Conductor Material and Sizes - Section 4

Question 1

Why would one care about conductor sizes?

Answer 1

Because smaller conductors have a higher resistance which, when current passes through them, a large heat is developed. By “sizing up” we reduced the heat lost (line loss).

Question 2

What table is referenced when determining a flexible cord for certain conditions of use?

Answer 2

Table 11

Question 3

Conductors get hotter, when installed next to other conductors. If installing more than 3 conductors in a raceway, what tables should be referenced to adequately determine ampacity?

Answer 3

Table 5c and

• Table 2 for copper
• Table 4 for aluminum

Question 4

What are the default conductor termination temperatures for equipment?

Answer 4

• 60 degrees for current of 100 amperes or less and when using #1 awg or smaller wires.
• 75 degrees for current of more than 100 amperes and when using greater than #1 awg wires.

Question 5

What are tables 1 and 3 used for?

Answer 5

Ampacities of single conductors in free air.

• Table 1 is for copper
• Table 3 is for aluminum.

Question 6

The ampacities of flexible cord is determined from…?

Answer 6

Table 12 (Close attention should be paid to the number of wires in the cord, correction factors still apply).

Question 7

When determining ampacities of conductors in single phase 3 wire systems, how many wires are counted for each three wire circuit?

Answer 7

2! The neutral wire is not counted. (When determining box fill and conduit fill, be sure to count the neutral)

Question 8

When can a neutral conductor be bare?

Otherwise what kind of identification is required?

Answer 8

In a consumer’s overhead service.

• A white or grey insulation up to and including #2 awg (after this, phase tape or other suitable marking at every accessible end of the conductor is acceptable)
• A longitudinal ridge along the conductor

Question 9

If installing a switched light in conduit, could one splice a white wire to be switched (so that a black wire can return to the load)?

Answer 9

No, this method is only acceptable when using manufactured cables.

Question 10

What three colours of wires are used in a single phase 3 wire system?

Answer 10

Black Red White

Question 11

In general should a 20 amp breaker ever be used in a #14 awg circuit.

Answer 11

No, see rule 14-104

Question 12

What is the minimum size of conductors allowed in flexible cords?

Answer 12

18 awg, with a few exceptions.

• Tinsel cord can be #27 awg
• Cords for specific devices can be #20 awg

Question 13

When used as luminaire lighting, equipment wire will not be smaller than…?

Answer 13

18 awg copper