Preliminary evaluation of a qualitative model-based fault detector for a central air-handling unit

A Temperature Controller for VAV Air-Handling Units Based on Simplified Physical Models

“…Note the abrupt transitions in the AHU characteristic at the points where operation changes from one subsystem to another (u = 0.33 and u = 0.66). The points t 1 → t 4 on the left of Figure 3 are the corresponding transition temperatures between the subsystem ranges and are important operating points related to performance (Glass et al 1994). The overall gains of each subsystem are labeled to the right of Figure 3 as: G c (cooling coil); G r Figure 3 at a given control signal is the plant gain relevant for control loop performance.…”

Cooling mode fault detection and diagnosis method for a residential heat pump

“…In previous investigations within the HVAC field, several investigators suggested steady-state identification techniques for FDD purposes (Glass et al, 1995, Rossi, 1995, Breuker and Braun, 1998a, Li, 2004. Since the goal of these investigations was mainly fault detection, the evaluation of the steady-state detectors was not performed in detail.…”

“…Several methods of steady state detection were investigated by other researchers. Glass et al (1995) formulated a steady-state detector using a geometrically weighted running method. In this method, the old data are exponentially and automatically attenuated through multiplication with a "forgetting factor", which is based upon a system transition time constant.…”

A Survey of Control Technologies in the Building Automation Industry

“…At this point, the inlet and outlet temperatures across the possible problems heat exchangers should be approximately equal at steady state. Significant differences between these temperatures can indicate a fault condition such as leaking valves, sensor error, stuck valve, etc (Glass et al, 1994).…”