Dual Premix Blower Control for Wide-Range Water Heater Modulation
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Solution Overview
Problem
Conventional water heating appliances face challenges in achieving continuous modulation of heat input over a wide range of heat demands due to inherent physical limitations, leading to increased complexity in plumbing and control systems when using multiple units.
Innovation Solution
A dual blower assembly system with a low range and high range blower feeding a common burner assembly, allowing for coordinated control to provide continuous modulation over a wider operating range, achieving a turndown ratio of 25:1 by selecting blower operating ranges such that the lower end of the high range blower equals the high end of the low range blower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single water heating apparatus is used, then the device complexity is low, but the turndown ratio is limited and cannot provide continuous modulation over a wide range of heat demands
Solution Approach 1:
The blower assembly is segmented into multiple independent variable speed blowers, each capable of operating within a specific flow rate range. This segmentation allows each blower to handle a portion of the overall turndown ratio requirement, enabling the system to achieve a combined turndown ratio greater than 15:1 while maintaining continuous modulation capability across the full operating range.
2Adaptability or versatility
If multiple commonly controlled heat exchangers are used, then the turndown ratio increases, but the plumbing and control system complexity increases
Solution Approach 1:
Multiple variable speed blowers are merged to feed a single burner assembly, combining their airflow capabilities to achieve a high turndown ratio. This merging approach eliminates the need for multiple separate heat exchangers and their associated plumbing, while the blowers are commonly controlled to operate in coordination, simplifying the control system compared to independently controlling multiple heat exchangers.
Solution Approach 2:
The single burner assembly serves multiple functions by receiving premixed fuel and air from multiple different variable speed blowers. This multi-functionality allows the burner to operate across a wide turndown ratio range while using a single heat exchanger unit, thereby avoiding the plumbing complexity that would arise from multiple heat exchangers.
3Use of energy by moving object
If a fixed flow rate burner is used, then the device complexity is low, but the energy efficiency decreases when heat demand varies
Solution Approach 1:
The system uses variable speed blowers that can dynamically adjust their airflow rate to match the actual heat demand. This dynamic adjustment capability allows the burner to operate efficiently across a wide range of heat demands by continuously modulating the air and fuel flow rates, thereby maintaining high energy efficiency while avoiding the need for complex staged burner systems.
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 dual blower system enables continuous modulation of heat input over a large range, exceeding previous turndown ratios while maintaining a high capacity and reducing complexity compared to multiple unit systems.
Implementation Method 1
A variable flow premix low range blower assembly supplies premix fuel and air to the burner assembly
Data Source
AI summary
A water heating apparatus includes a burner having first and second zones. First and second blowers provide premixed fuel and air to the first and second zones, respectively. An automated control system controls the two blowers.