Lightning, surges and grounding for the barn link

Why long runs get hit

A copper data cable ties two buildings’ electrical grounds together. A nearby strike can raise the ground at one building far above the other, and the difference pushes current through the cable into whatever is plugged in at each end: switch ports, cameras, the router. You don’t need a direct hit for this to happen.

Protect a copper run

1. One surge protector per building, mounted where the cable comes in, before any equipment.
2. Ground it. An Ethernet surge protector does nothing until it’s grounded. Ubiquiti’s, for example, must be grounded to a grounded metal structure or by a drain wire to a grounding point.
3. Keep the bond wire short and straight to the building’s grounding electrode. The electrical code’s rule for communications protectors (NEC 800.100) uses at least 14 AWG copper and no more than 20 ft, as one reference point.
4. Bond masts for bridge radios to the building’s grounding system, and put a surge protector on the radio’s cable inside.

What’s electrician work

Digging safely

• Call 811 first. It’s free; contact it a few business days before digging. Utilities mark their buried lines.
• Hand-dig near marks. Machines stay back from painted lines.
• Depth: NEC Table 300.5 covers power wiring. Burial depth for Class 2/communications cable is not settled by a source we read; check the local inspector.unverified One cable maker suggests 18–24 in without conduit and 8–10 in in conduit.
• Mark your own run on a sketch, and lay warning tape above it if you have it.

After a storm

• Check link lights at both ends of each outbuilding link.
• Look at each surge protector; some show damage or a dead indicator.
• Reboot the switch, bridge radios or converters at the far end.
• If a port is dead, move the cable to another port and replace the switch later.
• Repeated damage on a copper run: replace it with fiber.