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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Ryan Parker, PhD Project Engineer rparker@cppwind.com Questions? For More Information Ryan Parker, PhD Project Engineer rparker@cppwind.com CPP, Inc. 2400 Midpoint Drive, Suite 190 Fort Collins, CO 80525 (970) 221-3371