The primary goal of this work was to develop, demonstrate, and evaluate a fault detection and diagnostics (FDD) system that incorporates integrated virtual sensors and fault impact models for decision support. FDD systems have the potential for improving energy efficiency along with reducing service costs. To achieve this goal, virtual sensors and fault impact models that only require low cost measurements are implemented to detect the cause of the fault, diagnose the severity of a fault and assess the performance reduction. The integrated virtual sensors can handle multiple simultaneous faults to isolate a specific fault from other faults. The fault impact models can decouple performance impacts of individual faults under multiple fault conditions. A complete diagnostic FDD system was implemented and demonstrated for a rooftop air conditioner. The test conditions included a wide range of fault and operating conditions with multiple simultaneous fault situations. Laboratory tests were performed to define reasonable thresholds for the FDD system with multiple simultaneous faults to assess whether RTU service should be performed. The FDD system provided the following diagnostic outputs for and impacts of: 1) loss of compressor performance, 2) low or high refrigerant charge, 3) fouled condenser, 4) evaporator filter, and 5) faulty expansion device.

这项工作的主要目标是开发，演示和评估故障检测和诊断（FDD）系统，该系统集成了集成的虚拟传感器和故障影响模型以提供决策支持。FDD系统具有提高能源效率以及降低服务成本的潜力。为了实现此目标，实施了仅需要低成本测量的虚拟传感器和故障影响模型来检测故障原因，诊断故障的严重程度并评估性能下降。集成的虚拟传感器可以处理多个同时发生的故障，以将特定故障与其他故障隔离。故障影响模型可以使多个故障条件下单个故障的性能影响脱钩。实施了完整的诊断FDD系统，并针对屋顶空调进行了演示。测试条件包括广泛的故障和操作条件以及多个同时发生的故障情况。进行了实验室测试以定义FDD系统的合理阈值，并同时出现多个故障，以评估是否应执行RTU服务。FDD系统提供以下诊断输出，并对以下方面产生影响：1）压缩机性能损失； 2）制冷剂充注量过少或充实； 3）冷凝器结垢； 4）蒸发器过滤器；以及5）膨胀装置故障。