Protecting Network Equipment from Lightning and Power Surges

Every rainy season the same pattern repeats: a storm passes overnight, the internet is down in the morning, and the router or ONT won't turn on again. The lightning may not have struck your house at all. Hitting a power pole, a tree, or a cable at the end of the street is enough.

The good news is that most damage like this can be prevented with inexpensive equipment, as long as it's the right equipment on the right line.

Where surges come in

Direct strikes on a house are rare, and when they happen almost no household device survives. Far more common are indirect surges: a brief, very high voltage travelling along cables connected to the outside.

• The mains supply. The most common path. A strike near the distribution network spreads to many houses at once.
• Network cables leaving the building. A LAN cable to a guard post, the house next door, or an access point in the yard acts like a long antenna.
• Copper lines from the provider, such as phone lines for older services or coaxial cable. Fibre itself doesn't conduct electricity, but the ONT is still plugged into the mains.

Surges don't always come from lightning either. Power cutting out and coming back, or a water pump and air conditioner starting together, can cause small repeated surges. Once does no harm. Hundreds of times a year shortens an adapter's life.

Four devices that get confused

An ordinary power strip. It only splits the outlet. The switch and indicator light provide no protection at all. Many people feel safe using one, yet nothing has changed compared with plugging straight into the wall.

A power strip with surge protection. Inside are components that divert excess voltage to the earth wire. The signs are clear: the packaging lists a joule rating or maximum current, and there's usually a small light marked protected or grounded. This is the most sensible basic protection for a router.

A voltage stabilizer. Built for voltage that drifts slowly, for example in areas where it often drops to 180 volts at night. A stabilizer isn't designed for brief lightning surges, and routers with modern adapters usually don't need one. The adapter already accepts a wide voltage range.

A UPS. Its main job is keeping equipment running during a power cut, as covered in a UPS for your router during outages. Some UPS units also include surge protection, but quality varies widely. Check the specifications rather than assuming.

Earthing decides everything

This is the part most often skipped. A surge protector works by dumping excess voltage into the earth wire. If the wall outlet has no earth, the protector has nowhere to dump it.

Many houses in Indonesia, especially older buildings or those wired on the cheap, use outlets without an earth, or earthed outlets whose earth wire isn't connected to anything. To check:

• Look at the indicator light on the surge protector. Many products only light the grounded lamp when an earth is detected.
• Use a socket tester, a small plug-in device that shows whether live, neutral, and earth are wired correctly.
• Ask an electrician if unsure. Installing a proper earth is electrical work, not network work, and it benefits the whole house.

If you're building or renovating, this is the cheapest time to sort it out. Planning it alongside network cabling is covered in planning your network when building a house.

Don't forget the LAN cables

Protecting the power outlet while leaving a LAN cable running outside unprotected is like locking the front door and leaving the back door open. Surges arriving through LAN cables often kill specific ports on a router or switch, and sometimes the device at the other end too.

• Fit an Ethernet surge protector on cables leaving the building, near where the cable enters, and connect it to earth.
• For outdoor PoE-powered devices, choose a protector that supports PoE so power still flows. The basics are in PoE for networks, and outdoor installation is in outdoor access points.
• For long runs between buildings, fibre is the most complete answer because it doesn't conduct electricity at all.

When the storm actually arrives

If thunder sounds very close and you don't need the internet right now, unplugging the router and ONT adapters from the outlet is the surest protection. No device is more reliable than a few centimetres of air.

A few notes so the habit doesn't cause other problems:

• Unplug LAN cables that leave the building too, if any, not just the power.
• Don't unplug while lightning is striking close by. Unplug before the storm peaks, or wait until it passes.
• Give it time after switching back on. The ONT and router need a few minutes to reconnect. If things don't return to normal, the checking order is in network problems after a power cut.

If the damage is already done

Check the cheapest thing first. Often only the adapter has failed, not the router. How to check and choose a replacement is in replacing a broken router adapter.

• Router powers on but one port is dead: most likely the surge came through the LAN cable on that port. Move the cable to another port, then protect that line.
• ONT completely dead: the ONT usually belongs to the provider. Contact them rather than buying a replacement yourself. Provider equipment is generally replaced at no cost when the damage wasn't due to negligence.
• Router restarting often after a storm: a sign the adapter or power components are weakening. The symptoms match those in a router that keeps restarting.

Internet trouble in the rain doesn't always mean damaged equipment. Sometimes it's the provider's network, and the difference is covered in internet problems when it rains.

A sensible setup

For most homes, these three steps cover most of the risk:

1. Make sure the outlet the router uses has a proper earth.
2. Plug the router, ONT, and switch into a genuine surge protector, or into a UPS that actually has surge protection.
3. Protect every LAN cable that leaves the building, or replace it with fibre.

Add the habit of unplugging during big storms, and your network equipment has a much better chance of reaching its normal lifespan. Other upkeep is in keeping your router going longer.

Frequently asked questions