Duct
- Function of Ducts
- Air distribution: Supply and return airflow in heating, ventilation, and air conditioning (HVAC) systems.
- Maintains air quality: Ensures proper ventilation and circulation.
- Temperature regulation: Delivers cooled or heated air efficiently.
- Types of Ducts
| Type | Description | Application |
|---|---|---|
| Rigid Ducts | Made from sheet metal, fiberglass, or plastic. | Used in central HVAC systems. |
| Flexible Ducts | Made of plastic or metal wire coil covered with insulation. | Used in tight spaces, small installations. |
| Round Ducts | Cylindrical shape, lower friction loss. | Efficient for large HVAC systems. |
| Rectangular Ducts | Flat design, space-efficient. | Used in commercial and residential buildings. |
- Duct Materials
| Material | Properties | Usage |
|---|---|---|
| Galvanized Steel | Durable, corrosion-resistant. | Commercial HVAC systems. |
| Aluminum | Lightweight, easy to install. | Residential ductwork. |
| Fiberglass Lined Ducts | Provides insulation, noise reduction. | Used in high-noise environments. |
| Flexible Ducts (Plastic or Metal) | Cost-effective, easy to install. | Small-scale HVAC systems. |
- Duct Insulation
- Reduces heat loss and energy consumption.
- Prevents condensation and moisture buildup.
- Common insulation materials: Fiberglass, Foam Board, Reflective Insulation.
- Air Distribution Methods
| Method | Description | Example |
|---|---|---|
| Constant Air Volume (CAV) | Supplies constant airflow, adjusts temperature. | Used in offices and homes. |
| Variable Air Volume (VAV) | Adjusts airflow based on demand. | Used in commercial buildings. |
| Mixing Ventilation | Mixes supply and room air for uniform temperature. | Used in large spaces. |
| Displacement Ventilation | Supplies cool air at low velocity near floor level. | Used in theaters, conference rooms. |
- 2. Air Flow Components in HVAC
- Air Handling Unit (AHU)
- Function: Regulates and circulates air.
- Components: Blower, filters, cooling/heating coils, dampers, ducts.
- Types: Rooftop units, modular units, custom-built systems.
- Fans & Blowers
| Component | Function |
|---|---|
| Fan | Moves air at low pressure. |
| Blower | Moves air at higher pressure. |
| Centrifugal Fan | Uses rotating impellers, high efficiency. |
| Axial Fan | Moves air in a straight path, used in exhausts. |
- 3. Air Filters in HVAC
- Function of Air Filters
- Removes dust, pollen, and pollutants from the air.
- Improves indoor air quality and prevents system clogging.
- Enhances efficiency and extends HVAC lifespan.
- Types of Air Filters
| Type | Material | Efficiency |
|---|---|---|
| Fiberglass Filter | Synthetic fibers | Low |
| Pleated Filter | Polyester or cotton | Medium |
| HEPA Filter | High-density fibers | High (99.97% particles removal) |
| Electrostatic Filter | Electrically charged plates | High |
| Activated Carbon Filter | Charcoal layer | Removes odors and gases |
- Effect of a Choked Air Filter
- Reduced airflow → Poor cooling and heating efficiency.
- Higher energy consumption → System works harder to push air.
- Overheating & system failure → Can damage components like compressors and motors.
- Maintenance of Air Filters
- Regular cleaning or replacement (every 3-6 months).
- Use high-quality filters for better performance.
- Monitor air pressure drop to detect blockages early.
- 4. Split A.C. (Ducted System)
- Construction & Working Principle
- Comprises indoor unit, outdoor unit, duct system, and thermostat.
- Works on vapor compression cycle (compressor, condenser, expansion valve, evaporator).
- Refrigerant absorbs heat indoors, releases it outdoors.
- Troubleshooting in Ducted Split A.C.
| Issue | Possible Cause | Solution |
|---|---|---|
| Poor Cooling | Dirty filter, low refrigerant. | Clean filters, check refrigerant. |
| No Airflow | Faulty fan, blocked ducts. | Check fan motor, clear ducts. |
| Water Leakage | Clogged drain pipe. | Clean drain pipe. |
| Unusual Noise | Loose components, faulty compressor. | Tighten parts, check compressor. |
- 5. Multi-Split A.C. (Ducted System)
- Construction & Working
- Similar to split AC but connects multiple indoor units to a single outdoor unit.
- Efficient space cooling for offices, homes, and hotels.
- Mechanical & Electrical Components
| Component | Function |
|---|---|
| Compressor | Circulates refrigerant. |
| Expansion Valve | Controls refrigerant flow. |
| Evaporator Coil | Absorbs heat from indoor air. |
| Condenser Coil | Releases heat outside. |
| Blower Fan | Circulates air through ducts. |
- Electrical Circuits & Testing
- Check voltage levels of compressor and fan motor.
- Use a multimeter to test continuity and resistance.
- Inspect relays and capacitors for damage.
- Fault Detection & Troubleshooting
| Problem | Cause | Solution |
|---|---|---|
| Compressor Not Starting | Faulty capacitor, relay, or low voltage. | Check capacitor, relay, and wiring. |
| No Cooling | Low refrigerant, clogged filter. | Refill refrigerant, clean filter. |
| Uneven Cooling | Duct leakage, blocked vents. | Seal ducts, clean vents. |
