Air conditioning is a technology used to control the temperature, humidity, and air quality within an indoor environment. It encompasses a range of systems and technologies designed to provide comfort in residential, commercial, and industrial settings. The field includes:

Heating, Ventilation, and Air Conditioning (HVAC): A comprehensive system that manages heating, cooling, and ventilation to ensure indoor comfort and air quality.

Refrigeration: Focuses on cooling processes, often used in commercial and industrial applications like refrigeration units and cold storage.

Climate Control: Involves adjusting and regulating indoor climate conditions based on external weather and internal requirements.

Key steps to design HVAC system

1. Load Calculation: Perform a detailed heat load calculation to determine the cooling requirements. This includes assessing factors like building size, insulation, window orientation, and occupancy.
2. System Selection: Choose an appropriate HVAC system based on the load calculation. Options include central air conditioners, ductless mini-splits, or heat pumps designed for cooling.
3. Duct Design: For systems with ductwork, design and install ducts to ensure efficient airflow and minimal leakage. Consider using insulated ducts to reduce cooling loss.
4. Cooling Equipment: Select high-efficiency cooling equipment, such as high-SEER (Seasonal Energy Efficiency Ratio) air conditioners or Chillers. In hot climates, investing in energy-efficient units can reduce operational costs.
5. Thermostats and Controls: Install programmable or smart thermostats to optimize cooling schedules and reduce energy use.
6. Ventilation: Ensure proper ventilation to enhance indoor air quality and reduce humidity. Consider energy recovery ventilators (ERVs) or heat recovery ventilators (HRVs) for efficiency.
7. Insulation and Shading: Improve building insulation and incorporate shading techniques to reduce heat gain. This includes reflective window films, shading devices, and proper attic insulation.
8. Maintenance: Establish a regular maintenance schedule for the HVAC system to ensure optimal performance. This includes checking refrigerant levels, cleaning filters, and inspecting components.
9. Energy Efficiency: Implement additional energy-saving measures like solar panels or advanced cooling technologies (e.g., evaporative coolers) to further enhance system performance in hot climates.
10. Compliance: Ensure the HVAC system meets local building codes and regulations related to energy efficiency and safety. 

The end results of heat load calculation are TR & Dehumidified CFM.
TR=GTH/12000
Where, GTH = Grand total heat gain in BTU/Hr
TR = Ton of Refrigeration (Unit of refrigeration effect or AHU load)
12000 = One ton
CFM = TRSH / (1.08 x (Trm-Tdp) x (1-BF))
Where, TRSH = Total Room Sensible Heat in BTU/Hr

CFM = Unit of air flow rate (Cubic Feet per Minute)
Trm = Room Temperature in °F
Tadp = Apparatus Dew point Temperature in °F (Surface Temperature of Cooling Coil)
BF = Bypass factor of Coil (Unit less number)
Notes:
1. ADP can be obtained by plotting pscychrometric process on psychrometric chart or can be obtained readily by tables published by ISHRAE handbook using Room Sensible heat factor, inside design conditions.
2. Bypass Factor of cooling coil can be assumed in the range of 0.8 to 1.0 based on number of cooling coil rows.

Brief Overview of HVAC System Selection:

1. Determine System Type: Decide between options like central air conditioners, heat pumps, ductless mini-splits, or packaged units based on your cooling and heating needs.
2. Assess Efficiency: Look for systems with high Seasonal Energy Efficiency Ratio (SEER) ratings for cooling and Annual Fuel Utilization Efficiency (AFUE) ratings for heating to ensure energy efficiency.
3. Consider Zoning Needs: If different areas require varying temperatures, opt for a zoned system or ductless mini-splits with multiple indoor units.
4. Check Capacity: Ensure the system capacity matches the load calculation results to avoid under or over-sizing, which can lead to inefficiency.
5. Review Features: Evaluate features like variable-speed compressors, smart thermostats, and advanced filtration for better performance and control.
6. Evaluate Installation Requirements: Consider the space for installation, ductwork needs, and any potential modifications to the existing infrastructure.
7. Budget and Costs: Factor in both initial costs and long-term operating costs, including energy consumption and maintenance.
8. Local Climate Considerations: Choose systems that perform well in your specific climate conditions, such as high-efficiency units for hot climates.

Brief Overview of  HVAC Ducts:

1. Duct Sizing: Use calculations to determine the appropriate duct sizes for each room or zone based on airflow requirements, avoiding undersized or oversized ducts.
2. Duct Layout: Plan a layout that minimizes sharp bends and long runs to reduce airflow resistance and energy loss. Aim for a design that balances airflow to all areas.
3. Material Selection: Choose appropriate duct materials such as sheet metal, fiberglass, or flexible ducting, considering factors like durability, insulation, and cost.
4. Insulation: Insulate ducts, especially those in unconditioned spaces, to prevent heat loss or gain and improve system efficiency.
5. Sealing: Properly seal all joints and connections to prevent air leaks, which can reduce system efficiency and increase energy costs.
6. Vent Placement: Position supply and return vents strategically to ensure even distribution of air and avoid hot or cold spots.
7. Ductwork Balancing: Implement balancing dampers to fine-tune airflow and ensure each room receives the appropriate amount of conditioned air.
8. Compliance: Follow local building codes and regulations for duct installation and design to ensure safety and efficiency

Brief Overview of HVAC cooling equipment :

1. Central Air Conditioners: These systems use refrigerant to cool air in a central unit, which is then distributed through ducts to various rooms. They are suitable for cooling large areas and homes.
2. Heat Pumps: Heat pumps can both heat and cool a space by transferring heat. In cooling mode, they function similarly to air conditioners, moving heat from indoors to outdoors.
3. Ductless Mini-Split Systems: These systems consist of an outdoor compressor unit and one or more indoor air handling units. They are ideal for homes without existing ductwork and offer zoning flexibility.
4. Packaged Units: These units combine the compressor, condenser, and evaporator into a single outdoor unit. They are often used in commercial buildings or homes with limited indoor space.
5. Evaporative Coolers (Swamp Coolers): These use water evaporation to cool the air and are suitable for dry climates. They are less energy-intensive but may not be effective in high-humidity areas.
6. Chillers : Used in larger commercial or industrial applications, chillers remove heat from a liquid via a refrigeration cycle and then distribute the cooled liquid through pipes.

Brief Overview of HVAC thermostats and controls:

1. Thermostat Types: 1.1 Manual Thermostats: Basic models requiring manual adjustment of temperature settings.

          1.2 Programmable Thermostats: Allow users to set temperature schedules for different times of day and days of the week, improving energy efficiency.

        1.3 Smart Thermostats: Connect to Wi-Fi and can be controlled remotely via smartphone apps. They often include learning algorithms to optimize energy use based on occupancy and preferences.

2. Temperature Sensors: Measure indoor temperature and relay information to the thermostat to maintain the desired temperature setting.
3. Zoning Controls: Manage temperature in different areas or zones of a building separately, often using multiple thermostats and dampers in the ductwork.
4. Humidity Controls: Some systems include humidity sensors and controls to manage indoor humidity levels, enhancing comfort and preventing issues like mold.
5. Integration with Home Automation: Modern thermostats can integrate with home automation systems, allowing for centralized control of HVAC along with other smart home devices.
6. Energy Monitoring: Many advanced thermostats provide energy usage reports and tips for improving efficiency, helping users manage costs.

Brief Overview of HVAC ventilation:

1. Types of Ventilation:

•    Natural Ventilation: Relies on natural airflow through windows, vents, and architectural design to provide fresh air.
•    Mechanical Ventilation: Uses fans and duct systems to actively bring in outdoor air and exhaust indoor air.

2. Ventilation Systems:

•    Exhaust Fans: Remove stale air from specific areas like kitchens and bathrooms.
•    Supply Fans: Bring in fresh outdoor air to indoor spaces.
•    Balanced Systems: Combine supply and exhaust fans to maintain balanced airflow and pressure.

3. Energy Recovery Ventilators (ERVs): Transfer heat and moisture between incoming and outgoing air streams, improving energy efficiency and indoor air quality.
4. Heat Recovery Ventilators (HRVs) : Similar to ERVs, but focus primarily on heat transfer, reducing energy costs for heating and cooling.
5. Air Filtration: Ventilation systems often include filters to remove dust, allergens, and other particulates from the air.
6. Duct Design: Properly designed ducts ensure efficient distribution of fresh air and removal of stale air, minimizing energy loss and improving comfort.

Brief Overview of HVAC Insulation and Shading:

1. Insulation:

• Purpose: Reduces heat transfer between the indoor and outdoor environment, improving the efficiency of heating and cooling systems.
• Types: Includes materials like fiberglass batts, foam board, spray foam, and reflective barriers.
• Applications: Insulation is commonly applied in walls, attics, floors, and ducts to minimize heat loss in winter and heat gain in summer.

2. Shading:

   Purpose: Minimizes solar heat gain through windows and walls, reducing the cooling load on the HVAC system.

   Types:

• Exterior Shading: Includes awnings, pergolas, and exterior blinds that block sunlight before it reaches windows.
• Interior Shading: Includes curtains, blinds, and shades that reduce heat gain from sunlight entering through windows.
• Window Films: Reflective or tinted films can be applied to windows to reduce heat gain and glare.

Brief Overview of HVAC energy efficiency:

1. High-Efficiency Equipment: Choose HVAC systems with high efficiency ratings. For cooling, look for units with a high SEER (Seasonal Energy Efficiency Ratio) rating, and for heating, consider systems with a high AFUE (Annual Fuel Utilization Efficiency) rating.
2. Proper Sizing: Ensure the HVAC system is correctly sized for the space. An oversized or undersized system can lead to inefficiencies and higher energy consumption.
3. Smart Thermostats: Use programmable or smart thermostats to optimize heating and cooling schedules based on occupancy patterns and preferences, reducing energy use when the space is unoccupied.
4. Regular Maintenance: Perform routine maintenance to keep the system running efficiently. This includes cleaning filters, checking for leaks, and ensuring all components are in good working order.
5. Insulation and Sealing: Improve building insulation and seal leaks in windows, doors, and ducts to reduce heat loss or gain and minimize the HVAC system’s workload.
6. Energy Recovery Ventilation: Implement energy recovery ventilators (ERVs) or heat recovery ventilators (HRVs) to improve ventilation without wasting energy.
7. Zoning Systems: Use zoning systems to heat or cool only occupied areas, optimizing energy use by avoiding unnecessary heating or cooling of unoccupied spaces.
8. Upgrade to Efficient Systems: Consider upgrading to newer, more efficient HVAC technologies such as variable-speed compressors or advanced heat pumps for improved performance and efficiency.

Brief Overview of HVAC compliance: 

1. Building Codes: Follow local and national building codes that specify requirements for HVAC system installation, including safety standards, energy efficiency, and proper ventilation.
2. Energy Efficiency Standards: Adhere to standards set by agencies such as the local regulatory bodies. This includes minimum efficiency ratings for HVAC equipment and guidelines for system design.
3. Refrigerant Regulations: Comply with regulations regarding refrigerant use, such as those outlined in the Clean Air Act or the Montreal Protocol, which address the handling, recycling, and disposal of refrigerants to minimize environmental impact.
4. Permits and Inspections: Obtain necessary permits before installation or major modifications, and ensure systems pass required inspections to verify compliance with codes and standards.
5. Safety Standards: Follow safety standards related to electrical connections, gas lines, and equipment placement to ensure safe operation and prevent hazards.
6. Documentation and Reporting: Maintain proper documentation of system design, installation, and maintenance to demonstrate compliance and facilitate inspections or audits.
7. Occupational Safety: Adhere to occupational safety standards for HVAC installation and maintenance, including proper training and use of personal protective equipment (PPE).

5.1 General

Ventilation of buildings is required to supply fresh air for respiration of occupants, to dilute inside air to prevent vitiation by body odours and to remove any products of combustion or other contaminants in air and to provide such thermal environments as will assist in the maintenance of heat balance of the body in order to prevent discomfort and injury to health of the occupants.

5.2 Design Considerations

 5.2.1 Respiration

Supply of fresh air to provide oxygen for the human body for elimination of waste products and to maintain carbon dioxide concentration in the air within safe limits rarely calls for special attention as enough outside air for this purpose normally enters the areas of occupancy through crevices and other openings.

 5.2.1.1 In normal habitable rooms devoid of smoke generating source, the content of carbon dioxide in air rarely exceeds 0.5 percent to 1 percent and is, therefore, incapable of producing any ill effect. The amount of air required to keep the concentration down to 1 percent is very small. The change in oxygen content is also too small under normal conditions to have any ill effects; the oxygen content may vary quite appreciably without noticeable effect, if the carbon dioxide concentration is unchanged.

 5.2.2 Vitiation by Body Odours

Where no products of combustion or other contaminants are to be removed from air, the amount of fresh air required for dilution of inside air to prevent vitiation of air by body odours, depends on the air space available per person and the degree of physical activity; the amount of air decreases as the air space available per person increases, and it may vary from 20 m3 to 30 m3 per person per hour. In rooms occupied by only a small number of persons such an air change will automatically be attained in cool weather by normal leakage around windows and other openings and this may easily be secured in warm weather by keeping the openings open.

 No standards have been laid down under the Factories Act, 1948 as regards the amount of fresh air required per worker or the number of air changes per hour. Section 16 relating to over-crowding requires that at least 14 m3 to 16 m3 of space shall be provided for every worker and for the purpose of that section no account shall be taken of any space in a work room which is more than 4.25 m above the floor level.

HVAC consultants play a crucial role in designing, installing, and maintaining heating, ventilation, and air conditioning systems. Their responsibilities include:

System Design: They create efficient HVAC system designs tailored to the specific needs of a building, considering factors like size, usage, and climate.
Energy Efficiency: They recommend and implement energy-efficient solutions to reduce operational costs and environmental impact.
Compliance: They ensure that HVAC systems meet local building codes and regulations.
Troubleshooting: They diagnose and resolve issues with existing HVAC systems to improve performance and reliability.
Cost Estimation: They provide cost estimates for system installation, maintenance, and upgrades.

HVAC installers are responsible for the physical installation and setup of heating, ventilation, and air conditioning systems. Their key roles include:

1. System Installation: They install HVAC equipment, including furnaces, air conditioners, ductwork, and thermostats, according to manufacturer specifications and building codes.
2. System Testing: They test installed systems to ensure they operate correctly, efficiently, and safely.
3. System Maintenance: They perform initial system maintenance tasks, such as calibrating and adjusting equipment to ensure optimal performance.
4. Troubleshooting: They identify and resolve any issues that arise during or after installation.
5. Customer Education: They educate customers on system operation, maintenance requirements, and energy-saving tips.

Brief overview of HVAC maintenance :

1. Regular Inspections: Schedule professional inspections to check system components, including refrigerant levels, electrical connections, and overall system operation.
2. Filter Replacement: Replace or clean air filters regularly (typically every 1-3 months) to ensure proper airflow and reduce strain on the system.
3. Clean Coils and Components: Keep evaporator and condenser coils clean to maintain efficiency and prevent overheating. Also, clean the blower components and check ductwork for blockages
4. Check Refrigerant Levels: Ensure refrigerant levels are correct to maintain efficient cooling performance and prevent system d
5. Inspect Thermostats and Controls: Test thermostats and controls to ensure accurate temperature regulation and system operation.
6. Lubricate Moving Parts: Lubricate motors, fans, and other moving parts to reduce friction and wear, improving system efficiency and longevity.
7. Examine Ductwork: Check for leaks or damage in ductwork and seal any gaps to prevent energy loss and improve system performance.
8. Clear Drain Lines: Ensure condensate drain lines are clear to prevent water damage and potential mold growth.