 115 or 120) Volt (magnitude determined by power company) lines that are 180 degrees apart from each other (two phase) plus the end to end Voltage of the center tapped transformer which is either 220, 230, or 240 Volts.
How people got started referring to it as 110/220V, 115/130V or 120/240V I don't know. I guess they measured the single phase input line Voltage in their area and was aware that the end to end secondary Voltage of (1:2)V step up transformer was also available to them. They must have started calling it which ever was closest to the input line Voltage that they had measured.
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- PhilomelLv 71 year ago
The voltage to the home is set by the Power station and has a voltage drop depending on how far away from the station you live. There is a range of ~+ - 8% so your 115v could be 105.8 to 124.2 V. People round off to:110 or 115 or 120. Two phase power is just twice as much.
- 異域秦後人Lv 71 year ago
USA USES BOTH VOLTAGE IN ALL HOUSES, 120V FOR WALL POWER OUTLETS AND 240V FOR STOVE AND DRYER.
- MartyLv 61 year ago
110V or 115V or 120V is single phase voltage
220V or 230V or 240V is three phase voltage
- 1 year ago
The regular mains voltage in the USA is 115v. There are applications that use 230v, but that needs a special connection and outlet. The mains voltage in Europe is 230v. The voltage is nominal and fluctuates depending on how well the generating grid can meet demand.
Some electrical devices are more broad-minded than others. Switched-mode power supplies can usually work on any voltage between 100v & 250v and they are labelled 100-250v (note the dash). Some electrical devices are switchable between voltages and they are labelled 115v/230v (note the slash) 110v, 220v, 120v & 240v are older standards although 110v & 120v appliances can be used safely in a 115v outlet and 220v and 240v appliances can be used in a 230v outlet.