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Both the ASHRAE Standard 90.1 and California Title 24 Building Energy Efficiency Standards require AHU supply duct pressure setpoints onvariable-air-volume (VAV) systems with direct digital controls (DDC) be reset at the zone level. While many different implementation methods havebeen proposed, the Trim and Respond (TR) method is one of the more popular strategies. Although the TR methods are popular many are difficult tosuccessfully implement due to difficulities maintaining stable control, complexity of tuning parameters, or sacrifices in zone level comfort. A newer TieredTrim and Respond (TTR) strategy has improved control stability and increased response time, yet has an equivalent ease of field implementation andsimilar fan energy savings compared to traditional TR methods. The TTR method compares the maximum VAV damper command or position value tothree different tiers of high/low thresholds, and responds by varying the trim and respond rates to adjust the static pressure set points. The targeted averagemaximum VAV damper value is lowered from the traditionally recommended 95% or 98% open position to a lesser range of 80% to 90% open. TheTTR method pushes the setpoints slightly off the "ideal static pressure curve", but provides a more stable system control while maintaining a quickresponse to load changes. The TTR method is being implemented in a year-long demonstration at five military building sites with varying building typesand DDC systems. Preliminary demonstration results show seven AHUs fan energy savings vary from 15% to 57% with TTR compared to the existingfixed static pressure (FSP) control setup. Four of the RTUs indicate the fan energy savings vary from 22% to 36%. Two of the demonstration AHUsimplemented two different versions of customized Trim and Respond strategies and are used to compare control performance and zone comfort with theTTR method. The TTR method is more stable and has better temperature control compared to existing TR methods. This paper describes the TTRmethodology, the five demonstration sites and demonstration setup and protocol, the preliminary energy savings compared to fixed static pressure control,and control performance characteristics compared to two different TR methods.

Citation: 2016 Annual Conference, St. Louis, MO, Conference Papers