Differential pressure responsive switch

A system of a differential pressure responsive switch with an operating diaphragm having a position controlled by a pressure which is to be monitored and acting via a transmission member upon an electrical switch in a gas heated boiler with combustion air being supplied under pressure to a combustion chamber comprising

• a first chamber divided by a control diaphragm,
• an inlet means applying the pressure which is to be monitored to one side of said control diaphragm,
• a bleed valve having a closure member carried by the other side of said control diaphragm and a valve seat,
• a throttle means connecting the side of said valve seat which is opposite to said control diaphragm to a source of operating pressure,
• pipe means connecting said side of said valve seat to a second chamber which is closed by the operating diaphragm,
• a spring means engaging the transmission member and acting against the pressure acting on the diaphragm in the second chamber,
• a third chamber divided by a second control diaphragm and located adjacent to said first chamber,
• a compression spring provided between said two control diaphragms,
• a first flow connection to said third chamber as an inlet for a second pressure to be monitored with said connection being provided at that side of said second diaphragm which is opposite to said first diaphragm,
• a second flow connection from said inlet means for said first chamber to the exhaust side of the combustion chamber,
• a third flow connection from said first flow connection to said third chamber to a combustion air supply,
• a fourth flow connection from the bleed off side of said bleed valve to the combustion chamber and
• a fifth flow connection from said throttle means to an operating pressure supply pipe.