Est. 1998 — 27 years of woodworking knowledge
220 = 2- 110
olbuck
YOU AINT CONVINCE ANYBODY THAT THE THIRD WIRE(ground in 220) ever carries ANY JUICE. AS IT IS SCREWED DIRECTLY TO THE WALL PANEL THAT IS GROUNDED TO THE OUTSIDE LEAD IN FROM UTILITY POLE. EACH HOT WIRE IN THE 220 CORD HAS 110 VOLTS. THAT VERY SAME THREE WIRE CORD IS GROUNDED TO THE WALL PANEL. COULD IT BE ETC., ETC.,ETC.
Er, You Fergettin
Mark Mandell - Gone Round In New Jersey
thet the power goes back ta the 'ectric comp'ny by ways o' the dirt? Thet's wha' cher groun's fer.
Use yer groun fer a nootral and versavisa and yer asking fer the brigade boys to pay you a visit
Sure...
John in NM
You could use that third wire as a common, or grounded wire.
But then you would have two problems - first, a common that was undersized for the return current of TWO hots. Second, you would have no ground wire - the purpose of which is to prevent YOU from becoming the path of least resistance in the event of a short.
Having once had 110 VAC go from a drill in one hand to a driver in the other - ie across the chest - I can tell you that the safety ground is important.
An
Mark Mandell - Gone Round In New Jersey
'Taint nobody here deef in thar eyes. Ya don't need to be hollerin' to be her'd.
(Message Deleted by Poster)
Re: Clarification
Larry Clinton At Frankfort, (Central) Indiana
First, codes in some areas require that the Neutral (the white wire that comes from the Utility service) be grounded to the entrance panel ground. In other areas that is not only not required but banned! Earth grounds are actually needed by the power companies to keep the "hot" lines from "floating" and having a higher potential than the normal 120V to the ground. The Floating is caused by capacitance and induction from the other lines in the system.
Second the "Earth ground" is not intended to carry any current in normal use. It is only there to keep the "grounded" portion of 3 prong plugs at the potential of the earth and prevent shocks to users. in the case of a short the "earth ground" will cause the breaker/fuse to open.
Third, the 120V power in a standard home is measured from the neutral to either of the 2 hot lines. Power input to these homes is a sine wave at 60 Cycles per second and the potential (voltage) on one hot line is 120V RMS "Above" the neutral/ground and the other hot line 120V RMS "Below" the neutral / ground. The 240 Volt power is obtained by measuring between the two "hot" lines. In a properly functioning 240V circuit NO POWER is carried on the neutral / ground.
(Explanation of RMS these letters stand for Root Mean squared and is a formula for measuring the usable potential voltage. The actual peak voltage of the sine wave is quite a bit above the 120v or 240V description.
As to the neutral carrying an excess load in a split circuit when both circuits are under load it in not true. If both circuits are carrying the same load, again there is no current carried by the neutral!
Now as to your initial question, you can legally split a 240 Volt circuit into two 120V circuits, however this is only to code If THE EXISTING WIRING HAS 4 CONDUCTORS AND YOU CHANGE THE BREAKERS. If the existing wire feeding the 240 V outlet has 2 hot lines (normally a black and a red) a White neutral and a Bare Copper ground then it is to NEC code. If it doesn't have the 4 wires then you cannot,
I do wish to caution everyone here that electrical wiring should not be done without proper knowledge. There are a lot of people that have some knowledge of wiring and believe they have answers to your questions, often that information is incorrect and in some cases dangerous. If you are not sure of what is to code and know how to do the wiring it is a whole lot less expensive to hire a qualified electrician than to burn your home down or electrocute someone!
Tenets of business communication:
Mark Nowicki
Tell the customers what they wants to hear
in the language they can understand
without saying anything negative about yourself.
I think you got two out of three 
Re: Clarification
Forrest Addy
Thank you, a real clarification. Cogent and well presented.
The neutral conductor carries current but on the the unbalance current between the two 240 lines thus it doesn't need to be "double the size" of the line conductors.
The ground is intended as ground reference and is intended to carry only fault current. If a line conductor shorts to ground, the ground conductor provides the current return path to trip the overload protection (fuse, circuit breaker, etc). Since it carries this current for only the time delay of the current protection device, there is little resistive heating so the ground conductor can be one merchant size smaller than the line conductor.
This information is repeated in every home center DYI electrical project book, every electrician apprentice text, EE course content, countless web sites. If you have a need to understand home and shop electrical distribution a week of evening's study and some simple experiments will clarify the subject and provide you with vocabulary so you can observe safety precautions, describe problems, plan improvements, and sensibly purchase materials with a minimum of confusion and frustration.
Electrical ignorance is easily fixed with a little study. Electrical stupidity is self-regulating via consequences.
Re: olbuck, I hope you'll come back
olbuck
YONAK - shoot, i might jes back outta heaw. i'uz bout to run som PVC frum compressor fer air lines. I might not no how ta do that either. I mean that stuff is cheap and bust pressure is way over 100 pounds. Maybe I should jes stick with another hobby, no what I mean?
Anywho 'preciate the invite, didn't intend to PO anybody, jes an ol redneck tryin ta find mu way,thanks.
Most, Here
Mark Mandell - Gone Round In New Jersey
have learned from our mistakes or those of others. Some of those lessons were "hard" indeed, and those of us who care to respond do so to pass on what we've experienced in an effort to inform questioners who have both the ability to at least suspect what they don't know and the intellectual courage to reveal their lack of knowledge to others.
If you ask a question here, you should expect a variety of answers, some in agreement, others with different views, but always well intentioned. Personal rants are very rare on this board.
Woodworking, like any "manufacturing" activity, carries significant danger of personal injury and/or death. Many on this board carry the scars that prove the premise. The greatest danger is lack of useful knowledge and the willingness to ignore it.
That you mention using PVC piping for compressed air indicates that you at least suspect it may not be the best course to follow. If you'd like to know more, post a new question. Just don't ask us "hold my beer while I do this."
Re: olbuck, I hope you'll come back
John K Jordan
Hope the pressurized PVC was a joke.
"2
Mark Mandell - Gone Round In New Jersey
out of 3 ain 't bad" as the song goes.
I'm curious...
John in NM
I mentioned below that I was initially in error to say that the common needed to be larger to carry the return of both hots - assuming the two hots are 180 degrees out of phase.
What I don't understand is why you suggest the common would only carry the the unbalance current between the two 240 lines. The OP was suggesting using each hot for a different appliance, so the other hot line could not carry the return of the other. While the common would not need to be oversized, it would need to carry the full load return current of the appliance, would it not?
Only if...
Jason Roehl in Lafayette, IN
One appliance is being used and the other is not.
If only one appliance is on and drawing 15A, then the neutral carries 15A also--the difference between the two, 15 and zero. If both appliances are on, and one is drawing 15A and the other 5A, then the neutral is only carrying 10A, the difference, because they are 180º out of phase.
Jason
Re: Only if...
John in NM
How can that be the case when the two hot lines going to separate appliances do not form a circuit between them?
What the OP seemed to describe was using the two hots for two different applications - in which case one hot cannot serve as the out of phase return for the other -- because they go to different appliances and have no connection beyond the common or safety ground.
I don't doubt what Forrest said - he knows a lot more about this stuff than do I - I would simply like to understand it.
Re: Only if...
Jerry Roberts
Tell ya what I found out about my delta table saw.
about 6 months ago the male ground pin broke off the plug. I thought I could just run a wire to case gnd and temperaly run it to 3rd wire gnd. I checked the broken pin to the saw case grnd. with a meter and no continuity. Now, I don't know where that third gnd wire goes inside the saw but it don't go to case gnd. So, in case the hot wire should touch the case, that power will not go to the gnd wire and out so it doesn't go to the operator.
Re: Only if...
Bill Howatt
I'll try to explain it but I'm afraid I may cause further confusion!
The two hots are connected to the same source one hot at each end of a transformer winding (on the pole outside supplying your house) and thus are indeed part of the same circuit. To go a step further, the neutral wire is connected to a tap in the center of the this transformer winding which provides the 110V from the center tap to each hot. Because the hots are on each end of the winding, giving 220V between them, they are out of phase by 180 degrees.
Regardless of what you may plug in between each hot and the neutral there is still a path back through the other hot if there is a load connected to it.
When dealing with 110V circuits we normally don't worry about this and just think of it as the current going back on the neutral wire when in reality, it is only the difference current, if any, between the loads on each hot that goes onto the neutral. The other portion of current that you think goes down the neutral is cancelled out by the out-of-phase current coming from the load on the other side. The "neutral current" from each hot does indeed add but since they are out of phase, it actually is a subtraction. For example: +10 plus -7 (minus since out of phase)=3A down neutral conductor.
All of the circuits in your panel work this way and just like the case of a single load on each hot to neutral, the only current that goes out the big neutral back to the pole transformer is the difference between the total load current on each side of the panel.
Bill
Strange
Bill Howatt
I'd check that finding out a bit more. The metal part of the motor and for that matter, the saw itself, should be grounded.
Bill
Re: Only if...
John in NM
Thanks Bill, most of that is familiar.
Here's the thing:
"Regardless of what you may plug in between each hot and the neutral there is still a path back through the other hot if there is a load connected to it."
So why then won't a 110 appliance run with just the hot connected, assuming an equally balanced load on the other phase? The way I see it, two hots with no return to ground from the appliances are just open switches and nothing happens.
Re: Only if...
Bill Howatt
John, I'm not clear on what you mean exactly.
You always need a complete circuit for the current to flow through the device; so for a normal 110V load the current flows from a hot to the neutral. For a 220V device the current flows between the 2 hots and the neutral is out of the picture. In this case there is no current flow to ground via the neutral.
If you have 2 equal 110V devices that draw the same current you could connect them in series between the 2 hots and not bother connecting the neutral and they would work normally (even if it should never be done this way).
In the series connection above, if one device draws more current than the other then the voltage will not be divided between the 2 equally and the one that requires less current (has a higher resistance) will have too much voltage across it and will be destroyed. Having the neutral connected to them prevents this from happening since it forces the voltage to be 110V between each hot and neutral.
Bill
Re: Only if...
Larry Clinton At Frankfort, (Central) Indiana
John, I hope I don't confuse the issue farther but here is a fairly simple explanation. If you hook up a light bulb to one hot line of a 240V circuit, then hook up another light bulb of exactly the resistance / wattage to the other 240V hot line then tie the open side of the light bulbs together to a neutral and cut the neutral off so it doesn't lead anywhere else except to the two bulbs, the bulbs will light exactly as they would across a 120 volt hot/ neutral lines. This is because the voltage is divided between the two bulbs and each is dropping 120V across the bulb.
However if you change one of the bulbs to a different one of higher wattage, with the neutral cut off, the lower wattage one will be very bright and burn out soon, and the other will be very dim. Now if you hook the neutral up properly to the entrance panel the in the voltage drops will be eliminated as the neutral (which is hooked up to the center tap of the transformer on the utility line) will carry the "difference" in the amperage so both bulbs will have 120V across them. Clear as mud huh?
Ahah....
John in NM
That explains it:
"If you have 2 equal 110V devices that draw the same current you could connect them in series between the 2 hots and not bother connecting the neutral and they would work normally (even if it should never be done this way)."
I never thought of connecting them in series (I suspect the OP did not either). So basically, this whole thing about not "needing" the common is a rabbit hole. In the configuration that the OP tried to describe, the common is indeed needed to complete the circuit, but as the two hots are 180 degrees out of phase, it need not be oversized.
Very clear...
John in NM
The confusion is that you guys were talking about a 220V line with two 110V appliances connected in series, and the OP (as far as I know) and I were talking about two 110V appliances used in parallel.
I thought there had to be a simple explanation for all the confusion, now I see what it was 
THIS MAY HELP
olbuck
110v + grnd= usuable circuit of 110v maybe 120?
220v + grnd = usuable circuit of 220v
110v + no grnd = NO USABLE CIRCUIT
220v + no grnd = no usable circuit
ALRIGHTY,,,, Ground wire ONLY carries electricity when it is NOT GROUNDED.
Oh you don't believe that, hook yourself up to 110v,you standing on thick fiberglass or non-conductive matt.
Remember matt material is very importan. Now touch something that is a ground & you'l experience 110v going THRU YOU TO GRND! Be sure and have yur life insurance paid up.
Wiring installed as it should be: soon as something ''shorts out'' the grnd is right there and breaker thrown. AW ya say, I don''t kno what i'm talking bout. Standing in ''bucket attached to two fiberglass lengths of Pole that will life the bucket 47'. With my gloves OFF, I took 7200 volt distribution line in my bare hands just to feel it. Barely a sting going on being filled with 7200 volts. Today their is metal suits a lineman puts on & is electrified(entire body) with what ever TRANSMISSION LINE VOLTAGE HE'L BE WORKING ON, YES YOU BET HE WONT COME NEAR A GRND. Cya.
AW ya say, I don''t kno what i'm talking bout. Standing in ''bucket attached to two fiberglass lengths of
Re: THIS MAY HELP
John in NM
The confusion was in the various descriptions, not in the concepts.