Problem Statement
Facility HVAC equipment routinely fails to satisfy performance expectations
envisioned at design. Often this is because of malfunctions, due either
to improper configuration or to equipment failure. Furthermore, such failures
often go unnoticed for extended periods of time. Additionally, higher expectations
are being placed on a combination of different and often conflicting performance
measures, such as energy efficiency, indoor air quality, comfort, reliability,
limiting peak demand on utilities, etc. To meet these expectations, the
processes, systems, and equipment being used in both commercial and residential
buildings are becoming increasingly complex. This increasing sophistication
both encourages the use of automated diagnostics to ensure fault-free operation
and enables diagnostic capabilities for the various building systems by
providing a distributed platform that is powerful and flexible enough to
perform FDD.
Most of today's emerging FDD tools are stand-alone software products that do not reside in a building control system. Thus, trend data files must be processed off-line or an interface to the building control system must be developed to enable on-line analysis. This approach does not scale well because all of the data must be obtained at a single point. In contrast, NIST has developed FDD tools suitable for embedding in commercial AHU and VAV box controllers. A series of research projects in which batch implementations of these tools were developed and refined using data collected from simulation, emulation, laboratory testing, and real buildings are documented in reports under the previous PIER Buildings Program (contract #400-99-011). These tools were found to be successful at finding a wide variety of faults including stuck or leaking dampers and control valves, sensor drift, and improper control sequencing. Preliminary investigations to study embedding the tools in AHU and VAV box controllers were conducted.
The research described in this project will build upon past work to resolve
the remaining barriers to commercialization of FDD: the lack of confidence
in automated diagnostics, the specialized knowledge required to embed FDD
in HVAC controllers, and the trial and error method of determining fault
thresholds. By having one or more manufacturer offer its controller products
with FDD "built in", competitive pressure will give the other
manufacturers a powerful incentive to provide their controller products
with similar capabilities. Securing the commitment of one or more potential
partners to commercialize AHU and VAV box diagnostics is critical to the
success of the proposed project. NIST has secured verbal commitments from
manufacturers and is currently working out the details of a written agreement.
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Current News:
- NIST Final Report 7365:
"Result from Field Testing of Embedded
Air Handling
Unit and
Variable Air Volume
Box Fault
Detection
Tools", October
2006
- Cooperative Research and Development Agreements
were signed with Automated Logic Controls,
(ALC), Alerton, Delta Controls, and Tour
Andover Controls to support the commercialization
of the algorithms. ALC has communicated the
availability of the algorithms to its global
dealer network.
- A Case Study of the use of the algorithms
at the PhilipBurdonFederalBuilding in San Francisco, CA is posted on the site. The algorithms are
installed
on 1200 VAV
boxes and
2 small AHU’s
in the building.
The algorithms
will be installed
in additional
AHUs. Significant
preventative
maintenance
benefits
have already
been achieved.
The alarm
output of
the algorithms
has been
integrated
with the
facility’s
Computerized
Maintenance
Management
System.
- The Iowa Energy Center requested a bid for implementation of the
algorithms
in a controls
system upgrade.
Invensys
won the bid
and the algorithms
are installed
and being
tested for operational
functionality
and will
become part of the
teaching
curriculum.
- The APAR rules have been adapted for testing
in fan coil
unit as part
of a Hartman Loop
control system.
- Pacific Northwest National Laboratory completed
a review
of the AHU
and VAV box algorithms
and their
integration
with a Johnson Controls
Metasys system.
The code
is now available.
- The project has completed a robust set of
algorithms
developed
with some initial market
entry and
interest.
- Pseudo-code versions of the AHU and VAV box
algorithms
are available.
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