1. Introduction to Energy Management

2. Week/Lesson 13 Control Strategies for Occupant Comfort

3. After completing this chapter, you will be able to:  Describe zone control strategies for temperature and humidity  List four methods to control air handlers  List control strategies for hot and chilled water and a condenser water system  List control strategies for duct and pipe systems Control Strategies for Occupant Comfort

4. Zone control  Actual load is monitored  Load is balanced by the controller response  System responds when load changes  System will counterbalance the load Heat, Temperature and Pressure Basics

5. Control methods  Two-position  Floating  Proportional  Proportional plus integral  Proportional plus derivative Heat, Temperature and Pressure Basics

6. Control methods – two-position  ON-OFF control  No modulation  Differential – difference between high and low temperatures  Crude form of control Heat, Temperature and Pressure Basics

7. Control methods – proportional  Controller output is proportional to the controlled variable  Controller settings Sensitivity Throttling range adjustment Bandwidth (analog electronic) Heat, Temperature and Pressure Basics

8. Control methods – proportional plus integral/derivative  Load changes cause movement of the controlled device  Often used where temperature and humidity requirements are critical Heat, Temperature and Pressure Basics

9. Thermostat placement and tampering  Thermostat should accurately sense the space temperature  Should be located in an open area  Settings can be changed by occupants at will  Locking covers/concealed adjustments Heat, Temperature and Pressure Basics

10. Zoning  By location (interior, exterior)  By orientation (north, south)  By occupancy levels  Zoning control usually handled by terminal unit or reheat coil Heat, Temperature and Pressure Basics

11. Terminal equipment controlled from the zone  Baseboard radiation – exterior  Reheat coils – hot water valve controlled by zone thermostat  Unit heaters/ventilators  Variable air volume (VAV) boxes Heat, Temperature and Pressure Basics

12. Control of air handling units  Ensures correct temperature and humidity are being supplied  Economizers select efficient air stream  Helps to maintain air quality Heat, Temperature and Pressure Basics

13. Temperature control – zone/room control  Thermostat located in the zone  Sends signal to air handler to provide desired conditions Temperature control – return air control  Thermostat located in return air stream  Uses the “average temperature” concept Heat, Temperature and Pressure Basics

14. Temperature control – discharge air control  Sensor locate din the discharge duct  Discharge air temperature is kept constant Temperature control – room reset of discharge  Uses two sensors – discharge and zone  Two feedback loops are used Heat, Temperature and Pressure Basics

15. Humidity control – room/return air humidity control  One setpoint Maintains constant humidity level Requires constant use of energy  Two setpoints Maintains a range of humidity Less power consumption Heat, Temperature and Pressure Basics

16. Humidity control – dew point control  Used where precise humidity control is needed  Cooling equipment is controlled Dry bulb sensor downstream of cooling coil Discharge air maintained close to saturation  Temperature and saturation are controlled Heat, Temperature and Pressure Basics

17. Economizer cycles – dry bulb switchover  Senses dry bulb temperature of outside air  Operates on a switchover temperature  OA temp > switchover = closed  OA temp < switchover = open Heat, Temperature and Pressure Basics

18. Economizer cycles – enthalpy switchover  Senses sensible and latent heat of the air  Dry bulb temperature and humidity are measured in return air and outside air  OA(h) > RA(h), OA temp > RA temp = closed  OA(h) < RA(h), OA temp < RA temp = open Heat, Temperature and Pressure Basics

19. Economizer cycles – floating switchover-adjustable differential  Uses computer-generated differential (generated form historic weather data)  OA temp + differential > RA temp = closed  OA temp + differential < RA temp = open Heat, Temperature and Pressure Basics

20. Ventilation  Supplying and removing air from a space  Ventilation rate – air volume being supplied  Ventilation rates vary depending on location  Outdoor air is subject to quality standards Heat, Temperature and Pressure Basics

21. Control of primary equipment – hot water systems  Packaged controls – maintain temperatures  Cold water added to the water leaving the boiler Reduces effects of overheating Energy is wasted  Inversely reset from outdoor air temperature Heat, Temperature and Pressure Basics

22. Control of primary equipment – chilled water systems  Packaged controls  Chilled water temp ranges from 42ºF to 45ºF  Chilled water must be cooled at the tower  Cooling tower uses valves and/or dampers to maintain proper water temperature Heat, Temperature and Pressure Basics

23. Control of distribution systems  Fans – volume and pressure control Constant volume, variable temperature Variable air volume (VAV) Variable volume, constant temperature Static pressure controls ensure proper volume Heat, Temperature and Pressure Basics

24. Control of distribution systems  Pumps – volume and pressure control Can be constant or variable volume Constant volume – primary loops Variable volume – secondary loops Differential pressure control – supply and return water lines Heat, Temperature and Pressure Basics