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Application of Controls

Application of Controls. CAV with Humidity Control. Application of Controls. CAV with Humidity Control CAV AHU dedicated to a special area: clean room textile factory hospital operating theatre computer equipment room

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Application of Controls

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  1. Application of Controls CAV with Humidity Control

  2. Application of Controls • CAV with Humidity Control • CAV AHU dedicated to a special area: • clean room • textile factory • hospital operating theatre • computer equipment room • Environment requires humidity control as well as temperature control - energy efficiency is not as important

  3. Application of Controls • CAV with Humidity Control T Temperature and humidity sensors may alternatively be placed in return air duct Temperature sensor in space H Humidity sensor in space Return Air Cooling Coil Fan Heater Elements Outdoor Air Chilled Water Valve

  4. Application of Controls • CAV with Humidity Control • The valve is controlled by the humidity sensor to achieve the humidity setpoint. • The heating elements are controlled by the temperature sensor to reheat the air to achieve the temperate setpoint. • This works if outdoor air is used; if pre-treated air is used, cooling request may be greater than dehumidification request and valve is controlled by temperature sensor.

  5. Humidity Temperature Application of Controls CAV with Humidity Control Cooling CoilCommand HeatingCommand D.B. D.B. T S.P. P.B. P.B. S.P. H

  6. Application of Controls Mechanical Controls

  7. Application of Controls Mechanical Controls • FCU Control • A temperature switch in the return air controls the 2 position valve • A separate 3 speed switch is connected to the fan

  8. Application of Controls Mechanical Controls FCU Control A temperature switch in the room controls the 2 position valve The integral 3 speed switch is connected to the fan

  9. Application of Controls Mechanical Controls Condenser Fan As the condenser pressure increases, a fan is started As the pressure continues to rise, a second fan is started FromEvaporator ToCompressor

  10. Application of Controls Mechanical Controls Cooling Tower Fan As the temperature increases, the low speed winding is engaged As the temperature continues to rise, the high speed winding is engaged

  11. Application of Controls Mechanical Controls Cold Room As the temperature increases, the compressors are brought on in sequence Condenser fans controlled based on pressure C1 C2 C3 C4 Condenser Evaporator ColdRoom

  12. Application of Controls Mechanical Controls Compressor Safeties If the condenser pressure is too high or too low, the compressor will be shut down If the lube oil pressure is too low, the compressor will be shut down

  13. Application of Controls Chiller Plant Integration

  14. Application of Controls • Chiller Plant Integration • Single seat user interface • Consolidation of information • Facility wide strategies • Simplify operations / training

  15. Application of Controls • Chiller Plant Integration Local Area Network Operator Workstation (PC) NCU Integrator Dataport Carrier Comfort Network DDC RS232

  16. Application of Controls • Chiller Plant Integration • Chilled Water Setpoint / Control Point • Entering/Leaving Chilled Water Temp. • Entering/Leaving Condenser Water Temp. • Evaporator Refrigerant Temperature and Pressure • Condenser Refrigerant Temperature and Pressure

  17. Application of Controls • Chiller Integration • Discharge Temperature • Bearing Temperature • Motor Winding Temperature • Oil Sump Temperature • Oil Pressure Transducer • etc.... • In brief, anything visible from Control Panel.

  18. Application of Controls Chiller Sequencing

  19. Application of Controls • Chiller Sequencing 1 x 300 TR Chiller

  20. Application of Controls • Chiller Sequencing 3 x 300 TR Chiller 3 Chillers on 2 Chillers on 1 Chiller on

  21. Application of Controls • Chiller Sequencing 3 x 300 TR Chiller +30 HP associatedpumps/fans each 3 Chillers on 2 Chillers on 1 Chiller on

  22. Application of Controls • Chiller Sequencing 3 x 300 TR Chiller +30 HP associatedpumps/fans each Run 2Chillers Run 1 Chiller Run 3 Chillers

  23. Application of Controls • Chiller Sequencing DecreasingLoad Differential to preventshort cycling IncreasingLoad

  24. Application of Controls • Chiller Sequencing • 1. Plot curves for all combinations of chillers including pumps and cooling towers • 2. Take switchover points from graph • 3. Program switchover points with differential • 4. Use run time to choose lead and lag chillers

  25. Application of Controls Chilled Water Reset

  26. Application of Controls • Chilled Water Reset

  27. Application of Controls • Chilled Water Reset

  28. Application of Controls • Chilled Water Reset

  29. Application of Controls • RatioMax. Reset* • AHU 1 8%/Deg 9.1 Deg • AHU 2 6%/Deg 8.5 Deg • AHU 3 5%/Deg 8.0 Deg Chilled Water Reset * Assuming maximum valve position allowed is 85%

  30. Application of Controls • Chilled Water Reset • 1. Record step response of valve position for each AHU to measure system delay and calculate ratio (%/Degree) • 2. Automatically reset chilled water temperature • 3. Look for opportunities to add localized cooling to increase chiller savings

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