Heater calculator
9. Heater sized to the room
An electric heater needs about 0.8 kW for every m³ of room, measured inside the panelling. Undersized, it runs flat out and never makes löyly, the steam.
10. Glass counts as extra room
A glass door or wall leaks the heat that wood panelling keeps in. For each m² of glass, add 0.6 m³ to the room volume before you pick the heater size.
11. Lots of stones, loosely stacked
Stones store the heat that turns water into steam, so a deep bed gives soft, lasting löyly. Stack 5 to 10 cm stones loosely so air passes, over every element.
12. Stones take time to warm up
A deep stone bed takes about 1 h to heat through, longer than a bare-element heater needs to warm the air. The soft heat and the löyly are worth the wait.
13. Sensor above the heater
The sensor sits over the stones, just under the ceiling, where the manual puts it. By the door or the inlet it reads cold air and never stops the heater.
14. Safety first
Keep the heater's stated distances to wood, or it chars over the years and ignites. The circuit, cable and earth-leakage protection follow local code.