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 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 ft 2 area when one side is 1 o F 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

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 A/C UNIT Ductwork FURNACE Temperature & Humidity 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 Reheat Coil

T

Zone Thermostat

T

Variable Speed Return Fan Return Ducts

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Terminal Units Variable volume: Parallel Constant volume: Series

Hydronic systems Pumps Piping Valves

Control Devices 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 o F 55 o F and up 80 o F 85% outside air 85% exhaust 80 o F 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

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

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

Return Plenum Problems

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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

Historical Minimum Ventilation Rates (cfm/person) 70 60 50 Smoking 62-89 40 30 Billings 1895 Flugge 1905 Nightengale 1865 Smoking 62-81 20 10 ASHRAE 62-73 Tredgold 1836 Yaglou 1938 ASHRAE 62-81 0 1835 1842 1849 1856 1863 1870 1877 1884 1891 1898 1905 1912 1919 1926 1933 1940 1947 1954 1961 1968 1975 1982 1989 1996 ASH RAE 62-89

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 CO 2 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