Retro-Commissioning

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Retro-Commissioning
An SNL Experience Chris Evans, CEM Miguel
Atencio Sandia Energy Management Program A
Lessons Learned Activity
Sandia is a multiprogram laboratory operated by
Sandia Corporation, a Lockheed Martin
Company,for the United States Department of
Energys National Nuclear Security
Administration under contract DE-AC04-94AL85000.
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Retro-Commissioning at SNLIntroduction

• The Sandia Energy Management Team has developed a
  program to Retro-commission buildings at the
  laboratory. To date two buildings have been
  partially completed. The following presentation
  will explain the process and lessons we have
  learned.

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What is Retro?

• Retro-commissioning is a process to identify and
  resolve operating problems, improve comfort and
  optimize energy use in existing buildings to meet
  current building requirements. Typically the
  focus is on HVAC systems, controls and lighting.
  Most fixes tend to be low cost in nature.

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Why even do retro?

• Space complaints (temp, IAQ, etc)
• Rooms changed from original design intent
• System modifications
• Building not operating efficiently
• Energy costs ()
• Changes in building mission
• Building was not commissioned during construction
• More than 5 years have passed since the last
  retro-commissioning

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Benefits of Retro

• Excellent ROI/ Payback (lt1 year typical)
• Excellent energy savings (5 to 15 typical)
• Cost of lost productivity/ comfort is much higher!

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Top 10 Retro Measures

• 10.) Improve Boiler Efficiency, Controls
• 9.) Reset supply static pressure set point
• 8.) Review terminal unit operation
• Reheat is a major energy consumer and problem at
  Sandia
• 7.) Return VFDs to variable speed operation
• 6.) Lower condenser water temperature
• 5.) Improve chiller sequencing
• 4.) System level test and balance
• 3.) Optimize economizer
• 2.) Eliminate simultaneous heating and cooling
• 1.) Turn off equipment when not needed!!

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Retro Process

• 1.) Planning Phase
• 2.) Investigation Phase
• 3.) Implementation Phase
• 4.) Operating Phase

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Planning Phase

• Identify key players
• Building Owner/ Manager, Building Systems
  Engineer, Building Operators/ Mechanics,
  Building, Environmental Safety Health (ESH),
  buildings controls representative
• The team members are necessary to make the
  process a success. Everyone needs to be
  continuously informed and in agreement or the
  project will fail.
• For laboratory facilities industrial hygiene
  representatives

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Planning Phase

• Kick off meeting
• The kickoff meeting is important so everyone
  understands the goals, why we are
  retro-commissioning, what systems will be looked
  at and what systems are off limits. The kickoff
  meeting is where all members agree that
  retro-commissioning is the right process to
  proceed with.

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Planning Phase

• Benchmark past performance
• Past performance data is necessary to track
  improvements made during the retro-commissioning
  process. Data is often not available. For this
  reason, it is important to see what data is
  available as early as possible. It may be
  necessary to install portable meters to collect
  baseline data. Typical baseline data would
  include building electrical usage, natural gas
  use, average outputs of VFD drives on large fans
  and pumps, average airflow readings on air
  handlers and exhaust fans and run time profiles
  of air handlers, chillers and boilers.

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Planning Phase

• Discuss building operational issues
• Discuss operational issues with occupants and the
  key team members. This can provide some insight
  into whether components such outside air dampers,
  air washers or sensors are actually operating
  correctly.
• Identify problem areas
• Information from the previous planning steps can
  lead to identifying problem areas.
• Develop Retro plan
• Develop an initial plan identifying systems to
  investigate.

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Investigation Phase

• Determine how the system is supposed to
  operate?
• Look for design documents from the original
  construction. The building may have never
  operated according to the original design.
• The building management team, ESH coordinator
  and the building mechanic determine how the
  systems are supposed to operate. Determine
  operating schedule requirements, air flow
  requirements, special temperature requirements
  and lighting requirements.

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Investigation Phase

• How is the system actually operating?
• Fully automated control systems dont necessarily
  mean better control
• Decisions are often made without ever stepping
  foot into the building space
• The screen says the space temp is fine, why are
  they complaining?
• The reheat valve is 100 open, why are they
  still cold?
• The damper is 100 open, why are they still
  hot?
• They must be low on CFM, let me increase the
  static pressure set point
• The occupancy schedule shows that the fans shut
  off at 600 pm, why is the building base load so
  high?
• Do not trust everything the control system tells
  you
• There is no substitute for a good old fashioned
  field verification
• The results may surprise you!

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Investigation Phase

• Without performing a site visit, how certain are
  you?
• Is the valve actually closed?
• Is the damper actually open?
• Is the space temp being skewed by a false
  thermostat load?
• Is the room facing north with lots of window
  area?
• Are there obstructions near the room diffuser
  preventing proper air circulation?
• Are the fans really shutting off at 600 pm?
• Decisions made without proper verification result
  in systems that eventually run out of control
• Unwarranted set point changes
• Points placed in operator mode
• Control slowly shifts from automatic DDC control
  to manual operation
• System performance suffers resulting in increased
  occupant discomfort and increased whole building
  energy consumption
• This snowball effect can be avoided!

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Investigation Phase

• DDC control is only as good as the information it
  has available (garbage in garbage out). Typical
  DDC sensor issues that should be investigated
  include
• What inputs are used for control?
• Have these inputs been measured/ calibrated/
  maintained?
• What is the life expectancy of these inputs
  (sensors)?
• Are they on a PM or replacement schedule?
• What happens to system performance when they
  begin to lose accuracy (drift)?
• What happens to system performance when they
  fail?
• Prioritize those that are more critical

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Investigation Phase

• Control Strategy
• Many times, it pays to follow the keep it simple
  principle
• The more complicated the strategy
• The less likely operational staff will understand
  it
• The more likely the code will be by-passed and
  operated manually (operator pts)
• The more inputs are required (More possibilities
  for failure)
• The harder it is to update when changes are made
  to the system

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Investigation Phase

• Document all findings in a Retro-Investigative
  report
• As found conditions.
• Results of initial evaluation
• Make a list of recommended opportunities and
  deficiencies.
• Implementation costs and estimated savings or
  savings to investment ratio (SIR).

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Implementation Phase

• Implement recommended opportunities and correct
  any operational deficiencies
• Verify that changes/ modifications are working
  correctly
• Monitor building performance to verify energy
  savings

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Operating Phase

• Operational staff MUST be trained in order to
  sustain efficient operation.
• Document/ update the new sequence of operations
• Track monthly building energy use
• Compare historical energy data (similar months,
  different years)
• Compare energy usage vs. outside air temperature
  (OAT)
• If possible, sub-meter major HVAC systems
• Verify correct operation of all energy
  conservation control strategies
• Track equipment schedules
• Track systems to see if set points are being met
• Track DDC control operations

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SNL Retro Challenges

• Building owners are focused on meeting
  mission/programmatic needs
• Outside of the fence, building owners are focused
  on lowering utility bills/ over head
• Space chargeback is not necessarily set up to
  charge users for direct energy usage
• Everyone believes that energy is free
• These projects are great...As long as they are
  done in someone else's building
• Please dont touch my system, you might break it

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Things to Consider

• Do not assume a building with very few too hot/
  too cold calls is operating efficiently
• Many occupants simply adapt and no longer
  complain
• Many complaints are not submitted through proper
  channels and are never documented
• Occupants are very creative and find ways of
  making their space temperatures acceptable
• Space heaters
• Taped up diffusers
• Removing diffusers completely
• Fans
• Cardboard box air deflectors
• Heat source next to thermostat
• Cold source next to thermostat

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Things to Consider

• Many space temperature problems are unknowingly
  caused by occupants

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Things to Consider