Zone control with modulating boiler
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Solution Overview
Problem
Traditional heating systems, including those with outdoor reset controls, are inefficient as they require multiple sensors and settings, and rely on outdoor temperature to calculate boiler target temperatures, leading to overheating or underheating, and fail to account for varying heating demands within a building.
Innovation Solution
A zone controller that communicates with a modulating boiler, using a processor and memory to calculate duty cycles and maximum zone loads based on empirical data from thermostats, allowing for modulation of boiler output and flow to each zone, optimizing temperature and energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If outdoor reset control is used to calculate boiler target temperature, then the system can operate with fewer sensors and simpler configuration, but the heating efficiency deteriorates because the target temperature does not account for varying internal heating demands of different zones
Solution Approach 1:
The patent divides the building into multiple thermal zones, each with its own thermostat and heating demands. Instead of using a single outdoor temperature sensor for the entire building, the system segments the heating control into zone-specific duty cycle calculations. This allows each zone's unique heating requirements to be accounted for while using a single outdoor reset control, resolving the contradiction between system simplicity and heating efficiency.
Solution Approach 2:
The system implements feedback by continuously monitoring thermostat calls from multiple zones and calculating duty cycles based on actual zone heating demands. The outdoor reset control receives feedback about which zones are calling for heat and adjusts the boiler target temperature accordingly. This feedback mechanism allows the simple outdoor reset system to achieve high heating efficiency by responding to actual zone needs rather than relying solely on outdoor temperature.
2Device complexity
If outdoor reset control calculates boiler target temperature based solely on outdoor temperature, then the control system remains simple, but the temperature control precision deteriorates leading to overheating or underheating in specific zones
Solution Approach 1:
The patent makes the outdoor reset control dynamic by introducing duty cycle calculations that respond to changing zone heating demands. Instead of a static target temperature based only on outdoor temperature, the system dynamically adjusts the effective target temperature for each zone based on its specific heating requirements. This dynamic approach maintains simple control hardware while achieving precise temperature control for each zone.
Solution Approach 2:
The system changes the parameter used for temperature control from a single outdoor temperature-based target to multiple zone-specific effective target temperatures. By calculating duty cycles that reflect actual zone heating demands, the system transforms the outdoor reset control into a multi-parameter system that accounts for both outdoor temperature and internal zone conditions, achieving precise temperature control without increasing device complexity.
3Reliability
If a fixed boiler target temperature is used to meet heating requirements during cold days, then the heating system can reliably meet the coldest demands, but energy consumption increases because the boiler maintains temperatures much higher than required during most of the year
Solution Approach 1:
The patent applies partial action by calculating duty cycles that represent the fraction of time each zone needs heating at full capacity. Instead of running the boiler at fixed high target temperature continuously, the system runs at variable target temperatures proportional to actual zone demands. The duty cycle calculation ensures that heating reliability during cold weather is maintained by providing full heating capacity when needed, while reducing energy consumption during milder conditions when zones require less heating.
Solution Approach 2:
The system changes the boiler target temperature parameter from a fixed high value to a variable value based on outdoor reset calculations and zone duty cycles. This parameter change allows the boiler to operate at appropriate temperatures for current conditions rather than maintaining excessively high temperatures year-round. The duty cycle-based modulation ensures that heating reliability is maintained when needed while significantly reducing energy consumption during periods of lower heating demand.
Data Source
AI summary
A zone controller works with a modulating unit comprising memory storing an instruction set and data related to thermostats, a plurality of duty cycles for a plurality of zones, a plurality of time periods for the plurality of zones, and a maximum zone load. A processor is operative to provide a modulating signal to the modulating unit based on the maximum zone load. The modulating signal determines operation of the modulating boiler and the maximum zone load based on the plurality of duty cycles, time periods, and data related to thermostats. The zone controller may be further operative to: calculate a first duty cycle for the first zone based on a first time period; calculate a second duty cycle for the second zone based on a second time period; and determine a maximum zone load, which is a greater of the first duty cycle and the second duty cycle.