Difference Between 220v Romex and 120v Romex?

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Old 08-24-12, 11:41 PM
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Difference Between 220v Romex and 120v Romex?

I know 220v Romex has 4 conductors, the red and black are hot, the white is common and green is ground! I know 120v Romex has 3 conductors, the white is common, the black is hot and the green is ground! I want to splice a piece of 220v Romex into an existing 120v Romex to extend the circuit, should I connect color for color and leave red out or should I use both red and black hots and connect to black of the 120v romex?


 
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Old 08-25-12, 12:49 AM
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Is the 240v "Romex" 10/3g?... Which is red(hot), black(hot),white(neutral), and ground (Green/bare). AND, the 120v is probably 12/2 or 14/2 (Black, white, bare). Dont connect the red and black together on the (240v) wire. I would rip it out, and use 12/2 to extend/Fix the circuit if 15a or 20a . What is the current breaker, a 15a or 20a? If its 240v, it might be a 30amp double pole breaker. Im no electrition, and im sure there will be some posts here soon to help you. Im not sure if you can do what you want, but if you are going to do it, i wouldn't use the red wire, and just put a wire nut on both sides, and im sure the code people will not like it either...lol.
 
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Old 08-25-12, 03:22 AM
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No such thing a 220 Romex in the US. They do have 240 volt Romex in Canada but it is not what you have drawn. In Canada under CEC a 240 volt only supply use a Romex cable with red and black with ground but no white. No distinction is made in the USA code. The same two conductor cable, black, white, ground is used for both 120 volts and 240 volts. NEC does require the white be remarked some other color such as red or black but not white, gray, green, or green/yellow when the cable is used for 240 volts..

The cable in your diagram in the USA can be used for 120v or 120/240. Typically it would not be used for 240 volt circuits. There are no 220 volt residential circuits in Canada or the USA.

I know 220v Romex has 4 conductors
The cable in your diagram is 3-conductor not 4-conductor. The ground is not a conductor as far as terminology is concerned. 4-conductor in the USA would be red, black, blue, white, and ground.

You can extend a 2-conductor cable with 3-conductor cable but why do you want to? Is it just because you have the cable? I'd suggest saving it and buying more 2-conductor cable. If you just must, yes, cap the red on both ends. Please start from the beginning and explain what you have and what you want to do. As confused as you are about cable I may be giving you the wrong answer.
 
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Old 08-25-12, 06:39 AM
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I know 220v Romex has 4 conductors, the red and black are hot, the white is common and green is ground! I know 120v Romex has 3 conductors, the white is common, the black is hot and the green is ground!
Since you know these things, you probably also know why both cables are marked 600V.
 
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Old 08-25-12, 08:31 AM
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Thank you gentlemen for the excellent info! Ok the, (what I thought was 220v 4 con) says 14/3 and the, (what I thought was 120v 3 con) says 12/2! I've always heard it was 220v, not 240v! Just like I've always heard 110v, not 120v, lol, I am very confused!!! The reason I'm using the 14/3 is because I had a long piece laying around and I just needed to extend my circuit a few feet so why buy more? I'm not sure what the breaker is, 15a or 20a! Do they sell 20a 120v outlets or are they all 15a? I hope I'm not confusing you all more than myself, lol?
 
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Old 08-25-12, 09:53 AM
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says 12/2
Which is a very good indication it is on a 20 amp breaker there fore you can not use 14-3 to extend it assuming a 20 amp breaker. Look at the breaker handle. The amps is usually marked there.

Do they sell 20a 120v outlets or are they all 15a?
Yes but they are seldom used in residential applications. Code permits the use of 15 amp receptacle if there are two or more places to plug in. A single duplex receptacle satisfies that requirement.

I've always heard it was 220v
It was in many areas in 1910 but over the years the voltage was increased.

Wiring Simplified Is a good basic book on home electric work found a home stores, Amazon, and other retailers. You might want to read through it before starting any electric work.
 
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Old 08-25-12, 03:10 PM
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You're saying I can't use 14/3 to extend the circuit, I'm assuming the reason why is it's a code issue?
 
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Old 08-25-12, 04:46 PM
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Yes, a code and fire issue.
 
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Old 08-25-12, 09:34 PM
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My trade is called special systems, it's the installation/service of commercial security, fire, access control and CCTV systems so I'm all about codes but I'm not understanding why it's a fire hazard?
 
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Old 08-25-12, 09:50 PM
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Because 20A is enough power to melt 14AWG copper and start a fire.
Because it takes 12AWG copper to safely conduct 20A.

It's a code issue because it's a fire issue.
 
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Old 08-25-12, 09:51 PM
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14AWG wire is thinner, and thus, has a higher resistance. In a short-circuit or overload, the wire will glow bright red before the breaker trips.
 
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Old 08-25-12, 10:44 PM
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Thank you guys for clearing that up for me! I will buy the proper Romex for the job! I even thought Romex with a red wire was for 220v applications, or I mean 240v apps simply because the red was an additional conductor, thinking 240v needed an additional conductor! I think I'll buy that book you mentioned also, lol!
 
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Old 08-26-12, 05:52 AM
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There are actuallt three "services" commonly used in residences:
120v=2-conductor cable+ground
240v=2-conductor cable+ground
120/240v=3-conductor+ground

The last is what may have confused you because it is often called 240 though strictly speaking that isn't true it is both a 120v and a 240v service combined in one cable. Appliances like dryer are often basically 120 volt appliances with 120v motors and controls then the manufactures add a heat source. It may be a gas burner or an electric resistance element. The gas only requires 120v for the dryer to work but if electric heat they need 240v just for the heat thus they need both 120v for the dryer and 240v for the heater.
 
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Old 08-26-12, 10:55 AM
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The black/red/white can be for a 240 circuit, two 120 circuits in the same cable, or can be used like between three way switches or smoke alarms.
 
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Old 08-26-12, 07:12 PM
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I was basically going from a large conductor at the splice to a small conductor back to a large conductor! So you're saying the small conductor in the middle will heat up enough to melt or catch fire even if the small conductor is only about 15' in length?


 
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Old 08-26-12, 07:23 PM
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Yes, that would be the issue. The breaker must protect the smallest wiring in the circuit. If not the smallest can overheat and lead to a fire. This is also why when the breaker trips from overloads you cannot install a larger breaker.
 
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Old 08-26-12, 09:21 PM
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I really appreciate the info, I'm a low voltage DC guy so I never knew house wire sizes (gauges) were so important! I've known people who extended circuits with extension cords to a wall outlet! No one ever burned anything down so I thought using a smaller conductor Romex was fine because it was at least Romex! Thank you all again for clearing up this situation for me!
 
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Old 08-27-12, 05:08 PM
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I've known people who extended circuits with extension cords to a wall outlet! No one ever burned anything down
Maybe no one you know has ever burned anything down, but it has happened. The closest I ever came to seeing such an event was just watching the fire department leave after the fire was extinguished from an 18 awg extension cord inside a wall feeding an outlet where an air conditioner was plugged in. By the way, maybe you missed it above, but your typical NM B cable (aka Romex) is rated for and marked 600 volts.
 
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