Fault Detection and Diagnostics for Rooftop Air Conditioners

will be calculated to represent the whole group. The radius r is an important parameter for
the performance of clustering algorithm. For example, there are 256 of steady-state data
points after steady-state detection for the data taken during August 13 to 17 at Purdue field
site; there are 54 clusters after it is clustered.
4.3 Purdue Field Site Results
The interpolating performance of the polynomial plus GRNN model is very good, as
shown with laboratory data. The interpolating performance for field site data (partially
shielded condenser inlet air temperature) is also good, as shown in figures 4.10, 4.11 and
4.12.
To test extrapolating performance, three cases were considered, one using a partially
shielded condenser inlet air temperature, one using a fully shielded condenser inlet air
temperature and one using an unshielded condenser inlet air temperature. Since shields 1,
2 and 3 (figure 4.13) do not isolate the temperature sensors completely from solar
radiation, rainfall and wind the way the outdoor air duct does, “partially shielded” refers to
sensors shielded by shields 1, 2 and 3 and “full shielded” refers to the sensor in the
outdoor air duct (figure 4.13) which is totally isolated from the environment. Figures 4.14
to 4.22 show that models built with partially shielded condenser inlet air temperature have
reasonably good extrapolating ability which is the best among the three kinds of model.
Models built using unshielded condenser inlet air temperature extrapolate poorly. The
model that uses fully shielded condenser inlet air temperature data also extrapolates well
but a little worse than the partially shielded condenser inlet air temperature model except
that evaporating temperature is extrapolated better than with partially shielded model. So it
can be concluded that the solar radiation impact on the whole system is not so significant
as on the unshielded condenser inlet air temperature sensor. The readings of the
unshielded condenser outlet air temperature sensor exaggerate the solar radiation impact
on the system. In addition, the fully shielded sensor readings also underestimate the solar
radiation impact on the whole system. The exception is for the evaporating temperature
because the solar radiation and outdoor air temperature have very little impact on the
evaporator, which is mainly driven by mixed air temperature and humidity. In summary,
figure 4.23 shows an overview of the environmental factor impacts on modeling
performance.
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