Purdue CHPB / NIST /
NBI / CEC study validates that Field Diagnostics’ Service Assistant HVAC
Diagnostic Protocol is an effective and practical method for evaluating
refrigeration cycle faults
A recently released report (HL 2014-8, Herrick Laboratories,
Purdue University) that describes work funded by the National Institute of
Standards and Technology (NIST), the New Buildings Institute (NBI) and the
California Energy Commission (CEC) found that the performance of the diagnostic
protocol embedded in Field Diagnostics’ Service Assistant tool with SA Mobile
software, which has been available commercially since 1999, was markedly
superior to some other publically available protocols that were evaluated.
The investigation into the effectiveness of various HVAC
refrigeration cycle Fault Detection and Diagnostic methods was conducted by Dr.
David Yuill and Dr. James E. Braun at the Center for High Performance Buildings
(CHPB) located within the Ray W. Herrick Laboratories, Purdue University
(www.engineering.purdue.edu/CHPB). This study looked at not only the accuracy
of the fault detections, but at the “value” of following the tool’s advice. The
study compared factors such as cost of detection, sensitivity of detection,
number of false alarms, and the costs and benefits of addressing the faults
that are reported.
The Purdue team’s innovative evaluator of diagnostic
algorithms was used to estimate the value of eight products as well as two
hypothetical detectors—one “Correct” detector which reports all the faults
present, without consideration of the value of addressing them, and another
“Ideal” detector that only reports faults that would be cost effective to
address.
One of the conclusions of their study was that none of the
protocols tested could provide all the value that the “ideal” detector
provided: the SA protocol in fact provided only about a half of this value.
However, the study found that “the SA protocol provided significant benefit in
all cases” and “the value of the SA protocol was computed to be greater than
the value of the fictitious correct protocol”, which indiscriminately reports
all faults. “The other protocols did not perform well, generally providing
negative value for all cases (i.e. imposing a net cost as compared with the
baseline
·
the “RCA method,” sometimes referred to as “the
manufacturers’ method”, which is used extensively throughout the industry,
particularly as the specified method to test charge levels in California’s
current Title 24 – 2013 building energy code (CEC 2012), as well as in many
utility incentive programs and by Home Energy Rating System (HERS) raters,
·
the “ADM protocol,” which was developed as part
of an ASHRAE research project,
·
the “MPS protocol,” which combines elements of
the ADM protocol and CA Title 24 requirements, and
·
the “TM protocol (abbreviation for Thermodynamic
Metrics), which is a set of rules for typically measured metrics of performance
in air-conditioners.
On the other hand, the Field Diagnostic’s protocol has been
extensively tested over many years and the Purdue CHPB study validates that it
is a very effective and practical method for evaluating refrigeration cycle
faults.
For more information, contact: Todd M. Rossi, Ph.D., Field
Diagnostic Services, Inc., rossi@fielddiagnostics.com, 215/558-5415
Yuill, D. and Braun, J.E., Development of Methodologies for
Evaluating Performance of Fault Detection and Diagnostics Protocols applied to
Unitary Air Conditioning Equipment, HL 2014-8, Ray W. Herrick Laboratories,
Purdue University, December, 2014.
