of 24AWG conductors. Hence any IEEE standard compliant PoE system that supplies 60W or less does not
need additional cable consideration.
IEEE 802.3bt Type 4 systems (Class 7 and Class 8, 75W and 90W) do not qualify for the 0.3A exemption.
Therefore, the analysis for compliance to NEC moves to section 725.144:
Where Types CL3P, CL2P, CL3R, CL2R, CL3, or CL2 transmit power and data, the rated current per
conductor shall not exceed the ampacities in Table 725.144 at an ambient temperature of 30°C (86°F).
For ambient temperatures above 30°C (86°F), the correction factors of 310.15(B) shall apply.
Exception: Compliance with 725.144 shall not be required for installations where conductors are 24 AWG
or larger and the rated current of the power source does not exceed 0.3 amperes.
Types CL3P-LP, CL2P-LP, CL3R-LP, CL2R-LP, CL3-LP, or CL2-LP shall be permitted to supply power
to equipment from a power source with a rated current per conductor up to the marked ampere limit located
immediately following the suffix “-LP” and shall be permitted to transmit data to the equipment.
The following table is derived from Table 725.144, adjusted for 45°C ambient temperature using 310.15(B).
The values in green cells are accepted values for IEEE Type 4 PoE systems.
Figure 67: NEC 2020 Table 725.144 adjusted for 45°C ambient temperature
Analysis of the NEC 2020 Table 725.144, adjusted for 45°C, and the requirements of section 725.144 results
in Cisco’s recommendation to use Category 6a cables rated at 75°C, with 23AWG conductors, in bundles
sizes of 192 or less.
Cisco Catalyst 9400 Series Switches Hardware Installation Guide
180
Analysis of Cabling Requirements for IEEE 802.3bt Type 4 Devices
Analysis of Cabling Requirements for IEEE 802.3bt Type 4 Devices
To Next Page
Loading...
Need help?
General
