Selecting the right Air Handling Unit (AHU) is crucial for ensuring efficient ventilation, temperature and humidity control, and energy savings in commercial, industrial, and residential HVAC systems. The selection process involves air volume capacity, function requirements, energy efficiency, and installation constraints.

This guide will cover the key factors, selection criteria, and expert tips to help you choose the best AHU for your needs.

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1. Key Factors to Consider When Selecting an AHU

When choosing an Air Handling Unit, consider the following factors:

1.1 Air Volume & Airflow Capacity

  • Determine the required airflow (CFM or m³/h):
  • Small spaces (e.g., offices, homes) → Low airflow (1,000-5,000 m³/h)
  • Medium spaces (e.g., hotels, restaurants) → Moderate airflow (5,000-20,000 m³/h)
  • Large commercial/industrial spaces (e.g., malls, factories) → High airflow (20,000+ m³/h)
  • Ensure the unit provides sufficient fresh air while maintaining indoor air quality.

1.2 Cooling & Heating Capacity

  • Check the required cooling capacity (kW or BTU/h) and heating capacity (kW) based on climate conditions.
  • Determine if additional heat exchangers, cooling coils, or electric heating elements are needed.

1.3 Humidity Control Requirements

  • Does the AHU need humidification or dehumidification?
  • If precise humidity control is required (e.g., laboratories, museums), choose an AHU with:
  • Steam humidifiers
  • Ultrasonic humidifiers
  • Desiccant dehumidifiers

1.4 Filtration & Air Quality

  • Select the appropriate filter efficiency based on the environment:
  • Standard dust filters (G4-F5) → Basic filtration (offices, homes).
  • Medium-efficiency filters (F6-F9) → Hospitals, schools, hotels.
  • HEPA/ULPA filters (H10-H14, U15-U17) → Cleanrooms, pharmaceutical factories.
  • Consider activated carbon filters for odor and gas removal.

1.5 Fresh Air vs. Recirculated Air

  • 100% Fresh Air Unit (FAU): Suitable for hospitals, cleanrooms, and industries requiring continuous fresh air supply.
  • Mixed Air AHU: Recirculates part of the return air, reducing energy consumption in offices, malls, and exhibition centers.

1.6 Energy Efficiency

  • Choose high-efficiency motors, fans, and heat recovery systems to reduce energy consumption.
  • Consider adding:
  • Heat recovery wheels → Transfer heat between supply and exhaust air.
  • EC Fans → Energy-efficient electronically commutated motors.
  • Variable Frequency Drives (VFDs) → Adjust fan speed based on demand.

1.7 Noise Levels

  • Low-noise AHUs (≤55 dB) are ideal for offices, hotels, and residential areas.
  • Consider soundproof enclosures and silencers for quiet operation.

1.8 Size & Installation Space

  • Check the available installation space (mechanical room, rooftop, or ceiling-mounted).
  • Modular and compact AHUs are better suited for space-limited applications.

1.9 Control & Automation

  • Ensure the AHU supports BMS (Building Management System) integration.
  • DDC (Direct Digital Control) or PLC-based control systems provide remote monitoring and automatic adjustments.

2. AHU Selection Process: Step-by-Step Guide

Step 1: Define Project Requirements

  • Indoor space size and occupancy level.
  • Type of application (residential, commercial, industrial).
  • Required temperature, humidity, and air quality standards.

Step 2: Calculate Required Airflow (CFM or m³/h)

Use the formula:

Image
  • Example:
  • Room Volume = 500 m³
  • ACH = 5 (offices typically require 4-6 ACH)
  • Airflow = ( \frac{500 \times 5}{60} ) = 41.7 m³/min (2,500 m³/h)

Step 3: Choose the Right Coil & Fan System

  • Chilled Water or DX Cooling Coil?
  • Chilled water coil → Central cooling system (chiller).
  • DX coil → Direct expansion system (independent AHU).
  • Fan Type:
  • Centrifugal fan → High static pressure.
  • Plug fan (EC fan) → Energy-efficient, quiet operation.

Step 4: Select the Right Filtration System

  • Determine the level of air filtration needed based on industry standards (e.g., ASHRAE, EN, ISO).

Step 5: Verify Control System Compatibility

  • Does the AHU support automatic temperature, humidity, and CO₂ control?
  • Can it integrate with BMS (Building Management Systems)?

Step 6: Evaluate Installation & Maintenance Needs

  • Compact or modular AHU for small spaces.
  • Accessible filter panels for easy maintenance.
  • Drain pans and corrosion-resistant materials for long-term reliability.

3. Recommended AHU Configurations by Application

ApplicationRecommended Airflow (m³/h)FiltrationCooling TypeEnergy Efficiency Features
Offices & Homes2,000 – 10,000G4-F7DX or Chilled Water CoilEC Fan, VFD
Hospitals & Labs10,000 – 30,000HEPA H13+Chilled Water CoilHeat Recovery
Shopping Malls & Hotels20,000 – 50,000F6-F9Chilled Water CoilHeat Recovery, BMS
Industrial & Factories50,000+F7-F9Chilled Water CoilVariable Air Volume (VAV)
Cleanrooms (ISO 5-7)5,000 – 50,000HEPA H13-H14Chilled Water CoilULPA, Laminar Flow

4. Expert Tips for Selecting an AHU

✔ Consider long-term energy savings → Invest in heat recovery & efficient motors.
✔ Choose a reputable manufacturer → Look for certifications (ISO, AHRI, Eurovent).
✔ Ensure easy maintenance → Modular designs simplify service and repairs.
✔ Test performance before purchase → Request factory acceptance tests (FAT).
✔ Verify warranty & support → A good AHU should have at least a 2-year warranty.

5. Conclusion

Choosing the right Air Handling Unit (AHU) requires careful consideration of airflow, filtration, energy efficiency, and control options. By following this selection guide, you can ensure your AHU meets the specific requirements of your project while optimizing performance and operational costs.

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How to Select an Air Handling Unit (AHU)?