Boiler integrated control with non-linear outdoor reset methodology
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Solution Overview
Problem
Conventional hydronic water heating systems with linear outdoor reset curves are inefficient due to non-linear heat output from common heat emitters, requiring higher water temperatures on warm days to maintain comfort, and are complex to program and integrate with boiler controls.
Innovation Solution
An integrated boiler control system that generates a non-linear outdoor reset curve using three simple parameters: coldest design outdoor temperature, design supply water temperature, and desired indoor temperature, allowing for easy fine-tuning and compatibility with various heat emitters without requiring emitter-specific programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a linear outdoor reset curve is used to control boiler supply temperature, then the system meets regulatory requirements and is simple to implement, but the system cannot match the non-linear heat output of common heat emitters, requiring higher water temperatures on warm days and reducing energy efficiency
Solution Approach 1:
The patent applies parameter changes by transitioning from a linear reset curve to a non-linear reset curve that better matches the actual heat output characteristics of common heat emitters. The non-linear curve adjusts the supply temperature setpoint more aggressively at higher outdoor temperatures, reducing energy waste while maintaining comfort. This is achieved by modifying the mathematical relationship between outdoor temperature and supply temperature setpoint from linear to non-linear form.
2Loss of energy
If stand-alone devices are used to provide non-linear outdoor reset control curves, then the system can achieve optimal efficiency, but the cost of additional hardware and complexity of programming and wiring increases
Solution Approach 1:
The patent merges the outdoor reset control functionality directly into the boiler control system, eliminating the need for separate stand-alone devices. The non-linear reset curve calculation is integrated into the existing boiler control hardware and software, allowing the system to achieve optimal energy efficiency without adding external controllers, additional wiring, or complex inter-device programming.
Solution Approach 2:
The patent creates a universal non-linear reset curve methodology that can be applied across different boiler models and heat emitter types without requiring emitter-specific programming. The control system uses general parameters (outdoor design temperature, supply water design temperature, and heat emitter type category) to generate a reset curve that works effectively with common heat emitters, making the solution broadly applicable without customization for each specific emitter model.
3Ease of operation
If linear reset curves are used, then the control system is simple to program, but the system sets water temperatures higher than necessary on warm days to compensate for reduced convective heat transfer, preventing optimal efficiency operation
Solution Approach 1:
The patent modifies the control parameter relationship from linear to non-linear, allowing the supply temperature setpoint to decrease more rapidly as outdoor temperature increases. This non-linear parameter change enables the system to set appropriately lower water temperatures on warm days when heat emitters are less efficient, thereby reducing energy consumption while maintaining comfortable indoor temperatures.
Data Source
AI summary
A hydronic water heating system heats water for various types of heat emitters. A boiler assembly includes a user interface which receives user-defined water temperature set point corresponding to a minimum outdoor temperature, and an integrated controller generates a nonlinear outdoor reset curve between the user-defined set point and a second set point corresponding to maximum outdoor temperature for which heating is required, and regulates the boiler to heat water to a temperature corresponding to a set point along the nonlinear output reset curve and based on a detected outdoor temperature. The nonlinear outdoor reset curve may be generated based on aggregated heat output functions for various types of heat emitters. A linear outdoor reset curve may be generated between a maximum water temperature set point and the user-defined set point, having a slope equal to an instantaneous slope of the nonlinear outdoor reset curve at the user-defined set point.