| 摘要 |
<p>The duct for exhausting the combustion gases 13 opens out into the duct 1 for controlled mechanical ventilation in a zone which is at an underpressure with respect to atmospheric pressure, but having an underpressure whose absolute value is less than that of the zone of the duct 1 for controlled mechanical ventilation, which zone is situated downstream of the extraction mouth 4. An underpressure-generating member 3 is arranged in the duct 1 for controlled mechanical ventilation upstream of the extraction mouth 4. The duct for exhausting combustion gases 13 opens out into the duct 1 for controlled mechanical ventilation in a zone whose pressure is close to the pressure of the zone in which the combustion air required by the boiler is extracted. A pressure switch 5 measures the difference in pressure between a point in the duct 1 situated level with or downstream of the underpressure-generating member 3, and a reference pressure, and means are provided for triggering the safety device of the boiler when the differential pressure measured by the pressure switch 5 becomes less than a predetermined minimum value. <IMAGE></p> |
