System and method for preventing bacteria proliferation in an electric water heater tank
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Solution Overview
Problem
Existing electric water heaters fail to effectively prevent Legionella bacteria proliferation due to stagnant water and temperature stratification, leading to ideal conditions for bacterial growth in the bottom region of the tank, with previous solutions being costly or impractical.
Innovation Solution
A system and method that uses a pump controlled by a programmed controller to periodically transfer hot water from the top region to the bottom region of the tank, maintaining a temperature sufficient to kill bacteria, utilizing a pump with a pressure rating greater than the domestic water supply and connecting it to the existing conduits for easy installation as a retrofit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a dome-shaped bottom wall is used in the water heater tank, then the structural integrity and manufacturing ease are improved, but stagnant water zones and sediment accumulation are created that promote bacterial proliferation
Solution Approach 1:
The patent implements periodic circulation of hot water through the bottom zone using a pump and control system. The system periodically activates to circulate hot water from the upper tank through the bottom region and returns it to the upper region, preventing stagnant water conditions and sediment accumulation that promote bacterial growth, while maintaining the dome-shaped bottom wall structure.
2Use of energy by moving object
If the bottom heating element is positioned close to the bottom wall, then heating efficiency is improved, but access for replacement or repair becomes difficult
Solution Approach 1:
The patent introduces a circulation system with a pump as an intermediary mechanism. Instead of relying solely on the bottom heating element positioned close to the bottom wall, the pump circulates hot water from the upper tank through the bottom region, providing thermal treatment to the difficult-to-reach areas without requiring direct access to the heating element for maintenance.
3Object-affected harmful factors
If additional heating elements or complex circulation systems are added to prevent bacterial growth, then bacterial proliferation is reduced, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing circulation system multi-functional by programming the pump to serve dual purposes: (1) normal operation to distribute heated water throughout the tank, and (2) periodic sanitation mode to circulate hot water through the bottom zone to prevent bacterial growth. This eliminates the need for separate dedicated sanitation equipment while achieving bacterial prevention.
Solution Approach 2:
The system uses its own heated water to sanitize the bottom zone, eliminating the need for external sanitation equipment. The control system automatically programs the pump to circulate hot water through the bottom region periodically, allowing the water heater to self-sanitize using its own thermal resource.
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 Legionella bacteria growth by maintaining the bottom region of the tank at a temperature above 135 degrees F, reducing the risk of bacterial proliferation and outbreak, while being cost-effective and practical for existing water heaters.
Implementation Method 1
The pump has a pressure rating greater than the domestic water supply pressure and has an inlet end connected to the tank hot water conduit and an outlet end connected to the tank cold water inlet
Implementation Method 2
whereby to pump hot water from the upper region of the tank to the bottom end to maintain the temperature in the bottom end of the tank at a temperature sufficiently high to prevent bacteria growth
Data Source
AI summary
A system and a method for preventing bacteria growth and proliferation, and particularly the Legionella bacteria, in a water tank of an electric water heater is described. A small pump is mounted on the water heater and has a power rating greater than the domestic water supply. The pump is controlled by a controller to pump hot water from the upper region of the tank to the lower region of the tank. The pump is connected between the hot water outlet of the tank and the cold water inlet to which an elongated dip tube is secured and with its discharge end positioned in close proximity to the bottom wall of the tank. The controller has a timer and is programmed to pump the hot water during non-peak hours of the utility for a preset time and for a preset period of time depending on such criteria as water quality, public regulations and laws.