Which three control strategies are commonly used in zone control for HVAC units such as AHUs, VAVs, or fan-coil units?

Which three control strategies are commonly used in zone control for HVAC units such as AHUs, VAVs, or fan-coil units?

• A. All three techniques
• B. Variable air volume with zone sensing
• C. Reheat or VAV with outdoor air modulation
• D. On/off

Answer: (A)

Zone control in HVAC relies on a combination of approaches to match each space’s comfort needs with energy efficiency. On/off control is simple and robust, turning airflow or equipment fully on or off to meet demand in zones with little dynamic load. Variable air volume with zone sensing provides more precise control by modulating the supply air flow based on a local zone temperature, so the air delivered scales with cooling or heating needs and minimizes overshoot. Reheat or VAV with outdoor air modulation adds flexibility to handle zones with varying loads and ventilation requirements: the main air stream can be controlled for cooling, and reheating can bring the zone back to the setpoint, while outdoor air modulation manages IAQ without overcooling. Because AHUs, VAVs, and fan-coil systems benefit from both simple, intermediate, and flexible strategies, all three techniques are commonly used.

Zone control in HVAC relies on a combination of approaches to match each space’s comfort needs with energy efficiency. On/off control is simple and robust, turning airflow or equipment fully on or off to meet demand in zones with little dynamic load. Variable air volume with zone sensing provides more precise control by modulating the supply air flow based on a local zone temperature, so the air delivered scales with cooling or heating needs and minimizes overshoot. Reheat or VAV with outdoor air modulation adds flexibility to handle zones with varying loads and ventilation requirements: the main air stream can be controlled for cooling, and reheating can bring the zone back to the setpoint, while outdoor air modulation manages IAQ without overcooling. Because AHUs, VAVs, and fan-coil systems benefit from both simple, intermediate, and flexible strategies, all three techniques are commonly used.