8. The system according to claim 7 further comprising: an FDD engine configured to instantiate the HFM graph as a runtime system for the building HVAC control system; and an interface configured to access the building HVAC control system, wherein the FDD engine executes the HFM graph with HVAC control system process and control variable data and applies rules for detecting HVAC system faults.
8. The system according to claim 7 further comprising: an FDD engine configured to instantiate the HFM graph as a runtime system for the building HVAC control system; and an interface configured to access the building HVAC control system, wherein the FDD engine executes the HFM graph with HVAC control system process and control variable data and applies rules for detecting HVAC system faults. 10. The system according to claim 8 wherein an HFM node estimates upstream and downstream physical behavior parameters of connected HVAC components with the dynamic output data from the HVAC control system using instrument process and control variables and propagates the results through the HFM graph as parameter ranges.