IEEE 802.3bt (PoE++) enables up to 90W of power delivery over structured cabling. While this unlocks powerful applications — PTZ cameras, LED lighting, wireless access points, digital signage — it also creates an engineering challenge that many cable specifications don't adequately address: conductor temperature rise.
The Temperature Rise Problem
When current flows through a copper conductor, resistive heating occurs (I-squared-R losses). At 90W delivery (approximately 960mA per pair at 48V), all four pairs in a CAT6A cable carry significant current simultaneously. The heat generated must dissipate through the cable construction and into the surrounding environment. If it cannot dissipate fast enough, conductor temperature rises.
Why Temperature Rise Matters
Elevated conductor temperature increases insertion loss. The TIA standard assumes 20 degrees C operating temperature — every 1 degree C increase adds approximately 0.4% to insertion loss. In a fully loaded 100-metre PoE++ channel operating at 40 degrees C ambient (common in ceiling plenum spaces), the combination of ambient temperature and PoE self-heating can push conductor temperature to 60 degrees C or beyond. This can erode the insertion loss margin that separates a passing channel from a failing one.
Cable Construction Factors
Three construction elements determine how well a cable manages PoE++ thermal load. Conductor diameter: 23 AWG (0.57mm) provides lower DC resistance than 24 AWG, generating less heat per ampere. Insulation material: HDPE has better thermal conductivity than foam PE, allowing heat to dissipate more effectively. Bundle size: cables in large bundles (24+ cables) cannot dissipate heat as effectively as individual cables, creating a thermal stack effect.
The Channeltech Advantage for PoE++
Channeltech CAT6A cables are designed with PoE++ thermal management in mind. Our 23 AWG solid copper conductors with HDPE insulation provide a DC resistance of 93 ohm/km maximum per pair — well within the TIA-568.2-D requirement. More importantly, our insertion loss margins (4.4 dB better than standard at 500 MHz) provide the headroom needed to absorb temperature-related IL degradation without risking field certification failure.
Practical Guidelines
For sustained PoE++ deployments: derate channel length by 10% for ambient temperatures above 40 degrees C. Limit bundle sizes to 24 cables maximum for full 90W loading. Use LSZH jacket variants in plenum spaces (lower thermal insulation than PVC). Verify that the selected CAT6A cable has been tested for PoE++ sustained power delivery — not just rated for it. Channeltech provides PoE++ temperature rise data upon request for engineering evaluation.