Compressor Stage Control to Prevent Rapid Cycling in Air Conditioners
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Solution Overview
Problem
Conventional 1-stage unitary air conditioners with a 1-stage thermostat face challenges in connecting multiple-stage indoor or outdoor units, leading to difficulties in controlling compressor operation stages, resulting in rapid on/off cycles that reduce operational reliability and shorten the compressor's service life.
Innovation Solution
A method that adjusts the operation stage of the outdoor unit based on the previous operation stage and duration, using a variable-capacity outdoor unit with an outdoor unit control device to determine the next operation stage, preventing rapid compressor on/off by maintaining the operation stage for a predetermined period, and adjusting stages between high, middle, and low settings accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a 1-stage thermostat is connected to a variable-capacity outdoor unit, then the system can operate in multiple stages (high, middle, low), but the compressor experiences rapid on/off cycles that reduce reliability
Solution Approach 1:
The control device performs preliminary action by detecting when the compressor is stopped and predicting the next operation stage before the compressor actually starts. It sets a predetermined period after stoppage and controls the operation stage accordingly, preventing rapid on/off cycles by preparing the appropriate stage in advance rather than reacting immediately to thermostat signals.
Solution Approach 2:
The system dynamically adjusts the compressor operation stage based on the elapsed time since the last stoppage. The control device changes the operation stage according to the detected time period, creating a dynamic control strategy that adapts to the compressor's operational history and prevents rapid cycling between stages.
2Use of energy by moving object
If the compressor operation stage is changed frequently to match cooling loads, then energy efficiency improves, but the compressor service life is reduced due to rapid on/off cycles
Solution Approach 1:
The control device uses preliminary action by detecting compressor stoppage and predicting the next operation stage before actual startup. It establishes a predetermined period after stoppage and controls the stage based on this advance detection, allowing energy-efficient stage selection while preventing harmful rapid cycling that would reduce service life.
Solution Approach 2:
The system implements feedback by continuously detecting the compressor operation state and the elapsed time since stoppage. The control device uses this feedback information to determine the appropriate operation stage, creating a closed-loop control system that balances energy efficiency with compressor protection.
Data Source
AI summary
A method of preventing rapid on/off of a compressor in a unitary air conditioner comprises the steps of, when a unitary-capacity operation signal is inputted from a thermostat to start an outdoor unit, and a specific operation stage is continued for more than a predetermined period of time after the operation is started, changing the operation stage of the outdoor unit to an operation stage higher than the specific operation stage, and operating the outdoor unit in the changed operation stage, and, when the compressor is stopped according to a signal from the thermostat within a specific period of time after the operation stage is changed to an operation stage higher than the specific operation stage, starting the operation in the specific operation stage at the next operation, and still performing the operation in the specific operation stage although the operation state is continued for more than a predetermined period of time. Consequently, the compressor is prevented from being rapidly turned on/off, and therefore, operational reliability of the compressor is improved, and the service life of the compressor is increased.