Sauna breaker and wire size

Breaker and wire questions

How many amps does a 2,600 watt sauna heater draw on 220 or 240 volts?

A 2.6 kW heater draws 11.8 A at 220 V and 10.8 A at 240 V: watts divided by volts. A sauna heater is a continuous load, so the circuit is sized at 125 percent of that draw, which puts it on a 15 A breaker with 14 AWG copper wire at either voltage.

Do these figures apply to a 230 volt supply outside the US?

No. Every figure on this page follows the US National Electrical Code and US wire gauges. Where the supply is 230 V, as in Europe and much of Africa and Asia, local wiring rules and metric cable sizes apply, so ask a local licensed electrician.

Is a 30 amp 220 V breaker enough for a sauna heater?

On 240 V, the supply often called 220 V, a 30 A breaker covers a heater up to 5.7 kW, with 10 AWG copper; on 208 V it covers up to 4.9 kW. A 6 kW heater draws 25.0 A at 240 V, and 125 percent of that is 31.3 A, so the general rule puts it on a 35 A breaker with 8 AWG copper. Of the 72 saunas in our catalog with a 6 kW heater, 43 publish a 30 A circuit instead. That is not necessarily an error: where a listed appliance is marked with its own branch circuit rating, that marked rating is what the installer follows.

Is a 40 amp breaker with 10/2 wire right for a 3 kW sauna heater on 110 V?

No. On a 120 V circuit, the supply often called 110 V, a 3 kW heater draws 25.0 A, and the continuous load rule asks for 31.3 A. A household 120 V circuit tops out at 20 A, about 1.9 kW of heater, so 3 kW is not a 120 V circuit, and a 40 A breaker does not make it one. The wire is wrong too: 10/2 cable is 10 AWG copper, which carries 30 A in the 60 degree C column, less than a 40 A breaker. On 240 V the same heater draws 12.5 A and needs a 20 A breaker with 12 AWG copper.

What size breaker and wire does a 3 kW sauna heater need?

On 240 V it draws 12.5 A and needs a 20 A breaker with 12 AWG copper. On 208 V it draws 14.4 A and needs a 20 A breaker with 12 AWG copper. On a 120 V circuit, often called 110 V, it draws 25.0 A, past the 20 A ceiling of a household circuit, so it is not a 120 V circuit.

What gauge ground wire does a 9 kW sauna heater need?

On 240 V a 9 kW heater draws 37.5 A and needs a 50 A breaker with 6 AWG copper. The ground is sized from the breaker, not the heater: NEC Table 250.122 puts a 50 A breaker on a 10 AWG copper ground, the same size it sets for every breaker over 20 A up to 60 A.

Can I use a 40 amp timer on a 9 kW sauna heater with a 50 amp breaker?

The breaker and the timer answer different questions. A 9 kW heater on 240 V draws 37.5 A, and 125 percent of that is 46.9 A, so the general rule puts it on a 50 A breaker with 6 AWG copper; the breaker protects that wire. A timer wired in line with the heater carries the heater's full 37.5 A for the whole session, so whether a 40 A timer may do that is set by the timer's own rating and listing, and by the heater maker's installation manual, which names the controls the heater was tested with. This page does not rate timers.

What breaker does a three phase sauna heater need?

The tables on this page are single phase. A three phase heater spreads its draw over three hot conductors, so the current on each is the power divided by 1.732 times the voltage: a 9 kW heater on a 208 V three phase supply draws 25.0 A per conductor, and the 125 percent rule puts it on a 35 A breaker with 8 AWG copper, against a 60 A breaker with 4 AWG copper on 208 V single phase. A heater can be wired three phase only where its maker's manual shows a three phase connection, and a licensed electrician confirms the supply.

Do these figures apply to a UK 13 amp socket or a European 16 amp circuit?

No. Every figure on this page follows the US National Electrical Code and US wire gauges. A UK 13 amp socket and a European 16 amp circuit are on a 230 V supply, where local wiring rules and metric cable sizes apply, so ask a local licensed electrician.