fault detection and diagnostics for rtus

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

www.esource.com || © 2013 E Source2

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


Examples


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


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


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


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


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


Different Approaches

Quantitative Statistical

Airflow Refrigerant Cycle Economizer


Minimalist Approach – Using Sound


Economizer Only Approach


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


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


Standards will Allow Code Integration and Consistency of Products

ASHRAE Standard 207

California Title 24 – Building Energy Efficiency Standards

IECC (International Energy Conservation Code)


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


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


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!


Combined Devices: FDD + VFD

For constant speed RTUs Converts to variable speed and also adds FDD


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


David Podorson

Senior Research Associate, E Source

303-345-9103 [email protected]

For More Information

mailto:[email protected]

fault detection and diagnostics for rtus

Technology

fdd probability

data collects data

fault detection diagnosis

data report actionable

fdd mandatory requirement

fdd tools function

example faults

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