make sure I'm not a 220v idiot

[mhm993]

I have to admit that 220v electric eludes me intellectually. Two hots and no neutral? WTF. Well, never mind. Having said that....

Electrician roughed in a 20a 110v dedicated line for compressor. I should have spec'ed 20a 220. Just want to confirm I'm doing this right:

Shut power to sub-panel. Remove black wire from breaker, and white from neutral bar. Pop 2 pole breaker into available space. Old single pole breaker stays as a spare. Connect black to breaker. White to breaker, marked with red tape. Green stays on ground bar. At 220v 20a receptical, black and white (red tape) go to screws for line. Doesn't matter which is which. Green goes to ground. Close up and power up.

Am I good to go? Thanks.

 

[TRDon]

Right on man Sounds good to go

 

[Tech Guy]

Is the cable rated for 20 amp ? (just asking). 2 pole breaker must be mechanically connected so both turn off at the same time. Other than that sounds right.

 

[Rigmaster]

Is the cable rated for 20 amp ? (just asking). 2 pole breaker must be mechanically connected so both turn off at the same time. Other than that sounds right.

+1

This is the only real question, it sounds like you've got a handle on the hookup part. I'm ASSuming that since the electrician wired it for 110v 20a service he used the proper wire.......but you need to confirm.


Rig

 

[porschedude996TT]

To help you clear up your thinking 220v on two lines and no neutral, may I offer the following.

You are stuck trying to think in a "Direct Current" frame of mind. This is "Alternating Current" meaning that the voltage potential when referenced from line to line is shifting or alternating from + to - very quickly. It happens so quickly that the eye cannot see the flicker. It would be like swapping a battery back and forth very quickly. The devices that the energy powers is sometimes unique, like a motor. Light Bulbs really don't care if they run on AC or DC since it is only a resistive filament that is heated to produce light. But a motor is a different story. They are designed to alternate and use the energy in a alternating magnetic field. You can’t run a DC motor with AC and you can’t run an AC motor with DC.

This all goes back to Mr. Thomas Edison and Mr. George Westinghouse, see excerpt below:

In 1887 direct current (DC) was king. At that time there were 121 Edison power stations scattered across the United States delivering DC electricity to its customers. But DC had a great limitation -- namely, that power plants could only send DC electricity about a mile before the electricity began to lose power. So when George Westinghouse introduced his system based on high-voltage alternating current (AC), which could carry electricity hundreds of miles with little loss of power, people naturally took notice. A "battle of the currents" ensued. In the end, Westinghouse's AC prevailed.

Think of it as having two electrical services to your house. Each has a voltage of 110 when measured to neutral and a voltage of 220 when measured to each other. So the difference between the 110 and a 220 volt circuit or the supply is the peak of the potential, meaning the difference between “Zero” and the peak voltage in the circuit during the current phase from + to -. Sometimes it is explained to people that are more mechanical in their thinking as “pressure” The voltage is the pressure and the current is the flow.

I hope this helps.

 

[mhm993]

I'm good on both of those concerns: properly cabled, and connected breaker.

Thanks. Out to the garage with my screwdriver, and a quart of compressor oil. 220 compressor gets turned out today!

 

[mhm993]

996: Intellectually, my trouble is more deeply rooted than the difference between ac and dc. I'm not sure if the ac electrons are rushing back and forth from my motor to the power station at a gazillion mph, back and forth 60 times a second, or whether they're sort of just waves, interfering with each other at precisely timed frequency, on and off . Thanks for the details, however. Very well put and easy to understand.

BTW, I have trouble with 110 ac conceptually, too. If the electrons are moving back and forth constantly, then shouldn't the hot and neutral sort of alternate back and forth, with the electrons moving rapidly in both directions, first it's hot and then it's neutral and then it's hot......

.

I, in fact, worked a block away from Mr Edison's first major power station in lower Manhattan for many years. The only thing left is a bronze plate, mentioning something about the commercial failure of distributed DC.

Luckily, I follow directions OK and my conceptual "issues" don't get in the way of successful DIY projects

What region pca are you with?

And thanks to those others who commented.
MHM

 

[ddawg16]

The electrons are traveling at 186,000 miles per second...give or take a few mps.

The voltage is varying at 60 cycles per second...electrons still moving at the same speed.

Don't worry about if it's positive, negative or something in between....look at this way.

Say you are on the ground looking up the Empire state building...
Ground is ground and the top floor is say 220V.

Now go to the middle floor. At half way, it's 110 V down to ground and 110V up to the top. The middle floor is our common. Nothing really changes...it's still 220V from top to bottom....it's just a matter of where you reference it from.

In reality, the two 110V ac lines coming into your house are 180 deg out of phase as referenced to neutral (common). Your house is not 'directly' connected to that power plant....there are a lot of transformers in between....each one steping the voltage down until it gets to your house.

There is no magic to power transmission when looking at AC vs DC. The problem with DC is that there is no way to easily step down the voltage. They learned early on that the higher the voltage, the less the drop in the line and the smaller the wire you could use. With AC, you can use step down transformers....with DC, there is no single simple device.

So...if you look at the AC going to your house at a single moment in time...it's not different than DC....except that a moment later the voltage will be different.

One other thing....that 110/220 Volt # we talk about is RMS (Root Mean Square). In reality, a 220V line will actually peak to about 374 V peak. But for the sake of describing the energy, or how much work that line will do, we use RMS.....which of course only applies to true sine waves (had to put that in for all you ********* electronics guys). A square wave is a whole different animal....and you don't want me to talk about harmonics.

 

[bobs409]

Just don't put your tongue on that center bar inside the breaker box.


Bob

 

[mhm993]

Thank you all for the lesson, and for helping me understand the 'invisible forces" at work.


Ummm, pushing my luck, so if 220 is two 110 lines phased 180 degrees apart, what's three phase 220?

 

[walrus]

Ummm, pushing my luck, so if 220 is two 110 lines phased 180 degrees apart, what's three phase 220?

. 3 phase is 3 legs 120 degrees apart.

 

[Charles (in GA)]

I think it was the 1896 Chicago World's Fair that was the deciding moment for AC vs DC. Mr. Westinghouse won the contract to illuminate the fair site, and of course he chose AC current to do it with. The world was impressed, and AC current won out.

Charles

 

[Mellotron]

Mr. Westinghouse can thank Nikola Tesla BTW. Talk about pure genius.

 

[mhm993]

240v works. My grainger closeout compressor is happy. Thanks all.

Slight question: when wiring the new circuit breaker, the existing wires didn't reach the available circuit breaker location. I used wired nuts and correct 12 gauge wire to extend the leads. Any code issues about wire nuts in a sub panel? I wouldn't think so, but ??

 

[walrus]

Any code issues about wire nuts in a sub panel? I wouldn't think so, but ??

It depends on fill but I'd guess you're fine on that.

 

[timgr]

The electrons are traveling at 186,000 miles per second...give or take a few mps.
...

No, this is wrong. Really wrong. The electron (e-) has a mass, so it moves at real-world speeds. You're thinking of the photon (gamma), which moves at the speed of light in a vacuum, reduced some small amount to the propagation speed in the media like air or water.

The electrons of electricity actually move quite slowly. For a 100W light bulb connected with 16 ga lamp cord, about 1A at 120VAC, the speed of electrons in the circuit is about 3 inches per hour. The net movement (AC!) is much less than 1/10000th of an inch.

Current is the measure of flow of electrons. The propagation of current is instantaneous because the response to the change in potential (voltage!) is instantaneous. This is like having a long tube full of marbles - push another marble in one end, and a marble pops out the other end immediately. The specific marble does not move very quickly, but the effect of adding that marble to the tube does.

Voltage (due to electromagnetic fields) is mediated by the photon, which does propagate at near the speed of light. So the effect of connecting the electricity propagates at very near the speed of light, but the electrons do not move quickly at all.

hth!

 

[MikeB64]

I always thought that the red and black were the 2 hot wires going to the beaker...the white neutral and the green ground.....no?

 

[Fast Orange]

Mike-
Since Romex is only commonly avilable as black/white/ground,it is common practice and required by code to color designate the white wire to red,indicating that it is no longer a neutral,but a hot leg of a 240 volt circuit.
Note to the OP-All is OK,providig that the wiring you changed is a dedicated circuit for that one outlet.If there are any other recepticles or loads on that circuit,they are now also 240 volts. OOOPs-just noticed that it is a dedicated line as per original post-

 

[Tom2]

Lots of useful info on AC vs DC. Being a car guy, I still dont understand AC fully.. DC seems so much more simple. 1 hot - 1 ground. For everything. The end. Its hard to get out of that mindset..
But obviously AC is superior for most everything.

I believe Tesla used to work for Edison.. Edison screwed him, but Tesla had the better system.
Edison would test the "dangers" or alternating current by filiming the killing of animals with it. Claiming it was too dangerous for homes.

I used to look up to Edison as a kid...but that certainly tarnishes the image in my eyes.

 

[Aceman]

Mike-
required by code to color designate the white wire to red,indicating that it is no longer a neutral,but a hot leg of a 240 volt circuit.

My codebook says it can be any color other than white, gray or green.

Black tape or a sharpie is what I use. Seems wasteful to me telling everyone on here they need to buy a roll of red tape just to mark 12" of wire with it, when they can simply use the black tape/sharpie they probably already have on hand. Just my opinion....

 

[Fast Orange]

Aceman-
True-NEC only designates colors not to be used.As per customary practice of professional electricians in my area,the neutral is redesignated red,usually with color coding tape. The same practice is observed when using the white wire for the return in a switch leg.
The use of red tape is based on the traditional color coding used in industrial 3 phase systems.
Black,Red and Blue are traditional colors for 120/208/240 volt circuits
Brown, Orange and Yellow designate 277/480 volt hot legs-old timers used Violet in place of Brown,and gray was a neutral in 277 volt applications.

 

[mhm993]

Used an elegant red marker. Very chic color.

And yes, dedicated line.

 

[GarageDreamer]

This is the reason I went to college.. so I could hire someone. my ADD mind loses interest in electricity.. I'm learning slowly but my Dad with the Masters in EE is frustrated I still don't get it...

 

[mhm993]

SO while we're on the subject of 220v idiot, and since it's my thread, just why is "220" really 240 in my house, and seems to variously be any voltage from about 208 to 240?

 

[porschedude996TT]

SO while we're on the subject of 220v idiot, and since it's my thread, just why is "220" really 240 in my house, and seems to variously be any voltage from about 208 to 240?

It is all set via a varible tap on the transformers that bring the voltage down from the Really high voltage transmission lines outside your house which could be 5000 volts to to the individual transformer that converts it or steps it down to 220 to 240. I have noticed this for some time. It also transfers to the 110 or 120 volt discription. It is basically a range.

 

[nadogail]

!20, which was called 110 when I was a boy is a nominal, not absolute, value.

220, 240 and 208 are functionally equivalent nominal values. The differences are usually insignificant, and if adjustment is needed it is often just a choice of tap selection.

Nadogail
Journeyman Marine Electrician

 

[BigChevy80]

!20, which was called 110 when I was a boy is a nominal, not absolute, value.

220, 240 and 208 are functionally equivalent nominal values. The differences are usually insignificant, and if adjustment is needed it is often just a choice of tap selection.

Nadogail
Journeyman Marine Electrician

As far as I knew, 208v is the voltage between 2 legs of a 3 phase system. Although I have seen some 208V equipment used on single phase 240v. The motor on my air compressor states that it can be used with either 240 or 208V systems.

The voltage in my house measures 240/120 FWIW.....

 

[JOHNMAN]

To the original poster: It is up to the inspector if they allow the wire nut and wire extension inside the panel. Your methodology seems to be OK.

My big questions regarding single phase hots, neutrals, and grounds are:

(1)

In the MAIN entrance panel (at least in the USA), it seems typical to have a single ground rod bonded to the panel. The neutral bus bar is also bonded to the panel. In my mind, I don't understand why a sub panel would separate the grounds and the neutral wires instead of bonding them together as is done in the MAIN panel.

Since the ground and neutral wires are tied together at the main panel, they should always be at the same potential. Why then are they treated differently?

(2)

Do electrons actually move in AC circuits? It would seem to me that since it is alternating current, and electrons would flow back and forth in the conductor at 60Hz, the electrons would simply vibrate back and forth. Power companies don't really provide anything except the means to vibrate the electrons at 60Hz.