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 www.southface.org

HVAC Heating, Ventilation and Air Conditioning Provides comfort for people Allows humans to exist under adverse conditions.

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

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

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

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 Solar Heat Gain Coefficient (SHGC) The glazing’s effectiveness in rejecting solar heat gain. Part of a system for rating window performance used by the National Fenestration Rating Council (NFRC) Gradually replacing shading coefficient (SC) in product literature and design standards convert SC to SHGC by multiplying the SC value by 0.87

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

Basic Refrigeration Cycle Condenser Compressor Expansion Valve Evaporator

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

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

Packaged Rooftop Units                                                  

Split System Heating and Cooling Equipment Temperature & Ductwork Heating and Cooling Equipment FURNACE Temperature & Humidity Controls A/C UNIT An HVAC system consists of a heating and/or cooling source, a distribution system (e.g. ductwork or hot/chilled water piping) and temperature controls.

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

Geothermal Heat Pump Systems

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 Variable Speed Return Fan Return Ducts HVAC-17

Terminal Units Variable volume: Parallel Constant volume: Series                                        

Hydronic systems Pumps Piping Valves

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

Major Equipment Chillers Boilers Cooling Towers

Economizers Air Side Water Side

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

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

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

Return Plenum Problems HVAC-26

Additional Equipment Energy Recovery Units Desiccant Systems

Additional Equipment Heat Exchangers Humidifiers Silencers                                                              

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

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

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

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

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