When connecting the stove to the chimney below, cleaning the furnace of soot is generally unnecessary, for the soot falls as the gases flow ,to the chimney, not, they gather in the channels, cleaning is complicated in multi-channel furnaces connected to the chimney at the top. However, if in the furnace connected to the bottom, due to the use of the wrong type of coal, it will be necessary to clean the furnace, it does not require a skilled craftsman, because the soot is not removed to the outside, but they are skimmed into the chimney through the cleaning holes at the bottom of the furnace. For this type of stove, a chimney with a height is sufficient 3 meters.

I still need to add, that in stoves combined with a duct, chimney pit, Moreover, the exhaust gases heat the chimney walls along the entire height of the heated room.

At the bottom connection of the stove, in particular when using a furnace for the exhaust gas collection chamber, the heating surface of the furnace increases by the surface of the furnace (see chap. about furnaces with multipliers).

Obstacles to the proper movement of gases and conditions favoring the deposition of soot in the furnace are as follows:

a) design deficiencies in the furnace preventing proper fuel combustion in it,

b) unevenness and uneven sections of the channels in the furnace, roughness of the surface of the channel walls,

c) a large number of vertical channels, especially the horizontal ones.

Incorrect shape of the flue gas channels.

The collapse of the gas velocity in the multichannel furnace was determined as follows:
– at a bend at an angle of 45 °, the speed of gas flow decreases by 60%,
– at a refraction at 90 °, the speed of gas flow is reduced by 85%.