Retrocommissioning Works
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Eveline Killian and Daniel Tuhus-Dubrow from Cx Associates, Christopher Vintinner from Distech Controls, and John Grosvenor from Vermont Historical Society presented these slides at the 2018 Better Buildings by Design conference. The presentation discusses what retrocommissioning is/is not, along with a case study at the Vermont Historical Society. This presentation gives a unique look into retrocommissioning processes and achievements by discussing an owner's perspective.
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Retrocommissioning Works
- 1. Experience in Retrocommissioning Eveline Killian Daniel Tuhus-Dubrow Christopher Vintinner John Grosvenor Cx Associates Cx Associates Distech Controls Vermont Historical Society Presented by:
- 2. Agenda What is Retrocommissioning? The RCx program in Vermont Vermont Historical Society Case Study Issues Implemented Measures Beyond Retrocommissioning Impact of Measures Project Economics Typical RCx Measures Team is Critical
- 4. Retrocommissioning is NOT….. Capital improvement projects: However… Equipment at the end of its useful life will often be identified through the RCx process. Lighting retrofits Equipment replacement Window upgrades
- 5. Typical RCx Measures • Unnecessary power consumption • Simultaneous heating and cooling • Calibrating thermostats and sensors • Replacing worn parts (belts and valves) • Optimization • Air balancing systems • Economizers • Controls sequences • Variable-frequency drive speed
- 6. RCx from Controls Contractor Perspective An Exciting opportunity to showcase the benefits of a Building Automation System • Visualization & Graphical User interface • Control • Optimization • Measurement and Verification
- 7. Retrocommissioning to the Owner Maintenance for existing equipment Improved equipment and systems function Reduced operational costs (10-20%) Addressing VHS structural deficits Reduced energy use from deferred maintenance (30-60%)
- 8. Reducing Greenhouse Gas Emissions Commercial buildings consume nearly half of the building energy used in the United States (20% of total U.S. energy consumption and greenhouse gas emissions) Potential for Existing Buildings Saving Money Median whole building energy savings of 16% Median payback time of 1.1 years
- 9. The RCx Process in Vermont Programs from Efficiency Vermont and BED Qualify Develop Implement Verify
- 10. Steps in Qualifying Phase Pre-qualify Walkthrough by team Findings and Recommendations Estimate energy savings
- 11. Case Study Vermont Historical Society Barre, Vermont
- 12. Project Timeline Baseline Established December 2, 2016 April 3, 2017 RCx Complete Steam Humidifiers Installed August 2017 September 2017 LED Lighting Installed
- 13. Vermont Historical Society Pre-RCx Building Demand Profile 35 40 45 50 55 60 65 70 75 80 85 BuildingDemand(kW) Hour of DaySun Mon Tue Wed Thu Fri Sat Hol
- 14. Pre-Existing Conditions • Nuisance alarms • Bad sensors • Climate control set points • Hot and cold pockets in building. • Humidification not keeping up • Heating/cooling overshooting temps • Manual changes to lead pumps and boilers Problems: • Reactive maintenance vs. preventive/predictive • Deferred maintenance • Design deficiencies Causes: System wasn’t satisfactory or energy efficient!
- 15. Implemented Measures Avoiding Simultaneous Operation of: Chiller and Dry Cooler Both Boilers Trim & Respond Reset a.Chille r Pumps a.Boiler Pumps AHU-2 Fan Speed Sensor Calibration Chilled Water Temp. Boiler Water Temp. T-stats AHU Air Temp. Reset Schedule Boiler to Outside Air Temp. VAV Damper Position to AHU Supply Air Temp. Office Setpoints and Schedules Corrected Minimum Ventilation
- 16. Avoided Simultaneous Operation Avoiding Simultaneous Operation of: Chiller and Dry Cooler Both Boilers
- 17. Chiller & Dry Cooler
- 18. Chiller & Dry Cooler
- 19. Boilers
- 20. Boilers
- 21. Trim & Respond Reset Avoiding Simultaneous Operation of: Chiller and Dry Cooler Both Boilers Trim & Respond Reset Chiller Pumps Boiler Pumps AHU-2 Fan Speed
- 22. Chiller Pumps
- 23. Chiller Pumps
- 24. Boiler Pumps
- 25. Boiler Pumps
- 26. AHU-2 Static Pressure Reset
- 27. AHU-2 Static Pressure Reset
- 28. Sensor Calibration Avoiding Simultaneous Operation of: Chiller and Dry Cooler Both Boilers Trim & Respond Reset Chiller Pumps Boiler Pumps AHU-2 Fan Speed Sensor Calibration Chilled Water Temp. Boiler Water Temp. T-stats AHU Air Temp.
- 29. Sensor Calibration BMS Sensor Reads 43% RH Calibration sensor reads 47.6% RH Damaged Probe
- 30. Reset Schedules Avoiding Simultaneous Operation of: Chiller and Dry Cooler Both Boilers Trim & Respond Reset Chiller Pumps Boiler Pumps AHU-2 Fan Speed Sensor Calibration Chilled Water Temp. Boiler Water Temp. T-stats AHU Air Temp. Reset Schedule Boiler to Outside Air Temp. VAV Damper Position to AHU Supply Air Temp.
- 32. Office Setpoints and Schedules Avoiding Simultaneous Operation of: Chiller and Dry Cooler Both Boilers Trim & Respond Reset Chiller Pumps Boiler Pumps AHU-2 Fan Speed Sensor Calibration Chilled Water Temp. Boiler Water Temp. T-stats AHU Air Temp. Reset Schedule Boiler to Outside Air Temp. VAV Damper Position to AHU Supply Air Temp. Office Setpoints and Schedules
- 33. Office Setpoints & Schedules
- 34. Office Setpoints & Schedules
- 35. Corrected Minimum Ventilation Avoiding Simultaneous Operation of: Chiller and Dry Cooler Both Boilers Trim & Respond Reset a.Chiller Pumps a.Boiler Pumps AHU-2 Fan Speed Sensor Calibration Chilled Water Temp. Boiler Water Temp. T-stats AHU Air Temp. Reset Schedule Boiler to Outside Air Temp. VAV Damper Position to AHU Supply Air Temp. Office Setpoints and Schedules Corrected Minimum Ventilation
- 36. Ventilation
- 37. Post RCx Capital Improvements • Steam humidifiers and LED lighting replacement
- 38. The Outcome – Demand Impacts 20 30 40 50 60 70 80 90 100 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 BuildingDemand(kW) Outside Air Temperature Occupied Pre Occupied Post
- 39. Impact on Daily Load Profile 35 40 45 50 55 60 65 70 75 80 85 12:00 AM 1:00 AM 2:00 AM 3:00 AM 4:00 AM 5:00 AM 6:00 AM 7:00 AM 8:00 AM 9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM 3:00 PM 4:00 PM 5:00 PM 6:00 PM 7:00 PM 8:00 PM 9:00 PM 10:00 PM 11:00 PM BuildingLoad(kW)
- 40. 2016 – 2017 Utility Comparison
- 41. RCx Project Economics $(15,000.00) $(5,000.00) $5,000.00 $15,000.00 $25,000.00 $35,000.00 $45,000.00 $55,000.00 1 2 3 4 5 Year Investment Savings Cumulative
- 42. Outcome from the Owner’s Perspective No more nuisance alarms Systems respond appropriately to weather conditions Set points maintained Improved energy efficiency lead to other conservation projects Cost savings Noticed by the occupants and Facilities Manager
- 44. Throttled Valves
- 47. Damaged Sensors
- 48. Teamwork Have the right people! Team Commissioning Engineer Controls Contractor Facilities Staff Introduce Perspectives Brainstorm Identify Opportunities Evaluate Merit
- 49. Thank You! Eveline Killian Associate Principal Cx Associates Burlington, VT 802-861-2715 x15 eveline@cx-assoc.com Daniel Tuhus-Dubrow Senior Engineer Cx Associates Burlington, VT 802-861-2715 x21 daniel@cx-assoc.com Chris Vintinner Sales Support Engineer Distech Controls, Inc. 802-922-0039 cvintinner@distech-controls.com www.distech-controls.com John Grosvenor Director of Finance and Operations Vermont Historical Society Barre, VT 802-479-8513 john.grosvenor@vermonthistory.com
Notes de l'éditeur
- Cx has been doing a lot of rcx in the last 18 months Eveline, chris and john worked on vhs together
- We will present a case study of the first rcx project that was conducted under the evt rcx program in late 2016 and the impact that had on the building. We’re pretty excited about the significant impact we saw at vhs and also the kinds of opportunities we are seeing in the small to medium sized commercial buildings throughout the state. We’ll start off talking about what rcx is, what it is not, and what it is from the different perspectives of the market. We’ll also describe the rcx program that is currently offered by evt and bed. Then we will go into the case study of the vhs and discuss the measures we found, what we implemented, and what impact that had both from an energy perspective and the owner’s perspective. Then we’ll talk about the typical rcx measures and
- Dan Ensuring systems and equipment are operating per the current facility requirements Correcting operational and maintenance deficiencies Optimizing control strategies
- Dan
- Dan Improvements are typically low-cost, no-cost items that correct operational deficiencies like control sequences and sensor calibration. Sounds simple, but it can make a huge difference in the building's energy consumption and the occupants' comfort levels.
- Building Automation Systems are often not a highlight of a new building (there are a very small piece) There is almost always opportunity to make things better Buildings are static, people aren’t Buildings can be built and commissioned years after they are designed Overall just a great opportunity for Controls Contractors to shine and show their expertise in controls and building systems.
- John – what is RCx to owner – what did they expect and why did they request this project
- Dan –opportunity in the commercial sector for this country and the ROI of RCx Numbers are from LBNL study
- Dan – describe the process Barriers – difficult to have customers invest up front cost
- Dan
- Eveline – the first RCx project under the RCx program was done in early 2017. The VHS building is an historic 40,000sf building that houses the library, exhibits, historic artifacts, and offices It was built in 1892 and originally was the Spaulding School The mechanical and BAS systems were installed in 2001 and are comprised of: 11 VAV AHUs 61 ton Chiller dry cooler –used for OATs<40deg 2 Oil Boilers for heat and hot water – with efficiencies in the mid 80s 252 MBH steam boiler for humidification for the museum and artifact areas – the boiler was rusting and nearing its end of life The pumps all had VFDs introduce VHS and its HVAC systems – what made this building a good candidate?
- Eveline
- Eveline: Before we got involved, the building was operating at approximately 48kW demand during the unoccupied hours and between 68-78 kW average range during the occupied hours of the week. You can see here that the weekends had a lower demand of 45-56kW, Mondays the library is closed and the peak is about 10kW lower than other weekdays, and Wednesdays the museum is open longer than other days. Data from 2013-2016
- John talk about the issues that VHS had VHS Issues: System Alarms/ Pump alarms(nuisance 500/day), Bad sensors, design deficiencies, fans, airflow, economizers, chiller, climate control set points, exhibits, storage, offices, community room, filters. Hot and cold pockets in building. Humidification not keeping up, heating cooling overshooting temps, manual changes to lead pumps and boilers. Not energy efficient Cooling tower not staging correctly w/ dry cooler Reactive maintenance vs. Preventive or Predictive Deferred maintenance, budget restrictions.
- Chris or Eveline?
- Chris
- Explain general concept of the chiller system and using the dry cooler vs the Chiller. Chiller and Dry Cooler Control - to avoid the dry cooler and chiller from operating simultaneously, the chiller was disabled and the dry cooler enabled at outdoor air enthalpy of less than 18.0 Btu/lb. (52°F/40%RH).
- Graph showing the trends of the Chiller, Dry Cooler status and the controlling OAE and OAESP switch over. Benefits: Reduce Chiller Runtime Save Energy and Save Wear & Tear
- Explain General concept of Lead/Lag control for boilers Boiler Control – our original sitevisit observed both boilers operating simultaneously when this was unnecessary. During this FPT visit, we verified the control sequence to ensure proper boiler cycling.
- Boiler Control – our original sitevisit observed both boilers operating simultaneously when this was unnecessary. During this FPT visit, we verified the control sequence to ensure proper boiler cycling.
- Explain Trim and Respond Reset Theory: The T&R theory is the basis for the ASHRAE rp-1455 and GPC-36: Standardized Best of Class Sequences for HVAC Systems The basic logic is pretty simple. The goal is to try and match the supply of the system with it’s demand at a current time. This is achieved by adjusting the setpoint until one valve (or damper) goes nearly 100% open. Traditional Resets use something to estimate building conditions, For example, Outside air temperature can usually be used to estimate building heating load. Trim and Respond looks at the actual terminal loads of the system and try's to adjust supply accordingly. The setpoint begins at an initial setpoint and then looks at the valve positions. A valve that is at 85% or higher generates a request (it can’t satisfy the load without help from the central equipment). When the system sees more than X number of requests, it will respond by x every x minutes. If the requests are less than the ignored request it will trim by the trim amount. Considered easy to tune than PID (proportional, Integral, Derivative) loop control because the parameters are more intuitive. It can “respond” more quickly than it can “trim”. A very slow trim rate can improve stability while a fast respond rate ensures that the zones are going to maintained satisfied. PID tuning parameters effect “both sides” of the trim/response Easier to ignore rogue zones with a simple parameter Allows to adjust zones based on importance factors Chiller Pump Modulation - chiller pump CP 1 and CP 2 control sequences were verified to ensure pump modulation on differential pressure. Maybe think about reducing ignored requests on this one due to DDH unit.
- Chiller Pump Modulation - chiller pump CP 1 and CP 2 control sequences were verified to ensure pump modulation on differential pressure. Large reduction in pump speed = big reduction in energy consumption Pressure demand is maxed out a very small portion of the time.
- Boiler Pump Control - hydronic pumps CP 3 and 4 control sequences were verified to ensure pump modulation on differential pressure.
- Boiler Pump Control - hydronic pumps CP 3 and 4 control sequences were verified to ensure pump modulation on differential pressure. Huge reduction in pumping speed/energy
- AHU-2 Fan Speed Modulation - differential pressure setpoint reset control sequence was implemented and successfully tested. (Unit is scheduled off during this screenshot)
- AHU-2 Fan Speed Modulation - differential pressure setpoint reset control sequence was implemented and successfully tested. Explain reset. Looks like this loop could use some tuning. Excessive cycling
- Chris
- Chilled Water Temperature Sensor Calibration – sensors were calibrated to ensure proper readings. Other sensors - Thermostat Calibration – (6) thermostats were tested and found to be within 1°F deviation of a calibrated test instrument. Explain potential issues Equipment starting/stopping when not needed Over/Under conditioning the space
- Boiler Outside Air Temperature Reset Schedule – this schedule was written, but is overridden by the third-floor Modine unit requirement for 170°-180°F water. We recommend a solution in the next section of this report.
- Making sure different AHUs have appropriate schedules. Some AHUs are required 24/7, some are not. Some days have different schedules.
- Review Room Setpoints. In this case, because of the lack of the ability of the terminal units to control heating (no re-heat coils) the operator has override the local control and “calibrated” the system to the setpoints preferred by the different zones. VAV Damper Position Relative to AHU Supply Air Temperature - CTI implemented a control sequence that operates the VAV damper position based on AHU supply air temperature. Under these sequences, the VAV sequence modulates the damper by comparing the temperature requested by the room and the AHU supply temperature. If the room requires heating and the AHU is providing warmer air than the room temperature, the damper will open fully. If the room requires colder air than the AHU is providing, the damper goes to minimum position. The AHU supply temperature is set by the number of zones calling for heating or cooling.
- Eveline
- Eveline Minimum Ventilation – while conducting the FPTs, we discovered that the AHU fresh air dampers were overridden closed and the VAV boxes all had a minimum outside air damper position of 0 CFM. This was in response to requests from staff regarding outdoor air particulates getting into the spaces. The facilities manager has since replaced all the HEPA filters in the units. We released the overrides in the air handling units that serve occupied spaces and have programmed the VAV boxes to operate at a minimum 100 CFM position during occupied hours. This was not an energy savings measure, rather it was a health issue to provide adequate fresh air.
- Eveline During RCx, we identified and discussed other opportunities. One was the replacement of the old and failing steam boiler with electrode humidifiers in two air handling units. Later in the year they also worked with EVT to install LED lighting throughout the facility.
- Eveline Red dotted line is occupied and the purple dotted line is unoccupied pre. Notice the same curve and therefore no resets Now the post and red solid line is occupied post. You see the significant difference at all OATs
- Eveline: The comparison by hour of day shows that the demand savings are fairly constant throughout the day, saving approximately 10 kW for all hours of the day. Normalized, it’s about 120,000 kWh or 20% savings.
- Eveline Feb and Mar – hadn’t implemented fully Aug steam humidifiers – which don’t operate until winter Sept – lighting retrofit
- Eveline – RCx only (others taken out) Proj cost $13.2k Ann savings = $12.8 Total savings = $51k RCx measure life of 5 years – mainly due to facilities personnel knowledgeable of why and how the equipment is programmed Buildings should be retrocommissioned within 5 years to maintain optimization
- John - things the occupants and Facilities Manager noticed What the occupants and Facilities Manager noticed: No more nuisance alarms (used to have 500/day) Systems are keeping up with seasonal changes and outside temperature and humidity changes More energy efficient which lead to other energy conservation projects such as LED conversions Rooms staying within set points and review of them lead to cost savings.
- Eveline
- Dan
- Dan
- Dan
- Dan
- Eveline – the VHS project and the RCx program in VT works so well because we have the right people at the table from the start. The team is comprised of: A mechanical engineer that has hands-on familiarity with mechanical equipment (CxA) The controls contractor that has familiarity with the building and the BAS The owner’s facility people that have familiarity with the operations and issues of the building Everyone brings their own perspective to the table and works together to brainstorm identifying opportunities and their merit – will this work in this building?
- Eveline