Sauna Heater Contactor / also called a relay box or power box
Some sauna heaters controls work best when power switching is modulated thru a contactor. It’s a box separate from the heater and the controller
All 8,000 watt heaters and above usually require 40 amps or more at 240 voltage, a contactor limits the electricity flowing to the timer
A sauna heater contactor, e.g. on a 40 amp breaker will limit the electrical flow to the timer/controller to 30 amps, thus protecting the timer/controller against any electrical surges and being overwhelmed with too much power.
Freezing Conditions on a Relay / Power Box
Some sauna heater contactors (also called a relay boxes or power boxes) should NOT freeze. So if choosing a larger outdoor sauna, add this component to a well-insulated area in your home OR installed the contactor box in the area above the ceiling and below the roof line.