Electricity in the U.S

[DoubleD]

Hi HSV
I couldn't help you anymore 'cause I am electricity challenged  :D :D but I want to give you my welcome
If of any interest here in Italy we get 220 volts for the house use and small tools and 380 for bigger tools

[Woodwalker]

Welcome aboard HSV.
I have a question for you, do you "ground" or "earth" your equipment in NZ? (I was told by my old professor the term "earth" was used outside the US)
On the subject of varying voltage or voltage ranges, North American standards are set by the American National Standards Institute. Standards vary from state to state and utility to utility. The national standard in the U.S.A. is ANSI C84.1. Voltage regulation requirements are defined in two categories:
"Range A is for normal conditions and the required regulation is +/- 5% on a 120-volt base at the service entrance (for services above 600 volts, the required regulation are -2.5% to +5%).
Range B is for short duration or unusual conditions. The allowable range for these conditions is -8.3% to +5.8%. A specific definition of these conditions is not provided. "

In short, under normal conditions (range A) the average home can have a voltage range from a low of 114 to a high of 126.  Range B voltage could be from numerous reasons, usually result from faults. A limb bridging a primary phase will cause a "sag" in the voltage and may not trip a protective device before it clears. Lighting will create transient voltage "swells".  I happen to have recent first hand knowledge of transient voltage, lost a modem and ethernet card a couple of days ago.

[HSV]

Hi all!
Hey thats great, thank you so much to everyone who replied.  I understand a whole lot more about electricity in general now!  I'm glad i asked you guys.
Sorry I haven't replied in a couple of days, it's duck shooting season here right now, so I had to go take a couple of shots, it was great. I definitely lessened the duck population of NZ by a few.  (sorry to all those who are pest friendly, but ducks defacate in animals troughs and that's bad, oh, and shooting is fun).  Plus I help my boyfriend and his family out on their farms on my days off from Petersons, so it was busy all round.

To answer a couple of specific questions:
Woodwalker:  yep, we earth our equipment here, and we use both terms also, "earth" and "ground.
SCSmith42: yep, i sure will say hi to Rex and Marama for you when i get back to work tomorrow

Thank you all who welcomed me to this forum, very kind of ya.  Looks like it'll be fun  ;)

[HSV]

Uh oh, I have more questions.  Picking the brains of the intelligent masses, it's my favorite pastime.

Okay, throughout the U.S, in each home, do you have a 220-240v alternative socket, either in your shed or kitchen, as standard?  And what is the normal sized circuit breaker that is used?

Thanks everyone!

[Onthesauk]

Not as "Standard."  Here in the NW part of the country most houses are wired with 220 in a laundry room because electric dryers are more common here then gas.  Lived in California for a few years and had no 220 outlets in the house, dryer was gas.

In the house here that I built I put in a 220 outlet for the dryer and 2, 220 outlets in the garage for well pump and storage tank pump.  Added a 220 outlet in the barn as a temp for the well pump, will eventually use it for a welder.

What is Standard varies a bit around the country, based I thing on what has historically been the least expensive source of energy.

[scsmith42]

HSV, probably 70% or greater of US homes have a 30 amp 240VAC socket in the house for an electric dryer.  It usually has a 30 amp breaker, and is located in a small room that we call "the laundry room".   These outlets are a standard NEMA type.

The average home in the US will also have 240VAC circuits for water heaters, stoves, and air conditioners, but typically these are hard wired from the load center to the appliance, so there is not an outlet involved.

A very small portion of the garages at a US house may have either a 30A or 50A 240VAC outlet for a welder.  Maybe 2% - 5% of the general poplulation (or 50% - 90% of Forestry Forum members!).

So to answer your question, NO the typical kitchen or garage (shed) does not have a standard 240VAC outlet.  However, the typical laundry room does.

Hope this helps,

Scott

[HSV]

Hi again,
Those posts were great, Thanks Onthesauk and Scott.  You have been very helpful. 
;D

[WeeksvilleWoodWorx]

I've never seen a kitchen stove hardwired. (free-standing, not built in). ???

[scsmith42]

Good point Weeksville - I was thinking primarily of built-in stoves - seems like most of the new houses have them rather than the free standing units.

[caryr]

Okay, throughout the U.S, in each home, do you have a 220-240v alternative socket, either in your shed or kitchen, as standard?  And what is the normal sized circuit breaker that is used?

Like Scott said I would not say we have a standard plug always available, but 240V at 30A and 50A are fairly common and the components to add either are readily available at any good hardware store. I'm a little curious why you are investigating this. If it's for an electric mill you probably want to use the 50A as a minimum and a dedicated connection is probably better. I have a 100' and 50' 50A, 240/120V extension cords and believe me, you don't want anything much bigger than that!

Don, I have three phase, but it's manufactured locally. It's a fancy setup with regulated output from 0-20HP.

Cary

[HSV]

Hi Cary,
Hey, I would love to share the reason for my investigation, unfortunately I signed a confidentiality agreement when I signed up with Petersons...
but how much will you pay me for this information???  ;)
Don't worry, the time is near and FF members will be some of the first to know.

[caryr]

I understand! I have had to sign a few of those in my lifetime as well. I think I will keep my money and wait like everyone else. If you are thinking about motors, one thing to keep in mind is that to follow the code to the letter you are supposed to use HP rated switches and plugs. Which would rule out anything that is normally available.

Cary

[Beweller]

There is a lot of confusion and some mis-information in the responses.

So far as I know, the DESIGN CENTER voltage for consumer circuits is 117/235 volts.  There is no code/regulation that I know of that REQUIRES the power suppier to provide this voltage.  As has been said here, anlything in the general range of 110 to 125 volts seems to be satisfactory.  If too low, motors overheat or will not start, and flourscent lights do not start.

These voltages are RMS--root-mean-square--voltages, which makes the AC power calculations look the same as DC calculations--Power = volts times amps (assuming a power factor of unity).

The PEAK voltage is the square root of two times the RMS voltage--165/332 volts.  The voltage follows a sine wave from a peak positive voltage through zero to a peak negative voltage and continuously repeats.

The supplied power is a 235 volt single phase circuit with a grounded center tap (neutral).  Thus, two individual 117 volt circuits exist.  The current in a 235 volt circuit behaves exactly as the current in a 117 volt circuit--the current is identical in each wire.  The current in the two wires is NOT additive.  A balanced 235 volt circuit has the same current in each wire and zero current in the neutral.

The National Electric Code (Underwriters code), adopted in most juristrictions, specifies a maximum current for each wire size/insulation system/application, and the circuit most be fused or protected with a breaker at that current level.  Residential homes are supplied to the meter panel by the power supplier who specifies the maximum current that can be drawn and thus specifies the main breaker/fuses.  The individual circuits are protected according to the (primarily) wire size.  Typical modern installations are a 200 amp service with individual 117 volt circuits (many) wired with #12 Cu wire and protected at 20 amps.  I have not seen 117 volt circuits with heavier than #10 Cu protected at 30 amps, but I know of nothing prohibiting such circuits.  235 volt circuits are typically 30 amps and up.  60 amps is not uncomon, and I believe that with electric water heaters 80 amp circuits may be used.

Somewhere I heard that the 60 Hertz frequency was selected by Tesla as minimizing the total iron plus copper cost in machinery.  If optimized today, something different would surely be chosen.  I have never heard why the rest of the world uses 50 Hertz.  At least up into the 1950s, you could still find 25 Hertz systems.  I have a 1943 handbook that lists frequencies ranging from 25 to 76 Hertz in various countries.

[scsmith42]

Beweller, interesting post - thanks for sharing and clearing up some misconceptions.

Can you elaborate on this comment:  "The current in a 235 volt circuit behaves exactly as the current in a 117 volt circuit--the current is identical in each wire.  The current in the two wires is NOT additive.  "

If I have a motor that is set up to run off of either 120V or 240V, typically the manufacturers nameplate will list that 240VAC draws one half of the amps as the 120V configuration.  I had always understood that to reference the amps per circuit, not gross amperage across both circuits.

Based upon your comment, are you stating that, for the same motor, at the meter the gross kilowat hours will be less with the 240V configuration versus the 120?

Thanks. 

[caryr]

Somewhere I heard that the 60 Hertz frequency was selected by Tesla as minimizing the total iron plus copper cost in machinery.

Tesla chose 60Hz for his induction motor. At the time 133Hz was common because it was easier to transform. He was unable to get the motor to work at 133Hz. So as the saying goes "The mountain came to Mohammad."

Scott, What I think is being said is that if you are using either voltage you still only have two conductors and while they may carry the same magnitude of current one is out of phase with the other (they sum to zero). The current in a circuit will be whatever it needs to be to drive the load. If you rewire and drive a motor with twice the voltage the current will be half. The easy way to think about this, though not always correct, is that you have two 120V loads. You can connect them in parallel or in series. If you connect them in series you have to supply 240V of drive voltage and enough current to drive one load. If you wire them in parallel you only have to supply 120V, but you have to drive two loads or twice the current.

Cary

[scsmith42]

Thanks CaryR.  The question was poorly phrased on my part, as the current is a factor of total voltage and the reason that a 240VAC motor nameplate has half the amp rating of the same motor in 120 is because it's reflecting the voltage, ie amps x volts.

[caryr]

Thanks CaryR.  The question was poorly phrased on my part, as the current is a factor of total voltage and the reason that a 240VAC motor nameplate has half the amp rating of the same motor in 120 is because it's reflecting the voltage, ie amps x volts.

A slightly more verbose answer is that because the currents are specified at a particular HP, which can be directly converted to Watts, we get to us the P = V * I equation mentioned previously. So if you have a fixed P and you double the V the I goes down by half. It's also why you like to drive motors with a voltage on the high end of the scale.

Cary