| 摘要 |
In a heating boiler intended for solid fuels in heating installations, having a draught control device, which is used for preventing or reducing chimney-side heat losses and which has a shut-off valve and a thermostatically adjustable servo-motor intended for adjusting the latter shut-off valve, to which heating boiler combustion air is delivered via an electrically driven fan, air is inadvertently drawn in from the outside, even when the fan is at a standstill, through the free intermediate spaces between the blades of the fan, with the result that the fire in the heating boiler does not come to a standstill, as intended. This disadvantage is eliminated by virtue of the fact that a louvre element is arranged securely on the outside of the fan, the slats of this louvre element being forcibly pivoted into the closure position when the fan is shut off.
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