Converting Constant Volume, Multizone Air Handling Systems to Energy-Efficient Variable Air Volume Multizone Systems
EW-201152
Objective
The objective of this project is to demonstrate a low-cost technique to convert a constant volume (CV) multizone (MZ) air handling unit (AHU) to a more energy-efficient variable air volume (VAV) MZ AHU.
Technology Description
An MZ system consists of multiple ducts where each duct supplies a zone. The airflow quantity supplied to each zone is constant while the temperature of the air delivered to the zone is varied by positioning a set of "zone dampers" to mix air of two different temperatures.
The conversion of a constant volume MZ air handler to variable volume focuses on equipment, instrumentation, and controls, most notably the installation of a variable speed fan. The conversion also includes upgrading the controls via programming changes or controller replacement and the installation of new or replacement actuators and sensors--including the addition of outdoor airflow measurement--needed to support the conversion.
Whereas a conventional MZ system performs simultaneous heating and cooling in order to meet the demands of the zones, the technique to be demonstrated employs a variable frequency drive (VFD) to modulate fan capacity based on the position of the zone dampers to minimize the amount of simultaneous heating and cooling required to satisfy these demands. This results in savings in fan energy, heating energy, and cooling energy. In addition, the retrofit is expected to replace older pneumatic or single-loop digital controls with microprocessor-based direct digital controls, which provide improved accuracy and reliability and allow the application of additional energy savings techniques such as automatic adjustment of the hot and cold deck discharge air temperature setpoints, after-hours (unoccupied mode) zone temperature setback and system shutdown, outdoor ventilation air flow control, and demand controlled ventilation.
Benefits
Application of a low-cost and efficient method of converting MZ systems to variable volume has significant potential for energy savings across the Department of Defense. The technology saves heating and cooling energy along with fan energy. There is virtually no need to retrofit, demolish, or install ductwork or terminal units; thus this air-handler only retrofit can be accomplished for a much lower first cost than a full system VAV retrofit with VAV boxes. Due to the relative simplicity of this system, there is less system down time and disturbance to building occupants than there would be with a full VAV system retrofit. Improved performance of the renovated system also leads to improved occupant comfort and productivity. Simple payback estimates range from 2 to 15 years, depending on whether the system operates continuously or for 12 hours a day, 5 days a week. (Anticipated Project Completion - 2014)
Points of Contact
Principal Investigator
Mr. David Schwenk
U.S. Army Corps of Engineers ERDC-CERL
Phone: 217-373-7241
Fax: 217-373-6740
Document Types
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
- Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
- Model/Software - Computer programs and applications available for download.
- Database - Digitally organized collection of data available to search and access.