Harvia 20 SL Boiler is designed for people who want to conveniently heat their sauna from another room or outside the building. The recommended size of the sauna room is 8-20 m3. The stove can be connected to a separate water tank. All Harvia stoves for through-the-wall heating and Boiler models are equipped with a glass door to give that special feeling. The opening direction of the door can be changed.