Commercial Building Re-tuning: Overview and Key Operational Faults and Corrections
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Transcript of Commercial Building Re-tuning: Overview and Key Operational Faults and Corrections
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Commercial Building Re-tuning: Overview and Key Operational Faults and Corrections
Srinivas Katipamula, Ph.D.Staff Scientist, Pacific Northwest National Laboratory
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Better Building by Design – 2011February 10th, Sheraton Conference Center Burlington, Vermont
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Presentation OutlineLearning Objectives
Definition of Retro-Commissioning and Re-tuning
Why Retro-Commission a Building?
Washington State Project Approach to Re-tuning
U.S. Department of Energy Project on Re-tuning
Overview of Re-tuning TrainingIdentifying Low-cost/No-cost Operational Faults Using the Re-tuning ApproachCommon Operation FaultsExample Operational Faults
Results from Re-Tuning Buildings
Conclusions
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Efficiency Vermont is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.
This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.
Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
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Learning Objectives
At the end of this program, participants will be able to:
Understand an overview of Commercial Building Re-Tuning
Understand Key Building Operation Faults and Their Corrections (These presentations will provide an overview of the re-tuning process including the difference between re-tuning and other similar approaches)
Describe the various steps in the re-tuning process
Identify targets that commonly yield significant improvements in operation and decreases in energy use and discuss how re-tuning can yield a “gold mine” in savings
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Course EvaluationsIn order to maintain high-quality learning experiences, please access
the evaluation for this course by logging into CES Discovery and clicking on the Course Evaluation link on the left side of the page.
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Definitions
HVAC Retro-commissioningHVAC Re-tuningHVAC Re-commissioningHVAC Continuous CommissioningSM
Monitoring-Based CommissioningAll processes above in part relate to setting up control systems to some known design configurations, verifying set points and adding control algorithms
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Why Retro-Commission a Buildings?
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Retro-Commissioning Literature
A number of studies have shown that retro-commissioning buildings can lead to significant energy savings – 5 to 30%Cost of retro-commissioning varies between 0.1$/sf to 0.6$/sfCost savings can range between 0.1$/sf to 0.75$/sfSimple payback ranging from 3 months to 3 yearsA number of the measures addressed by retro-commissioning relate to our inability to control the building operations
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Why is Retro-Commissioning not Widely Used?
There is a perception that retro-commissioning can be expensive
It can be expensive, but typically has less than 3 year paybacks
There is a perception that measures addressed during retro-commissioning do not persist for a long time (>6 months)
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Re-tuning can Fill the Gap
Re-tuning can address both the cost and the persistence questionBecause re-tuning is implemented by leveraging information from building automation system and primarily targets operational problems, cost of implementation is significantly lower than retro-commissioningBecause re-tuning costs a fraction of retro-commissioning, it can be periodically done to ensure persistence
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Origins for Re-Tuning
In 1990s several researcher organizations were developing automated fault detection and diagnostics (FDD) tools – the researchers found that the FDD tools can indeed be used for commissioning building systemsAlso, at the same time Texas A&M University was using a process called continuous commissioning to retro-commission existing buildingsIn 2000s monitoring-based commissioning was being applied at many California campuses
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What is Re-Tuning?
A systematic process to identify and correct building operational problems that lead to energy wasteImplemented primarily through the building control system at no cost other than the labor required to perform the re-tuning processIncludes small, low-cost repairs, such as replacing faulty sensorsIncludes identifying other opportunities for improving energy efficiency that require investmentMight be thought of as a scaled-down retro-commissioning focused on identifying and correcting operational problems
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Major Focus Areas in Re-Tuning
Occupancy schedulingDischarge-air temperature controlDischarge-air static pressure controlAir-handling unit (AHU) heating & coolingAHU outside/fresh air makeupAHU economizer operationZone conditioningMeter profilesCentral plant
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Purpose of Re-Tuning
Improve the building’s energy efficiency through low-cost and no-cost operational improvements (mostly control changes)Identify opportunities to further increase the building’s energy efficiencyIdentify problems requiring physical repairCatch the big energy saving opportunities
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Life Cycle of Retro-Commissioning/Re-Tuning
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Time
Typical commercial building behavior over time
Periodic Re-tuning Ensures Persistence
Continuous Re-tuning Maximizes Persistence
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Washington State Re-Tuning Pilot Project
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Large Commercial Buildings Project
GoalEducate companies that large buildings can be re-tuned economically to save electricityTeach the proper techniques and skills to perform re-tuning, and Show that service providers can provide re-tuning as a service for a fee
ApproachRecruit 5 to 10 companies that provide HVAC services to commercial buildings to deliver re-tuning services and to help recruit customersEach of the selected service providers are required to recruit at least 6 buildings for re-tuningUse 10 to 20 of the buildings as training grounds for hands-on training of the HVAC service providers on how to perform re-tuning
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U.S. Department of Energy Re-Tuning Project
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U.S. Department of Energy Re-Tuning Training Outreach
Re-tuning Training was Originally Developed as part of a Project Funded by Washington State (www.retuning.org)
Extending Training Outreach Beyond WA State (www.pnl.gov/buildingretuning)
Organization with large building stock interested in getting trained in the re-tuning processTrain-the-trainer – secondary goal
Working with a number of organizations to recruit for both the above approaches
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Online Interactive Re-Tuning Training
PNNL is also converting the training into an online interactive training
Role based training with help of learning management system
Modular
Interactive with ability to create abnormal conditions
Questions and answers at the end each module and at the end of the course
PNNL is also looking to automate identification of the no-cost/low-cost operational problems
To improve persistence and cost of retro-commissioning
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Project Objective
Improve operational efficiency of the commercial building sector by transferring the skills to “re-tune” large commercial buildings
Training building operators and service providers in the general principles and practices of good energy management
Publicizing the results of the project to other building operators and HVAC service providers, who are not part of the training, and to customers to encourage widespread adoption of these energy-saving methods
Preparing case studies to quantify comfort impact and energy savings resulting from re-tuning
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Overview of Re-tuning Training
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Re-tuning Training
Training consists of two partsClassroom training
6 to 8 hours, limited to 20 to 25 people
Field training1 day to 3 days, depending on the size of the buildingLimited to 4 to 8 people
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Intent of Re-tuning Training
Provide an in-depth training of the re-tuning approachPrepare the participating technicians for hands-on field trainingProvide an opportunity to ask questions and get clarification on any aspect of the re-tuning process
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“Tell me and I'll forget; show me and I may remember; involve me and I'll understand”
Chinese Proverb
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Six Primary Steps of Re-Tuning
Collecting Initial Building Information: Basic building informationPre-Re-Tuning Phase: Trend-data collection and analysisBuilding Walk Down: Getting to know the buildingRe-Tuning: Identifying and correcting operations problemsPost Re-Tuning: Reporting re-tuning findingsSavings Analysis: Determining and reporting the impacts
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Six Primary Steps of Re-Tuning
Collecting Initial Building Information: Basic building informationPre-Re-Tuning Phase: Trend-data collection and analysisBuilding Walk Down: Getting to know the buildingRe-Tuning: Identifying and correcting operations problemsPost Re-Tuning: Reporting re-tuning findingsSavings Analysis: Determining and reporting the impacts
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Information to Collect
Overall building geometry Approximate gross square feet
Number of floors
General building shape
Type of HVAC system(s)Approximate number of zonesApproximate number of each major type of equipment
Boilers
Chillers
Air handlers
Type of building automation system (manufacturer, model, version)
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Collecting basic building information
If you manage the building, you probably have all or most of this information at your fingertipsGather information to guide selection of trend logs to set up in the next phaseDetermine the overall design of the building and its mechanical systems
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Six Primary Steps of Re-Tuning
Collecting Initial Building Information: Basic building informationPre-Re-Tuning Phase: Trend-data collection and analysisBuilding Walk Down: Getting to know the buildingRe-Tuning: Identifying and correcting operations problemsPost Re-Tuning: Reporting re-tuning findingsSavings Analysis: Determining and reporting the impacts
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Trend-Data Collection & Analysis: Purpose
Detect potential operational problems even before visiting the buildingIdentify problems that require time histories to detect – incorrect schedules, no use of setback during unoccupied modes, poor economizer operation
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Steps for Trend Data Collection
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• Develop a monitoring plan – develop forms to guide service providers through this. Plan includes the points to trend and for each point:– Planned trend start time
– Planned trend end time
– Length of measurement period (2 weeks recommended)
– Time interval between logged measurements (30 minutes or less recommended)
– Measurement units (e.g., F for temperature)
• Implement trend logs in control system
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Analyze Trend Log Data – Major Steps
Download trend log data files from BASFormat data files for compatibility with the spreadsheet analysis toolOpen data files in spreadsheet analysis tool and automatically generate graphsReview graphs to identify operational issuesRecord operational issues for reference during re-tuning
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Review Graphs & Identify Operation Issues
Issues to investigate with trend log dataPNNL spreadsheets automatically generate graphs neededWe’ll look at some examples of what to look forOnline reference document provides additional information and examples, which you can refer to any time you need to (see www.retuning.org)
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ECAM Software
ECAM ≡ Energy Charting And Metrics
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1. Select data from existing spreadsheet
2. Map points (optional; required for Re-tuning)
3. Create schedules (optional)
4. Input energy project dates (optional)
5. Create metrics and charts
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Re-tuning Menu
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ECAM: Example AHU Time Series Charts
Outdoor, return, mixed, and discharge air temperatures vs. time
Discharge air temperature and discharge air temperature set point vs. time
Outdoor air fraction and damper position signal vs. time
Outdoor and return air temperatures, damper position signal vs. time
Damper, chilled water valve, and hot water valve position signals vs. time
Damper position signal vs. time
Discharge static pressure vs. time
Supply fan speed, status, and static pressure vs. time
Return fan speed and status vs. time
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ECAM: Example AHU Scatter Charts
Discharge air temperature vs. discharge air temperature set point
Chilled water signal vs. hot water signal
Damper signal vs. outdoor air temperature
Mixed air temperature vs. outside air temperature
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ECAM: Example Zone Charts
Zone damper position signal, reheat valve position signal, occupancy mode, andZone temperature vs. time.
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ECAM: Example Central Plant Charts
CHW supply, return, ΔT, and outdoor air temperature vs. time
HW supply, return, ΔT, and outdoor air temperature vs. time
CHW flow and outdoor air temperature vs. time
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Six Primary Steps of Re-Tuning
Collecting Initial Building Information: Basic building informationPre-Re-Tuning Phase: Trend-data collection and analysisBuilding Walk Down: Getting to know the buildingRe-Tuning: Identifying and correcting operations problemsPost Re-Tuning: Reporting re-tuning findingsSavings Analysis: Determining and reporting the impacts
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Building Walk Down: Purpose
Get to know the building betterDevelop a general impression of:
Overall building conditionOverall building designHVAC system design
Collect some basic data on the building systems at a level of detail greater than the initial data collection
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Building Walk Down: Major Steps
Review electrical and mechanical printsWalk the outside of the buildingWalk the inside of the buildingWalk down the roofWalk down the air handlersWalk down the plant areaReview the DDC system (BAS) front end
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Six Primary Steps of Re-Tuning
Collecting Initial Building Information: Basic building informationPre-Re-Tuning Phase: Trend-data collection and analysisBuilding Walk Down: Getting to know the buildingRe-Tuning: Identifying and correcting operations problemsPost Re-Tuning: Reporting re-tuning findingsSavings Analysis: Determining and reporting the impacts
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Occupancy Scheduling
Shut off systems whenever possibleNight unoccupied schedulesWeekend unoccupied schedulesDaytime no or low use unoccupied schedules
Auditorium, class rooms, conference rooms
Includes lightingIncludes specialized exhaustDo not restart too early
Use a startup schedule based on building needs
Do not use fresh air during warm-up except last 30 minutes for flushing building
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Occupancy Scheduling (continued)
Shut off systems whenever possibleRefrain from starting up system for the occasional nighttime user or weekend userUse bypass buttons
Unoccupied mode is a major cost saverSimple to implementSimple to trackSimple to administer
Sometimes the least paid employee is the most costlyJanitors working at night with all HVAC running, all fresh air open & lights on Is this required?
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Occupancy Scheduling (continued)
When running at night for warm up, cool down, or maintaining temperatures, do not ventilate (no outside air)Run static pressure at ½ of normal set points, if it does not affect reheat controls
Check to make sure heated areas get full air in unoccupied modesPush unoccupied mode air to where it is needed
Set VAV boxes in interior zones to unoccupied with 0 air flow
Set VAV boxes with reheat to a high air flow in unoccupied mode, so box will be 100% open during night cycling
Air gets to zones needing heat
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Occupancy Scheduling (continued)
Building electric consumption should show significant energy drop for nights/weekends
Signifying setbacks are active on all HVAC systems Base load versus peak loads should be at least 30% difference and as much as 50% with aggressive setbacks
Trended data for zone temps should show 5-10oF deviations from set points when setbacks are active during non-shoulder months
Winter zone temps should drop down to 60-65oF and summer zone temps should rise to 80-85oF
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Occupancy Schedule (continued)
Trended data for discharge static pressures should show readings of 0” or at least 50% (half) of normal (occupied) static pressure readingsTrended data for main supply/return fan status should indicate “OFF” during unoccupied periodsTrended data for VAV boxes occupied status should indicate “Unoccupied” during unoccupied periodsTrended data for support systems (reheat pumps, reheat converters, reheat hot water boilers, chillers, towers, pumps, etc) should indicate they are turning off at night, if all areas of the building are also shut down
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Occupancy Schedule (continued)
Unoccupied periods should include weekends, holidays and night hours during work week periods
If facility has sporadic use periods, this may require additional efforts to succeed at implementing setbacks
Make sure the “tail” is not “wagging the dog” – janitors, special events, extreme weather events, overrides, etcHow does your organization respond to trouble calls (occupant complaints)? How do you respond? Is the response a “band-aid” or a long-term solution? Overrides on schedules are not long-term solutions
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Air Handler Data Analysis
Key conditions to look for while analyzing the charts:Unoccupied or 24/7 operation
Unoccupied hour setback
Lower/higher than expected supply air temperature
Excessive outdoor air intakeDuring occupied periodsDuring pre-/pre-cooling periods
Significant reheat during summer/cooling season
Is the supply fan modulating (if VAV)
Higher than normal static pressure
Set point and static pressure resets
Economizer is not utilized or not working properly
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Fan Operation During Occupied and Unoccupied Periods
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Air Handler Data Analysis: Static Pressure
Purpose: Determine whether the static pressure set point is too high or too low
Approach:For each air handler, review a plot of the damper positions of all VAV units vs. time
Look for situations where:Most dampers are nearly closed during cooling – static pressure too highSeveral VAV boxes on an air handler have dampers fully open – static pressure is too low and VAV boxes are not able to meet zone loads – starved boxesDampers are not modulating as conditions change – VAV boxes that are not being controlled or not responding to control signals
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Zone Heating and Cooling Demands (continued): Example Use of Graphs
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Plot of VAV unit dampers vs. time for all VAV units served by an air handler – Very Good Distribution – Most 50% to 75% open
Zone Damper Positions
0
20
40
60
80
100
5/2/20070:00
5/2/20074:00
5/2/20078:00
5/2/200712:00
5/2/200716:00
5/2/200720:00
5/3/20070:00
Time
VA
V D
am
pe
r, %
Op
en
Dam per 1 Dam per 2 Dam per 3 Dam per 4 Dam per 5
Dam per 6 Dam per 7 Dam per 8 Dam per 9 Dam per 10
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Zone Heating and Cooling Demands (continued): Example Use of Graphs
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Plot of VAV unit dampers vs. time for all VAV units served by an air handler – Distribution Marginally OK
Comparison of Zone Damper Position
0
20
40
60
80
100
120
5/2/20070:00
5/2/20074:00
5/2/20078:00
5/2/200712:00
5/2/200716:00
5/2/200720:00
5/3/20070:00
Time
Per
cen
t O
pen
Damper-1 Damper-2 Damper-3 Damper-4 Damper-5
Damper-6 Damper-7 Damper-8 Damper-9 Damper-10
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Zone Heating and Cooling Demands (continued): Example Use of Graphs
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Plot of VAV unit dampers vs. time for all VAV units served by an air handler – Bad Distribution – Too many near fully open
Zone Damper Positions
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20
40
60
80
100
5/2/20070:00
5/2/20074:00
5/2/20078:00
5/2/200712:00
5/2/200716:00
5/2/200720:00
5/3/20070:00
Time
VA
V D
amp
er, %
Op
en
Dam per 1 Dam per 2 Dam per 3 Dam per 4 Dam per 5
Dam per 6 Dam per 7 Dam per 8 Dam per 9 Dam per 10
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Zone Heating and Cooling Demands (continued): Example Use of Graphs
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Plot of VAV unit dampers vs. time for all VAV units served by an air handler – Bad Distribution – Too many near fully closed
Zone Damper Positions
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20
40
60
80
100
5/2/20070:00
5/2/20074:00
5/2/20078:00
5/2/200712:00
5/2/200716:00
5/2/200720:00
5/3/20070:00
Time
VA
V D
amp
er, %
Op
en
Dam per 1 Dam per 2 Dam per 3 Dam per 4 Dam per 5
Dam per 6 Dam per 7 Dam per 8 Dam per 9 Dam per 10
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Zone Damper Position
Some building automation systems provide information about the status of zone dampersPlotting the information as a function of time, will tell you whether or not the fan static pressure is appropriate
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162 - (82%)
27 - (14%)
8 - (4%)
50% or less
50~99%
100%
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Air Handler Data Analysis: Discharge Set point
PurposeReview discharge air temperatures for the air handlersDetermine whether discharge air temperatures are maintained relatively stableDetermine whether the discharge-air temperatures are too cool or too warm
ApproachFor each air handler monitored, review plots of discharge-air temperature and discharge-air set point vs. time and supply-air temperature vs. supply-air set pointLook for deviations between discharge-air temperatures and set pointsLook for unusually high (> 70F) or low (< 55F) discharge-air temperatures
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Air Handling Unit: Minimum Outdoor-Air Operations
PurposeReview minimum outdoor-air operations
Determine whether sufficient outdoor air is being supplied for ventilation
Determine whether more outdoor air than needed is being brought in at times (e.g., when the outdoor-air temperature < 40F or > 60F or when the zones served are unoccupied)
Determine whether outdoor-air dampers close during night and weekend setback and during startup mode in the morning.
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Air Handling Unit: Minimum Outdoor-Air Operations (continued)
ApproachFor each air-side economizer, review plots of:
Outdoor-air fraction (OAF) vs. timeOutdoor-air damper and occupancy mode vs. timeOutdoor-air fraction vs. fan speed (if available)
Determine if OAF > minimum OAF for ventilation when the system is not economizing
Determine whether outdoor-air ventilation is being provided when the building is unoccupied and ventilation is not required for some other reason
If OAF and fan speed are tracking each other, it is an indication of return-air problems
20% damper position is never 20% outdoor air
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Air Handling Unit: Minimum Outdoor-Air Operations (continued)
Potential issues to identifyInsufficient outdoor-air ventilation provided – minimum outdoor-air fraction (OAF) is too low
Too much outdoor-air ventilation provided when the air handler is not economizing
Too much outdoor-air ventilation provided during unoccupied times (nights and weekends), during setback
Use air fraction to find % of outside airWorks if air is mixed relatively evenly
OAF = ((Return-Mixed)/(Return-Outside))*100
Add into code for all air handlers and track history Especially schools and other public spaces
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Economizer FundamentalsThe Basics of Airside Economizers
Airside Economizer: “A duct-and-damper arrangement and automatic control system that, together, allow a cooling system to supply outdoor air to reduce or eliminate the need for mechanical cooling during mild or cold weather.”
Source: ASHRAE Standard 90.1-2004
Return Air
Relief Air
Supply Air
Outdoor Air
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Potential Economizer Savings from Enthalpy Control
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Source: Honeywell Controls
Approximately 15% Savings
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Economizer Operation
PurposeTo determine whether air-side economizers are operating properly
Do economizers open, close, and/or modulate under appropriate conditions?
At what temperature compared to the discharge temperature?
At what apparent control signal values do the economizers open?
Does the cooling coil operate (chilled water flow) during economizing?
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Economizer Operation (continued)
ApproachFor each air-side economizer, review plots of:
Outdoor-air temperature, mixed-air temperature, return-air temperature and discharge-air temperature vs. timeOutdoor-air damper position (% open), outdoor-air temperature, and return-air temperature vs. timeOutdoor-air damper position and chilled-water valve position (% open) vs. time
Look for outdoor-air dampers (economizer) open at unusual times of day or under unusual outdoor temperature conditionsLook for outdoor-air dampers not open to economizer under favorable conditions (outdoor-air temperature between 40F and 60F)Look for outdoor-air damper not closing to minimum position for freeze prevention when outdoor temperature is less than about 40F
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Economizer Operation (continued)
Potential issues to identifyIncorrect economizer operation – numerous causes (identified later during on-site work)
Incorrect control strategy
Stuck dampers
Disconnected or damaged linkages
Failed actuator
Disconnected wires
Failed, uncalibrated or miscalibrated sensors
2 X 4 in damper
Others?
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OutdoorReturn/Mixed/Discharge vs. Time
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40
50
60
70
80
3/12/077:12 PM
3/13/0712:00 AM
3/13/074:48 AM
3/13/079:36 AM
3/13/072:24 PM
3/13/077:12 PM
3/14/0712:00 AM
3/14/074:48 AM
Time
Tem
per
atu
re (
oF
)
Outdoor Return Mixed Discharge
Economizer Operation (continued): Example use of Graphs – 1 Day
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Return
Discharge
OutdoorMixed
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Economizer Operation (continued): Example use of Graphs – 3 Days
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Outdoor/Return/Mixed/Discharge vs. Time
30
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60
65
70
75
80
4/9/0712:45 PM
4/10/0712:45 AM
4/10/0712:45 PM
4/11/0712:45 AM
4/11/0712:45 PM
4/12/0712:45 AM
4/12/0712:45 PM
Time
Te
mp
era
ture
(o
F)
Outdoor ReturnMixed Discharge
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Economizer Operation (continued): Example use of Graphs – 1 Day - Faulty
Outdoor-Air Damper Stuck Fully Closed
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Outdoor/Return/Mixed/Discharge vs. Time
0
10
20
30
40
50
60
70
80
3/12/077:12 PM
3/13/0712:00 AM
3/13/074:48 AM
3/13/079:36 AM
3/13/072:24 PM
3/13/077:12 PM
3/14/0712:00 AM
3/14/074:48 AM
Time
Tem
per
atu
re (
oF
)
Outdoor Return Mixed Discharge
Return
Mixed
Discharge
Outdoor
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Economizer Operation (continued): Example use of Graphs – 1 Day - Faulty
Outdoor-Air Damper Stuck Fully Open
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Outdoor/Return/Mixed/Discharge vs. Time
30
35
40
45
50
55
60
65
70
75
80
3/12/077:12 PM
3/13/0712:00 AM
3/13/074:48 AM
3/13/079:36 AM
3/13/072:24 PM
3/13/077:12 PM
3/14/0712:00 AM
3/14/074:48 AM
Time
Tem
per
atu
re (
oF
)
Outdoor Return Mixed Discharge
Return
Discharge
Outdoor
Mixed
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ECAM: AHU Scatter Plot Sample
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Source: Financial Times EnergyJammed/Frozen Damper
Wired poorly
• Jammed or frozen outside-air damper
• Broken and/or disconnected linkage
• Nonfunctioning actuator or disconnected wire
• Malfunctioning outside air/return air temperature sensor
• Malfunctioning controller
• Faulty control settings
• Installed wrong or wired incorrectly
Disconnected Damper
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Poorly Designed Packaged Rooftop Units with Economizer Installed Next to Heat Source from Condenser
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Inefficient Designs on RTU Contribute to Poor Air Circulation at Intake Air
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Air Handling Unit: Outdoor-Air Lockouts for Heating & Cooling (continued)
Potential issues to identifyAir-handler heating and cooling coils operating simultaneously
Heating and cooling lockouts possibly overlapping (need to be confirmed in control-code settings during on-site re-tuning)
Unreasonable values are set for the heating and cooling lockouts
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Outdoor-Air Lockouts for Heating & Cooling (continued): Example use of Graphs
Air handler heating vs. cooling valve positions
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Chilled Water vs Hot Water Valve Signals
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10
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30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100
Chilled Water Signal (%)
Ho
t W
ater
Sig
nal
(%
)
Worse
Bad
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Zone Heating and Cooling Demands
Purpose Get a feel for how many zones on each monitored air handler are heating and how many are cooling at the same timeGet a sense of which areas are heating and which are cooling at any given timeDetermine if any individual zones are heating and cooling at the same timeOthers?
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Zone Heating and Cooling Demands (continued)
ApproachFor each air handler, count the number of zones served that are in heating mode and those in cooling mode under various conditions (e.g., time of day and approximate outdoor air temperature). Use a plot of number of zones in each mode and the outdoor temperature vs. timeNote which areas of the building (e.g., interior core vs. perimeter zones or zones facing certain directions) are in heating and coolingLook for any monitored zones that are using both heating and cooling over relatively short time periods or cycling between heating and cooling
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Zone Heating and Cooling Demands (continued)
Potential issues to identifySupply-air temperature too cool or too warmNo use of supply-air resetCertain zones (e.g., corner offices) driving air handler operationSome zones out of control, oscillating between heating and coolingOthers
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Importance of Terminal Units Re-tuning
Terminal boxes are major building HVAC components and directly impact comfort and energy costsTerminal boxes control may cause occupant discomfort and waste energy, if they have inappropriate operation and controlImproper minimum air flow setting and control may result in significant simultaneous heating and cooling, extra fan power consumption and higher energy consumption in the summer
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Sign of Problem with Zone Control!
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Sign of Problem with Zone Control!
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What’s Wrong with this?
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Thermostat
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Central Plant and Whole Building Meter Profiles
Training also coversChiller and boiler plantsMeter profiles
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Re-tuning Examples
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Re-tuning Example
VFD speed is greater than 80% before re-tuning; note the speed after re-tuning
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0
10
20
30
40
50
60
70
80
90
100
10/25 10/26 10/27
VFD
SPee
d (%)
TIME
VFD Speed
Before Re-tuning- Almost constant speed
0
10
20
30
40
50
60
70
80
90
100
11/2 11/3 11/4 11/5
VFD
SPee
d (%)
TIME
VFD Speed
After Re-tuning
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Re-tuning Example (cont)
Lockout chilled water consumption in winter
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0
20
40
60
80
100
120
10/25 10/26 10/27
Coil V
laves
(%)
TIME
CHWV HWV
Before Re-tuningBefore Re-tuning
0
20
40
60
80
100
120
11/2 11/3 11/4 11/5
Coil V
laves
(%)
TIME
CHWV HWV
After Re-tuning
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Re-tuning Example (cont)
Eliminated alternating cooling/heating
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0
20
40
60
80
100
120
10/25 10/26 10/27
Tem
pera
ture
(deg
reeF
)
TIME
SAT
Before Re-tuning
60~100F (heating/cooling)
0
20
40
60
80
100
120
11/2 11/3 11/4 11/5
Tem
pera
ture
(deg
reeF
)
TIME
SAT
After Re-tuning
Heating
Cooling
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Six Primary Steps of Re-Tuning
Collecting initial building information: Basic building informationPre-Re-Tuning Phase: Trend-data collection and analysisBuilding Walk Down: Getting to know the buildingRe-Tuning: Identifying and correcting operations problemsPost-Re-Tuning: Reporting re-tuning findingsSavings Analysis: Determining and reporting the impacts
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Post-Re-Tuning: Calculating Energy Savings – Overview of Approach
Calculated as the difference between the actual energy use in the post-re-tuning 12 months and the energy use that would have occurred during the same 12 months if the building had not been re-tuned.
jactualjbasejsavings EEE ,,,
90
= energy savings for a specific building (j)
= actual measured energy use of the building during the 12 months after re-tuning
= energy consumption of the building during the 12 months after re-tuning if it had not been re-tuned
jsavingsE ,
jactualE ,
jbaseE ,
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Highlights of Re-Tuning
Every set point adjustment made will have an impact of some sort on the utility meterCan save energy and keep occupants comfortableIt takes time to tune a buildingThere are no magic set points that work all the timeAlways monitor the utility meters (gas & electric) to see what affect you have hadLook at the big picture when making adjustmentsWatch the meter profiles weeklyLearn and know the building’s personality
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Questions?
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