Selected Highlights of the Labs21 2010 Annual Conference

Laboratory Ventilation Performance: Comparing Centralized Demand Control and Zone-Occupancy Control Systems

Matt Gudorf, LEED AP, University of California, Irvine
Geoffrey Bell, P.E., Lawrence Berkeley National Laboratory

Abstract

The University of California (UC), Irvine initiated a study to compare ventilation control systems in laboratories for their potential to reduce energy consumption while increasing researcher safety. Three systems were to be evaluated for managing laboratory air change rates: 1) a centralized demand controlled ventilation (CDCV) system; 2) a zone-occupancy control system; and 3) a combined control system using both CDCV and zone-occupancy. The following issues presented challenges during the implementation of the CDCV system:

  • Study protocol development
  • Monitoring-based Commissioning (MBCx) diagnoses
  • Building Management System (BMS) Control programming complications

A test protocol was developed that included a baseline energy evaluation. Functioning research laboratories were identified, studied with MBCx, and re-commissioned in preparation for the comparison study. BMS control programming installation, re-commissioning, and start-up efforts have provided a variety of lessons learned that need to be considered when implementing these advanced ventilation control systems.

Introduction

As demonstrated in an earlier pilot study at UC Irvine, laboratory ventilation rates can be reduced by using CDCV with a centralized suite of contaminant sensors. The CDCV system installed at UC Irvine allowed reduction of air change rates from ~12 and six air changes per hour (ACH) to four ACH, resulting in significant energy savings. Furthermore, acetone spill testing showed that there was no significant decrease in safety with the CDCV system. However, UC Irvine was interested in adding more safety to the laboratory air control system and comparing less-complex alternatives for managing laboratory air change rates.

1. Laboratories for the 21st Century (Labs21®) Technical Bulletin: Laboratory Centralized Demand Controlled Ventilation System Increases Energy Efficiency in Pilot Study (256 KB, 6 pp)

Accordingly, new testing was proposed to determine whether occupancy sensors alone could be used as a setback control device without installing a more complicated CDCV system. In addition, occupancy sensors can lower air change rates to a minimum when workers are not present in the laboratory. As an added safety enhancement, UC Irvine would install push-buttons to allow researchers to override the CDCV system. This feature would provide users with the ability to directly raise air change rates during a spill excursion event.

Compared Systems Description

UC Irvine intended to compare three ventilation control system arrangements for managing laboratory air change rates:

  • A CDCV system with a design minimum flow of four ACH. In previous testing, the system created a benchmark for use as a comparison for this testing.
  • A simple, zone-occupancy control-based air change rate reduction system providing six ACH during occupied periods and two ACH during unoccupied periods. For this test, the CDCV system was deactivated.
  • A combined test with CDCV and occupancy based control, providing a minimum of four ACH during occupied periods and two ACH during unoccupied periods.

Sequence of events

The project scoping began in December 2009. The official start was in January 2010. A draft test protocol was developed for the project by February 2010. A final test protocol was finished in March 2010, and a construction contract was let in April 2010. Initial installation during "Zero Week" provided a wealth of information regarding the state of the CDCV system installed a year prior. A great deal of recommissioning needed to be completed in order to get accurate baseline data. UC Irvine found exactly the operational issues that Zero Week was designed to detect, including BMS data trending multipliers set to incorrect values at two to three times actual, equipment placed in front of thermostats forcing air exchange rates artificially high, failed control valve poppets, and at least one blocked diffuser.

The recommissioning issues resulted in the first delays in the planned schedule. The amount of time to correct the unexpected deficiencies was not budgeted into the schedule. It was determined by the UC Irvine project team that the CDCV installer and BMS technician needed to go through the system control sequence, point by point, to ensure all of the data retrieved by the BMS was reliable. It would take many weeks to make corrections with the following tasks and summarized results:

  • Trend current conditions of both the CDCV and the building control systems. Analyze the data collected. Completed on 5/27/2010.
  • Review BMS set points and verify that all minimum, maximum, temperature, and voltage settings are correct. Completed on 5/27/2010.
  • Rewrite or modify code to alleviate maximum flow condition under both cooling and push-button override conditions. Maximum cooling flow rates were far too high after the implementation of the override buttons. Code was restored to design values and the override buttons rewired to a 6n1 High Select board. Completed 8/10/2010.
  • Identify and document issues not related to CDCV installation that were affecting heating, ventilation, and air conditioning (HVAC) performance. Completed list of issues is available in table form as the last page of the UC Irvine Trip Report completed 5/7/2010.
  • Write up solution to problems identified in Steps 1-4 above, and review the solutions with laboratory occupants. A meeting was held with laboratory occupants to explain the causes for fluctuations in environmental control and proposed solutions. Received agreement to implement corrections 6/23/2010.
  • Install hardware/software required to make the system function properly. Completed on 8/10/2010.
  • Correct problems identified in Step 4 (such as thermostats located near heat generating equipment). Completed on 8/10/2010.
  • Re-trend new conditions of both the CDCV and building control systems. Analyze the data collected. Completed on 8/30/2010.
  • Verify that building occupants find all changes acceptable. Completed on 8/30/2010.

Test Protocol

A test protocol was composed, evaluated, and scrutinized by the team to stipulate the steps of how the three control systems would be compared. It was decided early in the project that data collection and testing in a functioning laboratory would provide insight into which combination of CDCV, occupancy sensors, and push-buttons worked best for reducing energy use and increasing safety. Energy savings were to be compared between a CDCV system without occupancy control, occupancy control alone, and a combination using CDCV and occupancy sensing together. The study protocol included a baseline energy use evaluation.

CDCV Project Protocol

The UC Irvine team developed the following protocol with input from UC Irvine Environmental, Health, and Safety (EH&S) personnel, UC Irvine facilities personnel, and the Labs21 technical committee. Three test scenarios were developed to provide baseline operational functions and energy use, isolate capabilities of the three control arrangements, and test the CDCV system for its ability to monitor and remove specific contaminants during each scenario. The scenarios follow:

Scenario 1: Current CDCV System—Week 1

Facilities to trend kilowatt hours (kWh) of supply fan variable frequency drive (VFD), kWh of exhaust Fan VFD, zone temperature, total volatile organic compound (VOC) small particulate counts in parts per million (PPM), carbon dioxide (CO2), and cubic feet per minute (cfm)/air change rates. These data to be compiled forming the baseline for the California Institute for Energy Efficiency study. Environmental Health and Safety (EH&S) to perform a system challenge in one laboratory to ensure system response. Excursions to be tested include high VOC and CO2 levels.

  • Set system for four ACH base rate.
  • Energy Management System (EMS) providing space temperature control.
  • CDCV system monitoring indoor air quality (IAQ) responding to excursions above set points with increased ventilation rate.
  • Occupancy sensors logging but not controlling.
  • Push-button ventilation override installed at each exit.

Note that an acceptable baseline was not established due to the unexpected high flow rates during cooling demand.

Scenario 2: Occupancy Based Control—Week 2

Facilities to trend kWh of supply fan VFD, kWh of exhaust fan VFD, zone temperature, total VOC small particulate counts in PPM, CO2, and cfm/air change rates. This scenario will be compiled as an alternative to the more complex CDCV system. EH&S to perform testing in one laboratory to create a clearing-time baseline. Excursions to be tested include high VOC and CO2 levels. As there are no CDCV controls in this scenario, four ACH minimum with and without occupancy will be compared to a non-CDCV laboratory with six ACH minimum.

  • Set system for six ACH occupied and two ACH unoccupied.
  • EMS providing space temperature control.
  • Occupancy sensor installed with visual status indicator.
  • ODCV system deactivated (trending but not controlling).
  • Push-button ventilation override installed at each exit.

Scenario 3: Occupancy Based Control With CDCV—Week 3

Facilities to trend kWh of supply fan VFD, kWh of exhaust fan VFD, zone temperature, total VOC small particulate counts in PPM, CO2, and cfm/air change rates. This scenario is expected to provide the greatest energy savings and, at the same time, provide faster clearing times to EH&S challenges. EH&S to perform a system challenge in one laboratory to ensure system response. Excursions to be tested include high VOC and CO2 levels. Both occupied and unoccupied clearing times will be tested. The clearing times are expected to be equivalent.

  • Four ACH occupied and two ACH unoccupied.
  • EMS providing space temperature control.
  • Occupancy sensor installed with visual status indicator.
  • Push-button ventilation override installed at each exit.
  • CDCV system monitoring IAQ responding to excursions above set points with increased ventilation rate.

Commissioning

A thorough laboratory recommissioning effort was completed prior to implementing the control system protocol. A variety of problems were discovered during the recommissioning that would have been identified by UC Irvine with a comprehensive MBCx program. Even though the facility was recommissioned as recently as one year prior, many potentially energy-wasting issues were revealed including failed poppets in valves that control room differential pressure and heat-produced equipment placed in front of thermostats, which unnecessarily increased laboratory cooling demand.

2. Abbamonto, C., G. Bell; "Does Centralized Demand Control Ventilation (CDCV) Allow Ventilation Rate Reductions and Save Energy Without Compromising Safety?", Presented at the Labs21 2009 Annual Conference; September 23 , 2009.

BMS Control Programming

A BMS is a useful commissioning tool during acceptance testing. In VAV laboratories, acceptance tests require monitoring of numerous variables at once with precise timing. The control contractor should have BMS workstation available for the commissioning team to log data while the team performs and observes laboratory HVAC tests.

Two problems were identified during the test, adjust, and balance (TAB) of the laboratories fitted with the CDCV and occupancy-control systems: the BMS control sequence used identical laboratory airflow rates for achieving both normal space cooling and emergency purging of contaminants. A maximum airflow for purging is initiated by either the CDVCV system or the red-button override. This airflow rate provides excessive space cooling. Consequently, the maximized, purging airflow rate caused great discomfort for the laboratory occupants.

There are multiple temperature zones within each laboratory space. After visiting each laboratory, it was discovered that the multiple zones within a laboratory were in conflict or "fighting each other;" some were providing cooling at the same time as others in the same laboratory were providing heating.

Conclusion

The project resulted in two important lessons learned:

1. Implement a monitoring-based commissioning program.

A laboratory monitoring-based commissioning program will increase safety and reduce energy consumption. Note that a viable MBCx program depends on funding of trained personnel that are tasked to perform dedicated, ongoing observations and to complete repairs. The following points should be considered when putting a MBCx program into practice:

2. Monitor continuously

    • Recently completed commissioning does not guarantee efficient operation.
    • In laboratories, things change quickly and for no apparent reason.
      • Therefore, they will go unnoticed without ongoing checks/observation.
    • Provide quick and easy access to data.
    • MBCx benefits from simple, easy display of trend data.
    • Energy Management Control System (EMCS) is a great troubleshooting tool.
  • Optimize dashboard design
    • A "dashboard" display provides a quick, convenient review method.
  • Ensure feedback system is in place
    • Feedback is highly dependent on sensors being installed as part of the design.
    • Notification method of serious control issues is advised.
  • Commit to involving onsite personnel
    • Training and support for personnel using the EMCS is absolutely necessary.
    • The more the EMCS is used, the more it saves energy and money.

The CDCV system as installed at Croul Hall provides an interface that will meet the above requirements and allows for anomalies to be identified. The system is not a standalone troubleshooting tool, but when used in conjunction with the BMS and a trained field technician, it provides adequate monitoring to quickly identify and correct failures. UC Irvine was able to identify zoning conflicts within multiple laboratories that were resulting in simultaneous heating and cooling. This artificially raised the air change rates and was the source of a significant high temperature hot-water and chilled-water load. Using the CDCV system's graphical display of data, UC Irvine first determined that rooms were providing air flow rates that were different than previously expected. The resulting investigation revealed a core design problem of thermostat zones being located too close together. Rezoning led to significant energy savings and air change rates in line with design projections.

The CDCV system also trends the output signal produced by the occupancy sensors. UC Irvine has determined that monitoring the occupancy system should be a requirement if implemented in a laboratory environment for unoccupied setback. Without the CDCV system another system would be required to perform this task. Hence the combination approach of CDCV with occupancy as opposed to an occupancy-only system is the preferred method of control for UC Irvine based on our testing.

3. Coordinate BMS acceptance testing

A BMS control technician can inspect the building with the TAB contractor as a team, or the TAB contractor can be trained to adjust the BMS control system. It is recommended to have the BMS controls and TAB contractor available on site during the troubleshooting process. It is important to ensure that more than one onsite employee reviews the control sequence programming throughout the acceptance testing.

Coordinated BMS acceptance testing should include the following steps:

  • Determine existing control system capabilities.
  • Develop a building-wide sequence of operation.
  • Identify new control inputs for type and function.
  • Provide for fail-safe operation.
  • Allow for return to existing sequence.
  • Coordinate testing with users.
  • Verify control device operations and sensor inputs.
  • Perform system operational mode tests (SOMT).
  • Troubleshoot "what if" scenarios.
  • Test and, if possible, simulate control routines.
  • Re-evaluate control sequence.
  • Prove operation to all stakeholders.

Biographies

Matt Gudorf is the energy project manager at UC Irvine and a LEED Accredited Professional with 10 years of infrastructure project management experience. A graduate of The Ohio State University in electrical engineering with an emphasis on high voltage systems, Mr. Gudorf has worked for Dayton Power and Light in transmission and distribution, American Electric Power as a member of the ultra high voltage substation design team, and Southern California Pipeline managing multiple wet utility projects throughout Southern California. Mr. Gudorf has focused his efforts at UC Irvine on energy efficiency upgrades, utility and infrastructure retrofits, and project development.

Geoffrey Bell, P.E., received his Bachelor of Science in mechanical engineering from Newark College of Engineering. He then went on to receive his Masters of Architecture in environmental design from the University of New Mexico.

Mr. Bell is a registered professional mechanical engineer in both New Mexico and California and a certified state energy auditor in New Mexico. His resume includes: working for Lawrence Berkeley National Laboratory as a staff scientist and senior energy management engineer for more than 20 years; participating on the Technical Committees for Labs21 and Data Centers for the 21st Century; contracting with the U.S. Department of Energy as a principal investigator; teaching at the University of New Mexico and for Labs21; consulting to Sandia Corporation as an energy engineer; as well as providing renewable energy consulting services for various mechanical engineering and architectural projects for more than 35 years.

Mr. Bell is a co-inventor of the Berkeley Hood and is credited with a number of publications, best practice guides, technical bulletins, and magazine articles in his career. He was a principal author of the Labs21 Design Guide for Energy-Efficient Research Laboratories and is the chief editor of the Labs21 Tool Kit.

Mr. Bell is currently an energy engineer in the Environmental Energy Technologies Division at Lawrence Berkeley National Laboratory.