As you design a solar system the tables I provide help you determine how much current is allowed to pass through a conductor but these cables are limited to a maximum of 3 current carrying conductors in the raceway. As the quantity of conductors increases the combined heat from the conductors will increase so the amount of allowable current must decrease. After you adjust the conductors ampacity for temperature this table will provide you with the percentage of that ampacity that is allowed. For example you can only use 80% of a conductors ampacity when there are 6 current carrying conductors in a raceway.
What is a current carrying conductor?
The intention is to count only the conductors that carry current and will add heat to the overall installation. A ground or bond conductor does not normally carry current and is not counted. The neutral conductor is sometimes counted. With solar if your array has a bonded negative that makes it a DC neutral conductor it would count because current normally flows through this conductor. For AC systems phase conductors always count. If you have 3 wires in an AC system, 2 phase conductors with 1 neutral and the neutral is carrying the current from the phase conductors, the neutral does not count. Any 2 wire circuit where the is a phase conductor and a neutral, both will count. If you have a 3 phase system with 3 phase conductors and a neutral (wye system) and you are only powering something with 2 phase conductors and a neutral, the neutral counts in this case. If your application is industrial in nature and you have non-linear loads the neutral counts.
| Number of Conductors | Percent of Values |
|---|---|
| 4 to 6 | 80 |
| 7 to 9 | 70 |
| 10 to 20 | 50 |
| 21 to 30 | 45 |
| 31 to 40 | 40 |
| 41 and above | 35 |
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