Sacrifical anode control for a water heater
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Solution Overview
Problem
Water heater tanks with sacrificial anodes face excessive corrosion due to high anode current in high conductivity water, leading to premature failure, especially in gas-based systems without an external power source.
Innovation Solution
A controller is used to selectively complete and break an electrical circuit between the sacrificial anode and the tank, employing pulse width modulation to regulate the anode current based on measured conductivity, using a power source like batteries or thermoelectric generators, ensuring the anode current is only as high as necessary to prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the anode current is increased to adequately protect the tank from corrosion in high conductivity water, then the corrosion protection is improved, but the rate of anode consumption increases leading to premature failure
Solution Approach 1:
The patent applies dynamics by transitioning from a static, continuous anode current to a dynamic, pulsed anode current. The controller dynamically adjusts the anode current by periodically completing and breaking the electrical circuit, creating time-varying current pulses that maintain corrosion protection while reducing total anode consumption.
Solution Approach 2:
The patent implements periodic action through pulse width modulation (PWM) that repeatedly completes and breaks the electrical circuit connecting the anode to the tank. This periodic switching creates controlled current pulses rather than continuous current, allowing the system to maintain protective effect while reducing overall anode consumption and extending anode lifetime.
2Reliability
If a controller with power source is added to regulate anode current, then the anode current control is improved, but the device complexity increases
Solution Approach 1:
The patent applies self-service by designing a system where the water heater's existing components serve dual purposes. The controller utilizes the existing thermostat power supply and electrical circuitry to operate the anode control, rather than requiring entirely separate power sources and control systems. This reduces overall system complexity while maintaining effective anode current regulation.
Solution Approach 2:
The patent implements multi-functionality by having the controller perform multiple functions: it manages both the heating element control and the anode current regulation using the same power supply and control circuitry. This universal approach consolidates components and reduces system complexity compared to having separate dedicated systems for each function.
3Duration of action of stationary object
If pulse width modulation is used to reduce anode current, then the anode lifetime is extended, but the control system complexity increases
Solution Approach 1:
The controller leverages the existing power supply infrastructure of the water heater to generate and execute PWM signals for anode control. By using available circuitry and power sources rather than requiring dedicated PWM generation hardware, the system achieves pulse width modulation functionality with minimal additional complexity.
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
This method extends the life of both the sacrificial anode and the water heater tank by maintaining adequate corrosion protection while minimizing power consumption, suitable for systems without external power access.
Implementation Method 1
The combination of the sacrificial anode, the metal tank, and the water create a galvanic cell, wherein an oxidation reaction is concentrated at the sacrificial anode and a reduction reaction is concentrated at the metal tank, causing a current to flow through the anode and the tank
Implementation Method 2
an oxidation reaction is concentrated at the sacrificial anode and a reduction reaction is concentrated at the metal tank
Implementation Method 3
an oxidation reaction is concentrated at the sacrificial anode and a reduction reaction is concentrated at the metal tank
Implementation Method 4
The controller is also configured to measure a shorted anode current through the electrical circuit
Implementation Method 5
The controller is also configured to repeatedly complete and break the electrical circuit using the modulation duty cycle
Data Source
AI summary
A water heater includes a tank configured to hold a fluid, a sacrificial anode located within the tank, and a controller coupled to the sacrificial anode. The controller is configured to selectively complete and break an electrical circuit connecting the tank and the sacrificial anode. The controller is also configured to measure a shorted anode current through the electrical circuit, to determine a modulation duty cycle based on a current setpoint and the measured shorted anode current, and to repeatedly complete and break the electrical circuit using the modulation duty cycle.