Patent Application
20090004612
The present disclosure relates generally to gas-fired heating appliances and their controls, and more particularly to gas-fired heating appliance controls incorporating a flammable vapor sensor control device.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Residential and commercial gas-fired heating appliances, such as water heaters, typically comprise a main burner and a standing pilot burner disposed within a combustion chamber below a cylindrical water tank. The main and standing pilot burners are supplied with a fuel gas through a gas valve, and air through an air inlet screen. Such standing pilot water heaters vent the combustion air without the use of a fan, and operate independently of the electrical power within the building. While conventional water heater appliances of this type operate reliably and safely, there may exist the possibility that the burners could cause flammable vapors external to the appliance to be ignited. The resulting flame could potentially propagate out of the appliance into the ambient environment around the appliance.
Efforts to mitigate any potential hazard posed by the presence of flammable vapors in proximity to a gas burning appliance have been previously directed to a control circuit in connection with a sensor that responds to the presence of flammable vapors to effect a shut down of the burner (e.g., by closing the gas valve). In a known flammable vapor sensor control circuit, the sensor experiences a significant increase in electrical resistance when it is exposed to a concentration of flammable vapors meeting a predetermined threshold. In such an instance, the sensor element cuts off the electrical current to a solenoid-actuated gas valve to close the fuel gas supply to both the main burner and the standing pilot burner, thereby shutting off the burners. The control circuit can prevent further operation of the burners until service or replacement of the control circuit or sensor.
While replacement of the sensor is a routine procedure to restore operation of the burners, it is possible that an end user may short-circuit the flammable vapor sensor control circuit as a matter of convenience to restore operation of the gas-fired heating appliance. As such, the appliance would operate without the safeguard of the flammable vapor sensor control circuit, which is undesirable.
Several embodiments of the present disclosure provide for a tamper-resistant flammable vapor sensor control device to promote the safe operation of a gas-fired heating appliance. In one form, a control device for a gas-fired heating appliance includes a gas valve module, a flammable vapor sensor module and a power module. The gas valve module includes a gas valve adapted to supply a fuel gas to the gas-fired heating appliance. The flammable vapor sensor module detects the presence of a flammable vapor in an operating environment of the appliance. The power module provides an input to the flammable vapor sensor module. The flammable vapor sensor module provides an output to the gas valve module to maintain the gas valve in an open state. The flammable vapor sensor module interrupts the output to the gas valve module when a predetermined concentration of a flammable vapor is detected.
In another form, a gas-fired heating appliance includes a fuel gas burner and a flammable vapor sensor control device. The flammable vapor sensor control includes a gas valve adapted to supply a fuel gas to the burner when in an open state, a flammable vapor sensor module for detecting the presence of a flammable vapor in an operating environment of the appliance and a power module. The flammable vapor sensor module provides an output to the gas valve module to maintain the gas valve in the open state. The power module provides an input to the flammable vapor sensor module. The flammable vapor sensor module interrupts the output to the gas valve module when the flammable vapor sensor module detects a predetermined concentration of the flammable vapor in the operating environment.
In yet another form, a flammable vapor sensor control system for a gas-fired heating appliance includes a power module, a flammable vapor sensor module and a gas valve module. The power module includes a thermocouple. The flammable vapor sensor module is operable to detect the presence of a predetermined concentration of a flammable vapor within an operating environment of the appliance. The gas valve module includes a solenoid-actuated gas valve adapted to supply a fuel gas to the gas-fired heating appliance when energized. The thermocouple generates an electrical potential, which is applied to the flammable vapor sensor module. The flammable vapor sensor module energizes the gas valve in a first condition when a predetermined concentration of the flammable vapor is not present in the operating environment of the appliance, and de-energizes the gas valve in a second condition when a predetermined concentration of the flammable vapor is present in the operating environment of the appliance.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring to
The gas-fired heating appliance 10 further includes a control device 20 for the gas-fired heating appliance 10. The control device 20 includes a power module 22, a flammable vapor sensor module 24 and a gas valve module 26. The power module 22 includes a thermocouple 28 disposed adjacent to a pilot flame and includes a pair of output terminals 30.
The gas valve module 26 includes a gas valve 32 for supplying a fuel gas to the appliance 10 and a solenoid 34 for energizing or de-energizing the gas valve 32. The gas valve module 26 controls the supply of a fuel gas through a supply line 36 to the burner 14. The control device 20 includes a knob 38 that must be depressed to supply the fuel gas while lighting a pilot burner flame.
The flammable vapor sensor module 24 is connected between the power module 22 and the gas valve module 26 for detecting the presence of a flammable vapor 40 in an operating environment of the appliance 10.
The flammable vapor sensor module 24 includes a chemiresistor sensor 42 for detecting the presence of flammable vapor 40. When the chemiresistor sensor 42 is exposed to flammable vapor 40, the resistance of the chemiresistor sensor 42 changes, indicating the presence of flammable vapor 40. Exemplary vapor sensor circuits and resistive vapor sensor elements are disclosed in U.S. Pat. No. 7,112,304, entitled “Robust Chemiresistor Sensor,” and U.S. patent application Ser. No. 11/286,985, filed Nov. 23, 2005, entitled “Temperature Compensated Vapor Sensor,” both assigned to the assignee of the present application, Therm-O-Disc, Incorporated, the contents of which are incorporated herein by reference in their entirety.
The thermocouple 28 is disposed adjacent to a pilot flame. When the thermocouple 28 is heated by the pilot flame, a voltage is created across the output terminals 30 of the thermocouple 28. The output terminals 30 of the thermocouple 28 are connected to the flammable vapor sensor module 24 so that the thermocouple 28 provides an input to the flammable vapor sensor module 24. The flammable vapor sensor module 24 may include a flammable vapor sensor circuit (not shown), which is connected in series or parallel with the power module 22. The flammable vapor sensor module 24 receives the voltage input from the power module 22 and applies a voltage output to the gas valve module 26. When the voltage is applied to the gas valve module 26, the gas valve 32 of the gas valve module 26 is energized to an open position and allows the fuel gas to flow from a gas source (not shown) to the heating appliance 10.
When the chemiresistor sensor 42 is exposed to flammable vapor, the resistance of the chemiresistor sensor 42 increases or decreases depending on the type of sensor and its application. As the resistance changes to a value corresponding to a threshold concentration of the flammable vapor 40, this changed resistance causes interruption of the power applied to the gas valve module 26, thereby de-energizing the gas valve 32, causing it to close and discontinue the flow of fuel gas to the burner 14. By discontinuing fuel gas to the burner 14, the burner 14 of the heating appliance 10 cannot serve as a possible ignition source for the flammable vapor 40. The operation of the gas-fired heating appliance 10 can be restored, for example, after the flammable vapor sensor module 24 is replaced or the control device 20 is otherwise serviced.
An exemplary operation of such flammable vapor sensor is disclosed in U.S. Pat. No. 7,112,059, entitled “Apparatus and Method for Shutting Down Fuel Fired Appliance”, the content of which is incorporated herein by reference in its entirety.
It should be appreciated that a vapor sensor control circuit assembly may be modified from that described, above, to accommodate a capacitive vapor sensor element such as that disclosed in U.S. patent application Ser. No. 11/297,752, filed Dec. 8, 2005 and entitled “Capacitive Vapor Sensor.” This patent application is assigned to the assignee of the present application, Therm-O-Disc, Incorporated. The contents of this application are incorporated herein by reference in their entirety.
Because the output terminals 30 of the thermocouple 28 are connected to the flammable vapor sensor module 24, an end user cannot easily circumvent the flammable vapor sensor module 24. If the end user attempts to short-circuit the flammable vapor sensor module 24, the output voltage of the thermocouple 28 cannot be applied to the gas valve module 26 and no fuel gas can be supplied to the burner 14 in the absence of the flammable vapor sensor module 24. Accordingly, the flammable vapor sensor control device 20 of the present disclosure resists tampering to promote a safe operation of a gas-fired heating appliance 10.
This description is merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
