Gas valve control system for a water heater
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Solution Overview
Problem
Existing gas valve control systems in powered vent water heaters are inefficient due to the need for a large transformer to step down voltage, and they confuse operators by indicating errors when the gas valve is switched off but the control system remains energized, leading to unclear shutdown states.
Innovation Solution
A double-pole double-throw (DPDT) manually-operated switch is used to supply power only to the gas valve coil, allowing the controller to sense the switch position using existing circuits, and indicating the switch position to prevent calls for heat and operation when the switch is off, ensuring accurate shutdown and re-lighting attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a master on/off switch is used to switch all power to the appliance off, then the gas valve is disconnected from electrical power, but the control system remains energized and may indicate errors to the operator when it attempts to light-off the water heater, causing confusion
Solution Approach 1:
The patent segments the power switching function into separate controls: a master on/off switch for overall appliance power and a dedicated gas valve switch for gas supply control. This segmentation allows the control system to remain energized while the gas valve can be independently controlled, preventing erroneous error indications when the gas valve is off but the control system is on.
Solution Approach 2:
The patent introduces a position indication mechanism as an intermediary between the gas valve switch and the control system. The controller receives position signals from the gas valve switch and uses this information to determine whether to attempt lighting-off, thereby mediating the interaction between the switch state and control system operations to prevent confusion.
2Adaptability or versatility
If a gas valve switch only switches the gas valve off while the control system remains energized, then the gas valve is closed, but the control system attempts to light-off and indicates errors, creating unclear shutdown state
Solution Approach 1:
The patent implements feedback by having the controller continuously monitor the position of the gas valve switch through position indication circuits. This feedback allows the controller to adjust its operations based on the actual switch position, preventing erroneous error indications and maintaining clear state information throughout the system.
Solution Approach 2:
The gas valve switch serves multiple functions: it controls the gas valve closure and simultaneously provides position indication to the controller. This multi-functionality eliminates the need for separate switches and ensures that the controller has accurate information about the gas valve state without adding additional complexity.
3Power
If a large transformer is used to step down voltage for the gas valve control circuit, then sufficient power is provided, but system cost and complexity increase
Solution Approach 1:
The patent replaces the mechanical transformer-based voltage reduction system with an electronic control approach using solid-state components and circuitry. This substitution eliminates the need for a large physical transformer while maintaining the required power levels for the gas valve coil, thereby reducing system complexity and cost.
Solution Approach 2:
The patent changes the electrical parameters in the control circuit by using voltage regulation through electronic components rather than electromagnetic transformation. This allows for precise control of the gas valve coil power while using smaller, less complex components.
Data Source
AI summary
A system and method of operating a gas fuel valve control circuit are disclosed. The gas valve control circuit includes a gas valve assembly configured to control a flow of a fuel gas to a load and a switch assembly including a switch in each leg of a plurality of legs of a power supply to the gas valve assembly. The switch assembly is configured to supply power and a return to the gas valve assembly in a first position and to open the plurality of legs of the power supply to the gas valve assembly in a second position. The switch assembly is configured to indicate a position of the switch assembly.