What is FDD?
FDD is fault detection and diagnostics, the practice of finding faults in building and plant equipment after they occur, diagnosing the root cause and getting them fixed. It is reactive: the fault has already happened, and FDD shortens the time to find it, explain it and correct it.
What it is
FDD analyzes data from equipment and controls, such as temperatures, pressures, valve and damper positions, fan status and energy use, against rules or models of expected behavior. When behavior departs from expectation, it flags a fault and explains the likely cause.
Common faults include simultaneous heating and cooling, stuck dampers, failed sensors, equipment running outside schedule and fans that have stopped. FDD is not the same as predictive maintenance. FDD deals with faults that have happened. Predictive maintenance aims to catch early signs of wear before a fault occurs.
Who it applies to / where it is used
FDD is used in commercial buildings, hospitals, campuses, airports, data centers and industrial plants, wherever HVAC and plant systems are connected to a BMS or meters. Building codes and directives increasingly reference fault detection capabilities.
How it is measured / what evidence it needs
The value of FDD is measured by faults found and fixed, not alerts raised.
- Faults detected, with time of detection
- Root cause diagnosis in plain language
- Work orders created and closed in the CMMS
- Confirmation that the system returned to normal
- Energy or comfort effect of the fix
How Aqueduct helps
Aqueduct finds faults, diagnoses them and routes the fix. For example, an AHU fan stops, Aqueduct diagnoses a failed rotor shaft, routes a ticket and confirms airflow is back.
- Rules and models running on BMS points over BACnet and Modbus at 60-second refresh
- Plain-language diagnosis through aQ Assistant
- Tickets routed into the customer's CMMS with a recommended fix
- Verification at the meter or sensor that the fix worked