Sauna Electrical Requirements: Breaker, Cable and RCD

A commercial sauna heater is a fixed electrical load, so it needs a dedicated circuit sized by an electrician to the heater rating, with its own isolator and residual-current protection. Controls and lighting run on separate low-voltage circuits. We state the supply on the submittal before the electrician wires the room.

Sauna Dekor Spa Solutions engineering team, Istanbul · project and press enquiries: Alican Aykaç, Managing Partner

Updated: 10 November 2026

A guide from Sauna Dekor Spa Solutions, an Istanbul manufacturer of saunas, hammams and steam rooms since 1987 — 40 years — with 5,000+ projects in 41+ countries.

That last sentence is not a formality. Both heater makers state that the heater may only be connected by an authorised electrician following the regulations in force where it is installed, and the local wiring rules in Dubai, Abu Dhabi, Doha or Riyadh can be stricter than the manufacturer’s minimum. This guide sets out what the manufacturers publish, what the international standard for sauna rooms, IEC 60364-7-703, adds, and what changes on Gulf supplies, so that the architect, the MEP engineer and the electrician start from the same numbers.

Table of contents

• What are the sauna electrical requirements?
• What size breaker does a sauna heater need?
• How do you work out the current from the kW rating?
• What cable size does a sauna heater need?
• Single-phase or three-phase?
• What changes on Gulf electricity supplies?
• Does a sauna need an RCD?
• Where can cables and controls go inside the sauna?
• What operating time limits apply?
• What else in the sauna needs power?
• What should be on the electrical drawing?
• Frequently asked questions

Six things: a dedicated supply sized from the heater manufacturer’s table, the right cable cross-section, protection as the local code and IEC 60364-7-703 require, wiring kept on the cold side of the insulation or rated for 170 °C, controls placed as the standard allows, and a licensed electrician to connect it. A typical 9 kW heater draws about 13 A per phase at 400 V.

The list is short because the heater manufacturer has already done most of the engineering. Harvia and EOS both publish, for every heater, the supply voltage, the breaker or fuse rating and the minimum copper cable cross-section, and both require that the breakers and connection cables conform with the regulations valid where the heater is installed. The electrician’s job is to reconcile the two: the manufacturer’s minimum and the local code, taking whichever is stricter.

What the manufacturer cannot know is the building. The cable length from the distribution board, the way the cable is installed, the ambient temperature in a Gulf ceiling void and the spare capacity on the board all change the final cable size and are decided by the MEP engineer, not by the heater manual.

From 3 × 10 A for a 4.5 to 6 kW heater up to 3 × 25 A for a 15.8 kW heater on a 400 V three-phase supply, based on the manufacturers’ published data below. The 8 to 10 kW range, which covers most villa and hotel saunas, sits on 3 × 16 A in both Harvia’s and EOS’s tables.

Two patterns show in the table. First, the jump from 3 × 10 A to 3 × 16 A happens between 6 and 8 kW, and the jump to 3 × 25 A between 12 and 15.8 kW. Second, the single-phase column grows much faster: the same 9 kW heater that sits on 3 × 16 A at 400 V needs a 50 A breaker and 10 mm² cable on 230 V, because all of the current flows through one conductor.

The table is a starting point for a heater that has already been chosen. How the heater itself is sized from the room volume, and how glass or stone walls push that choice up, is covered in our guide to types of sauna heaters.

For a balanced three-phase heater, divide the output in watts by 1.732 × 400 V; for single-phase, divide by 230 V. A 9 kW heater therefore draws about 13.0 A per phase at 400 V and about 39.1 A on 230 V. The breaker is the next standard size above that current, which is why 9 kW sits on 16 A and 50 A.

The same arithmetic across the range: 4.5 kW draws 6.5 A per phase or 19.6 A single-phase; 6 kW, 8.7 A or 26.1 A; 8 kW, 11.5 A or 34.8 A; 12 kW, 17.3 A three-phase; 15.8 kW, 22.8 A three-phase. The manufacturers’ breaker ratings in the table above follow these figures closely, which is a useful cross-check when a heater’s data sheet is missing a column.

Sauna heaters are resistive loads with no motor start current, so the calculation is simple. What it does not include is the rest of the sauna: lights, a fan and the control unit’s own supply. On EOS systems of 10 kW and more used with the Econ series, the heater’s second circuit runs through a separate power extension unit with its own 3 × 16 A supply, so the distribution board sees two circuits, not one.

At least the cross-section the manufacturer lists, in copper: 5 × 1.5 mm² for a 4.5 to 6 kW heater on three-phase in Harvia’s tables, and 5 × 2.5 mm² from the mains to the control unit for 7.5 to 10 kW in EOS’s Cubo 2+ data, with 5 × 1.5 mm² from the control unit to the heater. The single-circuit 12 kW Cubo 2+ with a Compact D18 control unit needs 5 × 4 mm². EOS states that all its figures are minimum cross-sections for copper conductors.

Minimum is the key word. Cable sizing in the building also depends on the length of the run, how the cable is installed and the temperature around it. A cable run through a roof void in a Riyadh villa in July is in a hotter environment than the same cable in a basement in Hamburg, and the MEP engineer applies the local code’s correction factors to reach the final size. The manufacturer’s figure is never reduced; it can only be increased.

The cable type matters as much as the size. The Abu Dhabi Electricity Wiring Regulations 2020, clause 7.5.6, require cables for high-temperature appliances such as electric heaters to be heat-resistant rubber or PVC insulated, with an over-sheath and stranded copper conductors. Harvia’s North American manual asks for copper wire suitable for 90 °C inside the sauna walls, and EOS requires at least 170 °C for any installation laid inside the cabin.

Three-phase for most heaters of 8 kW and above, and for every commercial sauna. The 400 V connection spreads a 9 kW load over three conductors at about 13 A each, where 230 V would put about 39 A through one. EOS allows 230 V single-phase only for Cubo 2+ heaters up to 9 kW, with 6 mm² cable.

Single-phase is common in apartments and small villas where the flat has no three-phase supply, and it works within the limits the manufacturers publish. The cost is in the cable and the breaker: 10 mm² and 50 A for a 9 kW Harvia Vega on 230 V, against 2.5 mm² and 16 A on 400 V. On a long run from the distribution board, that difference in copper is significant, and a smaller heater on single-phase is sometimes the better answer.

Both control and heater must be suitable for the chosen connection. EOS’s manual warns of a fire risk from improper connection and states that the control unit and the heater must both be suitable for 230 V 1N~ before they are wired that way. Our guide to a sauna in a bathroom covers the apartment case, where single-phase is usually the only option.

The voltage and, in Saudi Arabia, the frequency. In Abu Dhabi the supply is 230 V single-phase and 400 V three-phase at 50 Hz, according to clauses 4.1.2 and 4.1.4 of the Electricity Wiring Regulations 2020. Saudi Arabia uses 230/400 V at 60 Hz, and Qatar 240/415 V at 50 Hz. A heater rated for 400 V draws slightly more current and power on a 415 V supply.

The Qatar case is worth working through, because resistive heaters change output with the square of the voltage. A 9 kW heater rated at 400 V delivers about 9 × (415 ÷ 400)² = 9.7 kW on 415 V, and draws about 13.5 A per phase instead of 13.0 A. That is inside a 16 A breaker, but it is a question for the manufacturer and the MEP engineer, not something to assume.

For Saudi Arabia, the heater and its control unit must be rated for 60 Hz. Harvia’s Vega pages and the EOS Cubo 2+ manual both list 50/60 Hz, but not every accessory does, so the check is made on each nameplate. On our projects in Riyadh, such as the villa sauna and hammam in the Sedra community delivered in 2024, the equipment schedule records voltage and frequency for every powered item before ordering.

Approvals are local too. In Abu Dhabi, the Electricity Wiring Regulations give inspection and testing to the Licensed Contractor, and Dubai and the other Gulf authorities work on the same principle: the installation certificate belongs to the licensed contractor who connects it. Our Dubai office provides the heater data sheets, wiring diagrams and load schedule to the project’s MEP engineer and electrician, so that the circuit is designed before the sauna cabin arrives on site.

Every circuit of the sauna except the heater itself, under IEC 60364-7-703, which requires additional protection by residual current devices rated at no more than 30 mA. Local rules can go further: Abu Dhabi’s wiring regulations require 30 mA protection for all circuits in a bathroom. EOS notes a heater leakage current of up to 0.75 mA per kW.

The heater exception exists for a physical reason that EOS explains in its manual. If a heater stands unused for a long time, the insulation of its heating elements can absorb moisture from the air, and on the first heat-up the leakage current may trip a residual current device. EOS describes this as a physical process, not a fault, recommends switching the heater on every 6 weeks when it is not in regular use, and says the installation must be checked again if the device trips at commissioning.

The arithmetic shows why it matters. At 0.75 mA per kW, a 9 kW heater can leak up to about 6.8 mA in normal operation and a 15 kW heater about 11.3 mA, before any moisture effect. EOS also warns that no other consumers outside the sauna system should share an RCD with it. Where the local code requires 30 mA protection on the heater circuit as well, as in some bathroom installations, the electrician chooses the device and grouping with those figures in mind.

As little as possible, and only as IEC 60364-7-703 allows. The standard defines 3 zones: zone 1 around the heater, where only the heater’s own equipment may go; zone 2 below 1.0 m, with no special heat requirement; and zone 3 above 1.0 m, where equipment must withstand 125 °C and cable insulation 170 °C.

Zone 1 is the volume containing the heater, bounded by the floor, the cold side of the ceiling insulation and a vertical surface 0.5 m from the heater. Zone 2 is the rest of the room from the floor to 1.0 m. Zone 3 is everything above 1.0 m outside zone 1. The standard prefers wiring outside all three zones, on the cold side of the thermal insulation, and requires at least IP24 for equipment in the room, or IPX5 where cleaning with water jets can be expected.

Three placement rules follow. Socket-outlets are not allowed in the room that contains the heater. Switchgear that is not part of the heater equipment, such as the light switch, goes outside the sauna. And the heater’s control unit is mounted where its manufacturer specifies: EOS requires the timer to be outside the cabin and not overridable. The insulation side of the same question is covered in our guide to sauna ventilation, because vents and cable sleeves cross the same foil.

Home saunas are limited to 6 hours of operation with no automatic restart, and public saunas must leave the heating elements unpowered for at least 6 consecutive hours in every 24, as the EOS Cubo 2+ manual sets out. The timer that enforces this disconnects the heater completely and sits outside the cabin.

For a hotel, the second rule shapes the operating schedule. A spa open from 06:00 to 23:00 has the sauna heated for up to 17 hours, which leaves 7 hours unpowered overnight and meets the 6-hour requirement with 1 hour to spare. A 24-hour gym sauna does not, and needs either a scheduled shutdown or a second room. Our note on the gym sauna covers commercial duty in more detail.

EOS adds that heaters in public saunas are operated under the supervision of personnel, which is why a hotel control unit can be set up differently from a villa one. The control unit’s instructions describe which operating modes are permitted in each case, and the electrician configures it at commissioning.

Typically 3 other loads: lighting, a ventilation fan and the control unit’s own electronics, plus accessories such as an evaporator or a fragrance pump in some designs. They are small next to a 9 kW heater, but each one needs a circuit that the IEC 60364-7-703 residual current requirement applies to.

Lighting in the room is usually low-voltage LED fed from a driver outside the cabin, which keeps mains voltage out of zone 3; a steam room uses the same separation for a different reason, water rather than heat, as our guide to steam room lighting explains. Harvia’s manual asks for a vapour-proof light with its box flush with the panelling, 150 mm below the ceiling and not above the heater or the upper benches. The fan sits in the exhaust duct outside the room where possible. Which light sources are rated for sauna heat, and where each one goes, is set out in our guide to sauna lighting.

Only one heater per room is the rule in Harvia’s manual. Large commercial rooms that need more output than one heater provides use heaters designed for that purpose, or heaters controlled together through the manufacturer’s own extension units, and that decision is made with the manufacturer, not improvised on site. The running cost of those loads is part of the budget picture in our article on what a sauna costs in Dubai.

10 items, each traceable to a manufacturer’s table or a clause of IEC 60364-7-703, so that the electrician does not have to guess. A drawing that states heater model, voltage, frequency, breaker and cable for each circuit can be checked in a few minutes by the local authority’s inspector.

1. Heater model, output in kW and the manufacturer’s room volume range.
2. Supply voltage and frequency, checked against the heater and control nameplates (for example 400 V 50 Hz in the UAE, 60 Hz in Saudi Arabia, 415 V in Qatar).
3. Breaker rating per circuit from the manufacturer’s table, for example 3 × 16 A for 8 to 10 kW.
4. Minimum copper cable cross-section from the manufacturer, and the final size after the MEP engineer’s corrections.
5. Cable type suitable for heating appliances, and 170 °C rating for any length on the warm side of the insulation.
6. Residual current protection for every sauna circuit, 30 mA or as the local code requires, with the heater’s leakage current noted.
7. The zone 1, 2 and 3 boundaries drawn on plan and section.
8. Control unit and timer position outside the cabin, as the manufacturer specifies.
9. No socket-outlets and no light switch inside the room.
10. A note that the final connection is made and certified by a locally licensed electrician.

Sauna Dekor has designed and built saunas, steam rooms, hammams and pools since 1987: 40 years of manufacturing in Istanbul, in our own facility in İkitelli OSB, with a team of 19 employees, working under TS EN ISO 9001:2015, and with 5,000+ projects in 41+ countries. We design the sauna room, manufacture the cabin and benches, and install it with our own teams travelling from Istanbul; the electrical connection on site is made by the project’s licensed electrician. An infrared sauna cabin is wired from its own emitter manufacturer’s data in the same way.

We do not manufacture heaters, control units or residual current devices. EOS and Harvia make the heaters and controls in this guide, and any CE marking or EN 60335 conformity on that equipment belongs to its manufacturer. The TS EN ISO 9001:2015 certificate is ours. The figures above are copied from the manufacturers’ published data and the standard, and a manufacturer’s current manual always takes precedence over this page.