Modulating Water Heater Control for Flow-Based Load Response
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modulating water heaters in cascading sequences face issues such as excessive cycling, which leads to wear and tear, difficulty in managing heat load changes due to lagging temperature responses, and condensation of water vapor in exhaust gases, requiring expensive venting materials and separate flues.
Innovation Solution
A control system that monitors water flow rates to predict heat load changes, varies boiler firing rates accordingly, maintains exhaust gas temperatures above condensation levels, and allows temperature variations within a defined range to minimize cycling and enable common venting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If modulating water heaters operate in cascading sequences with continuous modulation, then heat demand responsiveness is improved, but excessive cycling occurs leading to wear and tear
Solution Approach 1:
The control system performs preliminary action by anticipating heat load changes through water flow rate monitoring before temperature changes occur. This allows the boiler to adjust firing rate in advance, preventing excessive cycling while maintaining responsiveness to heat demand changes.
2Measurement precision
If temperature control is tightly maintained at setpoint, then temperature precision is improved, but cycling frequency increases causing wear
Solution Approach 1:
The system uses water flow rate monitoring to detect heat load changes before they manifest as temperature changes. This preliminary detection allows the control system to adjust the boiler firing rate in advance, maintaining temperature precision while avoiding the excessive cycling that would result from waiting for temperature deviations.
3Device complexity
If exhaust gas temperature is maintained high to prevent condensation, then venting system complexity is reduced, but energy loss increases
Solution Approach 1:
The control system dynamically adjusts the boiler firing rate based on monitored water flow rates and heat load conditions. By optimizing the firing rate parameter, the system maintains exhaust gas temperatures above condensation levels when necessary, preventing the need for complex separate venting systems, while minimizing energy loss by avoiding unnecessarily high temperatures when condensation is not a risk.
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
Reduces cycling and wear on boilers, improves responsiveness to heat demand changes, and allows for economical common venting by maintaining exhaust gas temperatures above condensation levels, thereby extending the life of the system and reducing costs.
Implementation Method 1
A control system for a modulating water heater or boiler varies the firing rate of a burner in response to monitored changes in water flow rates through the system
Implementation Method 2
a burner which receives premixed combustion air and fuel gas and heats water
Implementation Method 3
a variable flow blower delivers premixed combustion air and fuel gas to the burner at a controlled blower flow rate within a blower flow rate range
Implementation Method 4
maintains exhaust gas temperatures above condensation levels
Implementation Method 5
prevents condensation of water vapor in exhaust gases
Data Source
AI summary
A method of controlling a modulating water heater supplying water to a system includes sensing a parameter which changes corresponding to a change in system flow rate, the sensed parameter being a parameter other than system temperature, and then modulating output of the heater in response to a change in the sensed parameter. Early detection of system flow rate changes permits early modulation of water heater output before the changes in flow rate have had time to significantly impact the system temperature.