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Chapter 21

Heating, Ventilating, and Air-Conditioning (HVAC). Chapter 21. Overview. Code Requirements. Heating Systems. Zone Control. HVAC Drawings. 3 Methods of Heat Transfer? Hint (C.C.R). Introduction. Heating, ventilating, and air-conditioning (HVAC)

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Chapter 21

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  1. Heating, Ventilating, and Air-Conditioning (HVAC) Chapter 21

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

  3. 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°

  4. 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

  5. Thermal Calculations for Heating/Cooling (cont’d.) • 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

  6. Thermal Calculations for Heating/Cooling (cont’d.) • HVAC terminology (cont’d.): • Outdoor temperature • Outdoor wet bulb • R-factor • Sensible load calculations • Temperature difference • U-factor

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

  8. 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

  9. 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

  10. 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

  11. 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

  12. Minimum Dimensions • Furnace 24 x 30 • Water Heater 18-24” Diameter • Electrical Panel 30” open space • Pex Piping

  13. Duct Systems • Cold Air Return • Supply

  14. Central Forced-Air Systems

  15. 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)

  16. 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

  17. 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

  18. 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

  19. Alternate Method using Zone Controls • Individual rooms are heated and cooled as needed

  20. 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

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

  22. 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

  23. 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

  24. Heat Pump Systems • Forced-air central heating and cooling system • Compressor and circulating refrigerant system

  25. 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

  26. 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

  27. Gas lines • Meter • Pressurized Gas • 2lb • 4 oz

  28. 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

  29. 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

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

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