- Tables
- T10A
- T15
- T23- Pull box sizes
- T53
Make notes from the material that you are not familiar with and master those notes.
T10A-Dimensions of stranded conductors for calculating conduit and tubing fill. For solid conductors see T10C.
Add these notes to the top of T10A and highlight the 40% columns of T9G.
- Assume 600V Unjacketed if the type of conductor is not specified in the question.
- Use this table for different size and type of conductors, otherwise use T6
- On the bottom left side of T10A, take note that the meaning of crosses † is jacketed. * means unjacketed. In columns 2 and 3, write UJ beside the 600V for UnJacketed and the 1000V for UnJacketed. In column 4, write J beside the 600V for Jacketed. Note the largest size conductor is 2000 kcmil.
T15- Bending radii — High-voltage cable
There are four columns. The first column has the type of cable listed. The second column is for cables up to and including 25mm (1”), another column is for cables over 25mm diameter and up to and including 50mm in diameter. The third column is for cables over 50mm in diameter. Note that smooth aluminum cables and corrugated aluminum cables are available in both high and low voltage. If the question is about high voltage, use T15. If the question is about low voltage smooth aluminum cables or corrugated aluminum cables search in the index cables, radii of bends in 12-712. If the cable is high voltage, the voltage in the question will be over 750V or the word high voltage will be mentioned. Different size cable is delivered on the job site with different size spools. The size of the spool indicates the bending radius of the cable.
T23- Box sizes
On the exam, we will be asked to either calculate the box size or the number of conductors that can fit in a box. Rule 12-3034 is the second last rule in section 12 and belongs to T23. Subrule (2) (a) dictates that if we are to calculate the maximum number conductors in a box, we would subtract one conductor for every fixture stud or hickey
. Subrule (b) indicates that we need to subtract one conductor for every pair of wire connectors. If we have 28 marrattes then we would divide 28/2 and therefore subtract 14 conductors. 28 marrettes take the space of 14 conductors in a box. On the other hand, if we have 29 marrattes; this is an odd number and is not divisible by two, so we subtract one from 29 to make it an even number and divide 28 by two which will yield 14 conductors. Numbers 28 and 29 is the pair that takes the same space as 14 #14awg wires in a box. Subrule (c) indicates that we subtract two more conductors if the box contains one or more flush devices (switches, receptacles) mounted on a single strap. 
If asked to calculate the box size, we abide by rule 12-3034 and add instead of subtract.
Pull box sizes.
When using table 23, we can only use conductors in sizes of #14, #12, #10, #8, and #6. The next size up from #6 is #4. From #4awg conductors and up, we need to calculate our own box sizes. The last rule in section 12 is 12-3036. This rule indicates the three situations that we might encounter on the job.
There are eight letters in the word straight. So in a straight pull, we multiply the diameter of a raceway or cable coming into a box by 8. From diagram A) above, we can see that straight is 8x. So we use the raceway or cable diameter size of 53mm and multiply it by 8. The total box size will be 424mm. So we need 424mmX424mm box. From the box sizes not found in the code book list above, we would choose a 600mm x 600mm box to fill the 424mmX424mm. The boxes are also available in inches so we can convert mm to inches by dividing the total of 424mm by 25mm. In conclusion, straight is eight and the rest of the calculations are multiplied by six.
From diagram B), there is a raceway or cable entering a box from the side which is opposite to a removable cover, we need to multiply the diameter of the conductor that is projecting from the raceway or cable by 6 and then add the diameter of the raceway or cable that is entering the box. If we need to convert to inches, we can always divide by 25mm.
From diagram C), there are raceways or cables entering a box from different sides. To calculate the box side, we need to use the side of the box that has the most raceways or cables. We use the diameter of the largest raceways or cables 103mm x 6 plus the diameter of the rest of the raceways or cables. It is clear from the above calculations (below diagram C) that we need a 696mmX696mm or a 30“x30“ box.
There are still two outstanding problems that we need to take care of. We have a very sharp angle on the bottom left side of the box. We need to make sure this angle is not too sharp for our angle pull. So to find the proper place to make the knockouts in the box, we multiply the diameter of the raceway or cable (usually they are equal) by 6. Therefore, for optimum angle pull, it is (6x53mm) =318mm or 13“.
Another problem we have is the space between the two raceways or cables when we have a U-Pull. To optimize the space and not stress the conductors in the raceways or cables, we multiply 6x the larger of the two raceways. So (6x103mm) +25mm=643mm or 26“.
If we have only the angle pull in the box, we will use the 318mm for the size of the box. So we need a 318mmX318mm box fill. From the box sizes not found in the code book list above, we would choose a 400mm x 400mm box to fill the 318mm X 318mm. If we have only the U-Pull in the box, we will use 643mm for the size of the box. So from the box sizes not found in the code book list above, we would choose a 750mm x 750mm box to fill the 643mm X 643mm X and Y dimensions of the box.
T53-Protection of conductors, cables, or raceways underground
In T53, Non-vehicular areas are sidewalks/walkways and vehicular areas are driveways/lanes. A Lane is the space occupied by a car. An example of conductors or cable not having a metal sheath or armour would be NMWU cable and TWU. Conductors or cable having a metal sheath or armour would be Teck90. A side note is attached to this table-“if 38mm of wooden treated plank is used, we reduce T53 figures by 150mm. For example, if we supply a light post with an NMWU cable under a driveway, we would bury the cable 900mm according to T53 and if 38mm of wooden treated plank is used, we reduce the 900mm by 150mm. We would bury the cable in a shallower trench of 750mm.
Please close this module and open module 5. Thank you.