PILOTLESS, UNPLUGGED COMBUSTION CONTROL SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an automatic, self-sufficient combustion control method and system. In one aspect, this invention relates to fuel-fired heating equipment and appliances. In one aspect, this invention relates to electric-powered flow control valves. In yet another aspect, this invention relates to automatically controlled, unplugged water heaters.

2. Brief Description of Related Art

Approximately 56 million households in the United States and Canada use a non-powered atmospheric gas fired water heater to meet their domestic hot water needs. Each water heater consumes on average about 200 therms annually. One therm is equal to 100,000 Btu (British thermal units). At 450 Btu/hr, the water heater pilot light represents 20 percent of the gas use, or about 39 therms. If it is assumed that one-third, about 6.5 therms, is unused energy, the annual total waste energy from these pilot lights is 3.6 billion cubic feet of natural gas.

The current mechanism for eliminating the pilot light requires a powered (plugged) connection. However, a powered connection adds about $100 to the cost of the water heater and the cost of initially bringing power to the water is approximately $150. Thus, it is apparent that a transition from pilot-based water heaters to pilotless water heaters will save energy, save installation and retrofit costs, and reduce combustion emissions.

U.S. Pat. No. 6,561,138 teaches a conventional water heater comprising a hot water storage chamber in the top portion of a tank and a combustion chamber in the bottom portion of the tank. A fuel flow controller, which controls fuel flow to the main water heater burner and a pilot flame, is connected to a fuel supply line. A water heater thermocouple and a pilot flame thermocouple constitute the input sensing elements for the controller. The fuel control valve comprises inlet and outlet flow passages connected by a valve seat orifice. An opening and closing valve plunger is pressed on the valve seat by a coil spring. Additionally, a rod on which the valve is mounted is attached to a metal plate positioned proximate a fixed electromagnet which is connected to the thermocouple used for monitoring the burner. The magnet generates a predetermined magnetic force when normal ignition of the burner is detected. An ignition button is manually pressed at the time of the water heater startup to provide fuel flow through the valve. Once a flame is sensed and a current established, the fixed electromagnet is energized, thereby holding the valve plunger in an open position. If, for some reason, the flame goes out, the fixed electromagnet is de-energized, causing the valve plunger to move to a closed position, thereby shutting off fuel flow to the burner.

U.S. Patent Application Publication No. US 2003/0177818 teaches a water heater having a float activated electrical switch positioned in a water collection pan to automatically shut off both an electrically activated water supply valve and a gas shutoff valve in the event of a water leak. The water heater further comprises an adaptive connector for providing electrical connection between the gas control valve and a flame thermocouple and a normally closed relay for interrupting a thermocouple voltage supplied to the gas control valve.

U.S. Pat. No. 6,684,821 teaches a water heater having a pilot burner and two thermo-voltaic devices proximate the pilot burner electrically connected with a pilot gas valve through which fuel is provided to the pilot burner, wherein the pilot flame from the pilot burner provides heat energy to the thermo-voltaic devices which, in turn, create electrical energy to hold open a pilot valve located in the pilot gas valve. The pilot flame remains lit the entire time that the water heater is in operation.

U.S. Pat. No. 6,261,087 teaches a burner system for use in applications such as a gas fireplace insert having a main burner, a standing pilot burner, a burner control unit, and a fuel valve in which the fuel valve and burner control unit receive power from a power source such as a thermopile mounted to receive energy from the pilot burner. The burner control unit includes a switch for controlling power to the fuel valve and an RF receiver, thereby enabling operation of the system remotely using an RF transmitter.

U.S. Pat. No. 6,257,871 teaches a device for controlling a gas-fired appliance having a thermoelectric device such as a thermopile for controlling a millivolt vent damper and a main burner within the gas-fired appliance. The device includes a control circuit that selectively transmits current from the thermoelectric device to the main burner valve of the appliance and a damper motor. The control circuit also includes a temperature sensor and a plurality of single pole double throw switches. When the temperature sensor determines that the temperature of the medium to be heated is below a predetermined temperature, current is directed through the switches to the motor to open the damper, following which current is redirected through the switches to the valve to open the valve. When the predetermined temperature has been reached, current is again directed to the motor to close the damper and trap residual heat within the appliance.

SUMMARY OF THE INVENTION

It is one object of this invention to provide a combustion control system for material or medium heating appliances which is self-sufficient, requiring no external energy input.

It is one object of this invention to provide a combustion control system for material or medium heating appliances which includes energy storage capabilities.

It is yet another object of this invention to provide a combustion control system for material or medium heating appliances which is able to operate on less than 3 watts of energy.

These and other objects of this invention are addressed by a self-powered combustion control system comprising a burner and a fuel supply control valve having a fuel outlet in fluid communication with the burner. The fuel supply control valve comprises an ignition solenoid and a hold solenoid. The ignition solenoid is operationally linked with the hold solenoid such that energizing the ignition solenoid causes the hold solenoid to transform from a closed disposition, i.e. a non-energized condition, in which no fuel passes to the burner to an open disposition in which fuel flow to the burner is initiated for igniting the burner and subsequently maintained during heating of the material to be heated. The system further comprises an electronic system controller for controlling the ignition solenoid operationally connected with the ignition solenoid and an unpowered energy storage device providing all of the power required to operate the combustion control system. In accordance with one embodiment, the system comprises means for recharging the low power energy storage device.

The primary benefits of this invention include higher system efficiency and lower energy consumption due to the elimination of the pilot burner used with conventional systems, reduced standby power consumption, reduced emissions, avoidance of electric line power use, and stable and safe operation during power outages. Whereas conventional self-generating technologies rely on pilot burners as a primary source for thermoelectric generation, the system of this invention employs a burner for this purpose that is constantly on during heating of the material to be heated. In addition, whereas conventional self-generating technologies may rely on other power sources or battery change out during the life of the appliance, the system of this invention requires no external energy sources and no battery change out.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of this invention will be better understood from the following detailed description taken in conjunction with the drawings, wherein:

FIG. 1 is a schematic diagram of a self-powered combustion control system in accordance with one embodiment of this invention;

FIG. 2 is a diagrammatic representation of a low power valve operating sequence employed in the self-powered combustion control system in accordance with one embodiment of this invention;

FIG. 3 is a schematic diagram of a circuit for ignition of the burner of a water heater in accordance with one embodiment of this invention;

FIG. 4 is a schematic diagram of a circuit for controlling the fuel supply control valve in accordance with one embodiment of this invention; and

FIG. 5 is a flow diagram for a program integral with the electronic system controller for controlling the combustion control system in accordance with one embodiment of this invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The invention disclosed herein is a combustion control system for fuel-fired heating equipment and appliances which conventionally employ a pilot burner and pilot flame for ignition of the main burner employed therein, including gaseous fuel-fired residential and commercial water heaters and gas-fueled fireplaces, which eliminates the need for a pilot burner and pilot flame. Although the system generally is described herein for use with a water heater, it will be appreciated that the system as described may be employed in any heating apparatus or appliance which conventionally uses a pilot flame and burner for main burner ignition, and such applications are to be understood to be within the scope of this invention. Included within the range of applications to which this invention may be applied are residential, commercial, and industrial water heaters, residential and commercial space heaters and wall furnaces, residential and commercial stoves and ovens, gas-fired fireplaces with thermostatic or on/off remote control, outdoor living appliances including gas lighting, grills, patio heaters, and fire pits, and agricultural applications such as orchard heaters.

Accordingly, the combustion control system in accordance with one embodiment of this invention used in a water heater comprises a low power consumption fuel supply control valve and control/ignition management hardware as well as conventional elements widely available and used in tank-type water heaters, such as a spark igniter, thermocouple or thermopile, water temperature sensor, and the like. By low power consumption, we mean less than or equal to about 10 J of energy for each ignition cycle. The fuel supply control valve of this invention incorporates housing, plunger, and control elements similar to conventional water heater fuel supply control valves, thereby ensuring low cost and high safety of the disclosed system. In contrast to conventional systems which typically require human intervention to ignite the pilot flame, the additional control elements of the combustion control system of this invention provide on-demand ignition, shutdown, and automatic shutdown in the event of flame loss or power loss without human intervention.

The combustion control system in accordance with one embodiment of this invention as shown in FIG. 1 comprises a fuel valve 10 having a hold solenoid 11 having an open, energized disposition and a non-energized disposition and an ignition (startup) solenoid 12 having an energized igniting mode and a non-igniting mode, a burner 13, an electronic system controller 14 operationally connected with the ignition solenoid 12, and an unpowered rechargeable low power energy storage device 15 connected with electronic system controller 14 and providing all of the power required to operate the combustion control system. As used herein, the term “unpowered” refers to a condition in which no power is provided to the system by an external power source, such as an electrical line. Thermocouple 16 is provided for detecting the presence of a flame produced by burner 13 and is operationally connected with hold solenoid 11. Flame sensing spark igniter 17 connected with electronic system controller 14 provides a spark for ignition of the fuel provided to burner 13. As shown in the exemplary embodiment of FIG. 1, the system is used to provide heat to water tank 18 having water temperature sensor 19 operably connected with electronic system controller 14. In accordance with one embodiment, a thermoelectric system operationally connected with low power energy storage device 15 is provided for recharging the low power energy storage device. Suitable recharging systems include thermopiles and integral hydro-generators. In accordance with one embodiment of this invention, the low power energy storage device is a battery. In accordance with another embodiment of this invention, the low power energy storage device is a supercapacitor or capacitor.

Hold solenoid 11 is operationally linked in accordance with one embodiment of this invention by a shaft or rod 23 with ignition solenoid 12 such that when the ignition solenoid is in the energized igniting mode, the hold solenoid is in an open disposition. The open disposition of the hold solenoid corresponds to a position, shown in FIG. 1, in which the fuel supply control valve is open, enabling fuel to flow to the burner. Energizing of the hold solenoid is maintained by a signal generated by thermocouple 16 when a flame from the burner is present. Hold solenoid 11 includes a spring 21 and plate 22. In the event that the flame should be extinguished, the spring acts to push the plate toward the valve opening, thereby shutting off fuel flow. During ignition of the burner, the ignition solenoid, by way of shaft or rod 23, pushes against plate 22 of the hold solenoid, contracting the spring and causing the hold solenoid to assume an open disposition, thereby allowing fuel to flow to the burner for ignition by flame sensing spark igniter 17. Once the burner is lit, the ignition solenoid is de-energized and the hold solenoid is energized, enabling the continuous flow of fuel to the burner. In accordance with another embodiment of this invention, the ignition solenoid and hold solenoid may be in the same windings such that energizing the ignition solenoid results in a pulling of the plate 22 against the force of the spring to open the fuel supply control valve and de-energizing of the hold solenoid results in pushing of the plate by the spring to close the fuel supply control valve.

The spark ignition sequence is synchronized by the electronic system controller 14 with the energizing of the ignition solenoid. During ignition, the flame is monitored by measuring interelectrode conductivity of the electrodes of the flame sensing spark igniter 17. The flame ignition and stabilization results in heating of the thermopile source, e.g. thermocouple 16, that provides power to the hold solenoid similar to the design implemented in conventional water heater systems. The fuel supply can be interrupted by the electronic system controller by interruption of the hold solenoid circuit, which results in closing of the fuel valve. The electronic system controller initiates ignition and extinguishes the flame to maintain a desired water tank temperature that can be time-programmed to minimize energy consumption.

Operating sequence of the low power fuel valve of this invention is shown in FIG. 2. The sequence is initiated by an ignition request from the electronic system controller which starts a series of ignition trials, each of which trials involves light up of the flame sensing spark igniter for a predetermined time interval. The ignition solenoid is in an energized igniting mode and the hold solenoid is in a non-energized open disposition, being acted upon by rod 23, during the spark operation to allow the supply of fuel to the burner. The ignition trials are repeated several times until successful ignition is achieved or until a predetermined maximum number of ignition trials has been reached. Flame ignition is monitored by an ion conductivity sensor which measures the resistance across the spark gap. A drop in the resistance corresponds to flame ignition. The positive signal of the flame monitor causes a delay in the ignition solenoid shutoff, i.e., return to a non-igniting mode, which delay is sufficient for providing flame stabilization and for preheating of the thermocouple sensor. In turn, the hot thermocouple sensor provides enough electrical power to maintain the hold solenoid in the open disposition. At this point, the ignition solenoid is deactivated (de-energized) and the fuel supply control valve is held open by the signal from the thermocouple sensor, which essentially reduces the power drawn from the power source. The thermocouple sensor constantly monitors flame operation, and if the flame is extinguished, the thermocouple sensor, no longer sensing the presence of the flame, deactivates the hold solenoid, shutting off the fuel supply line. This operating sequence may be repeated by the electronic system controller monitoring the water temperature, water level, and other external factors. It will be appreciated that power is consumed by the system only during ignition of the flame. During the remaining portion of the cycle, power to the hold solenoid, and, thus, the fuel supply control valve, is supplied by the thermocouple sensor. In accordance with one embodiment of this invention, a portion of the electrical power produced by the hot thermocouple sensor also may be used to recharge the energy storage device.

The fuel supply control valve of this invention requires about 10 J of energy per activation of the ignition solenoid and, as previously indicated, the energy for holding the hold solenoid is provided by a conventional thermocouple source. Thus, an energy storage device with a capacity of about 1000 kJ will permit more than 100,000 ignition cycles. Also, as previously indicated, the energy storage device is preferably rechargeable. However, batteries employed as storage devices in accordance with one embodiment of this invention may merely be swapped out for a new battery rather than recharged, if desired.

FIG. 3 shows an exemplary circuit for controlling the power and holding time intervals of the ignition solenoid and hold solenoid in accordance with one embodiment of this invention. Other circuits may be suitable for this purpose as well. The circuit comprises a time relay K1 (Model H3CA, Omron, Inc.) operating as an “interval on relay” (Mode C). The ON state of the relay is activated by application of power and may be set from 0.1 seconds to a few hours. At the end of the ON state, the relay is switched off and the power to the ignition solenoid is supplied via a bypass resistor. The value of the resistor is preferably selected to provide the minimum voltage required for holding the solenoid. A bypass resistor with a value of 72 ohms is shown in FIG. 3. Using this circuit, a time interval of only 0.1 seconds is sufficient to complete the power stroke of the solenoid. After that, the control voltage may be reduced to as low as 2 VDC, allowing for significant power saving during an ignition cycle. The power and energy requirements for a single ignition cycle of the lower power valve are shown in Table 1.

TABLE 1

Power and energy requirements for a single flame ignition cycle

Regime
Duration, s
Voltage, VDC
Power, W
Energy, J

Power stroke
0.1
24
38
3.8

Hold
20
2
0.25
5

As shown therein, the power dissipated during the power stroke, i.e. fuel valve activation, is equal to about 38 W. However, the power stroke duration is only 0.1 seconds, resulting in a total energy input of about 3.8 J. A holding time is defined by a characteristic thermal constant of a thermopile sensor used in the control circuit. This time is typically close to 20 seconds. However, the power required for holding the solenoid is only 0.25 W; so, the energy input during the holding interval may be evaluated as about 5 J. As a result, the overall energy input from a battery source would be below about 10 J.

FIG. 4 shows a valve control circuit suitable for controlling the fuel valve using battery power. This microprocessor controlled circuit is designed for direct burner supervision and provides ignition sequence, flame monitoring, and safety shutdown for intermittent water heaters and other heating appliances. To satisfy the battery powered operation requirement, a DC/AC converter and a low power 120/240VAC transformer are included in the circuit. The circuit includes a commercial ignition module (Model 23114, Capable Controls, Inc.). The control module has a “Pilot Valve” output signal which is activated at the beginning of an ignition cycle and a “Main Valve” output signal which is activated after a successful ignition event is detected by the flame sensing circuit. The circuit includes two time relays K3 and K4 to control the durations of the power stroke and the initial solenoid holding time. These relays are “interval on relays” that are activated by application of power to the relay inputs. By way of example, relay K3 may be set for a time interval of 0.1 seconds and relay K4 may be programmed for a holding time interval in the range of about 5 to 60 seconds.

Flame ignition and sustainment tests using this circuit have been performed using a “pancake-type” burner commonly used in conventional residential gas-fired water heaters. The burner was connected with a compressed methane supply and a pressure regulator was used to drop the pressure of methane to about 4″ of water column. The ignition sequence was initiated by a control circuit that activated the ignition solenoid, thereby initiating a spark discharge. A soft start of the system was provided by ignition of a pilot flame which was supported for the period of time required to preheat the thermopile. The main flame was ignited at the end of the ignition cycle, at which time power to the ignition solenoid was terminated, allowing gas flow to the main burner. The fuel supply control valve was maintained open by the thermopile sensor. A flame interruption resulted in fast thermopile cool down and closure of the fuel supply control valve.

While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

PILOTLESS, UNPLUGGED COMBUSTION CONTROL SYSTEM

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