Uploaded byJitendra Jha
HVAC Basics
This document discusses HVAC systems and their energy consumption. It describes how HVAC systems maintain temperature, humidity, and ventilation levels in buildings. HVAC systems circulate air through air handling units, which heat, cool, filter and distribute air to rooms using boilers, chillers, pumps, and other mechanical equipment located in mechanical rooms. The document explains the functions of key HVAC components like AHUs, VAV boxes, economizers and how they work to condition air and ensure thermal comfort. It also notes some differences that can occur between theoretical HVAC diagrams and real-world systems.
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HVAC Basics
- 1. HVAC Basics Jitendra Jha HVAC– Heating, Ventilation, Air-conditioning
- 2. HVAC Energy Consumption 2 Cooling642 kWh/m2 Heating 623 kWh/m2 Electricity 414 kWh/m2 Annual Energy Use >60% A lab building on campus 32% DOE numbers
- 3. HVAC 3 HVAC – Heating,Ventilation, Air-conditioning Temperature Humidity Pressure Ventilation 68°F (20°C) and 75°F (25°C) 30% relative humidity (RH) and 60% RH A slightly positive pressure to reduce outside air infiltration. Rooms typically have several complete air changes per hour Diagram of mechanical system on the blackboard
- 4. Where? 4 Mechanical Room: Boilers,chillers, pumps, heat exchangers… Air Handling Units (AHUs): heat, cool, humidify, dehumidify, ventilate, filter and distribute the air. Room Controls: thermostats and Variable Air Volume (VAV) boxes
- 5. In the mechanicalroom 5 Boiler Chiller
- 6. Heating 6 Also to radiators,terminal reheat, domestic hot water.
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- 9. AHU – AirHandling Unit 9 Return air Exhaust air Outside air Supply air Where does air come from and go to?
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- 11. AHU - Economizer 11 Economizermode: Using outside air for cooling rather than mechanical cooling. Linked Minimum in summer More outside air in winter 55°F
- 12. AHU – Heatingand Cooling 12 dehumidification 55°F
- 13. Humidification 13 Why before thecooling coil?
- 14. VAV 14 Two variables –Temperature & Air Volumedamper The box you can see in the hallway. IF temperature too high First reduce reheat till fully closed Then increase air volume IF temperature too low First reduce air volume till minimum Then start reheat
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- 17. 17 The Real World Anydifference? Anything wrong? 52°F
- 18. 18 The Real World 52°F Chilledwater is still used when outside air is far below 52F Temperature increased after humidification. Sensor error. Separate control caused counteraction.
- 19. What we havelearned? 19 What’s in the mechanical rooms. What happens in air handling unit. How VAV works. What can happen in the real world. The system that ensures the thermal comfort.
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