Pulsed Current Testing of Water Heater Elements for Dry-Fire Protection
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Solution Overview
Problem
Electric water heaters often experience 'dry firing' when their heating elements are energized before the tank is filled with water, leading to costly repairs and warranty claims, as existing technologies fail to effectively prevent this issue.
Innovation Solution
A pulsed power-based dry fire protection system that measures current flow through the heating element using a signal conditioning circuit and microcontroller to detect and prevent dry firing by comparing average current values to a threshold, activating an alarm and preventing energization if a dry fire condition is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing dry fire protection technologies are used, then some level of protection is provided, but they fail to effectively prevent dry firing incidents
Solution Approach 1:
The system performs preliminary testing of the heating element by applying a test voltage and measuring current flow before allowing normal operation. This preliminary action detects dry fire conditions before they can cause damage, preventing the harmful effect from occurring in the first place
Solution Approach 2:
The patent replaces complex mechanical sensing mechanisms with electrical measurement techniques. By measuring current flow through the heating element during a test cycle, the system detects dry fire conditions using electrical properties rather than mechanical sensors, simplifying the overall system
2Measurement precision
If pulsed power-based detection system is implemented, then dry fire detection accuracy is improved, but device complexity increases
Solution Approach 1:
The system applies voltage to the heating element in periodic pulses rather than continuously. This pulsed operation allows for controlled measurement cycles where current flow can be accurately measured during each pulse, improving detection precision while allowing the system to return to a stable state between pulses
Solution Approach 2:
The signal conditioning circuit acts as an intermediary between the heating element and the microcontroller. It condition the measured signals to appropriate levels for the microcontroller's analog-to-digital converter, enabling accurate measurement without requiring the microcontroller to directly interface with the high-voltage heating element
3Reliability
If continuous monitoring is performed, then detection reliability is improved, but energy consumption increases
Solution Approach 1:
Instead of continuous monitoring, the system performs periodic testing at predetermined intervals. The microcontroller applies test voltage pulses at specific times and measures current flow during these pulses, providing reliable detection while consuming minimal energy during the intervals between test cycles
Solution Approach 2:
The system maintains readiness for detection by continuously monitoring basic electrical parameters, but only activates the full test sequence when needed. This allows the system to remain responsive to dry fire conditions while minimizing energy consumption during normal operation
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 system effectively prevents dry firing of electric water heater elements by accurately measuring current flow, reducing warranty costs and repair frequencies through reliable and efficient operation.
Implementation Method 1
electric resistance type heating element(s)
Data Source
AI summary
A water heater having an electric heating element therein is provided with apparatus for preventing dry firing of the heating element. The apparatus is operative to (1) power the heating element with electrical test pulses having first predetermined durations and being separated by rest periods of second predetermined durations during which the heating element is depowered, (2) determine the average electrical current flow through the element during each of the test pulses, and (3) preclude energization of the heating element if the average current flow therethrough during an electrical test pulse subsequent to the first test pulse is less by a predetermined magnitude than the average electrical current flow through the heating element during the first electrical test pulse.