IEEE 802.3af / 802.3at / 802.3bt Electrical Standard

PoE Voltage Drop & Cable Resistance Calculator

Verify terminal operating voltage and thermal power dissipation for IP CCTV cameras, Starlink PoE injectors, and Wi-Fi 6 access points. Prevent dusk camera brownout reboot loops caused by inferior CCA cabling.

Cable Run Length (Metres)

45m

Maximum standard certified Ethernet run length is 100 metres (328 ft).

Cable Conductor Material

PoE Power Class & Standard

Night Mode EXIR Infrared Boost

Simulate Night Mode Inrush Current (Peak draw when high-power EXIR LEDs ignite)

Electrical Telemetry

Loop Resistance

3.30 Ohms (Ω)

Round-trip conductor pair resistance

Voltage Drop

1.90 Volts (V)

Dissipated along conductor run

Terminal Voltage at Camera

50.1 V

PASS: Well above minimum 42.5V operating threshold. Zero reboot risk.

Why Cameras Reboot at Dusk: When daylight drops and high-power EXIR LEDs trigger, current draw doubles. On high-resistance CCA cables, voltage plummets below 37V, triggering a brownout reboot cycle.

Ohm's Law & The Physics of PoE Transmission

Power over Ethernet delivers direct-current (DC) power alongside high-frequency gigabit data over unshielded or shielded twisted pairs. Voltage attenuation across the run is governed by Ohm's Law and Joule heating:

V_drop = I_load × R_loop | P_loss = (I_load)² × R_loop | V_delivered = V_switch - V_drop

The Copper Clad Aluminium (CCA) Hazard: Inexpensive cables bought from online marketplaces often use aluminium wire with an ultra-thin electroplated copper skin. Aluminium possesses nearly 60% higher electrical resistance than solid annealed copper. Under high PoE+ loads (such as PTZ cameras or infrared illuminators), CCA generates dangerous thermal resistive heating inside ceiling voids and causes premature hardware failure. ADI Communications exclusively specifies pure solid copper Cat6 (23 AWG).

Experiencing Dropped Camera Connections or Night Reboots?

Gary Pearce diagnoses PoE voltage drops, replaces degraded cabling with solid bare copper Cat6, and certifies installations with professional network analyzers across Yorkshire.

Call Gary Pearce: 07860 244 274 Visit ADI Communications

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Need On-Site Engineering in Yorkshire?

Gary Pearce • 25+ Years Experience • £10M Public Liability • CAI-Benchmarked Materials

Call 07860 244 274 Visit Main Site