Fault Detection and Diagnostics for Rooftop Air Conditioners

3. Comparison of black-box modeling approaches using
laboratory data
3.1 Laboratory experimental data
Breuker (1997) gathered data under controlled conditions in a laboratory on a test unit
at a number of controlled operating conditions and used the data to test the ability of
several model types to produce accurate estimates of unit performance. This test unit
is a three ton packaged rooftop unit (Carrier Model 48DJE004610) which has a
constant speed and hermetically-sealed reciprocating compressor (Copeland Model
CRH3-0275-TFD) and uses fixed-orifice type expansion devices for refrigerant flow
control. The grid of indoor conditions used in the testing is shown in figure 3.1. The
larger set of data, labeled "Training Data" in the figure, was gathered at indoor dry
bulb temperatures of 70, 73, 76, 79, and 82 F, indoor wet bulb temperatures of 55, 58,
61, 64, and 67 F, and ambient temperatures (not shown in figure) of 60, 70, 80, 90,
and 100 F. The smaller set of data, or "Test Data", was gathered at indoor dry bulb
temperatures of 71.5, 74.5, 77.5, and 80.5 F, indoor wet bulb temperatures of 56.5,
59.5, 62.5, and 65.5 F, and ambient temperatures of 65, 75, 85, and 95 F. As the
figure shows, however, not all dry bulb conditions were simulated at all wet bulb
conditions. A total of 40 distinct combinations were simulated in the "Test Data" and
94 combinations were simulated in the "Training Data" set. The conditions were
selected because they completely cover the normal comfort region defined by
ASHRAE (1993). The reason for gathering the data in two distinct sets was to allow
for training and testing on separate sets of data. Training on the large set and testing
on the small set of data tests the ability of the model to interpolate accurately.
Training on the small set will test the ability of the model to extrapolate beyond the
training data.
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