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 Institute Sensible Solutions for Environmental Living
Energy Code Workshops
Greenprints
Commercial Systems
EarthCraft House

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

4. Comfort Mold 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
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

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

12. 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

13. Packaged Rooftop Units
                                                 

14. 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.

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

16. Geothermal Heat Pump Systems

17. 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

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

19. Hydronic systems
Pumps
Piping
Valves

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

21. Major Equipment
Chillers
Boilers
Cooling Towers

22. Economizers
Air Side
Water Side

23. 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

24. 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

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

26. Return Plenum Problems
HVAC-26

27. Additional Equipment
Energy Recovery Units
Desiccant Systems

28. Additional Equipment
Heat Exchangers
Humidifiers
Silencers
                                                             

29. 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

30. 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

31. 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

32. 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

33. Additional Information / Resources
ASHRAE – The American Society of Heating, Refrigerating and Air-Conditioning Engineers
Southface Energy Institute
Geothermal heat pump consortium