Short answer
Surge protection diverts a short voltage spike to earth, so equipment does not have to absorb it. Such spikes come from lightning strikes nearby and from switching operations on the grid. With a detached home, solar panels on the roof or expensive equipment it is sensible. It only works if the earthing is sound.
Who this article is for Anyone wondering whether that little device in the meter cupboard is worth it. Fitting it is installation work.
What a spike is
With a lightning strike in the area, even a few hundred metres away, a voltage spike is induced in the cables. That spike lasts microseconds but can be thousands of volts. Electronics cannot cope with that.
The same happens on a smaller scale with switching operations on the grid, when heavy motors are switched on and with faults in the street.
What a surge protector does
Normally it just sits there doing nothing. When a spike comes, it becomes conductive in the blink of an eye and diverts the energy to earth, after which it closes again. The voltage your equipment sees therefore stays within what it can handle.
That only works if the earth is sound. A surge protector on a poor earth has no way of getting rid of the energy. That is why I always measure the earthing first, see earthing and earth rod.
When it is really worth it
| Situation | Why |
|---|---|
| Solar panels on the roof | the cables on the roof pick up induction |
| EV charger outdoors | long cable, electronics in the charger |
| Detached home or rural area | long supply cable, more chance of induction |
| Home workspace, network, home automation | the damage is big, even with a small spike |
| Business premises with machines | downtime costs more than the surge protector |
In these cases the surge protector is nothing compared to what a spike costs.
In a terraced house without panels and without expensive equipment it is less urgent, but with a new consumer unit I usually include it anyway: the cost is negligible compared to the whole and the space is there anyway.
Types, briefly
There are three classes. In a home it is almost always type 2 in the meter cupboard, sometimes supplemented with type 3 right next to sensitive equipment. Type 1 is for buildings with a lightning protection system, so usually commercial.
With solar panels, a surge protector also goes on the DC side at the inverter if the cables are long.
Maintenance: just take a look
Every surge protector has a small window. Green means good, red means the cartridge has done its job and needs replacing. That is a matter of clicking out a module.
Look at it once a year, and certainly after a heavy thunderstorm. A surge protector showing red no longer protects anything, and you only notice at the next spike.
What the insurer does with it
Some policies give a discount or make it a requirement with solar panels. Ask. In the event of damage you are sometimes asked whether a surge protector was present; a test report or an invoice is then the proof.
From my own work
After a thunderstorm in Meerssen I came to a home where the router, the boiler, the inverter and two televisions had all broken at once. Lightning had not struck the house but had struck nearby. For the amount of that damage, a surge protector could have gone in the consumer unit three times over. With the new consumer unit it is in there now.
When to call an electrician
- You have solar panels or an EV charger and no surge protector in the consumer unit
- You live in a detached house or in a rural area
- There has been damage after a thunderstorm
- The insurer asks for it
Adding a surge protector is usually an hour's job, provided there is space in the consumer unit. Call +31 43 204 18 26 or request a quote.
Frequently asked questions
Is a surge protector compulsory?
In a home not always, but with solar panels and certain installations it is prescribed. Some insurers make it a requirement.
How do I know whether my surge protector still works?
Every surge protector has a small window. Green is good, red means the cartridge has done its job and needs replacing.
Does it protect against a direct lightning strike?
No. It catches the spike that arises in the cables when lightning strikes nearby. Against a direct strike on the building you need a lightning protection system.
Further reading
Is my meter cupboard still safe? 10 things you can see yourself
Ten things you can see yourself without unscrewing anything. If you recognise three or more, it is time for a chat.
How old is my installation really: these are the signs
Cloth-covered wiring, no RCD, screw-in fuses and unearthed two-pin sockets: each feature tells you something about the year it was built and the risk.
Type A, type B or type F RCD: which do you need
Type A is the standard. Type B only where DC leakage can occur, and that is less often than sellers say. Saves hundreds of euros.
Questions and comments
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