HVAC 101

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HVAC 101

• The Basics of Heating, Ventilation and Air
  Conditioning
• Presented by Mike Barcik and Jeff Ross-Bain, PE
• Southface Energy Institute

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Southface Energy InstituteSensible Solutions for
Environmental Living

• Energy Code Workshops
• Greenprints
• Commercial Systems
• EarthCraft House

www.southface.org
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HVAC

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

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Comfort

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

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Load Calculations

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

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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
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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

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Psychrometrics

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

Psychrometric Chart
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Basic Refrigeration Cycle
Condenser
Compressor
Expansion Valve
Evaporator
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Basic HVAC Equipment

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

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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

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Packaged Rooftop Units
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Split System
Ductwork
Heating and Cooling Equipment
FURNACE
Temperature Humidity Controls
A/C UNIT
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Heat Pump

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

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Geothermal Heat Pump Systems
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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
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Terminal Units

• Variable volume Parallel

Constant volume Series
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Hydronic systems

• Pumps
• Piping
• Valves

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Control Devices

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

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Major Equipment

• Chillers
• Boilers
• Cooling Towers

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Economizers
Air Side
Water Side
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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
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Zoning and Economizers

• Economizers provide free cooling when outdoor
  conditions are optimal
• Proper orientation zoning yields comfort
  efficiency

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Air Distribution

• Ductwork
• Metal
• Flexible
• Ductboard
• Grilles, Louvers,
• Registers
• Dampers
• Shut off
• Fire
• Smoke
• Sealants
• Supports

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Return Plenum Problems
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Additional Equipment

• Energy Recovery Units
• Desiccant Systems

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Additional Equipment

• Heat Exchangers
• Humidifiers
• Silencers

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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
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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
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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

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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

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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