Fault Detection and Diagnostics for Rooftop Air Conditioners

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5. Three case studies were investigated to validate the proposed approaches.
(Deliverable 2.1.5). One case study provided initial validation of the decouplingbased
FDD approach using laboratory data where single faults were artificially
introduced into a 3-ton Trane rooftop unit (RTU) with a fixed-orifice as the
expansion device. The second case study demonstrated the whole FDD
methodology by artificially introducing multiple-simultaneous faults into the
Purdue field emulation site, where a 5-ton York RTU with a TXV as the expansion
device is installed. Finally, the decoupling-based FDD approach was applied to
California field sites.
6. Finally, an initial economic assessment of the proposed FDD technique was
performed. Conservative estimates of the lifetime net savings ranged from $4,000
to $10,000 per RTU, with annual net savings ranging from $400 to $1,000 and a
payback period of less than one year.
Research on further improvements and evaluations of the FDD methodology will
continue as follows:
1. Obtain more detailed RTU information for all the California field sites and apply
the proposed FDD technique more completely to these field sites.
2. Further improve the performance of the unified FDD technique by improving the
modeling approach that is based on manufacturers’ data and find an efficient and
practical way to tune these models using low-cost sensors. Improve other virtual
sensors’ performance and consider trying to remove pressure and humidity sensors.
3. Improve the overall performance model for assessing performance degradations of
packaged air conditioning equipment under faulty operation using limited sensor
and manufacturers’ rating data.
4. Expand the service cost database and build a more detailed economic assessment
model to more accurately evaluate the potential savings associated with the FDD
technique and to provide guidelines for the fault evaluation and decision step.