Outdoor Units Failing in Storm Season: Surge Protection and Earthing

What it looks like

After one storm, outdoor APs, bridges and even switch ports in the same area fail together. Damage concentrates at network ports, PoE ports and power inlets — the classic surge entry paths.

Likely causes

Ordered from most to least common:

• No equipotential bonding: the enclosure and pole are not earthed, leaving no path for surge energy
• Cable is the main entry path: outdoor cable behaves like an antenna and carries surge indoors
• No protector on the PoE side: surge travels down the PoE run into the switch
• High earth resistance or an over-long earth lead: the discharge path is ineffective
• Units on isolated high points such as standalone poles or roofs are more likely to be struck

Diagnostic steps

Follow in order.

• Map the damage: devices only, or switch ports too? The latter means surge came down the cable
• Inspect earthing: are enclosure, pole and cabinet bonded to one earth electrode, and does resistance meet spec
• Inspect cable routing: is the outdoor run in conduit, is it shielded, is the shield earthed at both ends
• Confirm a surge protector is fitted on the PoE side, mounted close to the device
• Check for a potential difference between separate earth points

Fix and prevent

Fix: complete the equipotential bonding and fit matched surge protectors at both the outdoor device and the switch. Prevent: put earthing and protection hardware in the outdoor project budget rather than treating it as optional, and record earth resistance measurements at handover.