System and method for controlling an HVAC unit based on thermostat signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional multiple-stage HVAC systems experience inefficiencies due to rapid switching between stages near temperature thresholds, leading to repeated on-off cycles and reduced overall efficiency, as they rely on simple ON/OFF signals from thermostats without granular control over capacity adjustments.
Innovation Solution
A method for controlling HVAC units that adjusts capacity percentages based on room temperature change rates and thresholds, allowing for more nuanced operation by increasing or decreasing capacity increments in response to temperature changes, thereby maintaining desired temperature levels more efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple-stage HVAC systems use simple ON/OFF signals from thermostats to control heating or cooling stages, then the system can respond to temperature changes, but the system experiences rapid switching between stages near temperature thresholds causing repeated on-off cycles and reduced efficiency
Solution Approach 1:
The system dynamically adjusts the capacity percentage of HVAC components based on the rate of temperature change rather than using fixed ON/OFF control. The controller continuously monitors temperature data and calculates the rate of change, then modulates compressor capacity accordingly, allowing smooth transitions between stages and eliminating rapid switching behavior near thresholds.
Solution Approach 2:
The invention changes the control parameter from binary ON/OFF signals to continuous capacity percentage adjustments based on temperature change rate. By using the rate of temperature change as the control parameter, the system can distinguish between temporary fluctuations and genuine temperature trends, preventing premature stage switching and improving operational stability.
2Ease of operation
If multiple-stage HVAC systems operate at fixed capacity levels, then the system can provide discrete heating or cooling stages, but the system cannot accurately maintain desired temperature levels and experiences unnecessary cycling
Solution Approach 1:
The system transitions from static capacity levels to dynamic capacity modulation. The controller continuously adjusts the capacity percentage of compressors and other HVAC components based on real-time temperature change rate measurements, enabling precise temperature maintenance while retaining the benefit of discrete stage-based operation architecture.
Solution Approach 2:
The system implements feedback control by continuously monitoring temperature data, calculating the rate of change, and using this information to adjust capacity settings. This closed-loop control ensures that the HVAC system responds appropriately to actual thermal conditions, maintaining accurate temperature levels and preventing unnecessary cycling between stages.
3Adaptability or versatility
If HVAC systems rapidly switch between stages near temperature thresholds, then the system can respond to temperature changes, but the repeated on-off cycles reduce overall system efficiency and increase wear
Solution Approach 1:
The system uses dynamic capacity modulation to maintain adaptability while reducing cycling. By continuously adjusting capacity based on temperature change rate, the system can respond to genuine temperature changes without switching stages unnecessarily, thereby maintaining energy efficiency and reducing mechanical wear from repeated on-off cycles.
Solution Approach 2:
The system takes preliminary action by monitoring the rate of temperature change and anticipating future temperature trends. By detecting whether temperature is rising or falling and at what rate, the system can prepare appropriate capacity settings in advance, preventing premature stage switching and avoiding the energy waste associated with frequent on-off cycles.
Data Source
AI summary
A method is provided for controlling an HVAC unit, including: receiving input signals from a thermostat; setting a mode of the HVAC unit to a heating mode when a heating signal is enabled, or to a cooling mode when a cooling signal is enabled; setting a capacity of the HVAC unit to a set capacity based on the input signals; calculating a heating/cooling change rate based on temperature data received from the HVAC unit; comparing the heating/cooling change rate with a threshold; maintaining the HVAC unit at the set capacity percentage if the heating/cooling change rate is equal to the threshold; lowering the current capacity by a first cooling increment, to a minimum of 0%, if the heating/cooling change rate is above the threshold; and raising the current capacity by a second cooling increment, to a maximum of 100%, if the heating/cooling change rate is below the threshold.