Method of and system for flame sensing and diagnostic
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Solution Overview
Problem
Existing HVAC systems face issues with accurately detecting the presence of a gas flame due to leakage current in inverters or capacitors, leading to false indications of flame presence, which can result in safety risks and inefficient operation.
Innovation Solution
A method and system for flame detection in HVAC systems using a tank circuit, first and second comparators, and a controller to determine the output states of these components, ensuring accurate notification of flame presence by distinguishing between actual flame conditions and component failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flame rectification with capacitors and inverters is used, then flame presence can be detected, but leakage current causes false indications of flame presence
Solution Approach 1:
The patent divides the flame detection function into multiple independent measurement channels (first and second comparators measuring different parameters). By segmenting the detection into multiple independent pathways, the system can cross-validate results and identify false indications caused by leakage current in any single channel.
Solution Approach 2:
The patent introduces an intermediary processing layer (the controller that receives and analyzes signals from multiple comparators) between the raw sensor signals and the final flame presence determination. This intermediary analyzes multiple parameters simultaneously and can distinguish between genuine flame signals and false indications caused by component leakage.
2Measurement precision
If simple flame detection circuitry is used, then device complexity is reduced, but measurement precision of flame presence deteriorates
Solution Approach 1:
The patent makes the existing detection circuitry multi-functional by having comparators measure multiple different parameters (voltage, current, or other electrical characteristics) rather than relying on a single measurement method. This allows the same hardware to perform multiple detection functions, improving precision without proportionally increasing complexity.
Solution Approach 2:
The patent changes the measurement parameters being monitored by the comparators, measuring different electrical characteristics (such as voltage across different capacitors or current through different paths) to detect flame presence. By monitoring multiple parameters simultaneously, the system achieves higher measurement precision while using standard circuit components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces false flame detection, enhancing safety and operational efficiency by providing reliable flame presence notifications, thus preventing unnecessary furnace shutdowns and hazardous unburned fuel accumulation.
Implementation Method 1
When a flame is present, the second capacitor discharges to ground through the flame which acts as a poor diode connected in series with a resistor.
Data Source
AI summary
A method of determining presence of a flame in a furnace of a heating, ventilation, and air conditioning (HVAC) system. The method comprises determining, using a controller, whether a processor signal (G) is active, responsive to a determination that the processor signal (G) is active, determining, using the controller prior to assertion of a flame-test input control signal, an output state of a first comparator, responsive to a determination that the output state of the first comparator is high, determining, using the controller prior to assertion of the flame-test input control signal, an output state of a second comparator, and responsive to a determination that the output state of the second comparator is low, transmitting, using the controller, a notification that a flame is present.