Networked Water Heater Control for Small-Flow Detection and Wear Balance
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Solution Overview
Problem
Conventional cascade water heater systems face challenges in efficiently managing varying hot water demands, leading to excessive wear on some units, inefficient energy use, and difficulty in detecting small system flows, while also lacking a robust method for estimating remaining life and distributing maintenance wear evenly across units.
Innovation Solution
A control system that uses overall efficiency and usage history to determine the heating load for each water heater, incorporates a flow limiting valve and sensor to detect small flows, and employs a true masterless control scheme for seamless addition or removal of units, distributing heating loads based on relative remaining life and minimizing disparity in usage across the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple water heaters are cascaded to meet varying demands, then the system can handle large water heating loads and provide redundancy, but the last water heater turned on experiences excessive cycling and wear when demand falls within a dead band
Solution Approach 1:
The patent implements dynamic load distribution where the controller continuously monitors system demand and adjusts which water heater serves as the modulating unit. When demand falls within a dead band, the controller dynamically switches the modulating role to a different heater in the cascade, preventing excessive cycling of any single unit and distributing wear more evenly across the system.
2Device complexity
If water heaters are arranged in a fixed cascade sequence, then control is simplified, but the first water heaters experience significantly higher accumulated usage than others, creating maintenance disparity
Solution Approach 1:
The patent implements periodic rotation of the modulating water heater role among units in the cascade. The controller cycles through different heaters, assigning the modulating function to different units at different time periods. This periodic action ensures that no single heater bears the brunt of modulation wear, distributing maintenance requirements more evenly while maintaining simple cascade control architecture.
3Ease of operation
If conventional flow detection methods are used in cascade systems, then system operation is straightforward, but small system flows cannot be detected reliably
Solution Approach 1:
The patent merges the flow detection capabilities of multiple water heaters in the cascade system. The controller aggregates flow signals from individual heaters to detect small system flows that would be below the detection threshold of any single unit. This combined detection approach maintains straightforward operation while significantly improving measurement precision for small flows.
Data Source
AI summary
Disclosed is a control system for controlling a plurality of fluidly and operably connected water heaters to meet a hot water demand such that overall efficiency is maximized and usage disparity between water heaters is minimized. There is further disclosed a method for detecting a small system demand in said network by adjusting the setting of each flow limiting valve of each water heater. There is still further disclosed a method for enabling seamless addition or removal of a heater in service and heating load distribution to water heaters.