With factors such as geographic altitude, air quality, temperature, and heating value due to gas blending affecting the combustion efficiency of gas appliances, engineers are looking for new ways to keep their systems running efficiently. That’s why Dexen Industries decided to explore the use of efi technology in gas appliance applications.
The company believes that combustion efficiency can be controlled by monitoring carbon dioxide (CO2)—not oxygen—in the flue gas and modulating gas flow. The higher the CO2 concentration, the lower the pressure needed to generate less gas flow to the combustion chamber.
Applying that knowledge, the South El Monte, California, U.S.-based supplier developed Opti Control™. The device samples and measures flue gases and signals the gas control to modulate the gas flow and air intake. This is said to create a closed loop of the system after feedback with adjusted concentration level to the sensor.
Here’s how it works: Gas pressure of the control is adjusted by an electronically modulating regulator. A 5-V CO2 sensor monitors CO2 concentration in the exhaust coming out of the appliance’s combustion chamber. A 5-V controller then takes the data from the sensor and activates the modulation of gas control and the speed of the fan for induced air. Increased gas flow to the combustion chamber mixes with a proportional amount of air and generates a higher concentration of CO2. This higher concentration triggers the system to lower gas pressure and gas flow, resulting in a lower concentration of CO2.
For example, if a system reaches a CO2 concentration level of 9 percent, the controller takes data from the sensor and activates the gas control to lower the gas pressure. The benchmark combustion efficiency is 7.5 to 8.0 percent CO2. For added safety, the controller shuts off gas flow when CO2 reaches above 11 percent. When CO2 drops below 7 percent, the sensor shuts down, and gas control returns to the high-pressure setting and fan speed.
According to Dexen, the device simplifies gas control and gas appliance designs. Fewer parts means fewer points of failure and increased reliability, the company says, resulting in a gas appliance that is easier to manufacture, operate and maintain with greatly enhanced functionality. The company does warn, however, that the control’s performance is tied to the burner for which it is designed, so it is critical to properly maintain burners.
Possible applications for the control include gas ranges, washers and dryers, although the technology is currently being used in furnaces, burners and water heaters.