Tandem Compressor Fault Isolation for Pressure and Temperature Trips
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Solution Overview
Problem
In HVAC systems with tandem compressors, existing pressure and temperature switches cannot identify which compressor is causing an over-pressure or over-heated condition, leading to the interruption of power to all compressors, potentially causing damage and failure, and preventing the system from meeting demand.
Innovation Solution
A controller is used to determine which compressor is causing the issue by sequentially turning on each compressor and monitoring for over-conditions, allowing only the faulty compressor to be powered off while the others continue to operate, thus maintaining system functionality and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure and temperature switches are used to protect against over-pressure or over-heated conditions, then compressor safety is improved, but the system cannot identify which specific compressor is faulty, leading to unnecessary shutdown of all compressors
Solution Approach 1:
The patent segments the protection function by providing separate pressure and temperature switches for each compressor in the tandem compressor group. This allows independent monitoring and protection of each compressor, enabling the system to identify and isolate only the faulty compressor while keeping healthy compressors operational, thus resolving the contradiction between safety and productivity
2Reliability
If all compressors are shut down when an over-pressure or over-heated condition is detected, then compressor damage is prevented, but the system cannot meet the cooling or heating demand
Solution Approach 1:
By implementing individual protection switches for each compressor, the system can selectively shut down only the faulty compressor while maintaining operation of healthy compressors. This segmentation enables the system to adapt to partial failure conditions and continue meeting demand, resolving the contradiction between protection and adaptability
Solution Approach 2:
The system changes the operational parameters by allowing different compressors to operate at different states (on/off) based on their individual conditions. This enables flexible adaptation where the system can maintain required capacity by adjusting which compressors are active, resolving the contradiction between protection and demand satisfaction
3Device complexity
If a single pressure or temperature switch controls all compressors, then device complexity is reduced, but the system loses the ability to identify and isolate specific faulty compressors
Solution Approach 1:
The patent applies segmentation by installing separate pressure and temperature switches for each compressor, allowing the system to maintain relatively simple individual switch mechanisms while gaining the capability to identify specific faulty compressors through the distributed switch configuration
Solution Approach 2:
The controller acts as an intermediary that receives signals from multiple distributed pressure and temperature switches, processes this information to identify which specific compressor is faulty, and controls the contactors accordingly. This intermediary function enables fault identification without requiring complex direct communication between switches and compressors
Data Source
AI summary
An HVAC system, comprising a plurality of sensors, a tandem compressor comprising a first compressor and a second compressor, and a controller communicatively coupled to the plurality of sensors and the tandem compressor. The controller may determine a first interruption of power to the tandem compressor and identify a sensor corresponding to the first interruption of power. The controller is further operable to determine that the first interruption of power was caused at least in part by the refrigerant associated with the first compressor exceeding a tolerance condition. The controller may also reconfigure the tandem compressor, wherein on or off settings of the first compressor and the second compressor are determined based on a required load operation of the tandem compressor and the determination that the first interruption of power was caused at least in part by the refrigerant associated with the first compressor exceeding the tolerance condition.