The function of a mass stove

What is unique to the mass stove is the dispersal of heat throughout the mass. Rising smoke and heat from the grate flows up and throughout several flues that come down the sides and around the back before exiting out the chimney - this "heat-flow" of the mass stove is called "contra flow."

The primary air comes from below the fire through the ash door and the grate. From the fireplace the fire and smoke presses through a narrow throat into the upper combustion chamber along with the secondary air.

The secondary air presses up along the inside of the doors and is preheated from the fire. Therefore the air will not be cold when it arrives in the upper combustion chamber.

The upper combustion chamber is essential to "clean combustion."

There is abundant space and high heat (900 degrees C) to burn the gasses mixed with the secondary air.

From there the heat, fire and smoke are pressed to both sides and forced all the way down on each side through the sidechannels in each side - typical 8x50-70 cm. in cross section and 160-180 cm. high (5-6 sq.m. in each channel).

The heat accumulates in the channels so that the difference from the 900 degrees C in the upper combustion chamber to the 170 degrees C in the chimney dissipates in the stove.

To prevent a high heat loss the damper, placed at the exit to the chimney is closed when the fire has gone out.

When using a wood-burning stove it is important that the living space is properly ventilated. The total combustion uses 8 cubic metres of air pr. kg. wood.

The chimney should inside by minimum Ø20 cm. Traditional build chimneys with an inside measure of 25 x 25 cm are good.

The consumption of wood in a mass stove is around 12-20 kg. of wood  over 24 hours, depending of the size and construction of the stove. Typically you only burn one fire in 24 hours. The fire lasts around 1 1/2 hours.

The foundation under a mass stove should be at least 30 cm high standing on firm ground (the pressure is around 1.5 kg/cm2).

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Phone: 57 80 45 22, E-mail:, 26108225
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