It is a common practice in power-drawing solutions to place orders based on the number of points and PoE ports. As a result, when fully loaded, the ports are shut down according to priority and the equipment is restarted repeatedly. The power account must be calculated in three layers: standard upper limit, equipment peak value, and overall machine budget. If the order is wrong, the work will be reworked.

Lock the upper limit of single port using power receiving standard

The output of the IEEE 802.3af port side is about 15.4W, and the power receiving end is about 13W after deducting the cable loss; the 802.3at (PoE+) port side is about 30W, and the power receiving end is about 25.5W; if you want to bring a high-power dome machine or a gimbal with electric heating and defogging, you can plan according to the 60W level of 802.3bt. The maximum working power of the camera should be written on the point table, taking into account full infrared, wiper and heating, instead of just reading the nominal typical value.

Then calculate the starting surge and simultaneous coefficients

• The instantaneous current when the gimbal is started and the infrared light is turned on can reach 1.5 to 2 times the steady-state power. It is safer to reserve port capacity at 1.3 times the steady-state power.
• Points in the same box will not enter the night vision peak at the same time. The simultaneous coefficient is generally 0.7 to 0.8, and the upper limit is used in high-density factory areas.
• Heated ball machines have hard peaks in winter, so it is recommended to calculate them as separate points and not share a budget with other points.
• Reserve 20% to 30% room for growth, and there is no need to replace the entire machine when adding points later.

Select equipment based on overall machine budget

The available power of a common 24-port PoE+ switch is often only about 370W, which is significantly lower than the theoretical value of 30W for each port. Ranking based on the theoretical value will inevitably exceed the budget. The method is to first summarize the actual total demand, and then select the equipment according to the 70% load rate: if the demand is 250W, it will fall to the 400W level. EB-LINK usually recommends writing this margin into the configuration sheet during project consultation, and comparing it with the actual measured port output power during acceptance. For the power supply division of fiber optic power taken from the pole side, please refer toSecurity video surveillance fiber optic transmission solution.