Choose a UniFi PoE switch or injector

Goal and prerequisites

Select a power source that supports each device and enough total capacity for the installation. Check three independent things: the endpoint's required PoE mode, the power available on its individual port, and the switch's overall PoE budget. Also check data speed, because an electrically compatible port can still limit network throughput.

Use the exact model and hardware specification. A product family name, an RJ45 socket or a wattage printed on an adapter is insufficient to establish compatibility. Some equipment uses passive power, and Ubiquiti warns that passive adapters can apply voltage without negotiation. Follow the supported pairing instead of experimenting with voltage or pin assignments. [1]

Build a power worksheet

The following is a planning example using the manufacturer's listed maximum device consumption. It is not a measurement of a running installation. [2] [3] [4]

Item Quantity Listed power method Maximum consumption each Endpoint total
U7 Pro access point 1 PoE+ 21 W 21 W
G5 Bullet camera 2 PoE 4 W 8 W
Endpoint total 3 Three powered ports needed 29 W

The USW-Lite-8-PoE has four PoE+ ports and a 52 W total PoE budget. Three suitable powered ports are available for this example, and the 29 W endpoint total leaves capacity for cable losses and variation. For this tutorial, use a planning target of at most 80% of the advertised switch budget: 52 W x 0.80 = 41.6 W. This 20% reserve is an example design choice, not a manufacturer requirement. Confirm the final installation's actual allocation and operation.

Select and connect the equipment

  1. Inventory every endpoint. Record model, required PoE mode, maximum consumption, data-link capability and location. Include any downstream devices powered through a passthrough device. For those products, the input supply and passthrough budget must be checked together.
  2. Check individual compatibility. Confirm that each proposed port supports the endpoint's required power method. PoE, PoE+ and PoE++ describe different power capabilities, but the precise specification and the manufacturer's compatibility list govern the pairing. Do not force a legacy passive mode merely because automatic power did not start.
  3. Count powered ports. A switch with eight Ethernet sockets need not have eight PoE outputs. In the example, only four are powered. Reserve an unpowered port for the uplink if practical, keeping the powered ports available for endpoints.
  4. Check the total budget. Add the maximum endpoint loads and compare them with the switch's budget using the actual power supply and input method. Some switches have different budgets under different supplies. Allow for distribution losses and future additions rather than allocating every advertised watt.
  5. Evaluate an expansion before buying it. Adding a second U7 Pro changes the example to 21 + 21 + 4 + 4 = 50 W. Four PoE ports would be occupied and only 2 W would remain below the nominal 52 W budget. That is too close for the reserve chosen here; select a switch with more capacity or use a separately powered, approved injector for an endpoint.
  6. Check the data path. The Lite 8 PoE has 1 GbE ports, whereas the U7 Pro supports a 2.5 GbE uplink. That pairing can power the AP but limits this wired link to 1 GbE. Choose a compatible multigigabit PoE switch when the required design includes faster AP uplinks. [2] [4]
  7. Label and connect one device at a time. Label both ends of each cable. For an injector, connect its data input to the LAN and its powered output to the intended endpoint. Apply power, wait for the endpoint to start and confirm both its identity and link before adding the next device.
  8. Inspect switch telemetry. In UniFi Devices, open the switch and its port information. Record negotiated link speeds, reported PoE draw and any overload or power-denied events. Compare the reported values with your worksheet, recognising that idle draw is usually different from the maximum specification.

Verify under realistic load

Operate all APs and cameras together. Include a wireless transfer and camera night mode if that is part of the actual use case. Watch for repeated disconnects or restarts and recheck the switch's power events. A brief idle test does not establish that a nearly exhausted budget is adequate.

Troubleshooting and recovery

If one device stays off, verify the exact power mode, powered-port selection and cable using a known-good supported pairing. If several devices fail only after another is connected, inspect the overall budget. If power is stable but speed is low, diagnose the Ethernet link separately.

Disconnect an incompatible or over-budget addition and return to the last working configuration. Update the worksheet whenever devices, power supplies or cable paths change.

Sources

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