Commercial Building Re-tuning: Overview and Key Operational Faults and Corrections Srinivas...

Commercial Building Re-tuning: Overview and Key Operational Faults and Corrections

Srinivas Katipamula, Ph.D.Staff Scientist, Pacific Northwest National Laboratory

1

Better Building by Design – 2011February 10th, Sheraton Conference Center Burlington, Vermont

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.

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

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

Why Retro-Commission a Buildings?

7

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

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

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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http://www.retuning.org/

http://www.pnl.gov/buildingretuning

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

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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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

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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http://www.retuning.org/

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

Re-tuning Menu

35

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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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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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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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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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



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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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Plot of VAV unit dampers vs. time for all VAV units served by an air handler – Bad Distribution – Too many near fully open


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

amp

er, %

Op

en




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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


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

amp

er, %

Op

en



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%

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

61

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

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

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

Economizer Operation (continued): Example use of Graphs – 1 Day

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Return

Discharge

OutdoorMixed

Economizer Operation (continued): Example use of Graphs – 3 Days

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Outdoor/Return/Mixed/Discharge vs. Time

30

35

40

45

50

55

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

Economizer Operation (continued): Example use of Graphs – 1 Day - Faulty

Outdoor-Air Damper Stuck Fully Closed

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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

)


Return

Mixed

Discharge

Outdoor

Economizer Operation (continued): Example use of Graphs – 1 Day - Faulty

Outdoor-Air Damper Stuck Fully Open

70


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

)


Return

Discharge

Outdoor

Mixed

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

Poorly Designed Packaged Rooftop Units with Economizer Installed Next to Heat Source from Condenser

73

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

76

Chilled Water vs Hot Water Valve Signals

0

10

20

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

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

78

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

79

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

80

Sign of Problem with Zone Control!

81

Sign of Problem with Zone Control!

82

What’s Wrong with this?

83

Thermostat

Central Plant and Whole Building Meter Profiles

Training also coversChiller and boiler plantsMeter profiles

84

Re-tuning Examples

85

Re-tuning Example

VFD speed is greater than 80% before re-tuning; note the speed after re-tuning

86

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

Re-tuning Example (cont)

Lockout chilled water consumption in winter

87

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

Re-tuning Example (cont)

Eliminated alternating cooling/heating

88

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


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

89

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 ,

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

91

Questions?

92

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