§443 — Surge Protection (SPD)

An SPD (Surge Protective Device) protects an installation against temporary overvoltages of atmospheric origin (lightning strikes, including those at a distance) or of switching origin (for example, switching off large inductive loads). This is a different risk from what an RCD (§531) or earth-leakage protection protects against — an SPD does not intervene on an earth fault, but limits a brief voltage spike on the mains.

When is an SPD mandatory?

NEN 1010 §443 makes surge protection mandatory when the consequences of an overvoltage affect:

1. Human life — for example, emergency services, medical facilities.
2. Public services and heritage — for example, data loss at data centres, damage to museums.
3. Commercial or industrial activity — hotels, banks, industry.
4. Large groups of people — large office buildings, schools.

The risk assessment of §443.5

If an installation does not automatically fall under the categories above, a risk assessment according to §443.5 must be carried out — a calculation method with a calculated risk level (CRL) that determines whether protection is required.

Important (fail-safe rule): if this risk assessment is not carried out, the installation must nevertheless be fitted with surge protection despite the absence of a calculation. Skipping the risk assessment is therefore not a way to escape the requirement — it has the opposite effect.

Type 1, 2 and 3 (§534)

The choice and placement of the SPD type is dealt with in §534, and installers often confuse this with §443 (the question of whether an SPD is needed), while §534 answers the question of which type and where:

A combined type 1+2 (or a combined device) is common for buildings with their own lightning protection system; type 2 alone is usually sufficient for an ordinary mains connection without its own LPS.

Practical example — PV installation

For solar panel systems (§712), surge protection is especially relevant: long DC cable runs across the roof increase the induced loop area during a nearby lightning strike. See the recommendations for type-2 AC and DC SPDs in the PV guide.

Common mistakes

1. Confusing surge protection with earth-leakage protection — an RCD detects leakage current to earth, an SPD limits a voltage spike; the two do not replace each other.
2. No risk assessment and no SPD — the statutory default when a §443.5 assessment is missing is precisely to install an SPD, not the other way around.
3. Installing only a type 3 at a socket outlet adapter, assuming this offers sufficient protection for the whole installation — type 3 only works as a supplement, close to the device, downstream of a type 1/2 further up.
4. Confusing SPD placement (§534) with the application obligation (§443) — an installer who only looks at §534 may miss that the application was already mandatory under §443.

Related

• §531 — Residual Current Devices (RCD)
• §712 — Solar power systems (PV): type-2 AC/DC SPD placement for PV.