Device and method for mixing combustible gas and combustion air, hot water installation provided therewith, corresponding thermal mass flow sensor and method for measuring a mass flow rate of a gas flow

A thermal mass flow sensor, comprising:

• a heating element;
• and
• a first, a second and a third temperature sensor,
• wherein the first and second temperature sensors are arranged on either side of the heating element and are arranged in one line with the heating element in a first direction, and wherein the third temperature sensor is arranged in one line with the heating element in a second direction, which differs from the first direction that lies substantially transversely of the second direction.

A method for controlling a device for mixing a combustible gas and combustion air for supplying to a burner, the device comprising:

• an air line for the supply of combustion air;
• a gas line for the supply of a combustible gas provided with a control valve;
• a first measuring line with a first outer end which is connected to the air line and a second outer end which is connected to the gas line;
• and
• a second measuring line with a first outer end which is connected to the first measuring line at a point between the first and second outer end of the first measuring line, thus forming a three-way intersection, and with a second outer end which is connected to the gas line and/or the air line,
• the method comprising:
• measuring a mass flow rate of a gas flow between the three-way intersection and the air line;
• measuring a mass flow rate of a gas flow between the three-way intersection and the gas line;
• opening the control valve if the mass flow rate of the gas flow between the three-way intersection and the gas line is a predetermined first threshold value smaller than the gas flow between the three-way intersection and the air line;
• and
• closing the control valve if the mass flow rate of the gas flow between the three-way intersection and the gas line is a predetermined second threshold value greater than the gas flow between the three-way intersection and the air line.

A method for measuring a mass flow rate of a gas flow in a device for mixing combustible gas and combustion air for supplying to a burner, the device comprising:

• an air line for the supply of combustion air;
• a gas line for the supply of combustible gas provided with a control valve;
• a first measuring line with a first outer end which is connected to the air line and a second outer end which is connected to the gas line;
• a second measuring line with a first outer end which is connected to the first measuring line at a point between the first and second outer end of the first measuring line, thus forming a three-way intersection, and with a second outer end which is connected to the gas line and/or the air line;
• a thermal mass flow sensor, comprising:
• a first temperature sensor arranged in the first measuring line and positioned such that it is situated in a gas flow between the three-way intersection and the air line during use;
• and
• a second temperature sensor arranged in the first measuring line and positioned such that it is situated in a gas flow between the three-way intersection and the gas line during use,
• the method comprising:
• determining the mass flow rate through the second measuring line on the basis of the value output by the first temperature sensor and the value output by the second temperature sensor.