Burner Temperature Control for Water Heater Air Starvation
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Solution Overview
Problem
Fuel-fired appliances, such as water heaters, face challenges in preventing carbon monoxide production due to combustion air starvation caused by flame arrestor fouling, which existing temperature-based shut-off mechanisms are ineffective in addressing, especially in newer designs with secondary combustion chamber relief openings.
Innovation Solution
A burner control system that monitors combustion chamber temperature during heating cycles, disabling the burner if the temperature rate of change falls below a threshold, using a microprocessor to compare temperature data to stored values and prevent unnecessary shut-downs by considering minimum and median temperatures, and incorporating external sensors for additional safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flame arrestor is used to isolate fuel burner from environment, then flammable vapor ignition resistance is improved, but combustion air supply is restricted causing carbon monoxide production
Solution Approach 1:
A temperature sensing device is introduced as an intermediary between the combustion chamber and the control circuit. This mediator detects combustion chamber temperature and provides critical information to the control system, enabling it to distinguish between normal and abnormal operating conditions without directly interfering with the combustion process or flame arrestor function.
Solution Approach 2:
The control circuit implements feedback by continuously monitoring temperature from the sensing device and adjusting burner operation accordingly. When temperature exceeds thresholds indicating air starvation, the system reduces or shuts off fuel supply, creating a closed-loop control system that prevents carbon monoxide production while maintaining safe operation.
2Object-generated harmful factors
If temperature-based shut-off mechanism is used to detect air starvation, then carbon monoxide production is prevented, but false shut-downs occur due to decreased operational temperatures in newer burner designs
Solution Approach 1:
The system changes the temperature parameter threshold dynamically based on burner operation phase. Different temperature thresholds are applied during startup/heating phase versus steady-state operation. This allows the system to accommodate the naturally lower operating temperatures of modern low-emission burners while still detecting true air starvation conditions that would indicate combustion problems.
Solution Approach 2:
The control system transitions from static temperature-based shut-off to dynamic control that considers multiple factors including temperature rate of change, absolute temperature thresholds, and operational phase. The system adapts its response based on real-time conditions, allowing flexible operation that prevents false shut-downs while maintaining safety.
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
Effectively prevents excessive carbon monoxide production by accurately detecting air starvation before it occurs, reducing nuisance shut-downs and ensuring safe operation by using a data-driven approach to manage temperature thresholds and external sensor inputs.
Implementation Method 1
combustion chamber temperatures during the heating phase are used to determine burner condition
Data Source
AI summary
A fuel-fired water heater is shut down when a predicted steady state combustion chamber temperature is below a known threshold. The predicted steady state temperature is based on combustion chamber temperatures during heat up of the burner and appliance.