Do Different Voltages Mean the Same Thing?

Just as with the plethora of different materials in the electrical industry, have you ever wondered why we have so many voltages that can mean the same thing? It can be confusing at best! In the latest episode of Electrician U, Dustin answers this question to bring some clarity to the subject.

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Early on in its life in the US, electricity was run to our streetlights somewhere around 100v. As time went on, this was increased to about 110v to increase the amount of light. This was the norm until recently (say the last 50 or 60 years +/-), where for the same reasons, it again was increased to 120v and 240v where we now currently reside in the voltage scale. However, when we talk about voltage at any particular point, we are referring to NOMINAL voltage, or in other words- Close to. A small percentage (up or down) will typically be acceptable in most instances. For our standard voltage of 120v, generally anywhere between 114v to 126v is common.
Now, you may notice that on some materials, say a light bulb for example, it will be stamped on it with its wattage along with 130v. This means that the lamp is RATED for voltages as high as 130v to handle the fluctuation of voltage throughout the day. Also, notice how on some devices like receptacles, it is labeled as 125v 20a or 125/250v 30a. All this means is that the device in question is rated for that many amps of current at the voltage range listed (usually a bit higher on the scale than normal). Remember from previous episodes, voltage and amperage are proportional to one another. Raise one and the other will also go up. So, if we were to raise the voltage above 120v, the amperage associated with it would also go up. So, they rate the devices at the amperage you are wanting to use at the higher end of the voltage available to have a bit of a safety buffer in there. If that were not to be the case, if your voltage went up, then your device rating (amperage wise) could potentially be exceeded, and a fire hazard could be present.
Another item to look for is dual voltage ratings on a device. Most of our dryer and range receptacles, for example, are rated either 30a or 50a at 125/250v. This simply means that the device is rated to carry the amperage it is stamped with at either 125v or 250v. It is manufactured to work at either voltage, but the equipment you are plugging into it may not be, so make sure to check the equipment requirements/ratings!
Motors on the other hand tend to be on the inverse of this scale. You typically see 230/460 which is on the lower end of the standard voltage scale of 240v or 480v. Knowing that voltages vary depending on load, the manufacturers rate their motors on the low scale to let us know that this is the lowest amount of voltage that should be applied to their motor so it can operate without damage. In any given facility, the more you have operating at once, the lower the voltage typically is overall, so the equipment manufacturers see LOWER voltages as more common than high. Now, damage can also happen by applying to HIGH of a voltage, but the manufacturers deem it more advantageous to label it with the low end of the voltage spectrum than the upper end. Again, check the equipment requirements/ratings before applying voltage to it!
We hope you learned something by watching the video. Continue to look frequently at the site as new videos and content are being added all the time!
#electrician #electrical #electricity
2:00 - Example 1
2:57 - Utility voltage
4:12 - Plug Examples

[thomasmaughan]

"Do Different Voltages Mean the Same Thing?"
No.

[drewgemus]

I shadowed an (older) electrician for a few days when I was much younger and just learning and we went to an outlet that was supposedly having problems. Put his meter on it and the meter read exactly 121.5 and he said "Well, we're getting 110 no problem." Confused the shit out of me at the time.

[leotexas]

I didn't realize how sensitive the grid was until I learned of Voltage Regulators in my apprenticeship; which makes sense as to why receptacles and loads are rated for minimal/maximum ranges, as you have depicted in your video. Thanks for the lessons!

[dtvjho]

5:20 I remember hearing of "negative resistance", where things like switching power supplies inside TVs and computers that will respond to a small drop in utility voltage by pulling a bit more current, trying to maintain a certain wattage draw. From the description you made about motors, it sounds a bit the same - lower the voltage a little and current goes up. That of course becomes the worry for an outlet getting hot if the Amp draw rises too far.

[jaym]

I'm a utility lineman. My company holds to a standard of delivering nominal voltage +/- 5%. So 120/240 could be anywhere from 114-126/228-252. The low end of that range is obviously more common than the upper.
I've seen transformers in service from as far back as the 1930s. I've never yet seen a plate rating anything less than 120/240 for a single phase transformer.

[afnDavid]

Used to repair old TV sets and old consumer electronics. Many old TV sets from the 50's had a selector switch on the back. 95v to 105v in one position and 105v to 115v in the other position. Run the set in the wrong setting and you had more risk of the picture tube producing X-rays because the 2nd anode voltage is too high. Also many of the components were already operating at close to their maximum peak ratings.

[kccvh]

4:42 With resistive loads, the current does rise in proportion to voltage. However, with the high-frequency commutating power supply used in so many appliances today, the output voltage is regulated, so the current demand from the mains decreases with increasing voltage. With electric motors, of the traditional types, it is even more interesting as the current may decrease with increasing voltage, though the relationship is non-linear, due to the change of phase angle between current and voltage (power factor).

[nathanmielke]

230/460 really needs to be understood as 3 phase motors and industrial equipment. Single phase vs 3 phase is big deal.

[algorithminc.]

Kind of going back in time ... some tube circuits, as in 1930's radios, maybe 40's TV's ... were designed to run on the 110v available back in those days (before my time, though fun to fix). Most work fine at 120v, but the higher-than-rated voltage can shorten the lives of some tubes, and can shorten the life of intermediate-frequency (IF) transformers (in some cases). This is way out of range for the topics on your channel ... but I figure electrical engineers, radio hobbyists, electricians, technicians, tinkerers, etc. should share info, instead of attempting to one-up each other - electronics is awesome fun from all points of view - lineman to supercomputers. You've got a great channel ... lots of solid practical info ... cheers ...

[dennisjoiner]

Very interesting! I'm 62 and have always wondered why we call a circuit by the values we do.

[RexMoore]

Voltage (E) and current (I) are inversely related. With a given load (P) if voltage goes down, amps go up to deliver a set wattage. Perhaps I misunderstood your explanation when you stated that volts go down, current goes down. This is why many utility transmission lines are 525 Kv. It’s to keep current as low as possible to reduce I2R losses.

[jlyn]

I want to thank all of you guys for your explanations on my problem. All I know is that when the power company come and checked at the meter, he pulled the meter and checked the houses below me, he called for a new transformer right away . I saw his meter and it was reading 168 volts and he said that was to much coming to my house . Thank you guys !

[mattheefisher]

A very good explanation from a retired Industrial Electrician. Good job.

[kaysonntag]

Similar to what we have here. Here in Germany, the mains voltage was increased from 220V/380V to 230V/400V to create a European standard. The older people here also still often talk about 220V/380V.
In reality, the voltage varies depending on the time of day (and place) so between 225V and 245V. The distance to the transformer also plays a role here. Here it is common that a single transformer supplies entire settlements, sometimes even whole villages.
Pole transformers are usually only found in very rural areas.

[billmoran]

The exception being 120/240 vs 120/208. The former is single phase residential supply voltage you might find on a suburban or rural road serving houses.
120/208 Is derived from three phase 4-wire Wye connected service where the voltage between each energized leg and neutral is 120V and the voltage between any two energized conductors is 208V. This is found in commercial buildings like office buildings condominium towers and industrial buildings where the electric service is three phase.
Incidentally, with only a very few exceptions, there is no such thing as 220V in the US anymore. However in a very few very old locations 115/230 V two phase service still exists although it’s not offered to new customers.

[nealtrevor]

Do you mean to say voltage and current are inversely proportional?

From my understanding for the same power (watts) delivered, if voltage goes up, current goes down. Conversely if voltage goes down, then current goes up. You tend to have problems is if the receptacle rated for 20a or 15 or whatever is pulling too much current due to an out of range voltage (lower than -5 to -10%). That low voltage means that a higher amount of current is needed to give the same power to the device that’s plugged in. P=I*V helps to show this a bit.

2400W at 120v is 20a
2400w at 120-(12(10% less))=22.22a

That low voltage has now subjected your receptacle to more than 20A and exceeds its rating. Thankful for all your explanations, Dustin!

[DapperChe]

I feel like I’m going to school all over again with these videos, i love them! Thanks!

[borntwice]

I’m in the plumbing industry and I found this to be very educational, thanks brother.

[nolongeramused]

Way back when I was building my own radios for kicks the standard for house voltage was listed in textbooks as 115V +/- 5V. Everything I ever designed could easily handle the entire expected range.

[lprice]

This question has been bouncing around in the back of my head forever. Thank you.