PoE switch for IP cameras: 802.3af, at and bt, and how to size it
One Ethernet cable carries a camera's video, control and power. The switch has to deliver enough power on every port and enough in total, and the standard each port speaks decides which cameras it can run.
PoE standards and classes
The switch puts out more than the camera receives, because some power is lost in the cable. Size cameras against the device column and switches against the switch column.
| Standard | Type | Class | At the switch | At the camera |
|---|---|---|---|---|
| 802.3af (PoE) | Type 1 | 0–3 | 15.4 W | 12.95 W |
| 802.3at (PoE+) | Type 2 | 4 | 30 W | 25.5 W |
| 802.3bt (PoE++) | Type 3 | 5 | 45 W | 40 W |
| 802.3bt (PoE++) | Type 3 | 6 | 60 W | 51 W |
| 802.3bt (PoE++) | Type 4 | 7 | 75 W | 62 W |
| 802.3bt (PoE++) | Type 4 | 8 | 90 W | 71.3 W |
802.3af and 802.3at power over two pairs of the cable; 802.3bt uses all four.
802.3af is enough for
Most fixed domes, bullets and turrets, including many with IR.
802.3at for
Cameras with strong IR, motorised lenses, small PTZ cameras and housings with heaters.
802.3bt for
Full PTZ cameras with heaters and wipers, multi-sensor cameras and cameras with built-in illuminators.
Sizing the switch
- Per port. Every port must support the class of the camera on it. A Type 4 PTZ will not start on an 802.3at port.
- Total budget. Add the maximum power of every camera from its datasheet, with IR on and heaters running, not the typical figure.
- Headroom. Keep about a quarter of the budget spare for cold nights, added cameras and aging power supplies.
- Uplink. The sum of the camera streams has to fit the uplink to the recorder, with room to spare.
- Management. A managed switch gives VLANs to keep cameras apart from office traffic, and lets you restart a camera by cycling its port.
Cable limits
- 100 m from switch to camera, the Ethernet channel limit, whatever the PoE class: 90 m of installed cable plus up to 10 m of patch cords.
- Heavier power needs better cable. Long 802.3bt runs lose more power on thin or copper-clad aluminium cable; use solid copper Cat 6.
- Beyond 100 m, put a PoE extender or a small switch in the run, or bring fibre to a switch near the cameras. Some switches offer a long-range mode at reduced speed.
PoE in CCTVplanner
- The design check compares the cameras' PoE draw with the budget of the PoE switches and recorders you place.
- It flags cameras whose datasheet power needs a higher PoE class than a standard port gives.
- Cable routes give every run its length, and copper runs longer than the 90 m installed limit are flagged before the cable is pulled.
PoE questions
What is 802.3bt?
The IEEE PoE standard from 2018, also sold as PoE++. It powers over all four pairs of the cable and delivers up to 60 W at the switch (Type 3) or 90 W (Type 4), which is 51 W and 71.3 W at the device.
Which PoE standard do IP cameras need?
Most fixed domes, bullets and turrets run within 802.3af. Cameras with strong IR, heaters or motors need 802.3at, and PTZ cameras with heaters or multi-sensor cameras often need 802.3bt. The camera datasheet states the class or the maximum power.
How big a PoE budget does my switch need?
Add up the maximum power of every camera from its datasheet, including IR and heaters, and keep about a quarter of the budget spare. Each port must also support the class its camera needs.
How far can PoE run?
100 m from the switch to the camera, the same limit as Ethernet. Longer runs need a PoE extender, a switch closer to the cameras, or fibre.
Can I use a PoE switch with any IP camera?
With any camera built to the IEEE standard, yes: the switch detects the camera and only then powers it. Passive 24 V PoE, used by some older equipment, is not IEEE and can damage devices that do not expect it.