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P2-3. Air
Handling Unit and VAV Box Diagnostics > Approach
Objectives:
The objectives of this project were to develop,
test, and demonstrate FDD methods that:
- detect common mechanical faults and control
errors in air-handling
units (AHUs) and
variable-air-volume
(VAV) boxes,
- rely only upon sensor data and control signals
commonly available
in commercial building
automation and
control systems,
and
- are sufficiently simple that they could be
embedded in commercial
building unit controllers.
Approach:
Test the APAR and VPACC rules using data
generated by simulation,
emulation, and laboratory
testing. The laboratory study examined the
breadth of faults
that can be detected
and
the conditions under
which they can be
detected.
The research involved
a complementary set
laboratory of experiments
using commercial
AHU and VAV box controllers
under both normal
operating conditions
and operation with
known
faults, emulations
using the NIST Virtual
Cybernetic Building
Testbed (VCBT), and
computer
simulations using
HVACSIM+. The VCBT
is an
emulator that combines
simulations of a
building
and its HVAC system
with actual commercial
controllers. It provides
a way to conduct
tests under a wide
variety of carefully
controlled
conditions and to
compare the results
of
several different
commercial products.
Emulation
provides a test environment
that is closer
to a real building
because it uses real
building
controllers but,
like simulation,
it also
provides carefully
controlled and reproducible
conditions.
Test the APAR and VPACC rules using AHU and
VAV box data from several field sites, including
an office building, a restaurant, as well
as community college and university campuses,
featuring constant- and variable-air-volume
systems. The effectiveness of these tools in detecting
commonly found mechanical faults and control
problems, the reliability of the tools across
several seasons, and the robustness of the
tools in handling data from a variety of
system types and configurations were investigated.
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