Perimeter drop — 212 W load, but Type 4 per port

PoE sizing runs two independent floors. The aggregate floor covers the summed draw plus a 30% margin; the per-port floor asks what IEEE class the single hungriest device needs at the PD end — 802.3af at or below 12.95 W, PoE+ at or below 25.5 W, 802.3bt Type 3 at or below 51 W, Type 4 at or below 71 W. The recommended tier is whichever floor is higher, because a switch that cannot deliver a device's class on one port cannot power it regardless of how much pool it has spare.

Here the device load is 2×55 + 4×12 + 6×5 + 2×12 = 212 W, or 276 W with 30% headroom — small enough that aggregate wattage alone would settle for a 24-port PoE+ switch. But the hungriest device is a 55 W heated PTZ, and 55 W is above the 51 W Type 3 PD ceiling, so it needs 802.3bt Type 4 ports. That per-port class floor outranks the aggregate floor and lifts all fourteen devices onto a 48-port PoE++ Type 4-capable tier — the whole teaching point that a low total can still demand a high-class switch.

The mechanism is monotonic in the largest device, not the total. Drop the heated PTZ for a standard 30 W PTZ and the per-port floor falls to Type 3; drop to IR cameras only and it falls to PoE+. Adding more low-draw readers or intercoms grows the pool but never lowers the class floor — so the single most demanding camera on the drop is what you size the switch ports around.

The tool sizes the port class and the shared pool; it does not model the long outdoor cable runs a perimeter drop implies, voltage drop or Cat6a distance derating, surge and grounding for exposed heads, or the heater duty cycle that makes a heated PTZ draw its full 55 W only in cold conditions. It assumes each PTZ can be fed at Type 4 from its port — verify the switch is genuinely Type 4-capable, not merely labelled PoE++.