Multi-stage control for electromechanical heating, ventilation, and air conditioning (HVAC) unit
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Solution Overview
Problem
HVAC units with only two stages of cooling may not meet efficiency standards, such as ASHRAE 90.1 and 90.2, and replacing the entire unit is often necessary to add a third stage of cooling, which is costly and wasteful.
Innovation Solution
A retrofit solution that includes a sensor and switch system, allowing for the selective enablement of multiple compressors based on temperature or other sensor values, enabling a third stage of cooling without requiring a new controller, using a bimetallic thermal switch or similar device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two-stage cooling system is used, then device complexity is reduced, but efficiency standards compliance deteriorates
Solution Approach 1:
The patent divides the cooling system into multiple independent stages with separate compressors (first compressor for first stage, second compressor for second stage, third compressor for third stage). This segmentation allows the system to meet efficiency standards by providing granular control over cooling capacity while maintaining manageable complexity through modular architecture.
Solution Approach 2:
The patent implements dynamic stage selection based on cooling requirements. The system can activate different combinations of compressors (first stage only, second stage only, third stage only, or multiple stages simultaneously) to dynamically adjust cooling capacity and meet varying efficiency requirements without requiring a complete system redesign.
2Reliability
If a third stage of cooling is added to meet efficiency standards, then efficiency compliance is improved, but device complexity increases
Solution Approach 1:
The patent segments the cooling system into three distinct stages, each with its own compressor and control logic. This segmentation allows the third stage to be added as a modular component rather than integrating it into the existing two-stage system, thereby meeting efficiency standards while keeping overall system complexity manageable through clear separation of functions.
Solution Approach 2:
The patent designs the control system to universally manage multiple cooling stages through a unified control architecture. The same control logic and infrastructure are used to manage the first, second, and third stages, allowing the system to provide multi-functionality (three stages of cooling) without proportionally increasing complexity.
3Reliability
If the entire HVAC unit is replaced to add a third cooling stage, then efficiency compliance is improved, but cost increases
Solution Approach 1:
The patent prepares the system for future efficiency requirements by pre-installing the third compressor and control infrastructure while maintaining backward compatibility with existing two-stage operation. This preliminary action allows the system to meet future efficiency standards without requiring complete replacement, thereby avoiding the high costs associated with full HVAC unit replacement.
Solution Approach 2:
The patent changes the operational parameters of the existing HVAC system by adding a third cooling stage and modifying the control logic to manage three stages. This parameter change (from two-stage to three-stage operation) enables efficiency compliance while preserving the existing hardware infrastructure, avoiding the need for costly complete replacement.
4Adaptability or versatility
If multiple compressors with different capacities are used, then cooling capacity flexibility is improved, but device complexity increases
Solution Approach 1:
The patent assigns different capacities to different compressors based on their specific roles in the cooling system. The first compressor has a different capacity than the second compressor, which differs from the third compressor. This local quality approach allows each compressor to be optimized for its specific function while maintaining overall system flexibility, managing complexity through differentiated but purposeful design.
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
Enables HVAC units to provide an additional stage of cooling, enhancing efficiency and compliance with energy standards without the need for a new unit, thereby reducing costs and environmental impact.
Implementation Method 1
The sensor and switch can be a single device. For example, in some embodiments, the sensor and switch can be a bimetallic thermal switch.
Data Source
AI summary
A control system for a heat transfer circuit, an HVAC unit containing a heat transfer circuit, and a method of retrofitting an HVAC unit are described. The control system includes a thermostat having a first cooling stage signal output terminal and a second cooling stage signal output terminal; a controller electrically connected to the thermostat; a sensor electrically connected to the controller; and a switch electrically connected to the controller, and that receives a first cooling stage signal output from the thermostat. The switch is in a first state when a sensor value from the sensor is less than a threshold, and a second state when the sensor value from the sensor is greater than or equal to the threshold.