Power-over-Ethernet for Outdoor Node Deployments
Power over Ethernet (PoE) is an excellent choice for outdoor nodes at sites with structured cabling infrastructure. It combines power delivery and network connectivity in a single cable, simplifying installation and enabling remote management.
PoE Standards
| Standard | Max Power (at PSE) | Typical Use | Common in |
|---|---|---|---|
| IEEE 802.3af (PoE) | 15.4W | IP cameras, VoIP phones | Most infrastructure |
| IEEE 802.3at (PoE+) | 30W | PTZ cameras, APs | Modern switches |
| IEEE 802.3bt (PoE++) | Type 3 = 60W; Type 4 = 90W (≈71W delivered at the powered device) | Laptops, high-power APs | Newer switches |
| Passive PoE (non-standard) | Varies | Low-cost IP cameras, some APs | Ubiquiti older hardware |
The 802.3bt maximum is 90 W at the power-sourcing equipment (Type 4), not 100 W — "100 W PoE" is a marketing rounding, not the IEEE spec figure.
For mesh nodes, IEEE 802.3af is more than sufficient. Most nodes consume 1-5W.
Active vs. passive PoE — not interchangeable. Standard (802.3af/at/bt) PoE negotiates voltage between the switch and the device (roughly 44 - 57 V) and is safe for compliant gear. Passive PoE simply puts a fixed voltage (often 24 V or 48 V) on the cable with no negotiation, and can damage equipment if mismatched. Match injector, splitter, and node carefully — a passive 24 V injector paired with a splitter that expects active 48 V may deliver no power or fry the node.
Maximum Cable Run Distance
PoE follows the Ethernet 100m (328 ft) cable run limit. Choose by distance:
- Single run ≤100m: a standard PoE run works directly.
- ~100 - 200m: use a PoE extender (repeater) at the 100m mark to extend another ~100m.
- Beyond ~200m: use a fiber optic run with a media converter.
- Use cellular or WiFi for power-independent remote nodes.
Note: independent of distance, a fiber optic break between the building and the node is also the strongest lightning isolation option (see below) because fiber is dielectric — consider it on any outdoor run in a high-lightning area, not only for long runs.
Lightning Protection for PoE Runs
An Ethernet cable run to an outdoor node creates a lightning risk - the cable can couple surge energy into your equipment:
- Ethernet surge protector: Install a PoE-compatible Ethernet surge protector (e.g. Ubiquiti ETH-SP-G2, ~$15 as of 2026-06-08 — confirm current price on the Ubiquiti store) at both the building entry and the outdoor node enclosure. This is essential for any outdoor Ethernet run.
- Fiber optic break: Insert a fiber optic run between the building and the outdoor node. Fiber is dielectric - it cannot carry surge current. Best protection option.
- Grounding: Properly ground your outdoor enclosure and the surge protectors. The surge protector's ground and the enclosure ground must be bonded to the same grounding electrode system as the building's AC ground (per NEC 250.94) — bonding to a separate, isolated ground rod creates dangerous ground-potential differences during a strike. Tie all ground connections into that single building grounding electrode system.