Surges come through the cable, not from the sky
The most common scenario does not look like a disaster movie. The discharge strikes a line, transformer, or the ground several hundred metres away - and the surge impulse travels to homes through power cables, sometimes also antenna and network cables. It lasts microseconds, nothing is heard, and in the morning the solar inverter, router, and boiler controller fail to start. There is more and more electronics in homes - and that is why this topic returns every summer.
A "surge protection" power strip is the last line of defence, not the first
A supermarket power strip contains a small varistor that can trim the remainder of a surge right at the device. The problem is that a large impulse can simply jump over it or destroy it - a single power strip is not able to absorb the energy we are talking about during a storm. Effective protection is layered and starts in the distribution board:
- Type 1 SPD - "heavy artillery" in case of a direct or nearby discharge; used where the building has a lightning protection system or overhead line power supply;
- Type 2 SPD - the basic surge arrester in the distribution board of a flat or house; it removes the main energy of the impulse before it spreads through the circuits;
- Type 3 SPD / power strip - only as a finishing touch for the most sensitive equipment (computer, studio, audio electronics), never instead of types 1-2.
Two conditions without which even the best SPD will not work: proper grounding (the arrester must have somewhere to discharge the 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
- solar inverter - the most expensive single "victim" of storms; the DC side requires its own arresters (we wrote about this in the guide on solar inspection);
- heat pump and heat recovery ventilation - controllers and inverters are sensitive, and repair often means replacing the entire board;
- gate automation, boilers, alarm, video intercom - small items whose replacement can add up to thousands of zł.
SPDs also wear out
An arrester absorbing surges wears out like brake pads. That is why modules have a status indicator (a window that changes colour) and replaceable cartridges. After every major storm, it is worth glancing at the distribution board: a red window means that the cartridge has done its job and needs replacement - the house is left without protection, even though everything "works".
Insurers are increasingly asking about surges when settling claims after a storm - an installation inspection report and documented surge protection make things easier.
Storm season ritual: after every major storm in the area, look at the SPD indicators in the distribution board and at the PV inverter messages. Don't have an SPD at all? Installation in an existing distribution board is usually a single visit - book a visit, you will know the quote upfront.
