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HVAC 101

HVAC 101. The Basics of Heating, Ventilation and Air Conditioning Presented by: Mike Barcik and Jeff Ross-Bain, PE Southface Energy Institute. Southface Energy Institute Sensible Solutions for Environmental Living. Energy Code Workshops Greenprints Commercial Systems EarthCraft House.

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HVAC 101

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  1. HVAC 101 The Basics of Heating, Ventilation and Air Conditioning Presented by: Mike Barcik and Jeff Ross-Bain, PE Southface Energy Institute

  2. Southface Energy InstituteSensible Solutions for Environmental Living • Energy Code Workshops • Greenprints • Commercial Systems • EarthCraft House www.southface.org

  3. HVAC • Heating, Ventilation and Air Conditioning • Provides comfortfor people • Allows humans to exist under adverse conditions.

  4. Comfort • Comfort is primary intent of HVAC systems. • Productivity • Building Durability • Health • Mold

  5. Load Calculations • Heating and Cooling • Accuracy important! • Design conditions • Building shell load • R, U value • Internal load • Ventilation load • Infiltration • Occupancy schedules

  6. Heat Transfer • Conduction • Convection • Radiation • Resistance (R-Value) • U = 1 / R • Q = U x A x T U-Value is the rate of heat flow in Btu/h through a one ft2 area when one side is 1oF warmer

  7. Solar Heat Gain Coefficient • The amount of solar heat energy allowed to pass through a window • Example: SHGC = 0.40 Allows 40% through and turns 60% away

  8. Psychrometrics • Dry bulb temp. • Wet bulb temp. • Humidity • Dew point • Moisture content • Heating • Cooling • Humidify • De-Humidify Psychrometric Chart

  9. Basic Refrigeration Cycle Condenser Compressor Expansion Valve Evaporator

  10. Basic HVAC Equipment • Fans / Blowers • Furnace / Heating unit • Filters • Compressor • Condensing units • Evaporator (cooling coil) • Control System • Air Distribution System

  11. System Types and Common Terms Constant Volume Variable Volume Indoor Air Quality Direct Expansion • Packaged Rooftop Unit • Split System • Heat Pump • Geothermal • Air to Air • Hydronic (water) • PTAC / PTHP

  12. Packaged Rooftop Units

  13. Split System Ductwork Heating and Cooling Equipment FURNACE Temperature & Humidity Controls A/C UNIT

  14. Heat Pump • Operate on simple refrigeration cycle • Reversing the cycle provides heating • Temperature limitations • Air to air • Water source • Geothermal • Lake coupled

  15. Geothermal Heat Pump Systems

  16. Variable Air Volume Variable Speed Supply Fan Supply Ducts VAV Box Filters Reheat Coil Return Air Heat Coil w/Temp Reset T T Cool Coil w/Temp Reset Zone Thermostat Return Ducts Variable Speed Return Fan HVAC-17

  17. Terminal Units Variable volume: Parallel Constant volume: Series

  18. Hydronic systems • Pumps • Piping • Valves

  19. Control Devices • Thermostats • Manual • Programmable • Optimum Start • DDC Systems • Variable Speed Drives • Automatic Valves and Dampers • Outdoor Sensors

  20. Major Equipment • Chillers • Boilers • Cooling Towers

  21. Economizers Air Side Water Side

  22. Economizers Free cooling source: When available, use cool outdoor air instead of mechanically cooled air. Minimum supply of outside air 55 oF and up 55 oF 85% outside air 85% exhaust 80 oF 80 oF Normal Operation Outside air dampers are positioned to provide the minimum outside air Economizer Operation Outside air dampers are fully open. Maximum outside air is provided HVAC-23

  23. N W Core E S Zoning and Economizers • Economizers provide “free cooling” when outdoor conditions are optimal • Proper orientation & zoning yields comfort & efficiency HVAC-24

  24. Air Distribution • Ductwork • Metal • Flexible • Ductboard • Grilles, Louvers, & Registers • Dampers • Shut off • Fire • Smoke • Sealants • Supports

  25. Return Plenum Problems HVAC-26

  26. Additional Equipment • Energy Recovery Units • Desiccant Systems

  27. Additional Equipment • Heat Exchangers • Humidifiers • Silencers

  28. Mechanical Dehumidification • Return air is mixed with ventilation air • Cold coil condenses moisture • Heat is added back (electric or gas) so that room air is not over cooled- Reheat Filter

  29. Historical Minimum Ventilation Rates (cfm/person) Smoking 62-89 Flugge 1905 Billings 1895 Nightengale 1865 Smoking 62-81 ASH- RAE 62-89 ASHRAE 62-73 Tredgold 1836 Yaglou 1938 ASHRAE 62-81

  30. Improved Ventilation Effectiveness • Mechanically provide filtered and dehumidified outdoor air to the breathing space • Vary ventilation based on the number of occupants and process loads - changes in occupancy can be measured by CO2 sensors • Consider designs that separate ventilation and space conditioning • Utilize heat recovery systems to reduce system size and ventilation energy costs

  31. Improved Ventilation Effectiveness • Effective mixing of ventilation air within space • Net positive pressure in the southeast; exhaust from appropriate spaces • Provide clean outdoor air, avoid: • loading docks • exhaust vents • plumbing stacks • waste collection • stagnant water

  32. Additional Information / Resources • ASHRAE – The American Society of Heating, Refrigerating and Air-Conditioning Engineers • www.ashrae.org • Southface Energy Institute www.southface.org • Geothermal heat pump consortium www.geoexchange.org • www.buildingscience.com • www.energycodes.gov

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