Fault Detection and Diagnostics for Rooftop Air Conditioners

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The fives types of faults are refrigerant leakage, compressor valve leakage,
condenser fouling, evaporator fouling and liquid line restriction. Each fault was
introduced at four or five different levels (see Table 2-2) and tested at five different load
levels (20%, 40%, 60%, 80% and 100%). In all, there are 120 sets of fault data available
to test the proposed FDD method. For each of the different load levels, the unit was on
for different amounts of time. The total cycle time was held constant at 43 minutes and
the on time was varied for the different load levels. For example at 20% load, the unit ran
for 9 minutes and was off for 36 minutes. Two consecutive transient start-up responses
were generated and data were recorded at 3-second intervals at each of the conditions and
fault levels.
Fault
Level
Table 2-2 Fault levels introduced to different faults
Refrigerant
Leakage
Liquid-line
Restriction
Compressor
Valve Leakage
Condenser
Fouling
1 0 0 0 0 0
2 3.5% 5.0% 7.0% 14.6% 12%
3 7.0% 10% 14% 29.2% 24%
4 10% 15% 19% 41.4% 35%
5 14% 20% 28% 56.1% NA
Evaporator
Fouling
2.2.2 Chen’s Data
Similar to Breuker’s data, two sets of laboratory data were collected under
controlled conditions for two packaged York rooftop air conditioners with TXV as the
expansion device: a 5-ton one stage system and a 7.5-ton two-stage system by Chen
(2000). In addition to the five faults considered by Breuker (1997b), two more faults,
refrigerant overcharge and non-condensable gas, were simulated.
2.2.3 Todd Harms’ Data
Although the data collected by Todd Harms were originally used for refrigerant
charge inventory research, they are useful to test modeling approaches and refrigerant