fault detection and diagnostics for rtus
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David Podorson, Senior Research Associate, E Source Rocky Mountain Association of Energy Engineers, 14th Annual Energy Forum presentationTRANSCRIPT
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www.esource.com Thursday, October 17, 2013
Fault Detection and Diagnostics for RTUs
David Podorson
Senior Research Associate, E Source
Rocky Mountain Association of Energy Engineers
14th Annual Energy Forum
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What is Fault Detection & Diagnosis (FDD)?
Add-on, embedded, or SaaS solution Identify a building’s mechanical system faults and
determine the causes behind those faults Attempts to provide persistent commissioning-like
savings Provide three fundamental tasks:
Collect data Analyze data Report actionable conclusions
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Examples
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How They Work
Collects data points Temperature Airflow Economizer runtime
Use proprietary algorithms to diagnose problems Strong differentiator in different products Some products rely on human experts Some products rely on software algorithms
Report results Generally prioritize faults based on energy-use impacts
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FDD is More Actionable than EMS
EMS alarms lack context and actionable recommendations
FDD features include: More computing power to crunch lots of data Analyze why faults occur Calculate repair costs Prioritize faults based on number of variables
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Example Faults Detected
Air temperature sensor failure/fault High/low refrigerant charge Compressor short cycling Refrigerant line restrictions/TXV problems Refrigerant line non-condensables High/low side HX problem Capacity degradation Efficiency degradation Not economizing when it should Damper not modulating Excess outdoor air
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OEM Alarm CodesAlarm Description T110 Circuit A Loss of Charge T111 Circuit B Loss of Charge T126 Circuit A High Refrigerant Pressure T127 Circuit B High Refrigerant Pressure T133 Circuit A Low Refrigerant Pressure T134 Circuit B Low Refrigerant Pressure T140 Circuit C Loss of Charge T141 Circuit C Low Refrigerant Pressure T142 Circuit C High Refrigerant Pressure T408 Dirty Filter
T414
Economizer Damper Actuator Out of Calibration
Economizer Damper Actuator Torque Above Load Limit Alert
Economizer Damper Actuator Hunting Excessively Economizer Damper Stuck or Jammed
Economizer Damper Actuator Mechanical Failure
Economizer Damper Actuator Direction Switch Wrong
Kristen Heinemeir 2011
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Economizers and Thermostats are the Most Common Problems
Refrigerant Circuit
Economizer Air flow Thermostat Sensors0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
46%
64%
42%
58%
27%
New Buildings Institute 2004
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Different Approaches
Quantitative Statistical
Airflow Refrigerant Cycle Economizer
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Minimalist Approach – Using Sound
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Economizer Only Approach
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Intensive Approach – Using Data
Collects data from the EMS Human analysts look over the data at some point
but software truly does the heavy lifting
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FDD Can Pay for Itself
Western Cooling Efficiency Center: Average kWh savings on the order of 12% Benefit/Cost Ratio 1.7
15 year analysis period Probability that fault will occur Probability that fault will be detected with FDD Probability that fault will be detected without FDD
Kristen Heinemeier 2011
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Standards will Allow Code Integration and Consistency of Products
ASHRAE Standard 207
California Title 24 – Building Energy Efficiency Standards
IECC (International Energy Conservation Code)
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ASHRAE Standard 207
Defines an FDD tool's function Defines an FDD performance test Timeline:
Internal draft by January 2014 Public review by January 2015 Expected to be published around January 2016
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California Title 24 –Building Energy Efficiency Standards
Requires all units ≥ 4.5 tons be equipped with FDD Mandatory requirement – not a compliance option Economizer controls only! Releases January 2014 California leads the way – other states to follow
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International Energy Conservation Code (IECC) Following CA’s Lead
IECC is implementing same requirement Many states rely on IECC for their compliance –
potential for much more widespread adoption!
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Combined Devices: FDD + VFD
For constant speed RTUs Converts to variable speed and also adds FDD
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Combined Devices: How Much Energy do They Save?
PNNL case study of 66 RTUs
Average savings of 57% Basically all savings are
from the VFD
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David Podorson
Senior Research Associate, E Source
303-345-9103 [email protected]
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