Surge comes via cable, not from the sky
The most common scenario doesn't look like a disaster movie. A discharge hits a line, transformer, or the ground several hundred metres away – and the surge impulse travels to homes via power cables, sometimes also antenna and network cables. It lasts microseconds, nothing is heard, and in the morning, the photovoltaic inverter, router, and furnace controller don't start. There's more and more electronics in homes – and that's why the topic returns every summer.
"Surge protector" strip is the last line, not the first
A market strip contains a small varistor that can trim residual surge right at the device. The problem is that a large impulse can simply bypass or destroy it – a single strip cannot absorb the energy we're talking about during a storm. Effective protection is layered and starts in the distribution board:
- Type 1 SPD – "heavy artillery" for direct or close lightning strikes; used where the building has a lightning protection system or overhead line supply;
- Type 2 SPD – basic arrester in a flat or house distribution board; it removes the main energy of the impulse before it spreads through the circuits;
- Type 3 SPD / strip – only as a refinement for the most sensitive equipment (computer, studio, audio electronics), never instead of types 1–2.
Two conditions without which even the best SPD won't work: effective earthing (the arrester must have somewhere to discharge energy) and correct installation – short connection cables, proper selection for the network system. This is a typical element of our measurements during distribution board modernisation.
What to protect first
- photovoltaic inverter – the most expensive single "victim" of storms; the DC side requires its own arresters (we wrote about this in the guide on photovoltaic inspection);
- heat pump and recuperation – controllers and inverters are sensitive, and repair often means replacing the entire board;
- gate automation, boiler controls, alarm, video intercom – small items whose replacement can add up to thousands of zł.
SPD also wears out
A surge arrester wears out like brake pads. That's why modules have a status indicator (a window that changes colour) and replaceable cartridges. After every major storm, it's worth checking the distribution board: a red window means the cartridge has done its job and needs replacing – the house is left unprotected, even though everything "works".
Insurers are increasingly asking about surges when settling storm damage claims – an installation inspection report and documented surge protection facilitate the process.
Storm season ritual: after every major storm in the area, check the SPD indicators in the distribution board and the PV inverter messages. Don't have SPD at all? Installation in an existing distribution board is usually a single visit – book an appointment, you'll know the price upfront.
