October 2014 Rod Rabold Vice President, SERBCA Board of Directors SERBCA TECH TALK BAS Control Strategies for Energy Savings in Buildings SOUTHEAST CHAPTER

Energy Conservation Measures with the Largest Impact at UNC AHU - Discharge Air Temperature (DAT) reset strategy AHU - Proper Economizer and Heat Recovery system operations AHU - Preventing simultaneous heating and cooling VAV - Terminal zone minimum cfm air flow setpoints

UNC BAS Control Standards Provided to Designers

AHU Required Sensors

AHU Required Sequence Logic

Preheat Valve Logic

CHW Valve Logic

DAT Setpoint Reset Logic Cooling Requests and Return Humidity Using Low Select to calculate DAT Setpoint

DAT Setpoint Reset Logic Cooling Requests and Return Humidity Using Cascade to calculate DAT Setpoint

DAT Reset Using Terminal Load Terminals must be calibrated and working properly to ensure correct cooling call request are being generated. Reset values are adjustable from the front end so each building can be fine tuned. If terminals are not providing accurate cooling call requests then consider return air temperature to reset the AHU

DAT Setpoint Reset Logic Return Air and Return Humidity using low select

DAT Setpoint Reset Logic Return Air and Return Humidity using cascade

DAT Reset Using Return Temperature Using return air temperature produces the best performance if zone temperature adjustment is limited and heating and cooling setpoints (with dead bands) are uniformly set.

Terminal Zone Temp Setpoint Heating and cooling dead bands and limited adjustment

Graphic Reset Information

Summary DAT Strategy AHU discharge air resets can provide significant energy savings. If terminals are calibrated and performing a cooling request logic can be used. If terminals are poorly performing use return air temperature for reset. Reset parameters must be monitored and adjusted per each building. The resets need to be displayed on the graphic so they are easily understood by the staff.