2020 Conductor Ampacity Code Refinements

“The 2020 edition of the NFPA 70® National Electrical Code® (NEC) contains minor refinements to Table 725.144, which specifies the maximum current that may be carried by a communications cable conductor as determined by the conductor gage (AWG) size, number of 4-pair cables in a bundle, and mechanical temperature rating of the cable.  This table was first introduced in the 2017 edition of the NFPA 70® NEC and only applies when the power supplied is greater than 60W (i.e., it does not apply to IEEE 802.3 Type 1 (15W), Type 2 (30W), and Type 3 (60W) PoE implementations). The updated table entries:

1. correct some errors in the original measurements,
2. increase the number of significant digits shown,
3. and reflect the final conductor ampacity rating tabulated by the application of true rounding (instead of rounding down) to the measured value.

In most instances, the conductor ampacity rating increases slightly, with the additional precision allowing more freedom in remote powering deployments. In no case, does the conductor ampacity rating decrease.

Siemon shielded category 6A and category 7_A cables (having 23 AWG and 22 AWG sized conductors, respectively) are mechanically rated to 75° C (167° F) and support 60W and higher dc power applications with the added benefits of greater heat dissipation, power efficiency, bandwidth, and noise immunity. The yellow highlighted cells from the 2020 NEC Table 725.144 excerpt above confirm that these cables are suitable for support of at least 500 mA per conductor/ 1 A per pair current levels in bundle configurations of up to 192 cables in 30° C (86° F) ambient temperature environments.”