What is the correct voltage designation?

[HenryAZ]

115/230
120/240
125/250

I had always thought (and used) 120/240 when I talk about household power, but I see all three designations being used in threads, on charts, etc. Which one does the NEC use? Are there really 3 different cases?

My house typically reads 122-124 and 242-245.

 

[Norcal]

115/230
120/240
125/250

I had always thought (and used) 120/240 when I talk about household power, but I see all three designations being used in threads, on charts, etc. Which one does the NEC use? Are there really 3 different cases?

My house typically reads 122-124 and 242-245.

115/230V is the rated voltages used for motors & welding equipment.

120/240V are the nominal supply voltages.

125V & 250V is rating of receptacles,wiring devices & fuses.

 

[Terry D]

To my understanding, and I could be wrong. The first power systems in the US was 110/220 volt, early 1900's. Due to increasing power demands, somewhere in the early 1930's they increased it to 115/230 volt for voltage drops. Then again somewhere in late 70's or early 80's they once again increased it again to 120/240 volt. With todays equipment, they can regulate that voltage within a few percent +/-.

As Norcal said. 125/250 was never a generated voltage in the US. It is how wiring devices and fuses are rated

 

[13mo]

115/230
120/240
125/250

I had always thought (and used) 120/240 when I talk about household power, but I see all three designations being used in threads, on charts, etc. Which one does the NEC use? Are there really 3 different cases?

My house typically reads 122-124 and 242-245.

The NEC discusses the supply voltages, which for nearly all residential is 120/240 volts. The actual voltage you see will be within 5% of this, often on the higher side.

Standard supply voltages as discussed by the NEC are 120, 240, and the three phase derived voltages of 120/208, 277/480, and 347/600.

The 115/230 is utilization voltage, and generally seen on motors. Other appliances may use the 115/230 volt ratings or may use the 120/240 supply voltage ratings. The voltage you actually see at the appliance should be within 10% of the rating.

125 and 250 volts are the voltage ratings for receptacles and switches for 120 and 240 volts. All of the other voltages use the supply voltage for switch and receptacle ratings (240, 277, 347, 480, 600.)

 

[HenryAZ]

Thanks for the explanations.

 

[dogdog]

It's always 110/220 for me.

 

[Norcal]

It's always 110/220 for me.

Only place still using 110V is the UK, 110V tools are required on building sites, each leg is 55V, stepped down from the normal 230V.


Knowing what voltage you are working with is very important, using the wrong one in calculations throw things off.

 

[wyliesdiesels]

It's always 110/220 for me.

where do you live? those are non-US voltages

 

[13mo]

where do you live? those are non-US voltages

I bet that person lives in the US.

Many people use the older, lower voltages rather than the current, slightly higher voltages as until the 1960s and 1970s, equipment was generally labeled using the older 110, 220, 440, and 550 voltages. If somebody grew up working on equipment marked as 110 and 220 volts, they often will refer to 120 volts as "110" and 240 volts as "220." If they trained somebody, that person often does so too.

The time when this becomes real nonsense is when somebody deals with wye three-phase as this came about later and those voltages are all based on the current, higher supply voltages. It's funny to see the same guy talk about line to line on a 277/480Y service being "440" but line to neutral is always referred to as "277."

 

[Norcal]

I bet that person lives in the US.

Many people use the older, lower voltages rather than the current, slightly higher voltages as until the 1960s and 1970s, equipment was generally labeled using the older 110, 220, 440, and 550 voltages. If somebody grew up working on equipment marked as 110 and 220 volts, they often will refer to 120 volts as "110" and 240 volts as "220." If they trained somebody, that person often does so too.

The time when this becomes real nonsense is when somebody deals with wye three-phase as this came about later and those voltages are all based on the current, higher supply voltages. It's funny to see the same guy talk about line to line on a 277/480Y service being "440" but line to neutral is always referred to as "277."

You forgot 110/208.

 

[dogdog]

I bet that person lives in the US.

Many people use the older, lower voltages rather than the current, slightly higher voltages as until the 1960s and 1970s, equipment was generally labeled using the older 110, 220, 440, and 550 voltages. If somebody grew up working on equipment marked as 110 and 220 volts, they often will refer to 120 volts as "110" and 240 volts as "220." If they trained somebody, that person often does so too.

The time when this becomes real nonsense is when somebody deals with wye three-phase as this came about later and those voltages are all based on the current, higher supply voltages. It's funny to see the same guy talk about line to line on a 277/480Y service being "440" but line to neutral is always referred to as "277."

You bet right... for me. it really doesn't matter what you are referring to when you are talking single phase to a non-electrician/ or EE. 110/220 120/240/ 115/230... Not doing any power management or needed RMS or Sqrt(2) or any sqrt(3) or doing any phase calculations. So us "ordinary" folks referring to a 110V or 120V or 115V is just as good as long as you are in North America that runs 60Hz...


Geeze you guys remind me of the Hot Water Heater folks.

 

[Showkey]

It’s been a while since we beat this one up..............use to be a regular occurrence.


It’s combination of vernacular vs nomenclature, just look a box label specifications all three versions are still used today with 110/220 fading away and 115/230 holding strong.

 

[wyliesdiesels]

You bet right... for me. it really doesn't matter what you are referring to when you are talking single phase to a non-electrician/ or EE. 110/220 120/240/ 115/230... Not doing any power management or needed RMS or Sqrt(2) or any sqrt(3) or doing any phase calculations. So us "ordinary" folks referring to a 110V or 120V or 115V is just as good as long as you are in North America that runs 60Hz...


Geeze you guys remind me of the Hot Water Heater folks.

lmao

 

[dogdog]

lmao

LOL She got prettier every beer consumed...

 

[charbar]

Geeze you guys remind me of the Hot Water Heater folks.

I genuinely laughed out loud at this


I'm the same way...pretty sure I say 110 and 220. Sometimes 240. Everyone knows what you're talking about when you say it anyway.

 

[jeffmoss26]

220, 221...whatever it takes!

 

[nadogail]

Sometimes old habits die slowly. We accept that many people refer to all facial tissue as Kleenex even though the product they are referring to might have a different manufacturer.

How many use Xerox as a verb?

 

[Crazyjake8493]

I bet that person lives in the US.

Many people use the older, lower voltages rather than the current, slightly higher voltages as until the 1960s and 1970s, equipment was generally labeled using the older 110, 220, 440, and 550 voltages. If somebody grew up working on equipment marked as 110 and 220 volts, they often will refer to 120 volts as "110" and 240 volts as "220." If they trained somebody, that person often does so too.

I hear it a lot, though this is not a recent change.

I believe the US has used nominally 120/240V for residential service since the 1960's, and 115/230 since the 1930's. Unless there's a 100yr old electrician out there still getting it done, there's really no excuse to be saying 110/220.

 

[American Locomotive]

1890s-1920s : 110/220
1920s-1950s: 115/230
1950s - Present: 120/240

Many people's grandfathers (or fathers) grew up with "110/220". Tons of old equipment was rated for 110/220. So 110/220 has stuck with a lot of people for a long time, and probably will not change any time soon.

We all know what you mean when your location is in the U.S. and you say "110/220". There is no ambiguity at all to that statement. But many on here insist on being pedantic to the point of absurdity.

But yes, the technically correct term is "120/240".

 

[gbynum]

You forgot 110/208.

The 208 wye 3 phase will have 120 phase-to-neutral. So while you were being cute, your voltages are incoherent. The voltages differ by sqrt(3), about 1.732

The standard way to refer to this is 208Y/120 even when only 2 "hots" and a neutral are in a single phase panel.

 

[theoldwizard1]

The NEC discusses the supply voltages, which for nearly all residential is 120/240 volts. The actual voltage you see will be within 5% of this, often on the higher side.

Your POCO will probably tell you +/- 10% and even then you will be lucky to get it when a large load starts up !

 

[theoldwizard1]

It's always 110/220 for me.

where do you live? those are non-US voltages

"Old people" speak !

Lots of old "filament" transformers said 117VAC !

 

[alfredeneuman]

Lots of old "filament" transformers said 117VAC !

Lots of new filament transformers say that too.

 

[dogdog]

LOL... man, some people are just very stubborn.

But anyways... the correct voltage designation of for single phase US voltage at home is 120/240Vrms But they do drop rms right from it. Some power Enginemaneer should be able to tell you why. That doesn't mean that is the peak voltage you see on the outlet.

Like I said, for us ordinary folks... 110V is just as good as 115V or 120V, and I would have know what you mean Jelly Bean..

 

[Norcal]

The 208 wye 3 phase will have 120 phase-to-neutral. So while you were being cute, your voltages are incoherent. The voltages differ by sqrt(3), about 1.732

The standard way to refer to this is 208Y/120 even when only 2 "hots" and a neutral are in a single phase panel.

If it's single phase panel 120/208V the Y should not be written as that would mean 3Ø was present in the panel, if it is 3Ø panel then 208Y/120V is correct.

I have seen 110/208 written in a panel, it is not possible to have those voltages which is why I wrote it, it's as ignorant as 110/220.

 

[alfredeneuman]

But many on here insist on being pedantic to the point of absurdity.

Electricity is highly dependent on math. There is no "about" in math. It depends on accuracy in terms.
It's absurd to believe otherwise

 

[13mo]

The 208 wye 3 phase will have 120 phase-to-neutral. So while you were being cute, your voltages are incoherent. The voltages differ by sqrt(3), about 1.732

That was the entire point of my comment, which he jokingly replied to.

 

[Stuart in MN]

There is no "about" in math.

My college math professor used this example when explaining limits in mathematics...say you were sitting at one end of the couch, and your girlfriend was sitting at the other end. You move halfway across the couch towards her, then half of the remaining distance, and so on. Theoretically you would never get all the way across the couch, but you'd end up close enough for all intents and purposes.

 

[American Locomotive]

Electricity is highly dependent on math. There is no "about" in math. It depends on accuracy in terms.
It's absurd to believe otherwise

My calc and physics professors would use "about" or "roughly" all the time. They would use all sorts of approximations and tricks.

 

[alfredeneuman]

Saying 110 instead of 120 is akin to cutting a board that's supposed to 120" to 110", or ordering a hose for a machine that's 10" short.
Is it "close enough" or not?

 

[alfredeneuman]

My calc and physics professors would use "about" or "roughly" all the time. They would use all sorts of approximations and tricks.

I'll bet they didn't consider 8-10% "about or roughly".

 

[Terry D]

I have seen this argued on here so many times. For us that are in the trade or has been in the trade, know what voltages should be and how they they are derived. We deal with it every day. But those who don't, might say 110 or 220. Who knows, maybe that's what their father always called it and it just stuck with them. I just had a customer call and asked me to put a 220 circuit in for a mini split. Do you think I'm going to put a buck/boost transformer in and actually give them 220, no. I know what they mean. I think someone that is in the field should call the voltages correctly. What about buying that 2x4. is it really 2 inches x 4 inches. Some people still call a refrigerator an icebox

 

[Stuart in MN]

That's the thing - no matter which number people use, everyone knows what they mean. It just isn't that big a deal.

 

[dogdog]

some of you people are really EngineMaNees.

 

[13mo]

Your POCO will probably tell you +/- 10% and even then you will be lucky to get it when a large load starts up !

That depends on the POCO and also your situation. If you are the very last person on that distribution line, you have a fairly long run from the transformer to the panel, your service is borderline or too small already, and your POCO scrimps on equipment (a 10 kVA transformer on a 200 A service, for example), your results will stink. If you are the first person tapping off of the main distribution line just after the substation, you have more than enough service for your loads, a short run from the transformer to the panel, and your POCO actually put in a large enough transformer, your results will be very different.

 

[DeeKay]

I grew up hearing my dad say 110/220 which I know isn't right but I still catch myself sometimes. I don't think it's a big deal though since we all know what someone means when they say 110/220.

Speaking of "impossible" voltages

At my last Job I got called in because a few different pieces of packaging and equipment "lost power" at the same time.
One popped it's own breaker, one popped a fuse etc...all on different feeds, weird stuff...seemed like a brown out or something at the time.
I checked voltage on everything, and everything looked good. I closed the breakers, replaced fuses, had them start up the equipment and checked voltage again with everything running, still checked out ok. Went back home and then got called out about 5 hours later, same thing.

This time I called the POCO(Ameren) to see if they had any reports of weird **** happening in the area and they said no. I re-checked everything, reset anything that was tripped and put my logging meter on the lines and waited.
Two hours later, same thing. Checked my trends and saw my voltage was dropping down around 160-170 something volts on 240, put on my bomb suit and checked the main, same thing.

So I called the POCO and said I have only 170 volts coming from them. The ****** on the phone told me that 170 volts is impossible and that I need to hire a "real" electrician who knows how to use a meter.

So after an hour of getting nowhere on the phone with Ameren I went outside to look at their transformer and found a big puddle of oil under it. They came out the next day and looked at it, checked voltage and said it was fine. (likely because it sat overnight and was now a happy 70° instead of borderline puddle of molten copper)

They left, we started up and shut down again a few hours later, same thing. Eventually I was able to get a competent lineman out from Ameren 3 days after this all started, he said he was surprised the transformer didn't explode.