PoE Switches for CCTV: How to Choose Ports, Power and Distance

IP cameras, Wi-Fi access points, IP phones and many access control devices take their power over the network cable, using PoE (power over Ethernet). The PoE switch at the centre of the system supplies that power, so choosing it correctly decides whether every camera stays on. It is also the easiest place to back up power for the whole system.

This guide covers port counts, power budgets, cable distance, uplinks and the choice between managed and unmanaged switches.

PoE standards in brief

PoE comes in several power classes:

• IEEE 802.3af (PoE): up to 15.4W per port, enough for most fixed cameras
• IEEE 802.3at (PoE+): up to 30W per port, for cameras with heaters, some PTZs and access points
• IEEE 802.3bt and Hi-PoE: 60W or 90W per port, for larger PTZ cameras and high-power devices

A camera's datasheet states its maximum power draw. Most fixed cameras draw only a few watts, a little more at night when infrared is on.

Power budget: per port and in total

Every PoE switch has two limits: the maximum per port, and the total budget for all ports. The total is often the one that catches people out.

The Dahua PFS3010-8ET-96, for example, has eight PoE ports with a 96W total budget. Eight fixed cameras drawing up to 7W each use 56W, which leaves comfortable headroom. Add a PTZ camera drawing 40W and the switch is near its limit.

To size a switch:

• List every powered device and its maximum draw from the datasheet
• Add them up, then allow 20 to 30 percent headroom for additions and ageing
• Check any high-power devices against the per-port limit and connect them to the high-power ports

Larger switches scale up: the has 16 ports with 190W, and the has 24 ports with 240W, each with two high-power ports for PTZ cameras.