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Key HVAC Design Concepts PowerPoint Presentation
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Key HVAC Design Concepts

Key HVAC Design Concepts

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Key HVAC Design Concepts

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  1. Key HVAC Design Concepts

  2. Agenda • Discuss relevance of thermal enclosure system to HVAC system. • Present the three major steps to design an HVAC system. • Hold question and answer session. 2

  3. Thermal enclosure system 1 • A well-insulated and air-sealed home, with good windows and doors, reduces the amount of energy needed to keep the home comfortable. Thermal Enclosure System 3

  4. Thermal enclosure system • Energy moves from more to less. • Over time, differences in temperatures dissipate. 90°F - Outside 70°F - Outside 70°F 90°F 40°F 120°F A cup of coffee A cooler with ice Cooler 4

  5. Thermal enclosure system • Energy moves from more to less. • Over time, differences in temperatures dissipate. 105°F 105°F 72°F 5

  6. FIBROUS NSULATION = AIR BARRIER Thermal enclosure system 105°F 73°F 72°F 105°F 6

  7. FIBROUS NSULATION = AIR BARRIER Thermal enclosure system • Heat transfer can be quantified in British Thermal Units (Btu’s). • 1 Btu is approximately equal to the energy in a single match. 7

  8. FIBROUS NSULATION = AIR BARRIER Thermal enclosure system 73°F 72°F 8

  9. FIBROUS NSULATION = AIR BARRIER Thermal enclosure system 72°F 105°F 9

  10. FIBROUS NSULATION = AIR BARRIER Thermal enclosure system 72°F 105°F 10

  11. FIBROUS NSULATION = AIR BARRIER Thermal enclosure system 72°F 105°F 11

  12. Thermal defects to avoid • Poorly installed insulation 12

  13. Summary – Thermal enclosure system • Energy moves from more to less. • Over time, differences in temperatures dissipate. • Heat transfer can be quantified in Btu’s. • A complete thermal enclosure system is critical to creating a home that is more comfortable using less energy. 13

  14. Heating & cooling systems 2 • Heating and cooling equipment that is: • High efficiency • Properly designed and installed • Combined with a duct system that’s insulated, sealed, and balanced • … maintains comfort with less energy. Heating, Cooling, & Ventilation System 14

  15. FIBROUS NSULATION = AIR BARRIER • Heating & cooling systems 73°F 105°F 72°F 15

  16. Three major steps to design an HVAC system • Calculate the heating and cooling loads. • Select equipment that meets those loads. • Design a duct system that gets air from the heating & cooling equipment to the rooms in the house, and then from the rooms back to the equipment. 16

  17. Step 1: Calculate Heating & Cooling Loads 17

  18. Step 1:Calculate heating & cooling loads • Cooling load is the maximum Btu’s likely to be added to the home in a single hour during the year. 18

  19. Step 1:Calculate heating & cooling loads • Heating load is the maximum Btu’s likely to be lost from the home in a single hour during the year. 72°F 35°F 19

  20. Step 1:Calculate heating & cooling loads • Standard process to calculate loads. • Provides a checklist of all input variables that can affect a home’s comfort level. 20

  21. Step 1:Calculate heating & cooling loads 21 North-facing home South-facing home

  22. Step 1:Calculate heating & cooling loads 22

  23. Step 1:Calculate heating & cooling loads Important to document window performance characteristics 23

  24. Summary of Step 1:Calculate heating & cooling loads • The first major step in the design process is to calculate the heating and cooling loads. • ACCA Manual J provides a reliable standard process for calculating loads. • By documenting and verifying major design parameters, the ENERGY STAR Certified Homes program helps ensure that the HVAC system has been designed properly. 24

  25. Step 2: Select the Heating & Cooling Equipment

  26. Step 2: Selectequipment that meets loads • Standard process to select equipment using the calculated loads. 26

  27. Step 2: Selectequipment that meets loads • Cooling Load – The number of btu’s per hour that is added to the home from the outdoors, people, lights, appliances, etc. • Cooling Capacity – The number of btu’s per hour that cooling equipment can remove from the home. • Heating Load – The number of btu’s per hour that is lost from the home because it’s cold outside. • Heating Capacity – The number of btu’s per hour that heating equipment can add back to the home. 27

  28. Step 2: Select equipment that meets loads Equipment capacity can be determined using manufacturer’s expanded performance data… 28

  29. Step 2: Selectequipment that meets loads • Select cooling equipment that can remove the number of Btu’s calculated for the cooling load. 72°F 73°F 72°F 29

  30. Step 2: Selectequipment that meets loads • Select heating equipment that can add the number of Btu’s calculated for the heating load. 72°F 71°F 72°F 30

  31. Summary of Step 2: Selectequipment that meets loads • The second major step in the design process is to select equipment using the calculated heating & cooling loads. • ACCA Manual S provides a reliable standard process for doing this and includes limitations on over-sizing. • By requiring that equipment be selected using this process, the ENERGY STAR Certified Homes program helps ensure that the HVAC system is efficient, durable, and effective. 31

  32. Step 3: Design the Duct System

  33. Step 3:Design the duct system • Design a duct system that distributes air from the heating & cooling equipment to each room, and back to the equipment. 33

  34. Step 3:Design the duct system • The airflow needed by each room is directly related to its heating and cooling load. Hallway Room B Room A 80 CFM 80 CFM 80 CFM 34

  35. Step 3:Design the duct system • The airflow needed by each room is directly related to its heating and cooling load. Load Distribution Airflow Distribution 35

  36. Step 3:Design the duct system • Proper airflow is needed to deliver or remove the correct amount of heat from each room. Room A – Correct Airflow Room A – Incorrect Airflow 150 btu 150 btu 95btu 75btu 100 btu 100 btu 100 btu 100 btu 100 btu 100 btu 300 btu’s out & 300 btu’s in 300 btu’s out & 170 btu’s in 36

  37. Step 3:Design the duct system • Factors that influence duct system design: • Duct length • Duct diameter • Duct type • Duct turns • Other components, like filters Duct length Duct turns Duct diameter Flex vs. rigid duct type 37

  38. Step 3:Design the duct system A fan uses energy to push air Like we use energy to push air into a balloon 38

  39. Step 3:Design the duct system Static Pressure = + 0.20 IWC Velocity Pressure = + 0 IWC Static Pressure = + 0.10 IWC Velocity Pressure = + 0.10 IWC The pressure inside the inflated balloon is the Static Pressure If the balloon has a leak, the pressure of that moving air is the Velocity Pressure 39

  40. Step 3:Design the duct system • Example: Duct system without registers & sealed tightly. Supply Ducts Air Handler ON OFF 40

  41. Step 3:Design the duct system • Example: Supply registers added to duct system. Supply Register ON OFF 41

  42. Step 3:Design the duct system • Example: Return side ducts and filters add additional static pressure to the system. Filter Return Ductwork ON OFF 42

  43. Step 3:Design the duct system • Thetotal external static pressure of the duct system includes both the supply and return side. + 0.20 + 0.20 - 0.15 - 0.10 0.20 0.20 0.15 0.10 0.65 ON OFF 43

  44. Summary of Step 3:Design the duct system • The third major step in the design process is to design a duct system that works with the selected equipment. • ACCA Manual D provides a reliable standard process for doing this. It ensures that the static pressure of the duct system and the air velocity are not too high. • These requirements in the ENERGY STAR Certified Homes program help ensure that the home is efficient, quiet, and comfortable. 44

  45. Summary • A complete thermal enclosure system is critical to creating a home that is more comfortable uses less energy. • The HVAC design process has three major steps: • Step 1 is to calculate the heating and cooling loads. • Step 2 is to select equipment with a capacity that can meet those loads. • Step 3 is to design a duct system that can get that heated & cooled air from the equipment to the rooms and back. • The ENERGY STAR Certified Homes program requires this important design process to help maintain the efficiency, comfort, and quality of every certified home. 45