1. Variable Air Volume (VAV) Exhaust System Implementation Challenges
Colorado I2SL Chapter Education Day
Colorado State University
August 28, 2018
Ryan Parker, PhD - CPP, Inc.

2. Learning Objectives
Understand the use of dispersion modeling to aid in development of a simple turndown or wind-responsive VAV exhaust system
Identify the key processes and interactions required for a successful simple turndown or wind-responsive VAV exhaust implementation
Understand challenges involved with the VAV exhaust implementation process as they pertain to mechanical operation, controls programming, and client expectation
Increase knowledge of future operation and maintenance considerations for VAV exhaust systems

3. Outline/Agenda Dispersion modeling Overview CPP Implementation Process
Wind Tunnel
Design Criteria Development
CPP Implementation Process
Overview
Sequence of Operation (SOO) Development
Implementation Challenges
Mechanical Issues
Variable Frequency Drives (VFDs), Isolation/Bypass Dampers, Pressure Sensors, Fan Curves
Building Management System (BMS)
Existing Conditions and Client Expectations
Operation and Maintenance
User Interface
Importance of Continued Maintenance

4. Dispersion modeling Overview
Wind Tunnel
Scale Model
Concentration Measurements
Meteorological Data
Probabilities and Turndown
Today’s Tour

5. Dispersion modeling Overview
VAV System Types
Laboratory/Fume Hood
Vivarium
General Lab Exhaust
Other Exhaust
Radioisotope, Perchloric Acid, Biological Safety Cabinet, Hazardous Storage Cabinet
Laboratory/Fume Hood
Teaching vs. Research
ASHRAE HVAC Applications Handbook , ANSI/AIHA Z9.5
Chemical Inventory, ACGIH
Vivarium
General Exhaust
Other
Radioisotope, Perchloric Acid, Biological Safety Cabinet, Flammable Storage Cabinet

6. CPP Implementation Process
Overview
Feasibility
Energy Optimization Wind Tunnel Assessment
Pre-Functional Testing (On-site)
Sequence of Operation (SOO) Code Development
Implementation Testing (On-site)
Commissioning/Final Reporting
Feasibility
Trend Data
Bypass Damper
Fan Speed
Duct Static Pressure
Motor Power
AHU Load
Energy Optimization Wind Tunnel Assessment
Simple Turndown vs. Wind Responsive
Pre-Functional Testing
On-Site Testing
Gather Fan Operation Data
Evaluate Fan Combinations
Determine Problem Areas
Sequence of Operation Code Development
Based on Energy Optimization Assessment and Pre-Functional Testing
Duct static pressure within acceptable limits
Maintain minimum fan speed at or above critical fan speed
Minimize bypass damper flow
Number of Fans/Staging
Controls Contractor Interaction/Review
Troubleshoot Prior to Implementation
Implementation Testing
On-Site Implementation
Method of Operation Procedure
VAV Exhaust and Anemometer
Evaluate SOO and Troubleshoot
Flip the Switch
Commissioning/Final Reporting
Obtain Trend Data
Compare with Metrological Data
Identify and Correct Anomalies and Deviations

7. CPP Implementation Process
Sequence of Operation Code Development
Based on Energy Optimization Wind Tunnel Assessment and Pre-Functional Testing
Control Priority
Duct static pressure within acceptable limits
Maintain minimum fan speed at or above critical fan speed
Minimize bypass damper flow
Priorities:
1) Building operation
2) Safety
3) Energy savings

8. CPP Implementation Process
Sequence of Operation Code Development
Simple Turndown vs. Wind Responsive
New construction or existing building

9. Implementation Challenges
Mechanical Issues
Building Management System
Existing Conditions and Client Expectations
Solution:
Pre-functional testing
Preventative maintenance
PID adjustment by experienced controls contractor

10. Implementation Challenges
Mechanical Issues
Isolation/Bypass Damper Operation
Not always functional
Slow response time
PID tuning difficulties once fan speed changes are introduced
Solution:
Pre-functional testing
Preventative maintenance
PID adjustment by experienced controls contractor

11. Implementation Challenges
Mechanical Issues
Pressure Sensors
Location
Calibration
Interaction with other mechanical systems
Solution:
Pre-functional testing
Relocation of pressure sensors
Redundant sensors rather than averaging

12. Implementation Challenges
Mechanical Issues
Fan Curves
Availability
Pulley/sheave sizing
Duct static pressure variation
Solution:
Pre-functional testing
Pulley and sheave measurement
Tachometer readings on motor/fan

13. Implementation Challenges
Mechanical Issues
Anemometer
Communication protocol
Error handling
Wind speed vs. wind direction averaging
Mast/anchoring
Testing and maintenance
Siemens input resistance from 250 ohm to 500 ohm
WindSonic could not have more than 300 ohm signal resistance
Optical isolator had to be used.
Need Ryan’s picture from Auburn

14. Implementation Challenges
Mechanical Issues
Building Management System (BMS)
Existing Conditions and Client Expectations
Solution:
Pre-functional testing
Preventative maintenance
PID adjustment by experienced controls contractor

15. Implementation Challenges
Building Management System (BMS)
BMS point mapping
Troublesome if incorrect or incomplete
Refresh rate
Availability of live trending
Controller upgrade
Solution:
Provide pre-functional checklist to ensure items are mapped before pre-functional testing can occur
Discuss trending requirements with controls contractor to ensure success

16. Implementation Challenges
Building Management System (BMS)
Sequence of operation interpretation
Lookup table interaction
Trend data

17. Implementation Challenges
Building Management System (BMS)
PID loop tuning
VFD ramp speed
Trend data
Control Priority
Duct static pressure within acceptable limits
Maintain minimum fan speed at or above critical fan speed
Minimize bypass damper flow

18. Implementation Challenges
Mechanical Issues
Building Management System
Existing Conditions and Client Expectations
Solution:
Pre-functional testing
Preventative maintenance
PID adjustment by experienced controls contractor

19. Implementation Challenges
Existing Conditions and Client Expectations
Safe response time vs. acceptable HVAC response time
Acceptable duct static pressure range
Static pressure limits
Scheduling

20. Operation and Maintenance
User Interface
Clear and informative graphics
Descriptive, commented code
Consistent message to BMS staff

21. Operation and Maintenance
Importance of Continued Maintenance
User access
Checks/alarms
Project documentation
Full realization of project benefit
Error
Anemometer Alarm
Error
Access to maintenance mode switches, system feedback, informative data
Communication Fault

22. Conclusions VAV Exhaust Implementation Challenges
Dispersion modeling is an important aspect in developing a simple turndown or wind-responsive VAV exhaust system
A variety of challenges exist with VAV exhaust implementation, but many can be overcome with planning and pre-functional testing
Tools include pre-functional testing, concurrent code review, sequence of operation bench testing, method of procedure documentation, informative graphics, and accurate trend data
Access to maintenance mode switches, system feedback, informative data

23. Ryan Parker, PhD Project Engineer rparker@cppwind.com
Questions?
For More Information
Ryan Parker, PhD
Project Engineer
CPP, Inc.
2400 Midpoint Drive, Suite 190
Fort Collins, CO 80525
(970)