2014 1 October 2014

Rod RaboldVice President, SERBCA Board of Directors

SERBCA TECH TALKBAS Control Strategies for Energy Savings in Buildings

SOUTHEAST CHAPTER

2014 2

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

2014 3

UNC BAS Control StandardsProvided to Designers

2014 4

AHU Required Sensors

2014 5

AHU Required Sequence Logic

2014 6

Preheat Valve Logic

2014 7

CHW Valve Logic

2014 8

DAT Setpoint Reset LogicCooling Requests and Return Humidity Using Low Select

to calculate DAT Setpoint

2014 9

DAT Setpoint Reset LogicCooling Requests and Return Humidity Using Cascade

to calculate DAT Setpoint

2014 10

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

2014 11

DAT Setpoint Reset LogicReturn Air and Return Humidity using low select

2014 12

DAT Setpoint Reset LogicReturn Air and Return Humidity using cascade

2014 13

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.

2014 14

Terminal Zone Temp SetpointHeating and cooling dead bands and limited adjustment

2014 15

Graphic Reset Information

2014 16

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.