Sauna cabins (§703) — temperature zones, heat-resistant cabling and switchgear outside the cabin

The 701-bathroom guide and the 702-swimming-pools guide cover two "wet location" chapters of NEN 1010. §703 (based on IEC 60364-7-703) is a third, separate chapter for a location that is not primarily wet, but extremely hot: the sauna cabin.

Three temperature zones

Unlike the water-based zone layout of §701/§702, §703 divides the space based on distance to the sauna heater and height:

Zone	Description
Zone 1	The volume around the heater itself, bounded by the floor, the cold side of the ceiling insulation and a vertical surface approximately 0.5 m from the surface of the heater.
Zone 2	Outside zone 1, up to a horizontal plane about 1 m above the floor — ordinary equipment can usually be installed here.
Zone 3	Above the 1 m boundary up to the cold side of the ceiling and wall insulation — elevated heat requirements for equipment apply here again.

Cabling is preferably installed outside these zones, on the cold side of the thermal insulation. If a wiring run must pass through zone 1 or zone 3, the heat requirements below apply.

Heat-resistant cabling: minimum 170°C

Ordinary PVC cable (70°C) or XLPE cable (90°C) is not adequate in the hot zones of a sauna cabin. §703 requires cabling rated for a minimum of 170°C — in practice almost always a silicone rubber cable (typically rated for 170-180°C).

Note: this is not simply a matter of "choosing a slightly more robust cable" — a standard PVC or XLPE sheath can actually harden, crack or melt at the temperatures found around a sauna heater, with a direct risk of short-circuit or contact hazard.

Degree of protection and RCD

Equipment in the sauna cabin must be at least IP24 (protection against solid objects ≥ 12 mm and against splashing water from all directions) — a higher IP rating applies where cleaning with a water jet is to be expected.
All circuits in the sauna cabin must additionally be protected by an RCD with I∆n ≤ 30 mA, with the only exception being the heater's own circuit — unless the heater manufacturer specifically requires RCD protection.

Switchgear and socket-outlets

Switchgear for lighting must be installed outside the sauna cabin — not in the hot zones themselves.
Socket-outlets are not permitted in the location containing the sauna heater.
Control elements specific to the heater itself (for example the heater's own thermostat) may remain inside the cabin if the heater manufacturer allows this.

Practical relevance

When connecting or inspecting a sauna installation (domestic or in a wellness environment), first establish which part of the cabling lies in zone 1 or zone 3 — this determines whether a silicone cable is required. Next, verify that all lighting switchgear is actually mounted outside the cabin, and that all circuits (except possibly the heater) are connected via a 30 mA RCD.

Common mistakes

Using standard PVC or XLPE cabling in zone 1 or zone 3 of a sauna cabin — this does not meet the required minimum heat resistance of 170°C.
Mounting a light switch inside the cabin — lighting switchgear belongs outside the sauna room, not inside it.
Fitting a socket-outlet in the room containing the sauna heater — this is not permitted, regardless of the socket's IP rating.
Forgetting the 30 mA RCD requirement for other circuits (for example lighting or ventilation) because attention goes entirely to the heater connection.