Heating, Ventilating, and Air-Conditioning (HVAC)

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Chapter 21

• Heating, Ventilating, and Air-Conditioning (HVAC)

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Overview
Code Requirements
Heating Systems
HVAC Drawings
Zone Control
3 Methods of Heat Transfer? Hint (C.C.R)
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Introduction

• Heating, ventilating, and air-conditioning (HVAC)
• Heating and air-conditioning equipment, and
  systems found in a building
• Also referred to as the mechanical system
• Regulates temperature
• International Residential Code (IRC)
• Requires a heating unit in any residence built in
  an area where winter design temperature is below
  60

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Thermal Calculations for Heating/Cooling

• Necessary to establish the correct
• Furnace
• Ductwork
• Supply
• Return register specifications
• Historical primary use
• Calculate design heat load of houses to estimate
  gas and oil heating systems size

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Thermal Calculations for Heating/Cooling (contd.)

• HVAC terminology
• Btu
• Indoor Air Quality (IAQ)
• Duct loss
• Cubic Feet/ Min. (CFM)
• Heat transfer multiplier
• Indoor temperature
• Air Changes per Hour (ACH)

• Indoor wet bulb
• Infiltration
• Internal heat gain
• Latent load
• Mechanical ventilation

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Thermal Calculations for Heating/Cooling (contd.)

• HVAC terminology (contd.)
• Outdoor temperature
• Outdoor wet bulb
• R-factor
• Sensible load calculations
• Temperature difference
• U-factor

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Thermostats

• Automatic mechanism for controlling heating or
  cooling by a central or zonal system
• Location is important

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Exhaust Systems Code Requirements

• Exhausts are part of the HVAC system
• Exhaust systems are required to remove odors,
  steam, moisture, and pollutants
• Refer to the text for basic general code
  requirements

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HVAC Code Requirements

• National Energy Conservation Code regulates the
  design and construction of
• Exterior envelope and selection of HVAC
• Service water heating
• Electrical distribution
• Illuminating systems and required equipment
• Refer to the text for general code requirements

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Code Requirements

• IECC is updated every three years and is designed
  to provide an energy efficient environment for
  humans
• Equipment in a garage must be protected from
  automobile impact (slab on grade construction
  would have a 18 platform)
• Programmable Thermostat
• Exterior (Building) envelope is space that is
  heated and cooled
• Conditioned (finished square footage)
• Unconditioned (basement unfinished)
• Must be separated by a door

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Code Requirements

• A door or access large enough to remove largest
  piece of equipment
• Unobstructed working space not less than 30 wide
  and high should be provided next to the control
  side of the equipment (Furnace, WH)
• An GFCI electrical outlet and lighting fixture
  should be provided near the equipment and have a
  switch at the doorway or access (In attic)
• Equipment located on the ground should be
  supported on a concrete slab and be at least 3
  above the ground. (AC units)
• Fuel burning warm-air furnaces must be supplied
  with combustion air
• All exterior ducting (Avoid at all costs) should
  be weatherproof and insulated
• In basements all supply lines should be insulated
  with R-4.2 insulation unless wall drapes are used
  to consider it conditioned space

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Minimum Dimensions

• Furnace 24 x 30
• Water Heater 18-24 Diameter
• Electrical Panel 30 open space
• Pex Piping

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Duct Systems

• Cold Air Return
• Supply

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Central Forced-Air Systems
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Forced Air Systems

• A fan forces air into ducts that connect to air
  supply registers
• Air is heated during the heating cycle and the
  combustion is vented out flue
• Cooled air is passed over a cooling coil which is
  cooled with a refrigerant (Puron)

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Forced-Air Heating Plans

• Complete forced-air heating plans show
• Size, location, and number of British thermal
  units (Btu) dispersed from warm-air supplies
• Location and size of cold-air return
• Location, type, and output of furnace
• Providing duct space (i.e., chase)
• When ducted heating and cooling systems are used,
  duct location becomes important

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Central Air Systems

• Rules to Design
• Place Central Air Condenser unit at shortest
  straight line to exterior side or rear of home
  for coil (efficiency)

• Place Ducting trunks cold air returns and supply
  lines to one side of bearing wall (Stairs)
• Add Combustion Air Intake direct line same
  direction floor joist are running

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Zone Control Systems

• One heater and one thermostat per room
• No duct work
• Only heaters in occupied rooms need to be turned
  on
• Types
• Baseboard
• Fan heaters
• Split systems

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Alternate Method using Zone Controls

• Individual rooms are heated and cooled as needed

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Hot Water System

• Water is circulated through a radiator after
  being heated in an oil- or gas-fired boiler
• One-pipe system has heated water pass through
  radiators and returns in the same pipe to the
  boiler
• Radiant Flooring is growing in popularity

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Hot Water Systems

• Water is heated in an oil- or gas-fired boiler
• Then circulated through pipes to radiators or
  convectors

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Radiant Heat

• Radiant heating and cooling systems
• Control surface temperatures
• Minimize excessive air motion
• Annual operating cost savings of 20 to 50
• Lower thermostat settings
• Superior, cost-effective design

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Heat Pump/ Geothermal / Passive Solar Systems

• Heat is extracted from outside air and pumped
  through a compressor into the structure
• Heat pump systems are 30 to 50 percent more
  efficient then forced air systems
• Air is cleaner and fresher with a heat pump system

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Heat Pump Systems

• Forced-air central heating and cooling system
• Compressor and circulating refrigerant system

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Exhaust System Code Requirements

• Vented hoods must have back draft damper
• Direct vent to exterior suggested for gas or
  exhaust fan in kitchen
• If gas dryer or other fuel burning appliance (Fan
  is good idea)
• Clothes dryer vents independent from all other
  systems.
• No screws in vent
• Back draft damper
• 4 duct no longer than 25
• Total length reduced 2.5 for each 45 bend and 5
  for each 90 bend

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Heat Recovery and Ventilation

• Uses a counter flow heat exchanger between
  inbound and outbound airflow
• Air pollutants
• Principle reason for installation
• Air-to-air heat exchangers
• Pulls polluted, stale, warm air from the space
  and transfers heat in that air to fresh, cold air
  being pulled into the space

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Gas lines

• Meter
• Pressurized Gas
• 2lb
• 4 oz

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HVAC Drawings

• Drawings for the HVAC system show
• Size and location of all equipment, ductwork, and
  components
• Use accurate symbols, specifications, notes, and
  schedules
• Form the basis of contract requirements for
  construction

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Residential HVAC Drawings

• Show Thermostat location
• Heat Register Locations
• 4 x 10 floor or 2 x 10 under cabinet
• Cold air return is needed for every 5 heat
  registers
• 14 x 8 single or 30 x 8 double
• Size of room and use determines number of
  registers needed 150 square feet Single

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Residential HVAC Drawings
Show Supply and Return Main Trunk Lines Dryer
Vent Location Combustion Air Location