# Why do we call 120v "120v"



## HARRY304E (Sep 15, 2010)

kaboler said:


> Why do we call 120v "120v" being phase to ground, and everyone seems to call the higher voltages, like "480" instead of 277 phase to ground, or "600" instead of 347 phase to ground?
> 
> Is it to make it sound impressive? I'm always running into guys talking how they've been hit with 600v, and then they say they were crawling in a ceiling and someone left a lighting bx out... 347. You know?
> 
> ...



480 volts phase to phase,,,277 volts phase to ground.

600 volts phase to phase,,,,347 volts phase to ground

208 volts phase to phase ,,,,,120 volts phase to ground,,,Ect,ect,ect


kaboler,

Get your self a copy of this book and find a new school to go to because the one you are going to now does not cut it...:thumbsup:


http://www.licensedelectrician.com/Store/MG/Amer_Elec_Hbk.htm


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## dronai (Apr 11, 2011)

kaboler said:


> with live stuff. (not too often, don't worry)
> 
> Anyway, I've been working with *Americans* lately, and they're always talking about their stuff as 480, but ours is 347, and yes, a higher voltage.


Where are you from ?


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## erics37 (May 7, 2009)

If I'm running a 480 volt circuit to something it means I'm running two or three legs with 480 volts between them, so I call it a 480 volt single or three-phase circuit.

If I'm running a 277 volt circuit to something it means I'm running one phase and a neutral with 277 volts between them, so I call it a 277 volt circuit.

If I'm running two or three hot legs AND a neutral I call it a 480/277 volt circuit.

If I'm running a 240 volt circuit to something it means I'm running two or three hot legs, so I call it a 240 volt single or three-phase circuit. Same with 208.

If I'm running a 120 volt circuit to something it means I'm running one phase and a neutral with 120 volts between them, so I call it a 120 volt circuit.

If I'm running two or three hot legs AND a neutral I call it a 240/120 or 208/120 volt circuit, depending on the transformer configuration supplying it.


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## HARRY304E (Sep 15, 2010)

dronai said:


> Where are you from ?


Alberta canada..


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## BCSparkyGirl (Aug 20, 2009)

Dude. Did you really ask these questions? Really? *facepalm*


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## TOOL_5150 (Aug 27, 2007)

This thread makes me want to stab out my eyes.


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## Roger (Jul 7, 2007)

kaboler said:


> Why do we call 120v "120v"


Maybe it should be called 170 V 

Roger


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## ce2two (Oct 4, 2008)

dronai said:


> Where are you from ?


 Plant krypton .....ahh, may be fantasy ISLAND :icon_wink: Sponge bob square pants school of hard knocks?


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## drsparky (Nov 13, 2008)

Roger said:


> Maybe it should be called 170 V
> 
> Roger


How about 169.68 V?


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## kaboler (Dec 1, 2010)

HARRY304E said:


> 480 volts phase to phase,,,277 volts phase to ground.
> 
> 600 volts phase to phase,,,,347 volts phase to ground
> 
> ...


Haven't been to school yet, but I know it's root3 x phase to ground = phase to phase (on 3 phase systems). 1.74 or so.

I'm just talking about a 120/208 panel is usually labeled 120, or people talk about it being a 120 panel. And rarely do I see a 277 panel labeled as 277 but almost always 480 and people talk about it being 480.

That's all.


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## chrisfnl (Sep 13, 2010)

Would it be unfair to blow his mind with a 120/69v service?


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## jza (Oct 31, 2009)

kaboler said:


> Why do we call 120v "120v" being phase to ground, and everyone seems to call the higher voltages, like "480" instead of 277 phase to ground, or "600" instead of 347 phase to ground?
> 
> Is it to make it sound impressive? I'm always running into guys talking how they've been hit with 600v, and then they say they were crawling in a ceiling and someone left a lighting bx out... 347. You know?
> 
> ...



480 is not the American equivalent to 347 you dink.




kaboler said:


> Haven't been to school yet, but I know it's root3 x phase to ground = phase to phase (on 3 phase systems). 1.74 or so.
> 
> I'm just talking about a 120/208 panel is usually labeled 120, or people talk about it being a 120 panel. And rarely do I see a 277 panel labeled as 277 but almost always 480 and people talk about it being 480.
> 
> That's all.


I don't know what you're talking about but I see as many 347/600v panels as I see 120/208 panels.


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## 480sparky (Sep 20, 2007)

If I'm working with 120v, I call it "120 volts" because that's the reading I would get if I put a meter between the two conductors.

If I'm working with 240v, I call it "240 volts" because that's the reading I would get if I put a meter between the two conductors.

If I'm working with 208v, I call it "208 volts" because that's the reading I would get if I put a meter between two conductors.

If I'm working with 277v, I call it "277 volts" because that's the reading I would get if I put a meter between the two conductors.

If I'm working with 480v, I call it "480 volts" because that's the reading I would get if I put a meter between two conductors.


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## jza (Oct 31, 2009)

Kaboler you should be more modest as you have _much_ to be modest about.

Nobody on ET cares to hear about how you outsmarted your journeyman or caught something he missed. You're on par with every other first year apprentice who enjoys his job. Get over yourself.


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## Roger (Jul 7, 2007)

drsparky said:


> How about 169.68 V?


Picky, picky, picky.


Roger


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## micromind (Aug 11, 2007)

chrisfnl said:


> Would it be unfair to blow his mind with a 120/69v service?


Odd as it may sound, that voltage actually does exist. I see it all the time as potential for relays protecting high voltage (over 35KV) systems.


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## user4818 (Jan 15, 2009)

TOOL_5150 said:


> This thread makes me want to stab out my eyes.



...with a dull knife.


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## chrisfnl (Sep 13, 2010)

micromind said:


> Odd as it may sound, that voltage actually does exist. I see it all the time as potential for relays protecting high voltage (over 35KV) systems.


Common in marine applications too, no neutral conductors. 

120v distribution panels are 120v/69v (Or at least on the ships I've worked on).


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## Mike in Canada (Jun 27, 2010)

kaboler said:


> Haven't been to school yet, but I know it's root3 x phase to ground = phase to phase (on 3 phase systems). 1.74 or so.


 The 1.7 factor is usually for amperage, not voltage. If you had a single-phase 240V feed supplying 170A with two conductors then a three phase feed of 240V would only need 100A per conductor to supply the same amount of power (i.e. watts). Using the 1.7 factor for voltage just confuses the issue. The only reason it works is because it happens to be the tangent of 60 degrees, and that's how many degrees exist between the three phase leg and a center-tap. Three phases have 120 degrees between each, and the center cuts that in half. Confused yet? Leave the 1.7 factor for amperage and just take in on faith that 480 goes with 277 and 600 goes with 347.



> I'm just talking about a 120/208 panel is usually labeled 120, or people talk about it being a 120 panel. And rarely do I see a 277 panel labeled as 277 but almost always 480 and people talk about it being 480.
> 
> That's all.


 In Canada we use 600V. Phase to phase it's 600V. If you take the phase-to-ground voltage of 600V then you get 347V. This voltage is used for industrial and commercial lighting, and precious little else. It uses a shared neutral, and no doubt kills and maims more Canadian electricians than any other voltage.
If you have 480V phase to phase and you take the phase-to-ground voltage then you get 277V, and it is used for exactly the same purposes as our 347V.
Anyone who says that they have 480V and we only have 347V is not comparing apples to apples. I don't actually know why we use the higher voltage, but I'm glad we do because 600V allows for a LOT of simple rules of thumb that makes the world an easier place to be an electrician in.

The question I thought you were asking at first was why sometimes it's called 110V and sometimes it's 120V. Similarly you find references to 230V and 240V. That's a much more interesting question, to me.


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## BBQ (Nov 16, 2010)

kaboler said:


> Why do we call 120v "120v"


Why do we call 'red' red? 

Why don't we call 'red' erst?


And how do we know that what I see as red looks the same to you?

Maybe when I look at something red the picture in my mind would look green to you but you have learned to call that color red?

While we are at it, how come sometimes when I sneeze I close my eyes but I see a bright light?


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## 480sparky (Sep 20, 2007)

How do I know all of you even exist?



BBQ said:


> .................While we are at it, how come sometimes when I sneeze I close my eyes but I see a bright light?


Click here. :laughing:


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## BBQ (Nov 16, 2010)

480sparky said:


> How do I know all of you even exist?


We don't, you are not even reading this. 





> Click here. :laughing:


I am sure I don't have to, I read the Straight Dope all the time.:thumbsup:


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## Mike in Canada (Jun 27, 2010)

480sparky said:


> How do I know all of you even exist?
> 
> 
> 
> Click here. :laughing:


 You don't. Descartes already did that thinking for us.


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## 480sparky (Sep 20, 2007)

Mike in Canada said:


> ........ Descartes already did that thinking for us.


Incorrect. It is all the Machines.


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## kaboler (Dec 1, 2010)

Mike in Canada said:


> The question I thought you were asking at first was why sometimes it's called 110V and sometimes it's 120V. Similarly you find references to 230V and 240V. That's a much more interesting question, to me.


From what I've heard, it's because back in the old days, we couldn't step up our voltages that high, so voltage drop was more of an issue, and most people thought 100 volts was the max we could get at the service end.

Dunno if that's true.


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## jza (Oct 31, 2009)

Mike in Canada said:


> Similarly you find references to 230V and 240V. That's a much more interesting question, to me.


Seriously. It's weird that from 208v to 250v, everyone is always talking about the same stuff. It always comes down to two or more 120v phases/lines.


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## 480sparky (Sep 20, 2007)

jza said:


> ......... It's weird that from 208v to 250v, everyone is always talking about the same stuff...........


Not down here. 208v is from a three-phase system, 230/240/250 is from single-phase.


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## macmikeman (Jan 23, 2007)

I knew there was a reason I wasn't going to want to read this thread until now, and even now there is no reason to have read any of it.


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## jza (Oct 31, 2009)

480sparky said:


> Not down here. 208v is from a three-phase system, 230/240/250 is from single-phase.


Same here. What I was saying is that regardless of it being 208, 220 or 240, they're all tossed around very freely here. 208 mistakenly being called 240, etc..


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## McClary’s Electrical (Feb 21, 2009)

kaboler said:


> Why do we call 120v "120v"


 

Be careful including yourself in this list you call "we". I don't think you're there yet.


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## oldtimer (Jun 10, 2010)

kaboler said:


> From what I've heard, (it's because back in the old days, we couldn't step up our voltages that high,) so voltage drop was more of an issue, and most people thought 100 volts was the max we could get at the service end.
> 
> Dunno if that's true.


 Where do you hear this stuff?????


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## Roger (Jul 7, 2007)

kaboler said:


> From what I've heard, it's because back in the old days, we couldn't step up our voltages that high, so voltage drop was more of an issue, and most people thought 100 volts was the max we could get at the service end.
> 
> Dunno if that's true.


It is true and although there will be those who will dispute this they don't understand delta/ex/wye/zee side grounded services and probably think corner grounded deltas have a high leg.

JK

Roger


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## Shockdoc (Mar 4, 2010)

I call 117 volts 120. I call 121 volts 120.


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## MF Dagger (Dec 24, 2007)

I've heard that the USA is 120 volts because that's what worked with the incandescent light bulbs of the time period and after we were entrenched in 120 filaments started being found that could burn longer than before at 240 so the rest of the world went with 240.


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## Big John (May 23, 2010)

oldtimer said:


> Where do you hear this stuff?


 In fairness to _Kaboler _when I was looking around online for an explanation and I kept seeing this one: We increased from 100V, to 110V, to 120V because of voltage drop caused by ever-bigger loads.

The vast majority of homes seem to operate pretty close to their nominal 120V, so saying that we increased to 120V because of voltage drop is goofy: Where's the voltage drop? 

I do know a lot of very old equipment is labeled 110 and 220. Don't know why.

-John


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## 480sparky (Sep 20, 2007)

Big John said:


> .............
> 
> I do know a lot of very old equipment is labeled 110 and 220. Don't know why.
> 
> -John



Because it was designed to operate on either voltage. In that case, it becomes a design issue.


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## Big John (May 23, 2010)

480sparky said:


> Because it was designed to operate on either voltage. In that case, it becomes a design issue.


I meant why is the old stuff labeled "110" instead of "120." It almost looks like single phase low voltage may really have been 110 nominal at some point, but why'd it change?

-John


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## 480sparky (Sep 20, 2007)

Big John said:


> I meant why is the old stuff labeled "110" instead of "120." It almost looks like single phase low voltage may really have been 110 nominal at some point, but why'd it change?
> 
> -John



Because that was the nominal voltage years ago. It's been raised from 110 to 115 to 120 over the years.


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## Phil DeBlanc (May 29, 2010)

Because we don't call it 110 volt like we did back in the old days when I started.
AND
On this side of the order we DON'T call it HYDRO!


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## Mike in Canada (Jun 27, 2010)

Perhaps there is something to the voltage drop argument, but caused by large motors like air conditioners. Maybe the voltage drop was causing transistor radios to cycle off and on or something.

Or perhaps we in North America just adapted to bring us closer to the standard used in the rest of the world to allow easier importing of foreign electronics etc.?


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## BBQ (Nov 16, 2010)

I think it is worth remembering there are number of different voltage ratings and we have to be clear which one we are talking about. 





Nominal Voltage

Service Voltage

Utilization Voltage

Nameplate voltage

I am sure there are others that I have left out.


Notice a motor labeled 230 is intended for a 240 nominal supply.


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## retiredsparktech (Mar 8, 2011)

480sparky said:


> Because that was the nominal voltage years ago. It's been raised from 110 to 115 to 120 over the years.


 I always thought it was strange that fluorescent fixtures were rated at 118V. years ago.


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## CheapCharlie (Feb 4, 2011)

Kaboler better grab a bucket to catch those voltage drops. Everything I read from this guy is garbage. Sounds like a 18 year old kid right out of high school that has never had a "real" job. Grow up son.


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## mdfriday (May 14, 2007)

480sparky said:


> Not down here. 208v is from a three-phase system, 230/240/250 is from single-phase.


Unless it is a 240V 3 phase delta...


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## teslacontracting (May 22, 2010)

The difference in reference lies in that 120V is the only American voltage measurement that electricians reference to ground, at least from daily use in my world, Everything else IE 277, 480 etc...etc... is measured from phase to phase in everyday talk and besides, who really wants to say 347V? Not cool.


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## Electric_Light (Apr 6, 2010)

Why do we call the voltage in our car 12v instead of 14v, but the new proposed system automotive electrical system 42v (14v x 3) instead of 36v?

http://www.popularmechanics.com/cars/news/4226979


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## Electric_Light (Apr 6, 2010)

MF Dagger said:


> I've heard that the USA is 120 volts because that's what worked with the incandescent light bulbs of the time period and after we were entrenched in 120 filaments started being found that could burn longer than before at 240 so the rest of the world went with 240.


Even today, 240v incandescent lamps of low wattage (<500W or so) are less efficient. 14v one is more efficient than 120v one. (car head lamp is about 25 lumen per watt, 100W 120v is 16lm/W, British 100W is even less) 

In the US, 120v is the "main" voltage, so I think 208 was the consequential phase-to-phase voltage.

Some places have 127v power, but I believe that's just a result of designing around 220v phase to phase (Mexico, Monaco etc are 220Y/127v)


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## robnj772 (Jan 15, 2008)

kaboler said:


> Why do we call 120v "120v" being phase to ground, and everyone seems to call the higher voltages, like "480" instead of 277 phase to ground, or "600" instead of 347 phase to ground?
> 
> Is it to make it sound impressive? I'm always running into guys talking how they've been hit with 600v, and then they say they were crawling in a ceiling and someone left a lighting bx out... 347. You know?
> 
> ...


 
The same reason we call a troll a troll


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## lefleuron (May 22, 2010)

Big John said:


> In fairness to _Kaboler _when I was looking around online for an explanation and I kept seeing this one: We increased from 100V, to 110V, to 120V because of voltage drop caused by ever-bigger loads.
> 
> The vast majority of homes seem to operate pretty close to their nominal 120V, so saying that we increased to 120V because of voltage drop is goofy: Where's the voltage drop?
> 
> ...


 John,

Your last sentence is what I am explaining. I worked in a plant with all these weird voltages marked everywhere- the cabinet, the prints, the notes, everywhere. Like 455 volts, 105 volts, 215 volts, 60 VDC.

Story was that ONE guy went around with an old analog meter, and whatever that meter read on that day was what went into the prints. This never dawned on me because everything was a straight forward number- not 107 volts, or 458 volts. That I would have caught onto, but 105 volts kind of threw me.:laughing:


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## RePhase277 (Feb 5, 2008)

I think the OP's question revolves around how we actually SAY the voltage. For example, most people I work with say "One-hundred twenty volts", but after that, they say "two oh eight", or "two forty", or four eighty".

In other words, they say the whole number with the unit of measurement (volts), but just use short hand for all other voltages.


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