NEWS

Installation & Commissioning Procedure

Proper installation is crucial to ensure the VAV system performs as designed. Key steps include:

• Mechanical Installation

• Mount and secure VAV boxes to the ceiling, ensuring airflow direction matches the sensor orientation (usually marked with an arrow).
• Connect inlet and outlet ducts, insulate if needed, and install flexible connectors to reduce vibration and noise.
• Install room temperature sensors in representative locations (avoid doors, windows, or vents).
• Connect pressure sensor tubing (if using remote-mounted sensors) and ensure no leaks.
• For reheat boxes, connect hot water pipes or electric heating wires correctly.
• Ensure all valves and dampers operate smoothly.

• ⚡ Electrical & Control Wiring

• Connect 24 VAC or 220 VAC power to actuators and controllers.
• Wire temperature and airflow sensors to the controller.
• Set up communication networks (RS485 or TCP/IP) between VAV controllers and the central control panel.
• Assign unique addresses/IDs to each VAV box to avoid conflicts.
• Perform insulation and continuity checks for electrical safety.

• 💻 Controller Programming & Configuration

• Load the VAV control application into DDC controllers.
• Configure parameters: network address, sensor-zone mapping, min/max airflow limits.
• Calibrate I/O settings using DDC software and commission each VAV box:
  • Check damper travel range.
  • Verify temperature sensor accuracy.
  • Zero differential pressure sensors if needed (especially if installed at different altitudes).

• 🌬️ Air Balancing

• Measure actual airflow at diffusers using a balometer at max, min, and intermediate damper positions.
• Calibrate airflow sensors to match measured values.
• Ensure each VAV box delivers airflow within ±5% of design values.
• Adjust AHU fan pressure: open all VAVs, measure pressure at the farthest point, and tune VFD speed accordingly.
• Test automatic pressure control by closing some VAVs and observing system response.

• 🧪 Testing & Commissioning

• Run the system under peak and low-load conditions to verify control stability.
• Simulate room heating to check VAV response and airflow increase.
• Test interlocks:
  • If AHU fan stops, VAV dampers should fail open.
  • If fire alarm triggers, VAVs should open 100% for smoke extraction.
• Test reheat function: simulate winter, verify hot water valve opens when airflow is at minimum but room is still cold.
• Record final calibration values and generate a commissioning report.

• ⚠️ Important: Clean ductwork before operation to prevent dust from jamming dampers. Ensure all AHU filters are installed to protect fans and sensors.

• 🧰 Common Issues and Troubleshooting

• 🔧 Sensor Failures

• Faulty or drifted temperature sensors can cause overcooling or overheating.
• Dirty or miscalibrated airflow sensors may misreport flow, leading to incorrect damper positions.
• Solution: recalibrate sensors regularly (every 6–12 months).

• ⚙️ Stuck Dampers or Actuator Failures

• Dust or mechanical wear may cause dampers to stick or actuators to fail.
• Symptoms: room temperature doesn’t change despite control signals.
• Some actuators fail-safe to 100% open, causing overcooling.
• Solution: inspect and replace actuators as needed.

• 💨 Airflow Imbalance

• “Starved box” issue: distant VAVs receive insufficient pressure, even at full open.
• Nearby boxes may receive excess pressure, causing noise.
• Solution: rebalance system, adjust duct dampers, or increase fan setpoint if capacity allows.

• 🖥️ Control/BMS Errors

• Communication loss or software bugs can disrupt operation.
• Example: VAV reverts to standalone mode, losing optimization features.
• Solution: check BMS logs and control logic.

• 💧 Condensation or High Humidity

• Too low supply air temperature or too little airflow can cause condensation at diffusers.
• Solution: set minimum supply air temperature (~13°C) and airflow limits.

• 🔊 Noise Issues

• High inlet pressure causes whistling when dampers close too much.
• Solution: reduce system pressure or install silencers.
• Fan-powered VAVs may produce noise if bearings wear out.

• 🧠 Expert Insight: After a decade, rubber and plastic parts degrade, sensors drift, actuators stick, and heating valves may leak—leading to poor temperature control and wasted energy.

• 🛡️ Periodic Maintenance

• 🌀 AHU & Chiller

• Replace AHU filters every 3–6 months.
• Clean cooling coils, check chilled water pumps, and inspect for condensation.
• Maintain chillers annually (check refrigerant, oil, clean condenser).

• 📦 VAV Box

• Check room temperature sensors with a reference thermometer.
• Verify airflow sensor accuracy using pressure taps.
• Clean inside the box, especially dampers and sensors.
• For fan-powered VAVs: lubricate or replace bearings if noisy.
• Test actuators manually for smooth operation.
• Inspect reheat valves: bleed air, check for leaks or stuck valves.

• 🧠 Control System

• Check controller backup batteries.
• Regularly back up BMS programs and databases.
• Update firmware as recommended.

• 📊 Tip: Use BMS trending to detect anomalies—e.g., rooms with large temperature swings or excessive reheat usage.

• 🧼 Duct & Diffuser Cleaning

• Clean every 3–5 years to maintain air quality and sensor accuracy.

• 👨‍🏫 Operator Training

• Train staff to recognize BMS alarms, understand system diagrams, and manually operate valves during failures.
• Keep maintenance logs and manuals up to date.