Condensation gas boiler connected to a controlled mechanical ventilation installation

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. LE CONDUIT D'EVACUATION DES GAZ DE COMBUSTION 13 DEBOUCHE DANS LA CONDUITE 1 DE VENTILATION MECANIQUE CONTROLEE DANS UNE ZONE EN DEPRESSION PAR RAPPORT A LA PRESSION ATMOSPHERIQUE, MAIS PRESENTANT UNE DEPRESSION DONT LA VALEUR ABSOLUE EST INFERIEURE A CELLE DE LA ZONE DE LA CONDUITE 1 DE VENTILATION MECANIQUE CONTROLEE, SITUEE EN AVAL DE LA BOUCHE D'EXTRACTION 4. UN ORGANE DEPRIMOGENE 3 EST DISPOSE DANS LA CONDUITE 1 DE VENTILATION MECANIQUE CONTROLEE EN AMONT DE LA BOUCHE D'EXTRACTION 4. LE CONDUIT D'EVACUATION DES GAZ DE COMBUSTION 13 DEBOUCHE DANS LA CONDUITE 1 DE VENTILATION MECANIQUE CONTROLEE DANS UNE ZONE DONT LA PRESSION EST VOISINE DE LA PRESSION DE LA ZONE DANS LAQUELLE EST EXTRAIT L'AIR COMBURANT NECESSAIRE A LA CHAUDIERE. UN PRESSOSTAT 5 MESURE LA DIFFERENCE DE PRESSION ENTRE UN POINT DE LA CONDUITE 1 SITUE AU NIVEAU OU EN AVAL DE L'ORGANE DEPRIMOGENE 3, ET UNE PRESSION DE REFERENCE, ET DES MOYENS SONT PREVUS POUR DECLENCHER LA MISE EN SECURITE DE LA CHAUDIERE LORSQUE LA PRESSION DIFFERENTIELLE MESUREE PAR LE PRESSOSTAT 5 DEVIENT INFERIEURE A UNE VALEUR MINIMALE PREDETERMINEE.