Breaker Size for a Sauna Heater
 

Planning to install a sauna heater with the following specifications:
5 KW
20.8 AMP
240 Volts

I have an existing 10/3 wiring that can be used to hook up the sauna heater to the Circuit breaker.

What amperage breaker size should I use for this connection?
Is a 10/3 cable sufficient for this type of sauna heater?

Appreciate your help!

30 amp breaker on the 10/3 cable will be fine. The heater likely only uses two of the wires for 240 volts. Simply cap of the white wire and leave it in the box.

Thank you and question
 

Thank you.

What would be the effect if a 20 amp breaker was used?

Does the manufacturer's installation instructions say which size and type of breaker to use?

No it does specify any breaker size. I was just wondering what happens if 20 amp breakers are used?

They will trip.

Unlikely at 20.8 amps.

If it runs at 20.8 I would suspect it would trip. If it occasionally hits 20.8 then I suspect it will not.

It would never trip at 20.8 amps...

The UL standard permits an OCPD to carry 134% of the device rating forever. It has to trip in no more than 60 minutes for 135% load.

Does that mean it would need 26.80 amps before it would trip?

Maybe, maybe not, depends on the actual trip curves of the manufacture, but, this is how UL tests a molded case breaker.

Depends on the breaker. I would NEVER put a known 20.8 amp load on a 20 amp breaker.

Neither would I, and that was never my intent, I was just sharing the true facts of UL standards.