Have you spent hours wondering why your POE device is not getting powered up? Replacing the cables and port on your network switch also does not help. Your device is not faulty, neither are the interconnects and switch. Where is the issue?
Let’s understand the concept of POE below that shall help unfold the mystery.
POE combines data and power over the same Cat-X cable making transmission of power and data simpler. IP cameras, VOIP phones, Wi-Fi access points are examples of equipment that run on POE eliminating the need to pull a separate power and data cable to each of them.
POE comes in 3 different variations
Standard POE: It delivers up to 15.4W of power per port
POE+: It delivers up to 30W of power per port
POE++: It delivers up to 60W / 100W of power per port
The network switches that you buy are rated for either one of these variants. POE++ / POE+ switch is backward compatible in the sense that it can work with devices that are POE rated. A POE switch on the other hand will not have enough power for a POE+ / POE++ device.
If you try to power a POE++ device using a POE+ or a POE switch you will be unable to power up the device. In some cases, the power LED on the equipment may turn on but it will not be able to function as designed.
You may also encounter situations where you have connected a POE++ device to a POE++ switch yet struggle to power it On. The catch here is the maximum POE power the switch is rated for. There are switches that are capable of supplying POE power on each of its port but have a maximum limit on the total power it can provide. Let’s try to understand this with an example.
We know that POE+ delivers up to 30W per port. For a 24-port switch that would mean it should be able to provide 720W of total POE power considering that each port consumes POE+ power to its maximum. However, on reading the specifications of network switches, you will often come across details which mention that a 24 port POE+ switch is rated for 360W of power. In simple words, it means that the POE+ network switch can provide 30W of power on each of its port but not more than 360W in total. Thus, if you already have 12 devices rated at maximum POE+ power consuming 360W, when you try connecting the 13th device it will not work.
Thus, selection of the network switch not only on the POE variant it supports but also its supported power budget for POE as a switch is important. If you are unsure of the POE rating of your equipment, POE++ is the safest bet to go with.
