HVAC System Notes

Course Overview

  • NAIT CSTN1245
    • Building Science
    • Residential HVAC
    • A leading polytechnic committed to student success.

HVAC Mechanical Systems

  • HVAC Definition:
    • Heating, Ventilation, and Air Conditioning.
    • Conditions interior spaces for occupant comfort.
    • Design considerations include minimizing heat loss in winter and heat gain in summer.
    • Balances passive energy systems with mechanical systems for thermal comfort.

Key Concepts Related to HVAC

  • Human Comfort / Thermal Comfort Factors:

    • Air Temperature
    • Relative Humidity
    • Mean Radiant Temperature
    • Air Motion
    • Air Purity
    • Sound
    • Vibration
    • Light
    • Comfort ranges vary for each factor, critical for HVAC design.

  • Heat Transfer Mechanisms:

    • Radiation: Heat emitted through electromagnetic waves.
    • Conduction: Heat transfer through direct contact.
    • Convection: Movement of warmer fluid areas to cooler areas.

Residential Mechanical Systems

  • Typical North American Forced-Air Heating System:

    • Uses air for heat distribution via mechanical convection.
    • Variable Volume, Constant Temperature System:
    • Air delivery based on space heating/cooling requirements.

  • Ventilation Requirements in Alberta:

    • 1981: Basic exhaust fans in electrically heated homes.
    • 1985 & 1990: Ventilation systems to exchange indoor air at specified rates.
    • 1997: Emphasis on air change rates and outdoor air distribution.

  • Current Ventilation System Requirements:

    • Simplicity in standards, addressing outdoor air distribution, and limiting depressurization of dwellings.

HVAC System Components

  • Indoor Air Exhaust:
    • Linked to outdoor air supply. Continuous operation required for adequate air quality.
  • Outdoor Air Supply:
    • Introduced via ducts; ensures balanced airflow.
  • Distribution Systems:
    • Utilize forced air systems for air circulation and proper air exchanges.

Additional Systems

  • Hydronic Heating:

    • Utilizes heated water for consistent temperature throughout a space. Pumped through pipes at specific pressures.

  • Energy Recovery Ventilators (ERV):

    • Exchange heat and moisture between incoming and outgoing air.
    • Ideal for homes with high fresh air needs.

Furnace Types

  • Non-Condensing Furnaces:

    • 80-83% efficiency. Single heat exchanger.
    • Separate supply and clean air for combustion.

  • Condensing Furnaces:

    • 90-98% efficiency. Two exchangers allow for better heat recovery.

  • Furnace Sizing Considerations:

    • BTUs, insulation ratings, and structure influences sizing.

Air Conditioning Systems

  • Refrigerant Cycle:
    • Compressing, condensing, expanding, and evaporating cycles to achieve cooling.
    • Typical residential air conditioners integrate cooling with the furnace.

Hydronic Systems - Components

  • Expansion Tanks:

    • Balance pressure in hydronic systems; equipped with pressure-relief valves.

  • Terminal Units:

    • Devices where heat is dispersed such as radiators and in-floor systems.

  • Hydronic Control Valves:

    • Motorized valves that open/close based on temperature.

Summary of Responsibilities and Duties

  • Commissioning Team:
    • Integrates operation effectiveness of HVAC across mechanical systems.
    • Ensures systems are installed correctly, functioning as design intended.

Conclusion

  • Understanding the fundamentals of HVAC systems including their components, comfort factors, and mechanical principles is essential for effective building science and residential HVAC design.