Definition:
Supply: Supply air refers to the conditioned air that is delivered to the occupied spaces through the HVAC system’s ductwork and diffusers. This air has been treated to meet the desired temperature, humidity, and air quality requirements for occupant comfort and indoor environmental control.
Return: Return air is the air that is drawn back from the conditioned spaces into the HVAC system through return grilles and ducts. This air is then recirculated, mixed with fresh outdoor air, filtered, and reconditioned before being supplied back to the spaces as part of the continuous air circulation process.
Additional Facts
- Supply Temperature: The temperature of supply air is typically cooler in summer and warmer in winter to maintain comfortable indoor conditions.
- Return Grilles: These are the openings through which return air is drawn back into the HVAC system, usually located on walls or ceilings.
- Filtration: Return air passes through filters to remove dust and contaminants before re-entering the HVAC system for reconditioning.
- Air Balance: Proper HVAC design ensures that the volume of supply air matches the volume of return air to maintain optimal system performance.
- Ductwork: Separate ducts are used for supply and return air to prevent mixing and maintain efficient air distribution throughout the space.
Fundamental Mechanisms
| Mechanism | Purpose | Key Components | Critical Issue | Impact of Failure |
|---|---|---|---|---|
| Air Handling Unit (AHU) | Conditions and circulates air | Fans, filters, cooling/heating coils, dampers | Improper maintenance, filter clogging | Reduced air quality, inefficient heating/cooling |
| Ductwork System | Distributes conditioned air | Supply and return ducts, diffusers, grilles | Leaks, poor insulation | Energy loss, uneven temperature distribution |
| Variable Air Volume (VAV) Boxes | Controls airflow to specific zones | Damper, actuator, flow sensor, reheat coil | Damper malfunction, sensor calibration | Improper zone temperature control, energy waste |
| Exhaust Fan System | Removes stale air from building | Exhaust fans, ductwork, roof vents | Fan motor failure, blockages | Poor indoor air quality, potential health hazards |
| Economizer System | Uses outdoor air for free cooling | Dampers, sensors, controls | Sensor failure, damper sticking | Missed energy-saving opportunities, increased costs |