PoE++ for PTZ and Heated Cameras: What Power Do They Need?

A fixed dome camera draws a few watts for its sensor, encoder and network chip. A PTZ camera adds motors that pan, tilt and zoom, and many add infrared illuminators for night work. Long-range illuminators can draw as much as the camera itself, and wipers add short bursts on top. Outdoor models often add heaters and blowers to keep the window clear of ice and condensation, and to warm the electronics before they start in sub-zero weather.

Those extras can take the draw from under 10 W to 40 W or more, beyond the 25.5 W that PoE+ guarantees at the camera. That is where PoE++, the IEEE 802.3bt standard, comes in.

Type 3 sources can also deliver the lower classes over all four pairs. Our guide to how much power PoE delivers covers the voltages and the lower classes in more detail.

These are rough planning ranges. Always check the camera’s datasheet for its maximum and its PoE class.

The worst case for a heated camera is starting in the cold. At −30 or −40 °C many outdoor cameras run the heater first, sometimes for many minutes, and hold off the image sensor and motors until the housing is warm. If the port cannot supply the heater current, the camera may cycle on and off or never finish starting. Datasheets usually give separate figures for normal running and for heater-on or cold-start conditions; size from the larger one.

Some cameras state their power in terms of a pre-standard high-power PoE scheme, or ship with their own 60 W midspan. These schemes are not always compatible with IEEE 802.3bt sources, so check that the camera lists 802.3bt and the class it requests.

Once the housing is warm, many cameras cycle the heater on and off, so the average draw is well below the peak. The port and the budget must still be reserved for the peak, because the next cold start can come at any time.

Check two figures: the class each port supports and the total PoE budget. A recorder with four 90 W ports does not necessarily supply 360 W at once. Add up each camera’s worst case at the PSE, allow 10 to 20% headroom and make sure the total fits the budget. Our guide to PoE budgeting for multi-camera systems works through the arithmetic.

Two 802.3bt features help. With Autoclass, a camera reports its real maximum draw so the source reserves only what it needs, and LLDP power negotiation lets a camera request a precise figure. Both free up budget for other ports.

PoE++ uses all four pairs, so use Cat5e or better with every pair terminated. In large bundles Cat6A is the safer choice, because the cables warm as current flows and a tight bundle sheds heat slowly. On vehicles, M12 X-coded connectors carry four-pair PoE and hold under vibration. Size the recorder’s DC input for the whole load as well: four cameras at 60 W is 240 W of PoE before the recorder’s own draw and conversion losses.

Many recorders and computers stop at PoE+, so check the port class first. Our industrial NVRs include fanless Jetson recorders with four 90 W PoE++ ports and EN 50155 design for rail. PoE computers cover the range from PoE to PoE++ ports, while industrial PoE switches and PoE frame grabber cards with 802.3bt ports add high-power ports to an existing system. If only one or two cameras need PoE++, a single 802.3bt injector beside a PoE+ recorder is often simpler than replacing the recorder.