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Conductors

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Conductors allow us to have a path to complete our circuit. The electrons travel through this material, and if installed correctly, it's a safe application. There are many considerations for choosing the proper conductor for a job, and the CEC has tried to add as much information as they can in order to guide you in what has worked in the past, and what hasn't.

The main objective is to get the job done correctly, so that your installation will safely protect the client that you are wiring for. Codes change because there were occurances that usually caused fires. Changing these codes are the first step, in fine-tuning a system that we can all work safely within. There are a huge amount of volunteers, from all walks of the trade, that donate their time to "help" make it better. So the next time you see a delta next to a code, know that the work that went behind it was extensive, and well meaningful.



Wire and Buses
There are two main types of conductors. Wire and Buses.

Wire...
Solid or stranded construction.


Buses...
- Bus Bar (Distribution, Splitters, Busways, Motor control.)

- High current electric distribution systems.


Types of Conductors
There are three commonly used metals used for conductors. Copper, Aluminum, and Steel.

Copper
Excellent Conductor. Easy to work with, and doesn't oxidize like aluminum or steel. Also used in circuits and motors. It's disadvantage is that it is expensive.

Aluminum
Lighter than copper but not as good a conductor. Aluminum oxidizes faster. Two disadvantages to aluminum are cold flow and electrolysis. These are outlined in the definitions page.

Steel
The strongest conductor mainly used for a supporting material. Used with grounding conductors, boxes, and connectors to complete grounding.


Oxidation
If a conductor is allowed to oxidize at the terminal point or splice, the current carrying ability will be seriously reduced. When copper and aluminum are brought into direct contact to the elements, a galvanic reaction takes place because of the dissimilar properties of the metals.
Aluminum conductors need to be wire brushed to remove the oxide layer, and apply an anti-oxide product to reduce the oxidation process.

The following examples are from Coppercanada.ca



Insulation of Conductors
The type of insulation used to surround a conductor is critical for protecting it. Insulation is also sometimes referred to as "dielectric" and in the case of insulation, an important factor for choosing the right wire would be it's "dielectric strength." This dielectric strength is it's resistance to break down under voltage.
Choosing the right wire is the difference between potentially killing somebody, and keeping them safe. A few things to consider for any job is:
#1) the voltage it's rated for
#2) the temperature it's rated for. (CEC Table 19)
#3) the material it's made of, and the places it's approved for.



Size of Conductors
American Wire Gauge (AWG)
Is a U.S. standard set of wire conductor sizes. No, sorry to disappoint, it's not Canadian. The "gauge" is related to the diameter of the wire. The higher the gauge number, the smaller the diameter and the thinner the wire. This is based on a solid conductor, and ranges between 40 and 6/0. Anything larger is normally calculated in kcmil. To check the current sizes you can visit the IEC to see current regulations.

Circular Mil Area
Get used to this measurement apprentices. Ever hear 500 Kcmil, or 750 kcmil on the job site? Ever wonder where it came from? You're about to learn. The circular mil is a unit of area used especially when denoting the cross-sectional size of a wire or cable. A circular mil is the equivalent area of a circle whose diameter is 0.001 (10-3) inch, or approximately 0.7854 millionths of a square inch. Sound like greek? Not that bad when you get used to it.

Square Mil Area
The square mil is the unit area of a square whose sides are one mil, or 1 x 10-3 inch

1 Circular Mil = 0.7854 Square Mil or (CMA = SMA x .7854)
1 Square Mil = 1.27 Circular Mils or (SMA = CMA x 1.27)
The square mil area is always a greater number, because it covers more area.

Diameter translated to CMA (the formula being ...CMA = d2)
Example d = Diameter
d = .250"
d = 250 mils
CMA = d2....so 250 x 250
CMA = 625,000


Resistance of the Conductor
Every wire/conductor has an inherent resistance. This is just a fact of life. So, in order to compute the amount of resistance that you start off with, without devices, motors, transformers, and adding confusing harmonics to the system - it's nice to know what you have to begin with. So this next portion explains the resistance of the wire itself. The K factor is something that is given by tables, but for the most part Copper (Cu) and Aluminum (Al) are outlined below. 10.4 and 17. Here is the formula for computing resistance.





Voltage Drop
The longer you run the more tired you get. The less spunk you have. The same is true with voltage drop. The longer the run of wire or conductor, the less the voltage. So the following formula using the basic principles you used above, still apply.




The role of the neutral? The role of the grounded conductor?
Which came first? The neutral or the grounded conductor? Well, you judge for yourself.
When parallel circuits were introduced to the scene, it created a whole new "balanced" and "unbalanced" scenerio. Instead of one path, the current had more than one path to follow. So an easy way to remember the "lingo" for grounded conductor and neutral is the following:

Neutral - carries the unbalanced load.
Grounded conductor - carries the whole load.
Having said that...you will hear the term "Identified" - this is the grounded conductor. Either white or gray. See the different circuits, and the way the current travels below.




Click to view calculations on an unbalanced parallel circuit.

Click to view calculations on an unbalanced series circuit.

Click to view calculations on a balanced series circuit.