Variable Capacity Compressor Control Using Staged Thermostat Signals
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Solution Overview
Problem
Traditional space conditioning systems with variable speed compressors are not fully utilized due to the need for corresponding variable speed control signals from thermostats, which is costly and requires retrofitting, limiting the benefits of infinitely variable capacity compressors.
Innovation Solution
A control module that allows the use of staged thermostats with variable speed compressors by outputting a speed reference signal with multiple values, enabling incremental control levels that approximate continuous variable control without requiring retrofitting of the thermostat or wiring, using control logic to detect input signals and adjust compressor speeds accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a stages thermostat is used with a variable speed compressor, then the system can operate with traditional control signals, but the variable speed compressor cannot achieve its full potential benefits due to limited control resolution
Solution Approach 1:
The patent segments the continuous speed control range into multiple discrete speed levels (e.g., 3-5 speed levels) that can be controlled by traditional staged thermostat signals. This segmentation allows the variable speed compressor to be compatible with legacy thermostat wiring while still providing stepped speed control that improves efficiency over single-speed operation.
Solution Approach 2:
The patent implements dynamic speed adjustment by allowing the compressor to transition between multiple speed levels based on system conditions. The control system dynamically selects appropriate speed levels from the available range, enabling the compressor to adapt its capacity to match actual cooling/heating loads while maintaining compatibility with staged thermostat control.
2Productivity
If a variable speed thermostat is used to fully utilize the variable speed compressor, then infinitely variable capacity control is achieved, but the cost increases and retrofitting is required
Solution Approach 1:
The patent implements a cost-effective control solution by using simple, discrete speed level selection rather than requiring expensive continuous variable control infrastructure. The system achieves satisfactory performance with limited speed levels (3-5 levels) controlled by traditional thermostat wiring, avoiding the need for costly variable speed thermostats and associated retrofitting.
Solution Approach 2:
The patent changes the control parameter from continuous variable signals to discrete speed level selections. By controlling the compressor at specific predetermined speed levels rather than allowing continuous adjustment, the system achieves good enough performance with simpler, less expensive control hardware and wiring configurations.
Data Source
AI summary
A control method for a space conditioning system operable with a stages thermostat, the method including: powering a control module comprising including an output terminal, a first input terminal, a second input terminal, and control logic; detecting receipt of the first input signal at the first input terminal; responsive to detecting receipt of the first input signal, outputting a first value of the plurality of values, the first value corresponding to the first input signal; after outputting the first value, outputting one or more values of the plurality of values, the one or more values being larger than the first value; detecting receipt of the second input signal at the second input terminal; and responsive to detecting receipt of the second input signal, outputting a second value of the plurality of values, the second value corresponding to the second input signal.