4-002 Size of Conductors

Except for flexible cord, equipment wire, control circuit insulated conductors, and cable, conductors shall not be smaller than No. 14 AWG when made of copper, and not smaller than No. 12 AWG when made of aluminum.

Permanent wiring in a house can’t be smaller than No. 14 AWG (copper) or No. 12 AWG (aluminum) if it is concealed. Although rarely used in residential construction due to the added rules regarding the connection of aluminum to switches, receptacles and copper components, aluminum conductors are allowable. They are not as electrically conductive as copper, and their exposure to oxygen in the atmosphere causes a buildup of aluminum oxide film, which causes resistance, which results in heat. Devices attached to aluminum conductors must be approved as such and interconnections to copper conductors usually require either lugged connections or the use of an oxygen-excluding conductive paste.

4-004 Ampacity of Wires and Cables (See Appendix B)

1. The maximum current that a copper conductor of a given size and insulation is permitted to carry shall be as follows:
   1. single-conductor and single-conductor metal-sheathed or armoured cable, in a free air run, with a cable spacing not less than 100% of the largest cable diameter, as specified in Table 1;
   2. one, two, or three conductors in a run of raceway, or 2- or 3-conductor cable, except as indicated in Item d), as specified in Table 2;
   3. four or more conductors in a run of raceway or cable, as specified in Table 2, with the correction factors applied as specified in Table 5C ……..

For the purposes of our studies, we will restrict our involvement with the sizing of conductors to the subrules listed above.

Table 1 applies to a single copper conductor which is bare, covered or insulated, in free air, with an ambient temperature of not more than 30°C. This practice of running single conductors is limited in its use, as most circuits encountered will have 2 conductors which are a hot and a neutral. In each of the tables listed above, the maximum amount of current that can be carried is dependent upon the size of the conductor and the level of insulation around it. The higher the insulation level, in °C, or the larger the diameter the more current the conductor can carry. For example, provided the ambient temperature surrounding the conductor is not more than 30°C, a single No. 8 AWG copper conductor in free air, with 90°C insulation, would be capable of carrying a maximum of 80 amps. If 110°C insulation is used, that maximum rises to 90 amps. If the conductor gauge is increased in size to a No. 6 AWG (the lower the gauge number, the larger the diameter) and the insulation rating remains at 90°C, the ampacity is increased to 105 amps.

Table 2 is used when there are 2 or 3 insulated copper conductors in raceway or cable, again based on an ambient temperature of not more than 30°C. For example, three No. 6 AWG copper conductors using 75°C insulation would have a maximum ampacity of 65 amps. According to Rule 4-004(1)(c), when there are 4 or more conductors in a raceway or cable, their ampacity is derated by applying the number of conductors to Table 5C and multiplying the normal ampacity of a conductor of its size and type of insulation by the deration factor given. For the example immediately above, the deration factor for 4-6 conductors from Table 5C is 0.80, meaning the conductors can only carry 80% of their original load from Table 2. The 65 amps would be multiplied by 0.80 to become 52 amps. The heading of Table 5C indicates that it applies to both Table 2 (copper conductors) and Table 4 (for aluminum conductors).

1. The maximum current that an aluminum conductor of a given size and insulation is permitted to carry shall be as follows:
   1. single-conductor and single-conductor metal-sheathed or armoured cable, in a free air run, with a cable spacing not less than 100% of the largest cable diameter, as specified in Table 3;
   2. one, two, or three conductors in a run of raceway, or 2- or 3-conductor cable, except as indicated in Item d), as specified in Table 4;
   3. four or more conductors in a run of raceway or cable, as specified in Table 4 with the correction factors applied as specified in Table 5C …….

Tables 3 and 4 for aluminum conductors are applied in the same fashion as Tables 1 and 2 are for copper conductors, choosing maximum ampacity based on the size of the conductor and its insulation rating. As mentioned above, Table 5C is used to derate those ampacities where there are more than 3 conductors in the same raceway or cable.

7. The correction factors specified in this Rule
   1. shall not apply to conductors installed in auxiliary gutters containing 30 conductors or less; and
   2. shall apply only to power and lighting conductors as follows:
      1. the ampacity correction factors of Table 5A, where conductors are installed in an ambient temperature exceeding or anticipated to exceed 30°C ……..

Tables 1 through 4 are based on an ambient temperature of not more than 30°C surrounding the conductors. If exceeding this temperature, the ampacities of conductors found in Tables 1 to 4 are to be de-rated by being multiplied by the factors in Table 5A that are applied to the anticipated maximum temperature and the insulation rating of the conductor(s). For example, a cable with three No. 4 AWG copper conductors with 90° insulation is installed in a raceway in an ambient of 47°C. The following steps would be taken to determine the maximum allowable ampacity of the conductors;

1. From Table 2, a No. 4 AWG copper conductor with 90°C insulation would have an ampacity of 95 amps.
2. From Table 5A, under the “ambient temperature” column, 50°C would be chosen because 47°C falls between it and 45°C; in other words default to the higher temperature.
3. Reading to the right on the table, choose the deration factor that falls under the insulation rating of the conductors, in this case, 90°C. The deration factor would be 0.82.
4. Multiply the original ampacity of the conductors by 0.82 to arrive at a new maximum allowable ampacity of 77.9 amps.

It is important to note the markings beside AWGs No. 14, 12 and 10 in Tables 1 and 2, and beside AWGs No. 12 and 10 in Tables 3 and 4. These indicate changes to the previous edition(s) of the CEC where the maximum allowable ampacities for these wire sizes were lower. Although there is now a higher ampacity allowed for these wire sizes, the markings beside those sizes direct the user to a note which says to “see Rule 14-104 (2)”. That Subrule states;

“Except as provided for by Subrule 1) c), the rating of overcurrent protection shall not exceed

1. 15 A for No. 14 AWG copper conductors;
2. 20 A for No. 12 AWG copper conductors;
3. 30 A for No. 10 AWG copper conductors;
4. 15 A for No. 12 AWG aluminum conductors; and
5. 25 A for No. 1 AWG aluminum conductors.”

In short, although the tables indicate that the conductors of those gauges and types may now carry more amperage than they were previously allowed, the fuse or circuit breaker is still limited to the “old” ampacities for those wire sizes, so nothing significant changed. It is unclear what the intent of the change was.

4-012 Ampacity of Flexible Cords

1. The maximum current that two or more insulated copper conductors of a given size contained in a flexible cord are permitted to carry shall be as follows:
   1. 2 or 3 insulated conductors, as specified in Table 12;
   2. 4, 5 or 6 insulated conductors, 80% of that specified in Table 12;
   3. 7 to 24 insulated conductors, 70% of that specified in Table 12; ………..

Table 12 is used in a similar fashion to Tables 1 through 4 for insulated solid conductors. The user corelates the markings on the exterior of the cord jacket with the size to arrive at a maximum allowable ampacity per conductor. There is no indication in the Code for derating due to ambient temperatures exceeding 30°C.

4-024 Identification of Insulated Neutral Conductors up to and Including No. 2 AWG Copper or Aluminum

1. Except as permitted in Subrules 2), 3), and 4), all insulated neutral conductors up to and including No. 2 AWG copper or aluminum, and the conductors of flexible cords that are permanently connected to such neutral conductors, shall be identified by a white or grey covering or by three continuous white stripes along the entire length of the conductor.

As seen in the “Definitions” section, a neutral conductor is to be identifiable as a neutral by having either a white covering or having raised ridges along its length. Without writing out the content of Subrules 2), 3), and 4), what they indicate is that, if conductors of different electrical systems occupy the same enclosure, the identified circuit conductor of the other system(s), if present, shall have a white covering with an identifiable coloured stripe (not green) running along the insulation, or identified in other ways acceptable to those Subrules. This is to visually separate the neutrals in each system from each other and from power conductors.

4-032 Identification of Insulated Conductors

1. Insulated grounding or bonding conductors shall
   1. have a continuous outer finish that is either green or green with one or more yellow stripes, or
   2. if larger than No. 2 AWG, be permitted to be suitably labelled or marked in a permanent manner with a green colour or green with one or more yellow stripes at each end and at each point where the conductor insulation is accessible.
2. Insulated conductors coloured or marked in accordance with Subrule 1) shall be used only as grounding or bonding conductors.
3. Where colour-coded circuits are required, the following colour-coding shall be used, except in the case of service entrance cable and when Rules 4-026, 4-028, and 6-308 modify these requirements:
   1. 1-phase ac or dc (2-wire) – 1 black and 1 red or 1 black and 1 white (where an identified conductor is required);
   2. 1-phase ac or dc (3-wire) – 1 black, 1 red, and 1 white; and
   3. 3-phase ac – 1 red (phase A), 1 black (phase B), 1 blue (phase C), and 1 white (where a neutral is required) ………

Bonding conductors in circuits using solid conductors are typically bare, whereas in flexible cords and equipment wire using stranded wires they will have the same insulation as the power conductors due to usage, and so need to be seen to be different from them. In house wiring, circuits are 1-phase ac, so either black or red is used to indicate a hot wire. Most hot conductors are coloured black, whereas red colouring is normally used for split circuits in kitchens, 240 V circuits to ranges, dryers and hot water heaters, and switched plugs such as for ceiling fans and living room lamps.

Now complete Self-Test 7 and check your answers, quoting applicable Code rules.

Self-Test 7