Gas/air ratio control apparatus for a temperature control loop for gas appliances

Fuel/air ratio control apparatus for controlling operation of a burner of an appliance for heating water, said fuel/air ratio control apparatus comprising:

• a) a temperature measuring device for determining an actual temperature of water heated by the appliance and a controllable fan adapted to supply a predetermined air stream that is related to the determined actual temperature of water heated by the appliance;
• b) an air supply line adapted to supply the air stream to the burner through a restriction arranged in the air supply line;
• c) a fuel supply line adapted to supply fuel to the burner through a nozzle,
• d) a pressure sensing line adapted to transfer the absolute pressure of the air stream produced by the controllable fan, and
• e) a pressure-controllable valve connected to the fuel supply line and having a fuel outlet connection communicating with said burner, said pressure-controllable valve including a diaphragm separating first and second chambers that are sealed from each other, a main valve connected to said diaphragm adapted to regulate fuel flow in the first chamber, and a control valve adapted to be externally controlled exclusively in response to the absolute pressure transferred by said pressure sensing line, wherein said control valve communicates with said second chamber to enable said diaphragm to adjust the position of the main valve,
• wherein the air/fuel mixture applied by the fan and said pressure-controllable valve can be modulated in a range of from 20% to 100%.

Fuel/air ratio control apparatus for controlling operation of a burner of an appliance for heating water, said fuel/air ratio control apparatus comprising:

• a) a temperature measuring device for determining an actual temperature of water heated by the appliance and a controllable fan adapted to supply a predetermined air stream that is related to the determined actual temperature of water heated by the appliance;
• b) an air supply line adapted to supply the air stream to the burner through a restriction arranged in the air supply line;
• c) a fuel supply line adapted to supply fuel to the burner through a nozzle,
• d) a pressure sensing line adapted to transfer the absolute pressure of the air stream produced by the controllable fan, and
• e) a pressure-controllable valve connected to the fuel supply line, said pressure-controllable valve including a diaphragm separating first and second chambers that are sealed from each other, a main valve connected to said diaphragm adapted to regulate fuel flow in the first chamber, and a control valve adapted to be externally controlled exclusively in response to the absolute pressure transferred by said pressure sensing line, wherein said control valve communicates with said second chamber to enable said diaphragm to adjust the position of the main valve,
• wherein said control valve reduces the fuel pressure at said outlet connection in response to an air pressure drop in said pressure sensing line.

Fuel/air ratio control apparatus for controlling operation of a burner of an appliance for heating water, said fuel/air ratio control apparatus comprising:

• a) a temperature measuring device for determining an actual temperature of water heated by the appliance and a controllable fan adapted to supply a predetermined air stream that is related to the determined actual temperature of water heated by the appliance;
• b) an air supply line adapted to supply the air stream to the burner through a restriction arranged in the air supply line;
• c) a fuel supply line adapted to supply fuel to the burner through a nozzle,
• d) a pressure sensing line adapted to transfer the absolute pressure of the air stream produced by the controllable fan, and
• e) a pressure-controllable valve connected to the fuel supply line, said pressure-controllable valve including a diaphragm separating first and second chambers that are sealed from each other, a main valve connected to said diaphragm adapted to regulate fuel flow in the first chamber, and a control valve adapted to be externally controlled exclusively in response to the absolute pressure transferred by said pressure sensing line, wherein said control valve communicates with said second chamber to enable said diaphragm to adjust the position of the main valve,
• wherein the fuel pressure in the fuel supply line has a predetermined value, and a pressure at said outlet connection varies in response to a control pressure in said air pressure sensing line which is the same or smaller than the fuel pressure in the fuel supply line.

Fuel/air ratio control apparatus for controlling operation of a burner of an appliance for heating water, said fuel/air ratio control apparatus comprising:

• a) a temperature measuring device for determining an actual temperature of water heated by the appliance and a controllable fan adapted to supply a predetermined air stream that is related to the determined actual temperature of water heated by the appliance;
• b) an air supply line adapted to supply the air stream to the burner through a restriction arranged in the air supply line;
• c) a fuel supply line adapted to supply fuel to the burner through a nozzle,
• d) a pressure sensing line adapted to transfer the absolute pressure of the air stream produced by the controllable fan, and
• e) a pressure-controllable valve connected to the fuel supply line, said pressure-controllable valve including a diaphragm separating first and second chambers that are sealed from each other, a main valve connected to said diaphragm adapted to regulate fuel flow in the first chamber, and a control valve adapted to be externally controlled exclusively in response to the absolute pressure transferred by said pressure sensing line, wherein said control valve communicates with said second chamber to enable said diaphragm to adjust the position of the main valve,
• wherein said pressure-controllable valve has a safety mechanism for closing off fuel flow through said pressure-controllable valve.

Fuel/air ratio control apparatus for controlling operation of a burner of an appliance for heating water, said fuel/air ratio control apparatus comprising:

• a) a temperature measuring device for determining an actual temperature of water heated by the appliance and a controllable fan adapted to supply a predetermined air stream that is related to the determined actual temperature of water heated by the appliance;
• b) an air supply line adapted to supply the air stream to the burner through a restriction arranged in the air supply line;
• c) a fuel supply line adapted to supply fuel to the burner through a nozzle,
• d) a pressure sensing line adapted to transfer the absolute pressure of the air stream produced by the controllable fan, and
• e) a pressure-controllable valve connected to the fuel supply line and having a fuel outlet connection communicating with said burner, said pressure-controllable valve including a diaphragm separating first and second chambers that are sealed from each other, a main valve connected to said diaphragm adapted to regulate fuel flow in the first chamber, and a control valve adapted to be externally controlled exclusively in response to the absolute pressure transferred by said pressure sensing line, wherein said control valve communicates with said second chamber to enable said diaphragm to adjust the position of the main valve,
• wherein said control valve increases the fuel pressure at said outlet connection in response to an air pressure increase in said pressure sensing line.